Offshore staff
PORT STANLEY, Falkland Islands -- Rockhopper Exploration has proven further oil close to last year’s Sea Lion discovery in the offshore North Falkland basin.
The 14/10-3 well was drilled by the Ocean Guardian to a TD of 2,830 m (9,285 ft) in license PL032, 8 km (4.9 mi) northwest of the discovery well. It was designed to explore the northern lobe of the Sea Lion fan feature, and is also the first well drilled in that area.
It encountered good-quality reservoir from 2,425-2,535 m (7,956-8,317 ft) within a sequence of four main sandstone intervals, including 64 m (210 ft) of gross reservoir sand with net sand of 54 m, or 177 ft (a net to gross ratio of 84%).
Rockhopper says wireline log interpretation was performed using Resistivity of formation water (Rw) drawn from downhole Modular Formation Dynamic Tester (MDT) water samples from each sand.
Logs indicate that sands 1, 2, and 4 have high water saturations with hydrocarbon shows during drilling and in cores, while Sand 3 has net pay of 7.3 m (24 ft) using a cut off of 70% water saturation (Sw).
The reservoir lies beneath a thick regional shale seal. Sands appear to be of good quality, with average porosity of 18-20% and peaks of up to 25%. Rockhopper believes that sands 1-3 are likely related to part of the main Sea Lion feature, while Sand 4 could be related to the S2 feature.
Oil and gas shows were detected throughout the reservoir intervals. Four conventional cores were cut through the reservoir totalling 101 m (331 ft), with bleeding of live oil and oil staining observed throughout. However, MDT samples on sands 1, 2, and 4 returned water.
Rockhopper adds that samples recovered from Sand 3, using a standard MDT tool, contained 20% live oil, thought to be of medium gravity.
During a subsequent DST on Sand 3, using a dual-packer MDT tool downhole, water was produced into the well. Further studies will be needed to determine why the mini DST produced water while the standard MDT recovered 20% live oil from the same sand interval.
MDT pressure readings taken over Sand 3 suggest it is lying on the same oil pressure gradient as the main Sea Lion fan in well 14/10-2, indicating potential for good lateral communication. Further drilling should reveal whether this is the case.
Rockhopper believes that the lowest sand (Sand 4) could form the downdip, distal part of the S2 feature, and plans further analysis to determine whether oil is present updip in the S2 lobe.
It will also investigate the likelihood of oil being present elsewhere in the northern Sea Lion lobe and the likely contribution of this latest well to any commercial oil development of Sea Lion.
The regional overlying seal seems to be intact and effective at the well location. With reservoir quality good, and oil shows and moveable live oil present, the main technical risks associated with the northern Sea Lion lobe are the effectiveness of the seal at the location of the feeder channel and the possibility of effective charge from the south if there is discontinuity within the reservoir.
The Ocean Guardian will next drill appraisal well 14/10-4, 2.3 km (1.4 mi) northwest of the discovery well. A further announcement will be issued on the spudding of 14/10-4.
02/14/2011
