This paper aims to improve reservoir characterization of sandstone reservoirs in the Khafji oil field, Arabian Gulf, by integration of well test analysis and fault location information from three-dimensional (3D) seismic survey.

There are several hundreds of normal faults in the Khafji field which were recently recognized by 3D seismic survey. Although the reservoir has strong edge water drive, water production is observed in some central upstructure area earlier than in peripheral area nearby. Existence of conductive faults, which causes fluid communication between the upper and lower reservoirs, was suspected from engineering analyses conducted. Conductive faults have great impact on reservoir water production and pressure behavior.

The main issues of this paper are:

  1. Well test analysis for wells near 3D seismic interpreted faults.

  2. Design of interference test to investigate vertical fluid communication through conductive faults between two reservoirs.

Well test data for 5 selected wells located near faults were analyzed and boundary effects such as sealing fault or constant pressure were interpreted. Faults located within 1000 feet distance from wells were characterized by integration of well test and 3D seismic results.

Field test was designed in an area where interference between the Upper Sand and the Lower Sand was suspected. 1 active well and 4 passive wells were designed and pressure behavior of each well was predicted. A fault was defined in the model by placing two adjacent rows of cells with 30 feet difference in depth. Fault conductivity was changed as a parameter 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 the simulation results because pressure drop was detectable even when fault conductivity was small.

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