Some estimates predict that 30 percent of all resources of oil and gas and 39 percent of the pools are in non-anticlinal traps. In the North Caspian depression reef trap are present along the borders, where numerous fields have already been discovered. Stratigraphic and fault traps here offer tremendous potential for new discoveries. Sectors of pinchout of Paleozoic clastics against highs have been found in the southeastern part of the depression and on the northwest flank of the South Emba high.
Since the moment of inception of the North Caspian depression and throughout all of its geologic history the region of the South Emba high has been the southeast border of an area of subsidence, and as a relatively uplifted zone it has served as a large region of oil-gas accumulation due to migration from deeper parts of the depression. Oil and gas shows of various degree of intensity have been found here in Middle and Upper Devonian, Lower Carboniferous, Lower Permian, Triassic, Middle and Upper Jurassic, and Lower Cretaceous in many arteas. These rocks are limestones, dolomites and sandstones of great thickness; they are persistent for considerable distances and contain good reservoirs and seals.
Geophysical surveys and deep drilling have demonstrated a regional rise toward the south for the Carboniferous strata on the northwest flank of the South Emba high. There is a rapid pinchout here of Permian and Carboniferous sediments due to truncation by an erosion surface. The line of pinchout has an embayment configuration and in places is along a fault. Oil pools have been found at the heads of strata beneath surfaces of unconformity. Similar zones may be present in the Tortay, Turesay, and other areas.
Wells 2, 3, 4, and 7 have been drilled in the Turesay area. The latter well penetrated Devonian sediments at no great depth. Since the Devonian is regionally oil-gas-bearing both on the East European craton and in the North Caspian depression, the area down dip from well 7 appears to have great potential. It is recommended that well 3 be deepened to 5000 m.
Taken from Stepakova, 1987; digested in Petroleum Geology
vol. 23, no. 11/12; two cross sections: Biikzhal-South Emba and
Tortay-Terusay.
Copyright 2002 James Clarke; you are encourages to print out
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