Originally discovered in 1993, the Stag oil field, on the North West Shelf of Western Australia, has proven to be both a prolific and complicated reservoir since production began in 1998. To date, more than 56 million barrels have been produced, in addition to significant volumes of water and glauconite, which has resulted in complex changes to the reservoir over time as the field has produced. Because the reservoir is shallow, at 680 m true vertical depth subsea (TVDSS) with shallow carbonates causing noise issues and imaging challenges, Stag Field remained largely invisible on seismic data. To address these issues, a 220-[Formula: see text] 4C-3D ocean-bottom cable survey (OBC) was acquired in early 2008. Subsequent processing and interpretation of these data, including a joint multicomponent inversion, have resulted in drilling six successful new wells with additional wells currently underway and planned in the near future.

Located on the North West Shelf of Western Australia, the Stag Oil field has proven to be a prolific reservoir, having produced more than 55 million barrels (MMbbls) of oil since 1998. This has not been without its challenges, however; with premature water breakthrough from injection wells occuring in several wells, potentially stranding large volumes of oil in the ground. Using the multicomponent processing and joint amplitude-versus-offset (AVO) inversion of an ocean bottom cable (OBC) seismic survey acquired in late 2007, new light has been shed on the distribution of unswept oil. This data has led to the succesful drilling of six wells and a marked increase in field production. Additionally, the seismic data has also been used to minimise drilling risks by using seismic coherency to steer the well around potential problems with a significant impact on well costs due to reduction of wellbore problems associated with horizontal drilling in the Muderong shale. To date, four wells have been drilled using this technique, resulting in a significant decrease in non-productive time while drilling during the most recent drilling campaign, which has a significant impact upon the profitability of these late-stage development wells.

No abstract