Forties Infill Drilling 8 Years Later: Development Driven by 4D Seismic
- Dennis Denney (JPT Senior Technology Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- March 2012
- Document Type
- Journal Paper
- 114 - 116
- 2012. Society of Petroleum Engineers
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- 133 since 2007
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This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 145433, "Forties Infill Drilling 8 Years On: Continued Success Through the Application of Thorough Development Geoscience Driven by 4D Seismic," by Philip Rose, Gregg Barker, Klaas Koster, and Jeff Pyle, Apache North Sea, prepared for the 2011 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 6-8 September. The paper has not been peer reviewed.
In the 8 years since Apache purchased the Forties field, more than 100 in-field targets have been drilled, with an overall success rate of 74%. The campaign resulted in a shortage of sidetrack-donor wells, with a return to surface drilling on all five platforms. To enable full exploitation of the target portfolio, Apache is installing a new 18-slot platform in 2012. Key to success has been a constant drive to push the boundaries of 4D-seismic interpretation and of the lithology prediction from seismic, and the ability to integrate this information with local production and well data.
The Forties field, in the UK central North Sea, was purchased by Apache in 2003, at which time it was a giant field in the decline phase of its life. Annualized average production was 41,000 BOPD and declining. No new wells had been drilled in the field since 2001. In the early 1980s, the field produced between 400,000 and 500,000 BOPD. By 2003, the field had produced 2.5 billion bbl of the 4.2- to 5-billion-bbl original oil in place. The field’s remaining recoverable reserves were listed as 144 million BO. Since the purchase, more than 100 drilling targets have been tested, resulting in more than 80 production and four injection completions. As a result of the drilling campaign, annualized average production has remained at approximately 60,000 BOPD since 2005, with total production of more than 150 million BO, of which 75 million BO has been produced from newly drilled wells. As shown in Fig. 1, approximately 70% of the current field production is from wells drilled since the purchase.
Foundation: Data Integration
Use of an integrated multidisciplinary interpretation approach was critical to identify new targets continually. The ability to display well-log-derived attributes with seismic amplitudes, seismic geobodies, and production information in a single interpretation environment was invaluable. The data book contains map locations, illustrations of the pay section with completion history, production history, workover record, and a current completion diagram for every well completed in the field. All interpreters have access to the company’s live production-allocation database. Although many of the infill-drilling targets were driven by seismic interpretation, including the identification of direct hydrocarbon indicators (DHIs) or unswept areas highlighted by time-lapse (4D) seismic, others were generated to replace mechanically failed wells having remaining production potential, and a few targets were generated following the analysis of simulation results.
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