8 minute read
Easing the fl ow
James Wood and Sergio Treviño, Southwest Research Institute (SwRI), USA, introduce a midstream heavy crude oil processing technique for cost-effective pipeline transportation.
Transporting heavy crude oils through pipeline or by other transportation means is challenging and often requires the petroleum industry to resort to rail transport for inland sources. Heavy and extra-heavy crude oils are diffi cult to transport via pipelines because of their high viscosities, asphaltene and paraffi n deposition, increased content of formation water, salt content, and corrosion issues.1
Heavy crude oil and bitumen production and transport are at least twice as capital- and energy-intensive as the production of conventional oil.2 The expenses and energy requirements associated with the production and transport of heavy crude oil arise from the high viscosity at reservoir conditions, as well as the presence of undesirable compounds such as asphaltenes, heavy metals, and sulfur. This makes heavy crude oils diffi cult to produce, move by pipeline, and refi ne. Pipelines are widely regarded as the most attractive option for transporting crude oils. They offer low costs and relatively low environmental impacts compared to other transport options that require loading and unloading oil in environmentally sensitive places. As such, several technologies have been developed to facilitate the transport of heavy crude oil via pipelines, including heating and injection of fl ow improvers.
Southwest Research Institute® (SwRI®) scientists and engineers have developed a new process for treating heavy crude oils, making pipeline transportation of heavy crude oil and similar commodities more cost-effective and less energy intensive. ‘EZ Flow’ combines hydrodynamic cavitation processing of the heavy crude oil with proprietary addition of chemical formulations to reduce the heavy crude oil’s viscosity by over 60%, helping it fl ow more easily through existing pipelines.
Background
There are several driving forces behind the development of a new process for making heavy crude oils fl owable in pipeline. First, heavy crude oil transport is a necessity for petroleum producers worldwide. For example, at least 50% of crude oil reserves in Mexico are heavy and extra-heavy crude oils.3 Canada currently relies on heavy crude oil to meet production needs, producing approximately 700 000 bpd of synthetic crude oil that comes from heavy crude oil, bitumen, and tar sands. These synthetic crudes are transported via pipelines to refi neries in Canada and the US.2 The pipeline technologies currently available to transport heavy crudes are expensive, requiring large volumes of chemicals or diluent, and tremendous energy resources in the form of heat. They often
Figure 1. Pre-mixing chemical with heavy crude.
require multiple treatment techniques simultaneously or the addition of diluent injections down the pipeline. Non-pipeline transportation methods, such as rail or tanker trucks, are expensive, incurring fuel costs, transport maintenance, and high environmental impact, in addition to risks for derailment and collisions. For example, when considering air pollution and greenhouse gas costs alone, the costs associated with moving a fully loaded 100-car train of crude oil from North Dakota, US, to the US Gulf Coast are approximately US$150 000 one-way. The same transportation to the US East Coast results in costs of approximately US$210 000. The total estimated air pollution and greenhouse gas damages for oil shipped by rail from North Dakota in 2014 exceeded US$420 million.4 A literature review of current heavy crude oil pipeline transportation technologies concluded that: “For the increasing exploitation of heavy oil and bitumen, it is necessary to develop technology to aid in their transportation through pipelines.”2 Globally, of more than 80 million bpd of crude oil that are produced, about 11 million bbl of that are classifi ed as heavy crude oils.5
Relevant theory
Logistically, transporting heavy crude oil and bitumen via pipeline is challenging at best and often impossible due to the high density and viscosity (≥1000 cP at 40°C) and very low mobility at reservoir temperature of the commodity.2 The asphaltene’s macromolecules precipitate and aggregate in the oil, contributing greatly to its high viscosity and density, as well as pipeline fl ow resistance. The most important factor infl uencing its high viscosity are the intermolecular forces between the large, branched molecules and the tendency of the asphaltenes and paraffi ns to coalesce, producing aggregates of heavy hydrocarbons. Those agglomerations generate structural compression of the oil and reduce its relative volume. That, in turn, increases the density or API (American Petroleum Institute) weight of the heavy crude oil. Because of these natural physical and chemical properties, heavy crude oils and extra-heavy crude oils are diffi cult to transport in general and very diffi cult to transport via pipeline over long distances.
Usage
According to API, the US has more than 190 000 miles of liquid petroleum pipeline that deliver crude oils, including heavy crude oils, to refi neries and chemical plants throughout the US. EZ Flow is a potentially cost-effective method for transporting heavy and extra-heavy crude oils over long distances by pipeline over various terrain.
The mechanism behind the method’s effectiveness is that the treatment reduces the intermolecular forces between and inside the agglomerates of the heavy crude oil and promotes a dispersion phenomenon, the opposite of aggregation. The chemical and mechanical treatment of the heavy crude oil work in unison to reduce viscosity. Chemical additives (Figure 1) reduce the interfacial tension in heavy crudes, whereas hydrodynamic cavitation (HC) provides enough energy to enhance the chemical action (Figure 2), break the aggregates, and disperse the asphaltenes. It is like intense local thermal treatment that does not raise the whole mass of oil to the target temperatures needed for the disaggregation.
The chemical formulation of the associated additive is a proprietary mixture of low concentration compounds, compared to other treatment options, designed specifi cally to optimise the hydrodynamic cavitation of the heavy crude oil that can reduce heavy crude oil viscosity by over 60%. The additives will not interfere with subsequent processing in the refi nery. The composition of the chemical formulations and hydrodynamic cavitation process may be further optimised to lower the viscosity of different types of heavy and extra-heavy crude oils from different regions to make any unconventional crude oil fl owable for transport through existing pipelines.
The advantages of this heavy crude oil treatment technology for pipeline transportation include very low chemical additive costs and environmentally friendly qualities. The technique is not technically demanding and treated oils can be stored for long periods of time without affecting the viscosity improvements. The process may be scaled-up to a commercially viable operation with low upfront and operational costs.
Benefits for oil refining
In addition to reducing viscosity to allow for pipeline transportation, EZ Flow could be used to upgrade heavy crude oil. The changes created in the heavy crude oil fi eld
will facilitate processing in the refi nery and within the encompassed operations.
Heavy crude oil upgrading associated with EZ Flow will require further research and optimisation, but it could produce signifi cant benefi ts for the oil refi ning industry. The research performed to date has been developmental, but the application of the technology to industry has the potential to change the dynamics of the unconventional crude oil market, bringing transportation costs more in line with those of conventional crude oil. The next phase of research will begin scaling-up the technology.
Figure 2. Schematic diagram of the high-speed rotor of an HC LabSPR.6
References
1. MARTINEZ-PALOU, R., ‘Transportation of Heavy and Extra Heavy
Crude Oil by Pipeline: A Review’, Journal of Petroleum Science and
Engineering, pp. 274 - 282, (2011). 2. HART, A., ‘A Review of Technologies for Transporting Heavy Crude
Oil and Bitumen via Pipelines’, Journal of Petroleum Exploration and Production Technology, pp. 327 - 336, (2014). 3. Investigación y Desarrollo, ‘New Technology Reduces
Transportation Costs of Heavy Oil’, Distrito Federal, Mexico:
Investigación y Desarrollo, (2016). 4. CLAY, K., ‘The External Costs of Transporting Petroleum Products by Pipelines and Rail: Evidence from Shipments of Crude Oil from
North Dakota’, National Bureau of Economic Research, (2017). 5. GOUNDER, R., ‘Introductory Chapter: Heavy Crude Oil Processing -
An Overview, Processing of Heavy Crude Oils’, IntechOpen, (2019). 6. RAJORIYA, S., CARPENTER, J., SAHARAN, V. K. and PANDIT, A. B.,
‘Hydrodynamic cavitation: an advanced oxidation process for the degradation of bio-refractory pollutants’, Reviews in Chemical
Engineering, vol. 32, no. 4, (2016), pp. 379 - 411.
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