YoungPetro - 16th Issue - Winter 2016

WINTER / 2016

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E ditor’s Letter

Dear YoungPetro readers, I’m very happy that you reached for our magazine.

Why? It means that despite the crisis in the petroleum industry, you still believe in the potential of the branch and you vest your hopes in its future development.

This issue of YoungPetro Magazine is special for me, as it’s the last one prepared by the team under my direction. Everything changes, life moves on and for some editors of YoungPetro it’s time to say goodbye.

We are ready to take on new challenges, but don’t worry! YoungPetro will stay in safe hands. The new team, consisting of young, energetic and smart people, will make an effort to create more and more interesting content for you!

In this issue, we want to present some current and very important topics. The article by Muhammad Akran Khan shows technical and economical differences between CNG and LNG marine transportation. Mian Tauseef Raza will try to familiarise you with the topic concerning the improvement of the shale gas production with the usage of geomechanics. If you would like to know more about

proppants don’t miss the article by Radosław Budzowski. Traditionally, you can also read about current affairs in On Stream and learn some interesting facts from How it works.

As it’s the last time for me to address a few words to you, so I would like to thank you all for being with us from the very beginning, from the first issue, especially thank you for the last 2 years. I spent this time working as the editor-in-chief of YoungPetro. It’s been a fantastic time, full of many challenges, surprises and successes. Every little thing was an important lesson for me. This adventure will stay forever in my heart! I hope you will remain with the new YoungPetro team and that you will become a new successful generation in the petroleum industry!

Simultaneously, 2015 has come to an end and the new year has started. On behalf of YoungPetro editorial board, I would like to wish you many successes in the new year. May all your dreams come true! Learn new skills, take on next challenges and just be happy!

May the force be with you! ;) 

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Editor-in-Chief Joanna Wilaszek j.wilaszek@youngpetro.org Deputy Editor-in-Chief Maciej Wawrzkowicz m.wawrzkowicz@youngpetro.org Art Marek Nogieć www.nogiec.org Editors Agata Gruszczak Natalia Krygier Alina Malinowska Jakub Pitera Marketing Barbara Pach Karolina Zahuta Proof-readers Paweł Gąsiorowski Logistics Radosław Budzowski Patryk Szarek

issn

2300-1259

Published by An Official Publication of

The Society of Petroleum Engineers Student Chapter P o l a n d • www.spe.net.pl

IT Michał Solarz Scienctific Advisor Tomasz Włodek Ambassadors Alexander Scherff – Germany Tarun Agarwal – India Mostafa Ahmed – Egypt Manjesh Banawara – Canada Rakip Belishaku – Albania Camilo Andres Guerrero – Colombia Moshin Khan – Turkey Ahmed Bilal Choudhry – Pakistan Muhammad Taimur Ashfaq – Pakistan Viorica Sîrghii – Romania Michail Niarchos – Greece Rohit Pal – UPES, India Usman Syed Aslam – India Publisher Fundacja Wiertnictwo - Nafta - Gaz, Nauka i Tradycje Al. Adama Mickiewicza 30/A4 30 - 059 Kraków, Poland www.nafta.agh.edu.pl

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On Stream 7 Radosław Budzowski

Proppant – Little Big Thing 10 Radosław Budzowski

The Technical and Economical Comparison between 15 Marine CNG and LNG Transportation Muhammad Akram Khan

Improving Shale Gas Production Using Geomechanics 27 Mian Tauseef Raza

When East Meets West 34 Karolina Zahuta

Actual and Future Scenarios of Shale Gas in Europe 37 Barbara Pach, Karolina Zahuta

How it works? 40 Maciej Wawrzkowicz

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InNovate, InNovate,Integrate, Integrate,Motivate Motivate

InNovate, InNovate, InNovate, Integrate, Integrate, Integrate, Motivate Motivate Motivate

7th International Geosciences Student Conference

7th International Conference 7th Intern Katowice,Geosciences Poland | 11 -Student 14 July 2016 7th International Geosciences Student Conference 7th Intern Katowice, Poland | Katowice, Poland | th

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Registration and call for papers

1 January 2016 30 april 2016 Reg Registration and -call for papers Registration and call for papers Reg 1 January 2016 - 30 april 2016 1 January 2016 - 30 april 2016 Keynote Oral and poster Keynote Short Keynote Oral and poster Soft-skills Oral and poster Short Workshops Short Soft-skills Soft-skills SEG Workshops W orkshops Social and sport SEG EG FSield Social and sport Social and sport Field Field

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CONTACT US: www.facebook.pl/IGSC7POLAND

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Radosław Budzowski

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On Stream – Latest News Radosław Budzowski

Syria encourages Russians to invest in their oil fields

Syrian Minister of Foreign Affairs – Walid Muallem and Deputy Prime Minister of Russian Federation–Dmitry Rogozin (responsible for the aerospace and defense industry) expressed strong hope that near the Syrian shores will be seen not only Russian warships but also oil rigs. This way, once again, Syria showed Russian energy entities its openness on their investment in Syrian oil fields. There is already government's decision to guarantee the primacy of Russian companies in the implementation of economic projects in Syria, especially in the construction and petroleum exploitation. Russian media reported that oil and natural gas resources in the Syrian shelf can have a huge potential. There are already preliminary information that the oil fields near the city of Banijas are probably the richest in the whole Mediterranean basin.

Iranian oil will be delivered to Europe next year, for gas we will wait even a decade

Europe has promised to buy gas from anyone, arguing it the decline of its own production and increased demand. The issue of gas consumption will be especially acute since 2017 when the European Union will stop using old coal-fired plants that will be converted to gas power plants. Many producers wants to sell gas to Europe, including those, who do not have adequate infrastructure or contracts for the export. Through Turkey–neighboring Iran–is being built TANAP gas pipeline, which is expected to deliver Azeri gas to Europe

starting in 2020. Due to geographical and economical reasons Turkey is the most obvious way to supply Iranian gas to Europe. Many years ago, Iran had the idea to build its own pipeline to Europe that would pass through Turkish territory.

These plans, however, remained only on paper.

Tehran needs the gas contracts as soon as possible. It wants to announce their willingness to take part in the market shares, even if this share both in the first phase and in the future will not bring income. This may be due to the fact that Iran does not want further sanctions and present sanctions may be removed in the next year.

The new old member of OPEC–Indonesia

OPEC made a surprising election of a new member. It is a country that consumes two times more oil than produces. After seven years of suspension of membership, Indonesia rejoins OPEC as its 13th member. The country ensures that as the only Asian member of the organization, excluding the Middle East countries, will be the basic combination of the cartel with their continent, where demand for oil is growing faster and faster. Apparently, OPEC has abandoned its role as a guardian of prices and focused on increasing its stake in the global market. In the opinion of many experts, nothing unusual had happened to rejoin Indonesia to OPEC. Country did not discover any new deposits. The International Energy Agency says that the new member of the organization intends to produce 850 thousand barrels per day, and that is about 739 thousand less than Indonesia consumed last year. 

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For online version of the magazine and news visit us at youngpetro.org

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Proppant – Little Big Thing

Proppant – Little Big Thing Radosław Budzowski

Exploitation of tight gas and shale gas reservoirs is economically viable only after a lot of extraction stimulation treatments, leading to creating the crevices system in rocks. The gas flow into the wellbore through the formed fracture is conditioned by adequate fracture prop. For this purpose, proppants are used. The three main categories of proppants used today include sands, resin-coated proppants and man-made ceramics or bauxite proppants. The choice of the proppant is dependent on the compressive stress occurring in the reservoir, the conductivity of fractures, and many other factors (e.g. temperature, formation pressure). Before using proppants in borehole conditions, its properties and parameters should be determined, according to relevant standards and procedures.

Process The purpose of the hydraulic fracturing process is to increase the efficiency of extraction of hydrocarbons from the well by increasing the contact area between the wellbore and rocks and thus increase gas & oil extraction. The process of hydraulic fracturing involves the pumping of the fracturing fluid at very high pressure (min. 600 atm) into the well. The fluid enters the horizontal well and goes further through the holes, causing the cracking of reservoir rock and the formation of large (150 m) and narrow (1-2 mm) networks of fractures, through which hydrocarbons come out.To prevent closing of these cracks as a consequence of the withdrawal of the pressure and the subsequent impact of the rock pressure, proppants are injected into the wellbore along with the fracturing fluid. Proppants maintain fractures open all the time. After finishing the process, a portion of the injected fracturing fluid (without proppants) returns to the surface, and a part of it stays inside the rock. A horizontal well is long (from 1 to

4 km), so it is divided into several sections. Each section is fracturing separately. The shape and size of proppants is of utmost importance in the process of extracting hydrocarbons.

Types of proppants There are three basic types of proppants used for the stimulation of unconventional reservoirs: quartz material, ceramic material, and resin-coated material. Natural sand belongs to the group of quartz materials. Its main component is crystalline silica (quartz) SiO2 , constituting approx.

80-99,8% of the proppant. Grains of sand are sieved, separated and mixed in the right proportions to achieve proppant with suitable properties and standardized granulation. The bulk density of proppant from quartz is 1.5 g/cm3, while the apparent density (specific gravity) is 2.6 g/cm3.

Proppants from natural sands exhibit low resistance to compressive stress (crushing), and thus are most commonly used for small depths, where such stresses are not greater than 41.4 MPa (6000 psi). The advantages of using sand proppants include a significantly lower manufacturing cost in relation to the ceramic proppants and the fact that these materials are easily available.

Ceramic proppants have different content of alumina Al2O3. For the fracturing of conventional reservoirs, proppants based on sintered bauxite should be applied. They are characterized by high specific gravity (approx. 3.5 g/cm3) and high resistance to compressive stresses. Ceramic proppants, in which the alumina content is 5-35%, are used for the fracturing of unconventional reservoirs (slickwater fracturing technology). For the production of ceramic proppants, mixtures of clay, kaolinite, bauxite are used. Light ceramic proppants usually have in their mineralogical composition such components as mullite (60-85%), silica (5-35%),

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Radosław Budzowski

Fig. 1 – Types of proppants and cristobalite (0-20%). Ceramic proppants show better properties than sands: better roundness and sphericity of grains, and the greatest resistance to crushing. Hence, they can be used at medium depths (2000-3500 m), where compressive stresses are up to 69 MPa (10 000 psi) and the temperature of the reservoir is approx. 80-100 °C. The use of ceramic proppants can increase the efficiency of extraction of hydrocarbons from the reservoir compared to sand proppants. As a result, the total cost of exploration is significantly lower when compared to the use of proppants from bauxite.

The third kind of proppants are materials coated with resin. The improvement of the roundness and sphericity parameters of grains and its resistance to compression (compression stress) are the main aims of coating. Resin-coated proppants can limit the phenomenon of movement and leaching proppant grains from the generated slots. In order to cover the proppant grains, epoxy resins with amine hardener or cross-linking agent and phenolic resins containing a mixture of resin and hexamethylene tetramine may be used. In both cases, the properties of the cured resin are dependent on the stoichiometry of the resin and crosslinking agent.

Resin-coated proppants must be compatible with reservoir fluids and fracturing fluid, so this kind

of materials cannot degrade its rheological properties. The resins may release chemicals, which in contact with the fracturing fluid can cause a change in its pH. In recent years, during the fracturing process with the use of slickwater fracturing technology, a new idea has been born. Light proppant grains were mixed with the addition of small amounts of grains that exhibit a high resistance to crushing. This was to ensure the increase in the strength of proppants with low specific weight. Then, I also started research on new proppants, ultralight, whose density relative to water is 1.05, which allows them to practically float on its surface. It is almost perfectly spherical proppant with a smooth, shiny surface.

However, this type of material is very expensive and therefore costs of fracturing process can be much higher.

The choice of proppant must provide the proper conductivity of the entire fractures system and placing proppants in farthest parts of fractures after the fracturing process (Fig. 2).

Laboratory tests The objective of the laboratory tests is to determine the conductivity and permeability of

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Proppant – Little Big Thing

Fig. 2 – Comparison between well rounded ceramic proppant (A) and poorly sorted angular proppant sand (B) the fracture filled with proppants in function of compressive stress, including the time of action of the tension, the flow rate and temperature. Test parameters are chosen in such a way that laminar flow in porous media in the measuring chamber occurs, which is described by Darcy's law. In the case of high speed and turbulent flow, there may be a difference between the results obtained under the Darcy's law. It is caused mainly by kinetic effects. Therefore, parameters representing the kinetic energy and the β factor are added to the Darcy's equation. The literature data indicate that a significant decrease in the conductivity of the slot occurs in the first 30 hours. In the following test hours, the conductivity loss is much smaller.

This is related to the so-called "panning out" grains of proppants in the first phase of the compressive pressure, which is equal to pressure of closing the fracture. During the process, the porosity of the proppants is reduced considerably. This leads to the increased flow resistance and the reduction f conductivity. As a result of the lack of space for movement of the proppant grains, an increase of internal stress in grains occurs, which causes

their breaking. The resulting particles of proppant grains are floating in the measuring fluid, causing the closing of pore channels and further reduction of conductivity and permeability.

Proppants market Institution producing ceramic proppants are located in the vicinity of the deposits of clays, kaolin and bauxite. Currently, the US market consumes about 70% of world production of ceramic proppants annually. According to the data from PropTester Report, the value of worldwide market for ceramic proppants in 2010 amounted to $ 1.2 billion, in 2011 approximately $ 1.7 billion, in 2012 approximately $ 1.8 billion, in 2015 should amount to 2.6 billion USD, and in 2020 is expected to reach $ 5.2 billion. The market growth is achieved by the increasing volumes and prices growth. This means that in the ongoing decade, the global market for ceramic proppants will double its value every 5 years. It should be noted that the industry associated with the extraction of hydrocarbons from shale rock is at an early stage of development

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Radosław Budzowski

Fig. 3 – Graph comparing various properties of different types of proppants and has a very high potential for further growth.

Baltic Ceramics Company estimates that the consumption of proppants for one shale gas mine is approximately 5-10, and even 15 thousand tons of proppants.

The dynamic consumption growth of ceramic proppants has been observed since the beginning of the 21st century, when they were applied to horizontal hydraulic fracturing. In the years 2002-2010, the average annual increase in the use of ceramic proppants amounted to 23.3%. The main reason for the increase of ceramic proppants is their high compressive strength, which enabled the extraction of shale gas and thus started the shale revolution in the United States. The main ceramic proppant consumer is the United States, but recently an increase in the consumption of ceramic proppants in China and other countries has been observed.

In Europe, ceramic proppants are widely used in tight gas exploitation in Germany and the Netherlands, and on the offshore, among others, in Norway, Denmark, the UK and the Netherlands.

this process works, what its effects are, what the risks include, is also constantly increasing. However, the word "proppant" isn’t still widely known, and very few people know what it is, how it looks and what its application is. Proppant, despite being small, plays a major role in the process of fracturing. 

Conclusion The process of fracturing is currently very popular. In the coming years proppants market will probably grow and evolve. The awareness of how

Fig. 4 – Sand proppant (on the left) ceramic proppant (on the right)

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Proppant – Little Big Thing

References 1. American Petroleum Institute: Recommended Practices for Evaluating Short Term Proppant Pack Conductivity. API RP 61, First edition, 1989.

2. Dewprashad B.T., Abass H.H., Meadows D.L., Weaver J.D., Bennet B.J., Halliburton Energy Services: A Method To Select Resin-Coated Proppants. SPE Annual Technical Conference and Exhibition, 3-6 October 1993, Houston, Texas, USA. 3. Economides M.J. Nolte K.G.: Reservoir Stimulation Second edition. Prentice Hall, Houston 1989.

4. Kasza P.: Zabiegi stymulacji wydobycia w niekonwencjonalnych złożach węglowodorów. Nafta-Gaz 2011, nr 10, s. 697-701.

5. Masłowski M.: Materiały podsadzkowe do zabiegów hydraulicznego szczelinowania złóż niekonwencjonalnych. Nafta-Gaz 2014, nr 2, s 75-86.

6. Tiemann M., Vann A.: Hydraulic Hydraulic Fracturing and Safe Drinking Water Act Issues Congressional Research Service, 15th April 2011.

7. Baltic Ceramics Website: balticceramicsinvestments.com Photos: ceramic-proppants.com, thorsoil.com, pnlintrade.files.wordpress.com, fracsandfrisbee.com

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Muhammad Akram Khan

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The Technical and Economical Comparison between Marine CNG and LNG Transportation Muhammad Akram Khan

The worldwide consumption of natural gas is rapidly increasing. International Energy Agency (IEA) shows that overall gas use will be increased to 5047 billion m3 in 2030 and will keep rising continuously. Gas production is projected to increase from 2600 billion m3 in 2010 to almost 5100 billion m3 in 2030. According to WEO, International trade of Natural gas could approach 1300 billion m3 in 2020, about 30% of world production and 1700 billion m3 in 2030.

Due to The geographical mismatch between resource endowment and demand, The Gas markets are normally far away from production fields. There are many possible technologies of transporting gas from production fields to consumers elsewhere as a fuel or as a chemical feedstock in a petrochemical plant, where gas is converted into valuable products. The methods for transportation of natural gas include Pipelines (PNG), Liquefied Natural Gas (LNG), Compressed Natural Gas (CNG), Gas to Hydrates (GTH), Gas to Liquids (GTL), Gas to Commodity (GTC) such as glass, cement or iron and Gas to Wire (GTW) i.e. electricity.

CNG transport is not new, nor is the technology being introduced to CNG transport, but what is new is the application of these technologies into a CNG marine based system and the increased volumes of CNG proposed to be transported. The competitive advantage of marine CNG routes over other non-pipeline gas transportation processes is that they require simple technology as well as not a huge investment. These could be the options for handling niche markets for gas reserves which are stranded, associated gas which cannot be flared or re-injected, or small reservoirs which cannot otherwise be economically exploited.

**Warsaw University of Technology ÞÞPoland akram_khan@is.pw.edu.pl  University  Country  E-mail

In this work, based on the technical and economical comparison between marine CNG and LNG transportation of natural gas, NPV calculation, CAPEX, OPEX, the Processing Complexity; and Geopolitical sensitivity have been compared. The economic parameters for marine transportation of Gas from Eastern Med. to Europe (Lavrion, Greece) and far East ( Japan), as a case of study, has been obtained. Also, these values have been compared with Pipelines and the results are shown in the form of different tables and graphs.

Introduction Natural gas is expected to be the fastest growing primary energy source: its share in world energy demand will be increased to 28 % in 2030 [8]. Natural Gas has overtaken coal as fuel No. 2 by 2010.

The World Energy Outlook (WEO), published every two years by the International Energy Agency (IEA) shows that gas use will be increased to 5047 billion m3 in 2030. Demand grows most rapidly in the fledgling markets of developing Asia, notably China, India and in Latin America. Nonetheless, OECD North America, OECD Europe, and the Former Soviet Union (FSU) remain by far the largest markets in 2030. These three groups will account for 63% of gas demand in 2030, compared with 74.4% in 2001[8].

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The Technical and Economical Comparison between Marine CNG and LNG Transportation

Fig. 1 – World’s primary energy demand

Natural gas has also long been considered an alternative fuel for the transportation sector. In fact, natural gas has been used to fuel vehicles since the 1930′s. According to the Natural Gas Vehicle Coalition, there are currently 18.9 million Natural Gas Vehicles (NGVs) on the road worldwide by 2014, led by Iran with 3.50 million, Pakistan 2.85 million, Argentina 2.28 million, Brazil 1.75 million, China 1.58 million and India 1.1 million [8]. In recent years, technology has improved to allow for ÈÈ

a proliferation of natural gas vehicles, particularly for fuel intensive vehicle fleets, such as taxicabs and public buses. However, virtually all types of natural gas vehicles are either in production today for sale to the public or in development, from passenger cars, trucks, buses, vans, and even heavy-duty utility vehicles. Despite these advances,

ÈÈ

a number of disadvantages of NGVs prevent their mass-production. Below is the world Natural Gas demand by sector.

Increasingly Abundant Gas Reserves On the supply side, the gas increase is driven by increasingly abundant reserves and resources which CEDIGAZ and the U.S. Geological Survey confirm.

Over the last thirty years proven gas reserves increased almost continuously, from about 45 1012 m3 in 1980 to about 177.6 1012 m3 at the beginning 2010, representing sixty years of current production.

While gas consumption increased by a factor of 2.3 over the period, proven gas reserves increased by a factor of 3.5. Gas reserves are more widely distributed among regions than are oil reserves. On a country-by-country basis, Russia ranks first with 30% of worldwide reserves and Iran second with 16%.

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Muhammad Akram Khan

Fig. 2 – World’s natural gas demand by sector

Volume [1012 m3]

% of World Total

North America

6.9

3.9

Latin America

8.0

4.5

Europe

7.8

4.4

Former Soviet Union

55.9

31.5

Africa

13.1

7.4

Middle East

70.7

39.8

Asia - Oseania

15.2

8.5

World Total

177.6

Table 1 – Proved reserves of natural gas in the world All regions but OECD North America and Europe are pretty comfortable at today’s reserves to production ratio. The Middle East, which accounts for almost 40% of global reserves, holds a reserves/ production ratio of 260 years, significantly higher than for any other region, clearly illustrating the

scale and potential for exploiting these largely untapped reserves and probably under-explored gas resources [8].

Growing imbalances between supply and demand Although recent gas discoveries have affected all the continents, their distribution is far from harmonious with the size and growth of the regional markets. This creates growing regional imbalances between production and demand, at the continental scale, and even more, at the local scale of the countries. Gas production is projected to increase from 2500 billion m3 in 2000 to almost 5100 billion m3 in 2030. The projected trends in regional gas production reflect to a large extent the location of reserves. WEO projects that the production will grow mostly in absolute terms in the transition economies and the Middle East. Output also increases quickly in Africa and Latin America.

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The Technical and Economical Comparison between Marine CNG and LNG Transportation

Fig. 3 – Major natural gas trade movements

Fig. 4 – New trade routes of natural gas

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Muhammad Akram Khan

Fig. 5 – CNG transportation

International Gas Trade The geographical mismatch between resource endowment and demand means that international trade should witness a sustained expansion in the next thirty years, and that the main growth markets for gas are going to become much more dependent on imports. International trade could approach 1300 billion m3 in 2020, about 30% of world production and 1700 billion m3 in 2030 [8]. Below are the routes of international trade of natural gas.

Since, gas markets are normally far away from production fields. There are many possible technologies of transporting gas from production fields to consumers elsewhere as a fuel or as a chemical feedstock in a petrochemical plant, where gas is converted into valuable products. The methods for transportation of natural gas include Pipelines (PNG), Liquefied Natural Gas (LNG), Compressed Natural Gas (CNG), Gas to Hydrates (GTH), Gas to Liquids (GTL), Gas to Commodity (GTC) such as glass, cement or iron and Gas to Wire (GTW) i.e. electricity. Below is a comprehensive comparison of two most popular methods of transportation of Natural Gas (i.e. marine CNG vs. LNG).

Compressed Natural Gas Compressed Natural Gas (CNG) is gas compressed up to 275 Bar at ambient temperature but not condensed. 1cf of CNG is equal to 300cf of Natural Gas. It contains almost 95–98% methane (CH4). 1 m3 of CNG weighs 220 kg and produces 12.1 GJ of energy upon burning [7].

CNG has a long history of safe transportation onshore. Gas pipelines transport compressed natural gas. The transportation of CNG by trucks also dates back to 30 years. Worldwide, more than 18 million vehicles are operated on CNG. Large-scale marine CNG transport is historically unrealized due to the limitations of small pressure vessels. While these days, a number of well-known gas transportation companies are engaged in increasing the vessels capacity and minimizing the risks associated to them. E-g: Coselle system, VOTRANS, Flexible movable pipelines etc. have improved the CNG transport to higher extent, while the practical implementation of any huge-scaled project has not yet been observed.

CNG always remains the gas during the transportation process. It is chilled neither liquefied nor converted to any other material like electricity etc. which enables it to provide the capability of a pipeline. The loading is far simple than any other processes involved in transportation of gas. Initially, the raw gas is dehydrated and then compressed up to 2000–3000 psi. During loading both onshore as well offshore terminals (buoy/platform) can be used. The simple shuttle ships with relatively huge capacity are used to transport the gas. And the technology at the receiving port is also very simple. The gas is received from the CNG shuttle ships, decompressed and supplied to the consumers.

Processing Technology of CNG Natural gas is usually supplied by the pipelines from its production site to its processing site for

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The Technical and Economical Comparison between Marine CNG and LNG Transportation

Fig. 6 – CNG carrier view

CNG. Gas is delivered at the pressure of 15 Bar and 30 degrees Celsius Temperature and its pressure is controlled by a pressure regulator [3]. Gas will flow through metering system to measure the volume of gas for custody transfer. Possible liquid entrainment that is still carried out in the gas stream is separated into scrubber unit. Gas dryer is provided to control Gas dew specifications.

Gas then flows into electricity driven Gas Compressor, which then compresses it up to desired pressure to meet the CNG containment requirement. Gas is then supplied to the Buffer storage, and when necessary, transferred to the CNG ship via pipeline to store in the Cascade of CNG ship.

CNG compressors will be used for emptying the buffer storage after pressure balance is achieved between the Buffer Storage and Cascade of the CNG ship. An odorizing agent is then injected to the gas to detect the gas leakage during the transportation.

CNG Carrier Fleet After the formal processing and compression of Natural gas, it is loaded into fleets which transport it to the destination. Different companies

are using different technologies to store CNG in ships. The most popular among them are Coselle, VOTRANS, CDTS and Flexible pipelines. Both the pressure vessels and ships are well-established technologies in the industry and are individually covered by a proper set of rules regulating the design, fabrication and operation phase. The main Novel concept for this CNG technology lays in the application in a marine environment of pressure vessels carrying a high pressure gas.

Decompression of CNG After the CNG ship has arrived at the destination, CNG is transported by pipeline to Buffer Storage. CNG Gas compressors are provided to emptying the Buffer Storage after the equal pressure has been established between the Buffer Storage vessel and Cascade in CNG ship. Gas pressure is then reduced and adjusted according to the requirements of storage. The temperature of the Gas remains ambient throughout the process. The Gas is then supplied for usage via metering system to control the amount of gas being supplied. The whole summary of CNG supply chain is explained below in Fig. 7.

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Muhammad Akram Khan

Fig. 7 – Supply chain of CNG Technology Liquefied Natural Gas Liquid Natural Gas (LNG) is Natural Gas that has been cooled down and condensed to liquid state. 1cf of LNG is equal to 600cf of Natural gas.

The temperature of LNG at 1 Bar is -162 degrees Celsius. LNG contains 93–97 % methane (CH4). 1 m3 of LNG weighs 460 kg and produces 25.2 GJ of energy upon burning [5].

The method of transportation includes the liquefaction of gas. For this purpose, the raw gas undergoes several stages of treatments and then liquefied under a very low temperature. The liquefied gas needs to be stored in a special storage. This stored gas is then loaded to sophisticated and efficient ships through terminals either from onshore in harbor or from off-shore liquefaction. While at the receiving terminal the liquid gas is initially stored at the special storages where the process of regasification takes place. The gas is then compressed and finally supplied to the consumers. The detailed process is explained below.

Liquefaction Liquefaction plants typically consist of one or two processing trains. The Natural Gas is supplied by pipelines from the production site to processing plant. First of all the gas passes through the scrubber to remove any water particles present in the gas. After dehydration, gas is then cooled up to the temperature of – 162 degrees Celsius and then condensed to get the liquid gas [3]. The refrigeration and condensation process is a very expensive

process that makes the project much costly as compared to CNG. Technological progress achieved in the past decades has led to a sharp decrease in investment and operating costs of liquefaction plants.

Transportation The finally processed liquid gas is then loaded on to the LNG tankers, which mainly have their refrigeration system onboard to hold the Gas into liquid form during its transportation. Since, refrigeration is an expensive process, Transport costs are largely a function of the distance between the liquefaction and regasification terminals and the size of the vessel. Using a larger number of smaller carriers offers more flexibility and reduced storage requirements but raises unit shipping costs. The largest LNG carriers today have a maximum capacity of 135,000–138,000 m3. They cost around $170 million to build. Substantial reductions in cost have been achieved over the past decades thanks to economies of scale. Tanker sizes have increased from some 40,000 m3 for the first generation to a range of 130,000 to 140,000 m3 nowadays [4]. The typical construction of LNG carrier is shown below in Fig. 7.

Regasification After the LNG carrier has arrived at its destination, the Liquid Gas is then regasified. After regasification, the gas is again compressed according to the consumer’s need. Regasification plant

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22

The Technical and Economical Comparison between Marine CNG and LNG Transportation

Fig. 8 – Cross section of an LNG carrier

Fig. 9 – LNG supply chain

23

Muhammad Akram Khan

Fig. 10 – Volumetric difference between CNG and LNG

construction costs depend on throughput capacity, land development and labor costs (which vary considerably according to location), and storage capacity. Economies of scale are most significant for storage. These are maximized for storage tank capacities of about 150,000 m3 – the largest feasible at present. The short summary of LNG chain is shown below in Fig. 9.

Pressure

Temperature

CNG

275 BAR

Ambient

LNG

Ambient

−162°C

Table 2 – The processing technology of CNG and LNG Economical comparison of CNG and LNG transportation The following aspects are to be kept in mind while calculating the economic values of CNG or LNG transportation projects.

NPV calculations for CNG and LNG projects To access the economic merit of project, the net present value (NPV) is calculated for the project

over the definite period of time. The below is the standard form of NPV calculation:

NPV = PVGas sales −CAPEX [1] Where CAPEX refers, to project related capital expenditure; and PV refers to the present value (PV) of net cash from gas sales over a time period of N years, which can be calculated by equation 2: N

PV ( gassales) = ∑ DCF (after taxes), k = k−i

N

=∑ k−i

ACF (after taxes) (1 +i)k

[2]

Where, ACF after taxes, k is annual cash flow after taxes in year k; i is discounting interest rate; and DCF is the discounted cash flow.

Total CAPEX is assumed to be incurred instantly at zero time, and to comprise expenditures on Terminals and on the Gas transportation fleet, i.e.

CAPEX = CAPEX terminals (q ) + +CAPEX fleet (G fleet ( L , q )) [3] Where CAPEX terminals (q) depends on the Natural Gas Transportation rate that meets the consumption rate, q and CAPEX fleet (G fleet) de-

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The Technical and Economical Comparison between Marine CNG and LNG Transportation

pends on the natural gas carrying capacity of the fleet of natural gas transportation vessels, G fleet, which in turn depends on q and the transportation distance ,L, from natural gas source to delivery destination. [3].

Now let’s discuss CAPEX and OPEX separately for CNG and LNG. CAPEX calculation Let’s assume that, transported gas is consumed at uniform rate, q. It means that total CAPEX is the sum of CAPEX at the terminals which include the cost of compression/decompression and CAPEX for the transportation. So, the formula to calculate the CAPEX will be as follows: CAPEX = CAPEX terminals ×q + + CAPEX fleet ×L×q [4]

OPEX calcultaions The annual operational expenditure (OPEX) is also the sum of two terms; OPEX for gas volumes change (compression/decompression for CNG) and the OPEX for the gas transportation (voyages

costs) [1]. So, the formula to calculate the OPEX will be as follows: OPEX = C transport ×L×q + C volume change ×q [5]

Comparison of Offshore Gas production using Floating CNG ships (F-CNG) vs. Floating LNG ships (F-LNG): During offshore gas production, the production vessel or platform is much convenient and instead of compressing gas into a pipeline, reservoir gas is compressed into CNG ships on a continuous basis.

F-CNG

F- LNG

Capital Cost

Lower

Higher

Operating Cost

Lower

Higher

Process Complexity

Lower

Higher

Tolerance to gas impurities

Better

Worse

Turndown (or off)

Easier

Harder

Cargo Transfer in open ocean

Conventional

Novel

Access to markets

Regional

Global

Table 3 – Technical comparison between CNG and LNG

Fig. 11 – Difference between LNG and CNG capital cost allocation

25

Muhammad Akram Khan

LNG Transportation Value chain [US$/ MMBtu]

CNG

Onshore LNG 8.8 mtpa $1,500 /tpa

Floating LNG 1.5 mtpa $1,733/tpa

Subsea Pipeline 8bcm/a $5million/km

Marine CNG 3bcm/a CAPEX & OPEX

Cost of Gas at destination

$10.00

$10.00

$10.00

$10.00

Loading Compression and Liquefaction

$6.82

$7.88

Included

$0,85

Transportation

$0.30

$0.30

$3.81

$2.95

Off-loading or regasification/storage

$0.75

$0.75

Included

$0.19

Net Back

$2.13

$1.07

$6.19

$6.01

Table 4 – Regional Netbacks CNG vs. LNG vs. FLNG vs. Pipeline. Eastern Med. to European Regional Market (Lavrion, Greece). Shipping distance: 1100km LNG Transportation Value Chain

Onshore LNG 8.8 mtpa $1,500 /tpa

Floating LNG 1.5 mtpa $1,733/tpa

$14.00

$14.00

Cost of gas at destination Loading compression or Liquefaction

$6.82

$7.88

Transportation

$3.00

$3.00

Off-loading or regasification/storage

$0.75

$0.75

Table 5 – Global Netbacks to LNG and FLNG. Eastern Med to Far East Markets (Japan) .Shipping distance: 15 000 km Notes 1. Europe 2014, Natural Gas Price US $ 10.88/ MMBtu. Further drop in prices since then use $ 10/MMBTU [9].

2. STL Buoy Loading and offloading for CNG (deep water >300m).

3. Pipeline Capex of $ 5 million/km for deep water. Opex included and assumed at 2% of capex/a. [6].

Difference between LNG and CNG capital cost allocation

5% of total amount is consumed in loading and unloading process respectively due its very simple technology. The transportation comprises the major part of a CNG project. The graphical summary of the difference LNG and CNG capital cost allocation is given below: Pipeline vs. Marine CNG transport cost comparison Pipeline alternative ÈÈ ÈÈ ÈÈ

Generally, during an LNG project the loading process comprises almost 60% of the total expenses.

In the same manner, unloading also costs too much which is almost 30% of the total expense.

Transportation utilizes the 10 % of overall project expenses. While on the other hand, only 20% and

ÈÈ

CAPEX assumption: 5 million/km Project Term: 15 years IRR: 13% simple PMT calculation (no construction period interest calculated) NO OPEX included

Marine CNG alternative: ÈÈ

Continuous loading and offloading

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ÈÈ

ÈÈ ÈÈ ÈÈ ÈÈ

The Technical and Economical Comparison between Marine CNG and LNG Transportation

Uses same ship type for each of the capacity sensitivities: Fleet for a 220km distance : 3–5 x C48 Fleet for 550km distance: 3–5 C112 Project term 15 years @ 13% project IRR OPEX for ships and land facilities is included

ÈÈ

While Marine CNG is a simple, safe, reliable and flexible solution delivering higher netbacks in regional markets as compared to pipeline or LNG/FLNG for shorter distances up to 2500- 3000 km. While, if the distance is greater than the one mentioned above, LNG will be the best choice.

Pipeline vs. Marine CNG CNG

Pipeline

Lower

Higher – has to be built to meet final capacity

Stepwise Investment

Yes

Has to be built for ultimate capacity

Flexibility to supply alternative markets

Yes

Only fixed destination

Geopolitical Sensitivity

Less risk – can be moved, less sensitive

Initial Investment

The other priorities of marine CNG over LNG are as follows: ÈÈ

ÈÈ

ÈÈ

ÈÈ

ÈÈ

More risk – cannot be moved

Table 6 – Comparison of CNG and Pipeline Concluding Remarks ÈÈ

Pipelines and Marine CNG produce superior net-backs in regional markets as compared to LNG/FLNG

ÈÈ

ÈÈ

Marine CNG has fast implementation (due to its medium sized projects) Marine CNG is scalable and flexible to customer requirements Marine CNG has multiple loading/unloading options Marine CNG creates fewer Environmental and Community issues Marine CNG provides greater certainty of capital cost (ships approximately70% of CAPEX) Marine CNG has protection for geopolitical risks in politically sensitive regions Marine CNG needs smaller land “footprint” at loading and unloading sites.

Keeping in view the above mentioned facts and figures, it is obvious that Marine CNG offers highest net-backs along with its fewer environmental issues if the gas markets are within the range of 2000 nautical miles [2]. 

References 1. Britton P. S., Dunlop J. S. (2007). SS: CNG and Other LNG Alternatives—CNG Marine Gas Transport.

Solution: Tested and Ready. USA, Houston, Offshore Technology Conference, OTC 18702, 1–7.

2. Coselle Website (www.coselle.com).

3. Economides M., Sun K., Subero G. (2006). Compressed Natural Gas (CNG): An Alternative to Liquefied Natural Gas (LNG). SPE Production & Operations, vol. 21, no. 2, 315–324.

4. Gudmundsson J. S., Borrehang A. (1996). Natural Gas Hydrate: an alternative to Liquified Natural Gas. Norway, NTNU, Trondheim.

5. Guthire K. M. (1969). Capital Cost Estimating. Chemical Engineering. 76–114.

6. Mathworks Website (www.mathworks.com).

7. Nassar Y. I. M. (2010). Comparisons and Advantages of Marine CNG Transportation. SPE Projects, Facilities & Construction, 225–229.

8. U.S. Energy Information Administration (www.eia.gov).

9. YCharts Website (http://ycharts.com/indicators/europe_natural_gas_price).

27

Mian Tauseef Raza

¸¸

Improving Shale Gas Production Using Geomechanics Mian Tauseef Raza

The fraction of gas production from shale plays is growing steadily particularly in USA and Canada. Shale plays have several traits in common which comprise extremely low permeability.

Every shale play encompasses natural fractures that might be developed during maturation of kerogen.

Alongside these characteristics, shale plays differ in depositional environment, maturity, pore pressure and temperature, depth of burial and geomechanical properties such as in-situ stresses as well as fracture dispersal between or within a shale play. It is necessary to have indepth understanding of geomechanics for most favorable stimulation design and upgraded well placement in order to boost productivity and life of well. Stimulation in shale gas reservoirs occurs through a combination of shear slip and opening of pre-existing (closed) fractures and the creation of new hydraulic (tensile) fractures.

Similarly fracture may fail either by opening or shear slip. Stress regimes describe fracture failure. This paper deals with the stimulation effectiveness observance with respect to the in-situ stresses and develops a connection between intensity of stresses and stimulation plans. By focusing only on the consequences of variations in natural fracture characteristics and the in-situ stress state, it is possible not only to understand why these shale gas plays respond differently to stimulation, but recommendations can be made for operational changes based on geomechanical understanding. Various published data sets were observed and analyzed to illustrate the production enhancement using geomechanics that must play its part in meeting the demand supply gap and partake in the energy crunch of world.

**Univ. of Engineering & Technology in Lahore ÞÞPakistan mst.seefi@yahoo.com  University  Country  E-mail

Introduction Geomechanical problems are associated with the 40% of the drilling related nonproductive time in challenging environments of shale drilling. For field development, horizontal wells are drilled that are highly advantageous in anisotropic and highly fractured shale gas reservoirs and are used to enrich drainage volume per well in a given time period.

A geomechanical model is necessary for better and improved stimulation design. Geomechanical model involve mechanical properties of rock (Poisson’s ratio, Young’s modulus, coefficient of thermal expansion, Biot coefficient, sliding friction and internal friction), in situ pore pressure, vertical stress magnitude, horizontal stress orientation and magnitude, and natural fracture distribution network. Most important thing in shale gas production is the fracture handling. Identifying the natural fracture network and the stresses are keys to capitalize on production in a shale play.

Shale plays are highly anisotropic demonstrating a large change in properties even within a play.

Shale plays have several attributes in common as their matrix permeability is extremely low they must be stimulated to produce commercially. All shale plays contain natural fractures, generated during the process of in-place kerogen maturation, these plays can be quite different as their

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Improving Shale Gas Production Using Geomechanics

depositional environment, age, mineralogy, maturity, temperature, pore fluid pressure, depth of burial, natural fracture dispersal and in situ state of stress all vary, between and even within a single play. Techniques to achieve commercial and monetary production rates involve the drilling of long laterals in the direction of the minimum in situ horizontal stress, which are stimulated along their extent. These techniques have had to be improved based on experience in other shale plays because of high anisotropy and difference in their depositional environment, age, mineralogy, maturity, temperature, pore fluid pressure, depth of burial, natural fracture distribution and in situ state of stress States [3]. Such variants among or within a shale play cause deviation in the response of those plays to stimulation. By focusing on the consequences of variations in natural fracture characteristics and the in situ stress state, it is possible not only to understand why these shale gas plays respond differently to stimulation, but also to develop recommendations for operational changes based on that understanding. Stimulation design and intervals to be stimulated with time can be selected accurately by having an understanding of in situ stresses and other geomechanical parameters.

At the end, a model is recommended for safe and long lasting well.

Shale gas reservoirs are the gas reservoirs that are limited in shale formations. Shale forms under environmental settings that can supply abundant fines to calm water. Shale are sedimentary rocks, so, composed of fragments of pre-existing rocks that have been eroded, transported, deposited and lithified into new rocks. Shale also contains organic material which was lain down along with the rock fragments during its formation. Mostly it is formed in marine environments neighboring to a continent. Even though shales may show 20% porosity but the pore throats in shales are often smaller than the diameter of a water molecule which is about three angstroms. Pores in the 3-12 angstrom range are typically available for fluid flow in shales, which explains why shale permeabilities can be measured in fractions of nanodarcy. They option very less permeability to conduct flow of gas through. Owing to very low permeabil-

ity of these reservoirs, the gas must be produced by means of special techniques usually including drilling long laterals, horizontal wells and fracture stimulation, if to be produced commercially in an economical way. Low porosities and permeabilities with high compressive strength values limit not only fracture initiation but also identification of suitable intervals for fracturing. In shale matrix, contained gas is stored in two ways; in the form of free gas or adsorbed gas. The adsorbed gas molecules adhere to the surface of the organic matter (kerogen) and require pressure energy to initiate desorption. Thus, the desorbed gas moves slowly through the shale matrix by means of diffusion until it reaches a fracture face. Free gas slowly moves through the micro pores in the shale matrix to a fracture face. Gas molecules then move through the natural fracture system or hydraulic fractures created by stimulation towards the pressure sink provided by the borehole. Organic matter contained in shale is called kerogen, which is the source material for all hydrocarbon resources.

When a shale source rock matures, the oil and gas is generated from conversion of kerogen that causes micro fracturing in shale, providing escape routes for hydrocarbons to migrate from the shale source rock to some other porous and permeable bed trapped by a seal or a cap rock. But, in some cases, rate of generation of hydrocarbons beat the rate of leakage due to the insufficient micro fractures to offer a continuous hydrocarbon escape route out of shale. At the same time, increased maturity can crack the generated oil to smaller fractions, gas. Therefore gas shales are sources as well as reservoir rocks. They are good sealing rocks too due to their very small intrinsic permeability values. To properly interpret the hydraulic fracturing and micro seismicity data, it is essential to build a geomechanical model of the reservoir that includes the mechanical rock properties along with the state of in situ stresses. This model is particularly useful in understanding the evolution of stress before, during, and after stimulation or hydraulic fracturing. Geomechanical model counts for rock mechanical properties along with vertical stress magnitude, horizontal stress orientation and pore pressure. Mechanical properties used in geomechanical modeling are Poisson’s

29

Mian Tauseef Raza

ratio, Young’s modulus, coefficient of thermal expansion, Biot coefficient, brittleness, internal friction and sliding friction. In this paper, horizontal stress, vertical stress, pore pressure, brittleness, Young’s modulus and Poisson’s ratio are analyzed with a mineralogy approach to access the best fracable intervals.

Horizontal wells are essential to produce economically by increasing contact area between the reservoir and the wellbore. We can interpret it in another way that, in general, natural fractures tend to be nearly, but not quite, vertical, and thus are unlikely to be crossed in vertical wells. They often are sealed with a variety of minerals such as calcite hence the early belief was that shale gas plays are largely unfractured or, if there are fractures that do not contribute to flow. The increase in horizontal drilling and the use of image logs to detect fractures and faults has now revealed that most shale gas plays in fact have a quite noteworthy population of pre-existing fractures called natural fracture network, although their distribution can be quite different from play to play or even within different areas of a single play.

Geomechanics for shale gas reservoirs are different from that of conventional reservoirs because of: 1.

2.

3.

4.

5.

Low matrix permeability, Inelastic matrix behavior, Rock rheology, Rock anisotropy, Stress sensitivity.

Geomechanical studies for gas shales help in 1. Design and optimize hydraulic fracturing, 2. Selecting optimum mud weight and mud chemistry for safe drilling, 3. Underbalanced drilling feasibility, 4. Optimizing well trajectory in zone of interest, 5. Maximizing production from critically stressed naturally fractured reservoirs, 6. Optimize well trajectory, 7. Model depletion effect on the reservoir productivity and compaction.

Geomechanics is beneficial to hydraulic fracturing as it increases efficiency of job with identifying relatively easier fracable intervals. Geomechanical properties of rock decide the height and growth of hydrofractures, in fact geomechanics of a rock is controlling factor for fracture growth. Same is the case with orientation of hydrofractures. Geomechanics is also helpful in optimizing drilling direction so that hydraulic fracturingpressure can be minimized as it depends upon orientation of stresses and their magnitude in particular directions.

Pore Pressure Pore pressure is the pressure exerted by the fluids confined in formations. Pore pressure in gas shale is very difficult to find because of the very low intrinsic matrix permeability. It can be found by mud weight used for drilling when there is no gas intrusion in the wellbore and lost circulation to formation. This is the condition when pore pressure and mud weight can be assumed equal.

Interaction of pore fluid with heterogeneous formation along slip zone can affect rupture propagation in gas shale. An increase of pore pressure that reduces the effective compressive stress and facilitates slip propagation occurs if the compressive side of the slip zone is more permeable than the tensile side; conversely, a decrease of pore pressure that increases the effective compressive stress and inhibits slip propagation occurs if tensile side is more permeable.

Vertical Stress Stress regime is the dominant factor controlling direction and height or growth of hydraulic fractures. Due to the free surface of the earth, one of the principal stresses is usually oriented vertically depending upon the specific weight of overlying strata. The magnitude of this principal stress can be formulated from the weight of the overburden by following formula z

Vertical Stress = σv = ∫ ρ( z ) g [1] 0

Where is the vertical stress magnitude, ρ(z) is the density at depth z and g is gravitational acceler-

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Improving Shale Gas Production Using Geomechanics

ation [4]. Density log give vertical stress magnitude at different depths. In a porous medium, the weight of the overburden is carried by both the grains and the fluid within the pores. Accordingly, an effective stress, , is defined as σv’ = σv − α p [2]

Where is Biot’s poroelastic constant. It is dimensionless. And is pore or reservoir pressure in psi.

aries are generally considered to be “locked-inplace,” whereas the vertical stress follows the geologic history like erosion, glaciation, and deposition etc. of the overlying layers. Thus, the horizontal or pancake fractures are likely to occur in a stiff, shallow formation. As the hydraulic fractures are formed in the direction perpendicular to the least stress, so, in shallow and stiff rocks pancake fractures are generated.

Fracturing Pressures

Horizontal Stress and Poisson’s Ratio Poisson’s ratio can be predicted or estimated from acoustic log data or from correlations based upon lithology. Poisson’s ratio is defined as, “the ratio of lateral expansion to longitudinal contraction for a rock under a uniaxial stress condition.” All shale plays contain widely distributed planar weaknesses and fractures. If the differences in the stresses in a location get too large, slip on faults will occur and the difference in stresses will be reduced or relaxed. Thus, there is a maximum difference between the principal stresses beyond which the system will relax back to equilibrium through shear failure events, beyond this maximum difference, compressive failures occur when the maximum resolved compression exceeds the rock failure strength and tensile failures are resulted when the minimum resolved effective stress becomes negative and the rock fails in tension. The vertical stress is translated horizontally through Poisson’s ratio “ν” v s H’ =� sv’ [3] 1− v

Here is effective horizontal stress usually measured in psi. The absolute horizontal stress is arrived at by adding the αp term to the effective horizontal stress. Owing to tectonic components, the horizontal plane stress varies with direction. The above defined horizontal stress is the minimum horizontal stress; the maximum horizontal stress is: s H ,max = s H ,min + stect [4]

The upper limit of the imposed pressure required to fracture a formation from a vertical wellbore is given by the Terzaghi equation: pbd ,upper = 3s H ,min − s H ,max + To − p [5]

is breakdown pressure with tensile stress of the rock and is the reservoir pressure.

The lower borderline for the breakdown pressure is given as pbd ,lower =

3σ H ,min − σ H ,max + To − 2η p 2(1− η)

[6]

Where is given as η =α

1− 2 v [7] 2(1− v)

The breakdown pressure or fracture pressure is usually greater than the fracture extension pressure. Because once fracture generated, it is easier to extend it than to break in the formation. The breakdown pressure or fracture pressure is the pressure required to initiate a fracture from the wellbore to the best suitable and easier paths. The fracture extension pressure reflects the pressure required to propagate the fracture through the formation [1]. Stress magnitude is also denoted by S, by some authors, SHmax for maximum horizontal stress and Shmin for minimum horizontal stress.

For vertical stress magnitude, Sv is used.

Young’s Modulus

Where, is tectonic stress contribution in consistent units with horizontal stresses. Horizontal stresses contained within stiff or inflexible bound-

Young’s modulus is defined as “the ratio of stress to strain for uniaxial stress”. The stiffness of

31

Mian Tauseef Raza

the material is measured in terms of modulus of a material. Larger the modulus, more stiff is the material and vice versa. As a result of hydraulic fracturing, a stiff rock will result in more narrow fractures; conversely, if the modulus is low then the resulted fractures will be wider. The modulus of a rock depends upon the lithology, porosity, fluid type, and other variables. Strong and competent rocks have high young’s modulus.

Mineralogy and Geomechanics Major minerals of the shale are clay minerals and quartz. Thus, most abundant oxides are Al2O3 and SiO2. A particularly high silica content results when silica bearing shells or volcanic ash occurs in a rock along with detrital quartz. A high K2O content may be due to the detrital feldspar, authigenic feldspar, detrital muscovite, illite or potassium adsorbed by the clay minerals. Shales are rich in kerogen as they are source rock for petroleum. In short gas shales have predominantly quartz, carbonates and clays. These may vary in percentage compositions. Encounter of some more complex composition is not unusual due to the anisotropic behavior. Shale anisotropy properties are present in respect of elasticity parameters, such as Young’s modulus and Poisson’s ratio, which are used for stress profiling, and failure parameters, such as

tensile and compressive strengths, which are important for the evaluation of formation breakdown during hydraulic stimulation and wellbore stability.

In order to show the effect of composition of shale on hydraulic fracturing efficiency while keeping in view the geomechanical behavior, we have had to construct a ternary diagram. A graph is plotted between Young’s modulus and Poisson’s ratio in order to understand the brittleness of mineral or sample. Brittle intervals are most favorable for hydraulic fracturing. These intervals can be determined by brittleness index.

Y . M britt =

Y . M − Y . M min ×100 [8] Y . M max − Y . M min

For Poisson’s ratio, P . Rbritt =

P . R − P . Rmax ×100 [9] P . Rmin − P . Rmax

Brittleness can be found as BRITTavg =

Y . M britt + P . Rbritt [10] 2

In order to find the brittleness index, compressive and tensile strength measurements can be used.

To calculate brittleness index following formula can be used:

Fig. 1–Brittleness by Mineralogy

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Improving Shale Gas Production Using Geomechanics

10 9 8 7 Young’s Modulus



6 5 4 3 2 1 0

0

0.1

0.2

0.3

0.4

0.5

Poisson’s Ratio Fig. 2–Brittl intervals by geomechanical properties 1. Hunca& Das in 1974 suggested that BI =

s c − st [11] sc + sc

2. Altindag in 2002 gave following relation for calculation of brittleness index

BI =

sc ×st [12] 2

High clay-rich shales usually have low Young’s Modulus and, by extension, low brittleness index and difficult to frac. A ternary diagram is constructed that shows different compositions.

We can construct a ternary diagram that shows the brittleness [2]. As clays have least brittleness and quartz have maximum, so a general conclusion can be drawn after observing the different hydraulic fracturing designs for many a cases that were efficient in work.

It is concluded in the ternary diagram that as we move towards the increasing quartz content brittleness increases. This axis is the most brittle axis and brittleness decreases towards the carbonate and is

least in clay corner. Mineralogy ternary diagram show brittle intervals, where to frac as shown in Fig. 1.

Another approach is the geomechanical that is shown in given graph.

Intervals with curve lying in brittle region are easily fracable and retain conductivity for longer. As indicated in Fig. 2.

Based on extensive study of stimulation models, it is concluded that: 1. For the intervals having 61% quartz or more, are easy to frac and sustain fracture for longer.

2. Intervals with 47 to 61% quartz have two possibilities ÈÈ If less clay content, hydraulic fracturing is feasible ÈÈ If high clay content, hydraulic fracturing require special attention 3. Ultimately, for less than 47% quartz content with fairly high clay usually more than 35%, not best choice for hydraulic fracturing.

33

Mian Tauseef Raza

Silica may be considered in terms of quartz. Clay content in excess of 35 to 40% is too high to be considered as perspective shale, because low Young’s modulus and high Poisson’s ratio shales are too ductile to be perspective.

Less anisotropic formations are more brittle and brittle rocks have higher YM and lower PR. In brittle rocks hydrofracture is more likely to be long enough to connect the highest amount of rock volume to the parent wellbore [4].

Thus, it is very important to find intervals that are brittle, in order to maximize hydraulic stimulation.

Recommendations Based upon our extensive work, I recommend that minimum Poisson’s ratio and maximum Young’s modulus intervals are best for hydraulic fracturing.

Summary and Conclusion Laboratory core tests of mineralogy, rock mechanics, and geomechanics should be conducted on every potentially viable shale. Results of these laboratory tests can be used to develop optimum water-frac designs for unconventional shale plays to maximize production and extended life of well. 

References 1. Economides M.J., Valko P. Hydraulic Fracture Mechanics. Texas, USA, A&M University, College Station.

2. Hopkinsand C.W., Jochen J.E., Holditch&Assocs., Fink K.J. A Comparison of Two Devonian Shale Wells: Why Is One Well Better Than the Other? SPE26918, Pittsburgh, USA, November 2-4, 1993.

3. Maxwell S. C., Cipolla C. What does microseismicity tell us about hydraulic fracturing? SPE 146932, Denver, USA, October 30– November 2, 2011.

4. Zoback, M. D. (2007). Reservoir Geomechanics. Cambridge, United Kingdom: Cambridge University Press.

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When East Meets West

conference | East meets West – International Student Petroleum Congress & Career Expo 2015

µµ When East Meets West Karolina Zahuta Last spring brought us a special annual event.

For the 6th time we participated in ‘East meets West’ International Student Petroleum Congress & Career Expo organized at AGH UST in Krakow.

The Congress brought together young people involved in O&G sector, scientists, authorities and industry representatives. Participants represented 29 countries from Africa, Asia, Europe and North America. During the Congress, students could share their knowledge, observations and scientific research as well as be inspired by experienced professionals. Each year, it is one of the most awaited student events, and that’s because it focuses on students’ issues mainly. Also, the place of the meeting is special–Krakow is a

beautiful city, known for its student – friendly atmosphere.

Traditionally, EmW started with an extra preday, which gave all of the participants a chance to spend some time together and do some sightseeing in the city. On that day, students from Gubkin SPE Student Chapter organized PetroOlympic Games, which checked participants’ knowledge about widely understood petroleum industry and was also a great opportunity for integration, since it was organized as a group competition.

The main part of this edition of the Congress was a debate called ‘Today and Tomorrow of Oil & Gas

Karolina Zahuta

35

Industry – Chances and Challenges.” The guests of the discussion panel included:

prices fall is just temporary and in the long run it will not really disrupt the economy.

Guido van den Bos – Vice President, Global Accounts for Rig Systems, National Oilwell Varco; Matthias Meister – SPE Regional Director South, Central & East Europe; Product Development Manager, Baker Hughes; Prof. Stanisław Nagy – Head of the Department of Natural Gas Engineering of the Faculty of Drilling, Oil & Gas on AGH UST; Parker Snyder – President, Poland Shale Coalition; Executive Director, Cleantech Poland LLC; Jeff Spath – 2014 SPE President; Vice President, Schlumberger Ltd.

The next important panel was HR session. This time, we could listen to the presentations of 6 companies: Schlumberger, ORLEN Upstream, Discovery Polska LLC, MOL Group, Poland Shale Coalition, and Baker Hughes. During the session, companies’ representatives presented their offers and possibilities of development for their future employees. Not only did it provide a general overview of career possibilities, but it also enabled the students to learn how to apply for a job properly.

The debate created a platform for discussion not only between professionals but also between professionals and students, who could participate in the discussion. Basing on their experience, the invited guests unanimously claimed that the oil

The first one was the Student Paper Contest. Its participants shared their knowledge and scientific research and also answered questions asked by the audience. In this year’s edition, 25 participants from 14 countries took part. First place was taken

ÈÈ

ÈÈ

ÈÈ

ÈÈ

ÈÈ

Student attendees could compete in two contests.

The papers presented in both of them were chosen from about 200 applications.

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by Lang Li (China University of Petroleum, China) with the presentation: “Low Permability CO 2 Flooding’s Research on Technology. Development of YuShuLin.” The second contest was the Student Poster Session. Its participants presented their research on posters. The authors also answered the jury’s questions. Elizaveta Laputina became the winner of 2015 edition (Tyumen State Oil and Gas University, Russia) with her poster: “Experimental Prediction of Reservoir Water Influence on Condensate Recovery Factor.”

For many student attendees, the most important part of the Congress was Career Expo. This part gave young people a wonderful opportunity to receive answers to any questions they had, interact with the company representatives, and take a closer look at career perspectives that wait for them after their graduation. This time, the students could visit the stands of: Schlumberger, ORLEN Upstream, MOL Group, and Poland Shale Coalition.

Each year, student participants can take part in a number of interesting workshops. This year, the

When East Meets West

workshop was organized by Discovery GeoServices Corporation as a part of Discovery Geo Workshops. Its topic was: “Practical Reservoir Analysis” and it was conducted by Michael Lewis (President/CEO). The workshop was coordinated by our YoungPetro team.

There was another new event in the Congress agenda: PhD research session. It was a panel discussion led by PhD students. Young scientists shared their knowledge presenting their research and answering questions.

East meets West gave us a chance to widen our knowledge, meet inspiring people and lead interesting conversations. As always, the Congress propagated the worldwide idea of bringing together students and the industry (especially O&G sector). Big thanks to our friends from ‘East meets West’ Organizing Committee for the great job!

We cannot wait for the next edition of the Congress, which will take place from 20 to 22 April 2016. If you want to know more, please check the website: emwcongress.org. 

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Barbara Pach, Karolina Zahuta

conference | CEE Shale Gas & Oil Summit 2015

µµ Actual and Future Scenarios

of Shale Gas in Europe Barbara Pach, Karolina Zahuta From 9th-10th of March our attention was attracted to the Eastern Europe Shale Gas&Oil Summit 2015 which was held in Radisson Blu Hotel in Warsaw. This event gathered many international authorities from the O&G industry; technical experts, professionals and students from Belgium, France, Germany, Hungary, Lithuania, Netherlands, Norway, Poland, Romania, Russia, UK, Ukraine and USA. The twoday conference, with four sessions each day, paid attention to the themes such as previous experiences and future predictions for shale gas in Europe. What we found the most interesting were the newest methods of extracting gas from shale with the usage of CO2, legislation of exploring shale gas in several countries, the public opinion on shale gas and many others.

These highly interesting presentations and discussions allowed us to prepare an overview of the current situation and the future of shale gas exploration in Europe. Marek Madeja, Poland Country Manager for Cuadrilla reminded the audience that it took about 18 years to start commercial shale gas production in the USA while in Poland it is still a fresh issue. That is why there is no comparison between the US and the current situation in Europe which still needs time to develop. Akshay Pasrija from United Oilfield Services mentioned another reason why we should not compare the two continents – the difference in geology which means that technology used in the USA cannot be implemented in Europe. Furthermore, there is a big difference in law–in the USA it is in a landowner’s business to explore potential hydrocarbons while in the European Union, the resources belong to

the state. Moreover the EU regulations and recommendations are restrictive.

Undoubtedly, the attitude of government matters too. It seems that there is a need for government investment in basic science and research (notice that the USA has spent a lot of money before achieving the success in production). “Behind a ‘yes’ decision there is a risk,” the experts said, that is why important decisions are made with concern, postponed or avoided by executives. Summarizing the discussion, which took place during the third session of the second day of the conference, when it comes to the situation in Poland, it looks like the biggest oil & gas companies are not so convinced to step into the Polish market, because no one will risk losing money when it could take a long time to develop and stabilize the current situation. For entrepreneurs it is safer to go home rather than to invest money in Poland right now.

Moreover, Paweł Poprawa, expert in unconventional gas and oil, highlighted the importance of the much-needed good PR of shale gas exploration. Local communities should be informed and aware of the real dangers of shale gas exploration and extraction. An example for this is the situation in UK, where drilling was blocked many times by protests of citizens.

What more should be changed? According to lawyer Maciej Jóźwiak, we need a clear, transparent law. The process of giving licenses should be speed up and the problem with taxation should be solved looking at the experiences of other countries that produce hydrocarbons from un-

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conventional reservoirs. In Mr Poprawa’s opinion firstly we have to frack more, then extract and invest more money in research. Patience and changed approach may also play a big role in improving the situation.

Making a general conclusion, the market is unpredictable and many factors may influence the situation of shale gas in Europe. It can change very quickly and attract investors again, even within the next decade.

To sum up, as students, this conference gave us a view on current and future shale gas and oil exploration. Hearing about various interesting topics was very enlightening. We can see a chance for developing the current market situation, we just have to create the possibility for things to go in the right direction and be patient. As a YoungPetro delegation we are looking forward to more such interesting events. Special thanks to Charles Maxwell, the organizer of CEE Shale Gas & Oil Summit. 

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How It Works?

How It Works?

Maciej Wawrzkowicz

Welcome to ‘How it Works?’ section! Every time I try to discuss another technological aspect of our industry in simple and affordable form. The topic for today is processing of oil and gas, it means what is happening with reservoir mixture shortly after flowing out from the wellbore…

the bottom of separator and is removed by opening LCV (Level-Control-Valve) while liquefied hydrocarbons are flowing into stabilizer. Condensate stabilization removes lighter fractions and steam better. Sometimes, additional operations are deployed, in other cases condensate is ready for being stored and finally sold.

As you probably know, reservoir fluid is flowing under deposit pressure through the production string and then meets the ‘Xmass’ tree with all its equipment. Wellhead is fitted with numbers of electronic and mechanical tools designed to measure, convert and transfer an information about fluid parameters e.g. temperature or inflow pressure. From wellhead, via series of valves (including pressure control gauges) fluid is pushed into a pipeline. Of course, reservoir fluid is not eligible to use yet. In order to separate gas from oil and other substances number of processes are deployed.

Petroleum and chemical engineers used to call it reservoir fluid processing. Depending on various geochemical parameters, location and geological structure, composition of different compounds of fluid may vary. This is why every processing installation is designed for individual purposes of every plant. In some places crude fluid is contaminated with hydrogen sulphide what forces the engineers to fit additional sulphur recovery systems.

Gaseous phase however needs to be separated thoroughly in the further steps. If hydrogen sulphide is one of the constituents of natural gas we need to remove it. This is very crucial due to toxic properties of this substance. Firstly, amine sweetening process is conducted. H2S removal is possible thanks to absorptive features of amine compounds. Rich amine that is received after reaction in sweetening column is regenerated in high-temp conditions and comes back to the system. Recovered sour gas flows into Claus sulphur recovery unit where is transformed into elementary sulphur. What is interesting, sulphur is being sold in its liquefied form as a by-product and transported in specially designed tanks able to maintain temperature of around 120 degrees Celsius to prevent its solidification.

We have already said every plant is different and it is necessary to design processing system accordingly to individual needs of the field operator.

Although, some processes are quite common and widely utilized. Let us say something about them.

After passing a wellhead, reservoir fluid is treated with high temperature in heater. Then, mixture is passing to inlet separator where natural gas and other lighter phases vaporizes. Water, thanks to its relatively significant weight, is flowing down to

Gaseous mixture, called after amine treating as ‘sweet gas’ is going to Gas dew point control and LPG recovery unit in order to isolate the other, heavier phases like propane-butane. After proper measurements and eventually mixing with the other, natural gas is being sold to customer.

Processing described here is obviously just an example of treatment and every operator has its own technologies. Additional processes may include series of refrigeration, desalting or even thiols removal as a separated treatment.

See you soon in the next ‘How it works’ section! 

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AUTUMN / 2012

WINTER / SPRING / 2012

ISSN

2300-1259

SUMMER / 2013

ISSN

2300-1259

Call for Papers YoungPetro is waiting for your paper!

The topics of the papers should refer to: Drilling Engineering, Reservoir Engineering, Fuels and Energy, Geology and Geophysics, Environmental Protection, Management and Economics Papers should be sent to papers @ youngpetro.org For more information visit youngpetro.org/papers

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