The Statfjord Formation in Gullfaks South was discovered in 1978, and came on production in 1999 as part of the Gullfaks Satellite Development.
In the Plan for Development and Operations (PDO) The STOOIP was estimated at 35 million Sm3, with estimated recoverable reserves of 12.6 million Sm3. Start up of the first two wells in 1999 showed that the production rate was lower than expected, most likely as a result of poor reservoir communication. A third well was drilled in 2001 and experienced gas breakthrough shortly after startup. Based on these observations booked reserves were reduced to 2.4 million Sm3 in the reservoir management plan for 2002.
Production has been limited by low connectivity, reservoir heterogeneity and gas breakthrough. Surface operated downhole inflow control and multilateral wells have been identified as solutions to these limitations, which has lead to an increase in expected oil recovery.
This paper describes the process of implementing Downhole Instrumentation and Control System (DIACS) and Multilateral Technology (MLT) in three horizontal subsea wells drilled in 2003 and 2004. This has led to a twofold increase in the reserve estimate to 5.4 million Sm3 in the reservoir management plan for 2005.