An Improved Reservoir Characterization of Sandstone Reservoirs in the Khafji Field,Arabian Gulf, by 3D Seismic-Aided Well Test Interpretation

摘要

This paper aims to improve reservoir characterization ofsandstone reservoirs in the Khafji oil field, Arabian Gulf, byintegration of well test analysis and fault location informationfrom three-dimensional (3D) seismic survey.There are several hundreds of normal faults in the Khafjifield which were recently recognized by 3D seismic survey.Although the reservoir has strong edge water drive, waterproduction is observed in some central upstructure area earlierthan in peripheral area nearby. Existence of conductive faults,which causes fluid communication between the upper andlower reservoirs, was suspected from engineering analysesconducted. Conductive faults have great impact on reservoirwater production and pressure behavior.The main issues of this paper are:(1) Well test analysis for wells near 3D seismic interpretedfaults.(2) Design of interference test to investigate vertical fluidcommunication through conductive faults between tworeservoirs.Well test data for 5 selected wells located near faults wereanalyzed and boundary effects such as sealing fault or constantpressure were interpreted. Faults located within 1000 feetdistance from wells were characterized by integration of welltest and 3D seismic results.Field test was designed in an area where interferencebetween the Upper Sand and the Lower Sand was suspected. 1active well and 4 passive wells were designed and pressurebehavior of each well was predicted. A fault was defined inthe model by placing two adjacent rows of cells with 30 feetdifference in depth. Fault conductivity was changed as aparameter in simulation. Two kind of tests were discussed: (1)Short term interference test with 3 pulses of 12 hours each (2)Long term interference test with 3 pulses of 1 week each.Long term interference test was recommended from thesimulation results because pressure drop was detectable evenwhen fault conductivity was small.