In the eight years since Apache purchased the Forties Field from BP over 100 infield targets have been drilled with an overall success rate of 74%. As a result of this infill drilling campaign the field production rate has been held at a plateau rate of 60,000 bopd despite an average rate of 41,000 bopd in 2003, the year of purchase from BP. Indeed the success of this campaign has resulted in a shortage of sidetrack donor wells so there has been a return to surface drilling on all five platforms. Furthermore, to enable the full exploitation of the forward target portfolio Apache is installing a new 18 slot platform, the Forties Alpha Satellite Platform (FASP) in 2012. Key to Apache's success on Forties has been a constant drive to push the boundaries of 4D seismic interpretation and lithology prediction from seismic and the ability to integrate this information with local production and well data. In this paper case histories are presented to illustrate our approach to target generation and the evolution of target generation over time is evaluated. The above methodology has led to many convincing successes over the years. The acquisition of a new 4D seismic volume in 2010 has resulted in a significant boost to our drilling results, allowing us to have our most productive drilling 6 months to date, including one well with an initial production rate of 12,000 bopd, the highest initial rate recorded in the field since 1992.
Apache discovered the Maule field in October 2009 with the 21/10-A52 wellbore drilled from the Forties Alpha production platform. The discovery of a 14m TVD net oil column in Eocene aged Brimmond sands led to the development of the Maule field under the UK government's small field allowance scheme. The field was taken from completion of the discovery well to first oil from a horizontal production well in under 9 months.
The Maule field is located on the western margin of the Brimmond Formation turbidite fairway where re-mobilised sands are also present. Steep dips as seen in the development well and steep seismic features indicate that the Maule field reservoir was formed by remobilsation of Brimmond sands.
The A52 exploration well was drilled on the basis of a seismic amplitude anomaly. This seismic data along with LWD density image data was used to successfully place the horizontal production well which accessed a 114m MD pay section and flowed in excess of 11,500 bopd. A 2010 4D snapshot taken in early July 2010, 5 weeks after production started, identified the source of the well's rapidly increasing water-cut and identified further infill locations.
Despite modest production for an offshore North Sea development the first Maule producer has been an economic success for Apache as a result of integrated subsurface technical work, drilling performance, small field allowance incentives and a sense of urgency.
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