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Making strides against well integrity challenges
Well integrity is one of the biggest challenges facing the offshore oil and gas industry and is a growing concern for businesses. Currently, an estimated 30% of wells around the world experience integrity problems that have the potential to negatively impact both production and the environment.1
As the age of well stocks increases, the need for effective integrity measures to optimise production will grow.
When tackling annulus sustained casing pressure, the traditional way has been to start bleeding down the pressure, followed by a ‘lube and bleed’ operation. Further on, a complete workover is undertaken to cure the sustained casing pressure and return the well to production. However, the costs of deploying such rigs are significant and these have to be weighed against the anticipated economic returns from the well.
Meanwhile, the industry’s continuing quest for economic methods to extend output, regain shut-in and low-producing wells and ensure the sustainability of operations continues to demand advanced technical solutions and processes that can deliver more from less.
To this end, Expro has engineered a solution that allows the intervention of wells through the A, B, C or D annuli which, in turn, enables precision placement of wellbore treatment fluids deep into the targeted annulus. The minimally intrusive equipment allows the remediation of annular issues and reduces fugitive emissions. The system is opening up the potential for widespread annular intervention to resolve a range of well integrity issues and extend the life of wells previously classed as uneconomic.
Solving well integrity challenges through annular intervention
The company’s new OctopodaTM annulus intervention system is the only certified system in the world that allows direct access to live well annuli without the expense of a heavy workover rig and with a reduced environmental footprint.
The first system to enable intervention in an annulus, it provides full well control, assured well integrity and enhanced production without disrupting operations.
The system removes shut-in casing pressure, replacing annulus fluid to increase hydrostatic pressure in the annulus or sealing top of cement (TOC), casing shoe and casing-to-casing communication leakages. It is deployed through annulus valves while maintaining full pressure control, eliminating the need to remove wellhead components before operations.
The system can be rapidly deployed on all types of installations, including onshore and fixed platforms offshore, to maximise operational uptime while reducing overall HSE exposure.
With advanced corrosion protection extending the lifetime of the well, and through enabling the revitalisation of established wells, it can help create a sustainable impact on asset production and revenue.
The development of the annular intervention system followed the success of another Expro product – the CoilHose Light Well Circulation System, which is a smaller and faster alternative to traditional coiled tubing systems.
CoilHose was designed to be run in the main bore. However, following its introduction, the company received several additional requests for a smaller hose-based system that could be run in the annulus. By using its experience in hose technology, introducing some ideas from other industries and developing several prototypes, the company created a system specifically designed to answer the demand for annular intervention while enabling full well control.
Engineering a solution that could be deployed in a tight wellhead environment was critical to effectively supporting standard wellhead designs. Equally as important was the design of a hose that had the flexibility to bend and immediately straighten once in the annulus. Incorporating an injector and a heavy bottomhole assembly (BHA) into the design ensured the system would reach the required depths.
Following several successful trial projects, including breaking through salt barriers to monitor the pressure in a Southern North Sea gas well, Octopoda was officially launched in 2021 and has been used in locations ranging from the UK, Norway and Thailand to Colombia, Malaysia and Romania. These deployments include the world’s first project to help Chevron solve a base oil displacement challenge in Thailand and the achievement of record depths for annular intervention – firstly at 300 m in Colombia, then at 574 m in Romania.
Figure 1. Annulus intervention operations in Romania.
Case study: Thailand
The system was recently used on a Chevron well in Thailand to intervene in the A-annulus and replace Saraline base oil with water ahead of resin placement on top of the cement, successfully reinstating production.
Base oil significantly reduces the effectiveness of resin. Chevron had previously seen a 50% reduction in the impact of the resin when it was added to an earlier well containing base oil using traditional lube and bleed from the surface.
Having reviewed the effectiveness of conventional methods, Chevron was keen to try the new system to achieve base oil displacement at depth. Deploying the system meant Chevron avoided having to use the production tubing for circulation via a stimulation vessel or coil. This eliminated the need for communication between the production tubing and the A-annulus, meaning the barrier remained intact between the reservoir and the A-annulus.
The base oil was displaced and circulation was established by pumping fresh water through the annulus intervention system. Despite experiencing space limitations caused by control lines, clamps and centralisers, this was done
at 70 m, avoiding the conventional lube and bleed method or the need to punch the well.
This was the first time the A-annulus had ever been intervened using a conveying hose. Furthermore, it proved the efficiency benefits of annular intervention over conventional practices by reducing time, costs and personnel. The operation lasted 3 days compared to an estimated 10 – 13 days for lube and bleed.
The system’s small footprint, when compared to a pumping vessel or unit, reduced lifting risks and required only a two-man crew. The base oil was collected in a closed loop in the system, which meant exposure to the environment was avoided.
Case study: Colombia
Expro also successfully deployed Octopoda to restore annulus pressure integrity and return a well to production in the Piedemonte region of Colombia.
The system successfully reached 300 m in the annulus – a world record depth at the time – and sealed the C-annulus of the well. This removed the risk of casing collapse and gas migration, and enabled the well to produce and significantly extend its production lifespan.
The operation removed the need for a heavy workover rig to allow controlled circulation of annular fluids and the installation of a resin plug at the external casing shoe depth. This successfully sealed the annulus and enabled production to be resumed from the wellbore.
The client faced the risk of gas migration through the threads of a non-gas tight casing in a gas well. Due to the risk of communication of gas to the C-annulus in a high production gas well, it was necessary for a mechanical seal to be installed at the casing shoe and a hydraulic seal up to the surface.
Before the annulus intervention system was utilised, there was a risk that the inner casing would collapse, which would have led to a hazardous situation and the plug and abandonment of the well.
As the full hydrostatic column was close to the collapse pressure of the inner casing, it was required to work with low densities to perform the operation. There was no information about the physical location of the TOC in the C-annulus or the diameter of the openhole section behind the inner casing, which complicated the determination of the volumes to be pumped even more.
With the full cooperation of the client, a way to calculate the TOC was determined based on calculations of the density gradient and pumped volumes, which allowed control of the density value in front of the casing shoe and the setting of the resin plug.
By pumping from the bottom of the C-annulus, it was possible to reduce the resin pumping time and ensure the correct fluid density distribution of the brine to guarantee the correct setting depth of the resin plug. This is not possible while pumping from the surface as heavy brine becomes diluted in freshwater, generating a uniform density column in the C-annulus.
The C-annulus was fully sealed, ensuring the integrity of the well for the rest of its productive life. All operations were performed while the well was producing. The alternative solution for the well would have been a full workover intervention or well abandonment. The intervention operation was completed at a cost that was estimated to be approximately 25% less than the cost of a conventional workover rig-enabled repair. Moreover, the operation resulted in significantly lower carbon emissions than the conventional alternative.
Figure 3. The use of Octopeda by Chevron in Thailand saw the first time an A-annulus had ever been intervened using a conveying hose.
Removing the barriers to annular intervention
The development of Octopoda has opened up a wide range of possibilities for annular intervention. Its successful use in supporting well hydraulics, removing salt or other debris barriers is established; likewise, it has also proven to be highly effective in the exchange of fluids.
Further opportunities for annulus intervention include life extension survey operations in the surface casing conductor area, including camera corrosion inspections, cement location and conductor and surface casing wall thickness evaluations. The intention is to establish the potential for reuse of the conductor and surface casing, which would have both significant financial and environmental benefits when completing new wells.
Annulus intervention can also have a significant role to play in well plugging and abandonment. Installing secure and effective barriers in the annulus would avoid retrieval of the entire completion, which once again would generate environmental and financial benefits.
Conclusion
Through enabling an effective way to conduct annular intervention the use of Octopoda can empower operators to return shut-in and low-producing wells to profitability.
Reference
1. BRUFATTO, C., COCHRAN, J., CONN, L., EL-ZEGHATY, S.Z.A.A.,
FRABOULET, B., GRIFFIN, T., JAMES, S., MUNK, T., JUSTUS, F., LEVINE,
J.R., MONTGOMERY, C., MURPHY, D., PFEIFFER, J., PORNPOCH, T., and
RISHMANI, L.,‘From Mud to Cement – Building Gas Wells’, Oilfield Review (Autumn 2003), pp. 62 – 76.
