The challenge of the Lancaster basement reservoir

EPC Offshore has just completed a reference case for a phased development approach for Hurricane Oil’s Lancaster field, in UK block 205/21a, West of Shetland, to demonstrate that it is commercially viable,and the project is about to enter the next stage of its development. EPC Offshore CEO Keith Wallace discussed some of the challenges and the possible ways forward at the Subsea UK meeting.

About 4000ft below the seabed, Hurricane’s drilling has passed through a number of oilbearing fractures.

The Lancaster field is one of the biggest discoveries in the UKCS in recent years. Containing an estimated 200 million barrels of recoverable oil, with a further 200 million barrels of 2C contingent resources identified in operator Hurricane’s nearby Whirlwind asset, it has the potential to be a key strategic resource for the UK, but as a fracture basement reservoir it poses particular challenges. Hurricane Exploration was created in 2005 with the vision and purpose of finding oil in fractured basement reservoirs – a first for this approach in the UK.

Wallace explained that EPC has been working with Hurricane on Lancaster for about 20 months.“What we’ve been doing is going through the concept selection process and that’s really looking at all the viable solutions that could be deployed West of Shetland to develop the field fully, and what kind of investment that would require for each viable solution.”

He said that there were a number of challenges on basement oil at this stage. The first thing was really being able to be confident that the wells were full consistently,and, therefore, Subsea how many wells were needed so a phase development approach was adopted. One of the schemes involves a small, new DP FPSO,which would have to be pretty robust because of the West of Shetland environment. This could drill one or two wells initially to prove productivity prior to the full field development.

“This small DP FPSO doesn’t exist today, so we’ve been working with a contractor on a solution.” The DP FPSO concept is not a commonly used solution; there has really only been one so far,the Seillean, used by BP as its SWOPS vessel, and now in Brazil. Due to the severe weather conditions West of Shetland it can only produce up to 75% of the time,although it has to be paid for all of the time. Another option is an initial tieback prior to full field development to gain an understanding of the first couple of wells. Various other scenarios are also under review.

The next stage is to bring in a rig to drill a further well to do more testing. Hurricane has secured one rig slot this year and two slots next,subject to obtaining further funding.

Wallace is pleased with the way the project has gone so far: “EPC Offshore’s skill sets are all really geared around the facilities that you would deploy into each scenario to make it happen. Hurricane’s expertise is around basement oil reservoirs, exploration, the mechanisms, the modelling. So the two parties complement each other very well, in the thought processes, in the trying how to declutter this,and get to a solution that can be commercially backed.”

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