Integration of 4D Seismic Data into the Management of Oil Reservoirs with Horizontal Wells between Fluid Contacts

摘要

This paper describes how 4D seismic data have beenincorporated into the modelling and management of theAndrew and Harding reservoirs. These two fields pose similarchallenges in that both use horizontal wells to produce from a50 – 100 m oil column between gas cap and aquifer. Theseismic data must therefore be used to tell us about the verticalmovement of fluid contacts in different areas. The two fieldsalso have important differences, notably in verticalcommunication and aquifer strength, and demonstrate a rangeof data applications and consequences.Andrew 4D seismic data confirm strong aquifer influx,which has moved the oil-water contact above most wellbores,so that oil is now produced by coning from above. They alsoprovide a detailed picture in which tens of baffling faults, andextensive shales, cause pockets of oil to be poorly swept bythe producers, though without total pressure isolation. Thepaper describes how the 4D baffling fault picture and theconing process have been interpreted and included into historymatching of the Andrew FFM. It also discusses theconsequences and value of the new understanding, for welloptimisation, infill drilling and reservoir management.Harding 4D seismic data resulted in a significant change tohorizontal infill well locations, and were a key matchparameter in the new FFM. Prior to the 4D survey, theoriginal history-matched FFM indicated a fairly uniformvertical rise in OWC, with local cones around producingwells. The original infill concept was to drill between thesecones to drain unswept oil. However, 4D data indicated amonoclinal, tilted geometry to the OWC, suggesting asignificantly different sweep pattern than predicted by theoriginal FFM. The paper describes how 4D was usedsuccessfully to define infill locations, as well as the iterativeprocess between 4D and the reservoir simulator that wasrequired to develop a robust history match.