With 22.4 MMbbl of oil equivalent produced in 2009, the North Sea Forties Field accounted for approximately 11% of Apache’s worldwide production and comprised 7% of its year-end estimated proven reserves. The field uses ESPs for artificial lift; in June 2010, Apache announced that its new discovery, Maule reservoir, had commenced production at approximately 11,750 bbl/d of oil from Forties Alpha 5-4 (FA 5-4)—Apache North Sea’s biggest producer—with ESP at the time. Over the preceding few years, the company had actively sought opportunities to invest in facility upgrades and integrity-related projects to increase production efficiency and minimize unplanned downtime for the Forties Field.
LiftWatcher real-time surveillance service was initiated as part of these upgrades to provide continuous monitoring of all ESP operating parameters in this field. Experienced engineers monitor alarms and alerts 24/7/365 days a year, at one of many SLB Artificial Lift Surveillance Centers (ALSCs). Data are streamed to the ALSC and the engineers review alarm events for all wellsite measurements, from motor temperature to continuous flow. They analyze data summaries, poll data on demand, identify probable causes of any performance drop, and quickly report remediation options for rapid implementation.
On August 12, 2010 at 16:00, an ALSC engineer noticed that the ESP on FA 5-4 was running below its target frequency and the well was not flowing. The engineer informed the Apache platform control room that a deadheading event had been observed and recommended increasing the pump frequency to 42 Hz. Platform personnel were also advised to check for possible restrictions above the ESP, at the wellhead or on the surface. When increasing the frequency from 39 Hz to 42 Hz produced no change, the ESP was manually shut down after consultation with the DESC design and evaluation services engineer for Apache. Further investigation revealed that the hand-actuated lower master valve on the wellhead was closed. Once the valve was reopened, the pump was restarted and the well resumed flowing at 19:00.
With the help of such successful real-time monitoring interventions and improved technology, Apache’s North Sea ESP operations had 64% fewer unplanned downtime events in 2010 and 91% fewer in 2011 compared with the best year before LiftWatcher service commenced.
