Bringing Al Huwaisah's Volume to Value

摘要

The billion barrel Al Huwaisah Field is located in NorthwestOman and produces from heterogeneous rudist-dominatedlimestones of the Aptian Shuaiba Formation. It was discoveredin 1969 and has been on-stream since 1971. Production peakedat ca. 44,000 bbl/d in 1973 after which production declined toca. 19,000 bbl/d. Recently, production rates have increased toca. 28,000 bbl/d, but field-wide recovery factor is still only 18% indicating that potentially large scope volumes remain inthe field.In 2000, an integrated review of the Al Huwaisah fieldindicated a number of opportunities to mature these largescope volumes. It was noted that key to maturing theseopportunities was an improved understanding of the highlycomplex reservoir architecture, especially regarding thedistribution of fractures. Subsequently, a comprehensivefracture study was executed that included both geologicalinformation and production data. This study resulted in animproved understanding of the water movements in the fieldexplaining the highly variable first-year net oil rates (0 – 2,500bbl/d) of the Al Huwaisah wells.The results of the fracture study were incorporated innewly created static and dynamic models that also took intoaccount the small-scale sedimentological heterogeneities ofthe Al Huwaisah reef deposits. These models were usedtogether with the historic production review to identifyproduction optimization opportunities, like barefootcompletion strategies and water shut-off using expandabletubulars. A few of these opportunities have been implementedso far, resulting in sometimes more than 50 % increase in netoil production for the targeted wells. The barefoot completionstrategy has resulted in a 10 % cost saving per well. Inaddition, well planning using seismic amplitude informationwas tested, which resulted in more than doubling the initial net production in several wells compared to the average initialwell rates in Al Huwaisah.In identifying the most optimal long-term developmentstrategy for the Al Huwaisah field, the subsurface models arebeing used to test the benefits of introducing water injectionand miscible gas flooding. Based on the model data, a limitedwater injection field trial is ongoing which resulted in a ca. 20% increase in net oil production for the pilot area.Opportunities for implementing a miscible gas trial arecurrently being evaluated.