How to increase the oil recovery in GFS Statfjord ? Forslag til Gullfakslandsbyen

Gullfaks Sør Statfjord Formation PDO 1995: Large volumes in the Statfjord fm. Main reservoir in the Gullfaks Sat. 7 wells 2000 Sm3/d. 1999: F-4 T3H and G-2 T3H in production. Produced much less than expected. Statfjord Fm. on hold. 2001: G-3 T2H in production. Behave in accordance to new expectations. Unexpected gas breakthrough. 2002/2003: IOR project initiated. Identified problems: Limited reservoir communication Gas limitation

Development of GFS Statfjord reserves F-4 and G-2 drilled DIACS and MLT G-3 drilled

GFS Statfjord Challenge: Complex reservoir with low recovery, goal +18% (LTP 2003-2008) PDO – 12.6 MSm3. Today 5.1 MSm3 Wells drilled Additional perforation of G-2 H and F-4 H in lower Statfjord (summer 2003) G –1 H with DIACS (2003), periodically shut in. G –2 YH MLT with DIACS (2004) F –2 YH MLT with DIACS (2004) G-3 Y3H, 3 branch MLT with DIACS (2005), SHUT in GI MLT with DIACS (2006), only one branch injecting

How can we increase the recovery ? Could look into: Well solutions Technological solutions Drilling has so far been challenging. Simple or complex wells ? Wells spacing ? Increase of gas injection, number of GI ? Uncertainties in reserve estimates When start blowdown ? Economic considerations Economic development No economic limitations, KPI: recovery

Reflections could be made around What should be used as a KPI ? Recovery vs. NPV Who makes the decisions? Petroleum law, partners influence Prioritarisation of gas injection or gas export ? (high gas price: more economic to sell gas than inject in marginal oil reservoir) Subsea rig availability a challenge rig costs increasing Simulation model provided, already implemented at NTNU, 2006_students