--> Implications of Fault Geometry on Sealing Capacity in Paleozoic Unayzah Reservoirs - South Ghawar
[First Hit]

AAPG Middle East Region, Second EAGE/AAPG Hydrocarbon Seals of the Middle East Workshop

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Implications of Previous HitFaultNext Hit Geometry on Sealing Capacity in Paleozoic Unayzah Reservoirs - South Ghawar


Sandstone members of the Paleozoic Unayzah Group have a huge hydrocarbon potential in the Kingdom of Saudi Arabia. The South Ghawar trend proved to be gas bearing by discovering considerable accumulations in Unayzah Group at different locations. In the study area, the NW-SE trending master-Previous HitfaultNext Hit to the west of the main fields is assumed to provide the lateral seals to the hydrocarbon traps. To reduce the uncertainty associated with such faulted traps, it is important to study the geometry and the sealing capacity of the bounding Previous HitfaultNext Hit. The top of Khuff Formation, Khuff-C reservoir, Unayzah-Asand, Unayzah-B sand horizons, and the master-Previous HitfaultNext Hit west of the main fields were structurally mapped using 3D seismic data. The geometric relationships between horizons and the Previous HitfaultNext Hit were modeled in order to build the most geologically realistic 3D Previous HitfaultNext Hit model. Previous HitFaultNext Hit displacement attribute calculation has indicated three major elliptical displacement patterns along the Previous HitfaultNext Hit. This distribution of the Previous HitfaultNext Hit throw over the Previous HitfaultNext Hit surface suggests that the master-Previous HitfaultNext Hit has evolved as a group of NW-SE aligned faults that linked into one major Previous HitfaultNext Hit. A three dimensional Previous HitfaultNext Hit and horizons model was populated with lithological and petrophysical data (Volume of shale) of the wells around the bounding Previous HitfaultNext Hit. Previous HitFaultNext Hit displacement profiles and lithologies around the Previous HitfaultNext Hit have been incorporated into a simple Previous HitfaultNext Hit seal analysis workflow. Across Previous HitfaultNext Hit juxtaposition diagrams of reservoir and non-reservoir units were used as a predictive tool of whether the Previous HitfaultNext Hit plane is sealing or leaking. The sealing capacity of the studied Previous HitfaultNext Hit was found to vary vertically and along the Previous HitfaultNext Hit strike due to variations in layer thickness, lithology and Previous HitfaultNext Hit displacement. Information on pressure distribution plots and hydrocarbon water contacts have been used to calibrate and cross-check our findings, which appear to be compatible with the sealing and non-sealing regions along the studied Previous HitfaultNext Hit. The cross-Previous HitfaultNext Hit juxtaposition approach, like the one used in this study, can be routinely performed to address the risks and uncertainties associated with Previous HitfaultTop related prospects.