Following a recent client event hosted by Lloyd’s Register along with Heriot-Watt University, CMG and Nalco Champion in Aberdeen, focussing on the future of enhanced oil recovery (EOR) in the North Sea, Alison Kerlogue, Subsurface Technical Resource Manager provides an overview on the presentations delivered and discussions generated.
Addressing the challenges and overcoming the barriers
Improving the recovery of oil & gas reserves from the North Sea was the principal topic at the first external event to be hosted in Lloyd’s Register’s new Aberdeen office. More than 70 delegates attended the one-day training symposium to discuss Enhanced Oil Recovery.
The event was a great platform to initiate discussion on how we can work together to enhance oil recovery in the North Sea, and the value which can be released by adapting EOR techniques, a key directive of the Oil & Gas Authority (OGA). As the OGA state in their recent release of their publication ‘Polymer Enhanced Oil recovery – Industry lessons learned’. If Industry is to deliver on the OGA EOR ambition of 250 million barrels of incremental reserves by 2021, more help and support is needed to provide the industry with a balanced perspective of enhancing and implementing EOR.
Over the last year global oil consumption growth averaged 1.6 million barrels per day (Mb/d), or 1.6%, above its 10-year average (1.2%) for the second successive year . However, the OGA states that only 43% of the UKCS oil is expected to be produced, this coupled with an ageing basin, means improving the recovery rate of these reservoirs must be a priority as operators look to maximise recovery. It is believed that significant volumes of oil could be recovered from mature oil reservoirs through the use of enhanced oil recovery technologies, such as polymer injection, according to the International Energy Agency.
The United Kingdom Continental Shelf (UKCS) however is at a production stage where the potential benefit from EOR may be lost, if understanding and implementation plans are not advanced soon. As infrastructure, field installations and reservoir potential reduce due to age, it is more imperative than ever to maximise recovery from the remaining fields.
According to 30% of the delegates surveyed, decommissioning and the lack of infrastructure are the biggest challenges to be overcome in order to ensure continued development in EOR in the North Sea, over the next 10 to 15 years. While over half the delegates, 55%, believe that proving the benefits for future investment is the biggest barrier to EOR within the North Sea.
The principal objective of the symposium was to address these issues, by facilitating knowledge-sharing and showcasing technical excellence and to help advance understanding of chemical EOR. Discussion focused primarily on the EOR processes considered most likely to succeed in UKCS producing oil fields, specifically low salinity waterflooding and polymer injection, as well as providing an overview of current base recovery factor assessment and Improved Oil Recovery (IOR) methods.
Recent estimates predict that there are in the region of 11-15bn barrels of oil are remaining. Enhancing recovery from these fields therefore is crucial in maximising economic recovery and establishing an incremental prize.
Presentations at the event included topics on understanding your reservoir, challenges and pitfalls in EOR simulation, laboratory testing requirements for low salinity, the basics of polymer flooding, mechanistic simulation of polymer and low salinity flooding.
Understanding your Reservoir
Understanding the reservoir is key to successfully establishing EOR and delivering an incremental prize. In terms of reservoir management, it is crucial to understand the current dynamics of the reservoir and to know the limitations of your wells and facilities in order to be able to identify optimisation and improvement actions. It is important to exhaust IOR opportunities to maximise the base recovery factor prior to consideration of EOR opportunities. The event looked at how to assess hub potential through binary screening, analytical estimates and consideration of technical feasibility.
Low salinity waterflooding
Laboratory coreflood studies are a necessary stage of field appraisal to investigate the feasibility of low salinity waterflooding as a viable option towards EOR. As well as providing direct confirmation of low salinity EOR feasibility, these analyses can also provide the dynamic properties to be utilised in reservoir modelling.
However, as indicated in the book, “Core Analysis: A Best Practice Guide” , several issues with experimental and analytical processes can increase uncertainty and create poor quality data. Some of these issues include: variable laboratory standards, inexperienced design and supervision of test programmes, lack of cause-effect understanding of individual processes, unrepresentative sample selection, inappropriate data interpretation, etc. With appropriate processes and analyses you can however suitably assess low salinity potential and provide the necessary data for input to a dynamic model.
Polymer flooding is one of the most straightforward types of chemical EOR (CEOR). Polymer flooding is an EOR technique whereby polymer is added to a water flood to increase its viscosity, giving a piston-like displacement of oil and reducing viscous fingering.
While onshore polymer flooding is well established, its use in offshore environments is still at the pilot phase due to some major logistical challenges including; deck space, weight restrictions, offshore storage capacity, adverse weather conditions etc. These issues may result in large CAPEX and OPEX costs. We heard of a polymer case study from BP on tackling these challenges and progressing towards eventual field implementation.
Collaboration is key to ensuring EOR can maximise oil recovery from the UKCS and beyond. Through shared experiences, delegates gained a clearer view of the requirements and possible workflows to appraise chemical EOR feasibility for their fields.
The UKCS has shown, through recent collaborative initiatives, that by focusing on operational and production efficiencies IOR can be improved and oil production decline reduced. The challenge now, is to identify and make a commercial case for appropriate EOR techniques on a field by field basis before key infrastructure is decommissioned.
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