Structural Elements of Onshore Kuwait

ABSTRACT Five structural trends are recognized in Kuwait: (1) Three sub-parallel anticlinal trends (005°-015°) occur on the west flank of the Kuwait Arch and trap oil in Lower Cretaceous and Jurassic strata. (2) North-south trending structures, including the Kuwait Arch, are probably founded on basement horsts. These were reactivated from Late Jurassic to post-Turonian time and contain the largest oil pools in Kuwait (e.g. Greater Burgan) in Middle Cretaceous, Lower Cretaceous and Upper Jurassic strata. (3) A northwest trend (320°-340°) in north and west Kuwait reflects the structural grain of the underlying Arabian Shelf and while generally dry in Middle Cretaceous strata has proven oil in Lower Cretaceous and Jurassic strata. (4) East-northeast (030°-050°) anticlines are present mid-flank the Kuwait Arch to the west and north. They contain oil in Jurassic and Lower Cretaceous strata, and Middle Cretaceous strata where north-south trends are overprinted. They may be related to northeast trending shear zones. (5) The Ahmadi Ridge is a rare north-northwest contraction trend probably related to the Zagros orogeny and traps oil where it overprints the Kuwait Arch trend. The apparently simple anticlinal oil field structures are cut by normal faults, which are mapped as radial, with throws up to 50 meters but averaging 15 meters. Structural compartmentalization of reservoirs has not been conclusively identified. The faults are near-vertical and often occur in swarms; the majority deform strata below the Mishrif Unconformity while rare faults reach the surface. Reverse throws are evident on seismic and in one well. Dextral offsets along northwest and northeast trending fault and lineaments indicate strike-slip. Wellbore breakouts, processed borehole imagery data and outcrop joint data define a principal maximum stress field orientation of 040°-050° consistent with regional trends.