Buzachi Peninsula of western Kazakstan extends into the Caspian Sea on the south of the Tengiz region. Several groups of fields are now in production there. The Jurassic and younger section has been explored; however, the pre-Jurassic section remains insufficiently explored and is regarded as having potential for oil-gas discoveries.
The pre-Jurassic complex of Buzachi Peninsula consists of more than 4000 m of various sedimentary and volcanic rocks ranging in age from Late Devonian to Late Trtiassic. The Upper Devonian is represented by dark gray to black limy shale and fine-crystalline limestone. Penetrated thickness is 328 m. The Upper Devonian- Lower Carboniferous is variegated shale and some siltstone, sandstone, and limestone 810 m thick. The Lower Carboniferous consists largely of almost black limestone with thickness up to 1746 m. The Middle Carboniferous is shale, siltstone, sandstone, and tuff, and thickness is 346-472 m. The Upper Carboniferous- Lower Permian consists variously of clastic, carbonates, and volcanics in different parts of the region. Thickness is from 80 to 2373 m. The Upper Permian is red-brown shale and siltstone up to 910 m thick. All three divisions of the Triassic are represented largely by clastics.
The Upper Permian and Triassic of Buzachi Peninsula, North Ustyurt, and adjacent parts of the North Caspian depression have much in common, indicating a single sedimentary basin in a single climate belt.
The composition of the flora during the course of pre-Jurassic time underwent changes under the action of the various climatic conditions from arid in the Late Devonian, Late Permian, and Early Triassic to humid in the Carboniferous, Early Permian, and Late Triassic.
The largest structural feature of the study area is the Buzachi mega-arch. Its position and configuration indicate presence of two arches, which extend offshore into the Caspian Sea.
Palynological studies of the Jurassic and Cretaceous oils of Arman, Karazhanbas, and Kalamkas fields have disclosed a predominance of Devonian and Carboniferous micro-fossils, indicating extensive vertical migration of fluids from the Paleozoic complex. Light, mobile hydrocarbon fluids have been found in the Triassic and Paleozoic sediments in several fields. The pools in the Jurassic and Cretaceous of Buzachi Peninsula thus appear to have formed by vertical migration of hydrocarbons from the pre-Jurassic complex. Further, the oil and gas accumulations in the Jurassic and Cretaceous are at shallow depths where conditions were hardly sufficiently mature to generate hydrocarbons.
The north flank of the Buzachi mega-arch is given first priority for deep and parametric drilling. Important here is the presence of overthrusts, where anticlinal structures are abundant. There are definite prospects for finding biohermal buildups of the Tengiz type in the Caspian Sea.
Taken from Kozmodem'yanskiy, Salimgereyev, Avrov, Vinogradova,
and Lipatova, 1995; digested in Petroleum Geology, vol. 30, no. 3, 1996,
two maps and one seismic section.
Copyright 2001 James Clarke. You are encouraged to print out this
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