PGS' The PGS vessel Ramform Challenger began gathering London-based Borders & Southern Petroleum’s (B&S) 3D seismic program off the Falkland Islands in the South Atlantic Ocean. Located about 140 km south of the Falkland Islands and covering more than 1,000 sq km, the survey is in Quad 61, next to the company's 2007/2008 3D survey. Acquisition will take about six weeks to complete.
The 3D program has been designed to evaluate a number of fault/dip closed structures similar to the Darwin discovery, tracking the high quality shallow marine sands that comprise the Darwin reservoir. Additional objectives are to further investigate the Early Cretaceous slope fan system and to identify new prospects in areas where current data coverage is low.
Last month the company reported on its progress in the Falklands:
In April 2012, B&S announced a significant gas condensate discovery with its first well in the South Falkland Basin. The Darwin structure comprises two adjacent tilted fault blocks: Darwin East (which contains the discovery well 61/17-1) and Darwin West (untested). The fault blocks are clearly defined by high-quality, 3D seismic data.
Biomarker analysis of the condensate indicates that it was derived from marine source rocks of Cretaceous or younger age. Stable carbon isotope analysis of the gas has shown that it is an oil-associated gas, which has been derived from a source interval that is more mature than the source for the condensate liquid. Preliminary geochemical analysis of the condensate indicates that it is typical of an ultra-light crude oil and somewhat heavier than most condensates (API gravity of 44.5 to 49°).
Initial reservoir engineering studies suggested that 130 to 250 MMbbl of liquid could be recovered, with a middle case of 190 MMbbl (split almost equally between the two fault blocks). Subsequent studies have shown that, if there is strong aquifer support, the mid-case could be as high as 210 MMbbl. The reservoir engineering study also demonstrated that more liquid could be recovered by gas recycling than by gas depletion.
Darwin has a good quality, quartz rich, sandstone reservoir. Net pay in the discovery well was 67.8m, with porosity averaging 22%. The reservoir consists of one major sand unit that extends across the two fault blocks and is clearly represented by amplitude anomalies on 3D seismic. While the discovery well was not tested, reservoir analysis suggests that individual sustained well flow rates of up to 70 MMscf/d (gas) and 9,500 stb/d (condensate) could be achieved. Modeling suggests that Darwin East and West could be produced using three production wells and two gas reinjection wells (10 wells in total).
In Q4 2012, B&S commissioned E & P, part of the ThyssenKrupp Group, to undertake a screening feasibility study to determine if development of Darwin East and West would be technically viable, and to provide some cost estimates. The conclusion was that Darwin East and Darwin West are technically viable as stand-alone developments, phased developments, or could be combined in parallel development. Despite a harsh environment and lack of local infrastructure, there is sufficient confidence in current proven technology to develop the discovery. The most likely development option would be subsea wells tied back to an FPSO for processing and storage of the condensate, while re-injecting gas back into the reservoir to maximize liquids recovery. A development of this type is estimated to take three years from project sanction to first production.
Subscribe
