Sedimentation Study Identifies Exploration Targets In South Turgay Basin, Kazakhstan
After 40 years of exploration, large-scale structural reservoirs have become more difficult to find in Kazakhstan’s South Turgay basin. China National Petroleum Corp. (CNPC) has increased its reserves in the basin by targeting lithological-stratigraphic traps to find subtle reservoirs in depressions in the basin’s northern portion. Systematic research of stratigraphic sequences and sedimentary facies distribution can determine controlling factors of trap distribution and predict favorable hydrocarbon accumulation zones to further expand South Turgay basin exploration.
Future exploration in Kazakhstan’s South Turgay basin should focus on lithological-stratigraphic traps related to two large lake-flooding periods with emphasis on the western Aryskum graben’s fan bodies and the North Aryskum graben’s slump bodies in. Cap rocks with excellent sealing capacities are more favorable for oil and gas reservoir formation in the South Turgay basin than in large-scale reservoir rock developments. Tectonic-paleotopographic settings are dominant factors controlling development sequences and favorable sand body distribution in both the Lower Jurassic and the Middle-Upper Jurassic’s sedimentary facies belt.
This article identifies eight third-order sequences of the Jurassic in South Turgay basin by analyzing drilling logs, cores, and sedimentary and seismic facies from the region. The facies are characterized by lateral differences and vertical inheritances. The study also establishes corresponding relationships between seismic and sedimentary facies, which include fluvial, delta, fan delta, and lacustrine with other classified subfacies.
Its large coverage area, uniform classification standards, and an unclear understanding of stratigraphic sequences and depositional filling patterns have restricted exploration of the complex South Turgay basin.
South Turgay, in south-central Kazakhstan, is one of the largest petroliferous basins in the country with an area of 80,000 sq km. It is a Mesozoic-Cenozoic rift basin developed on the basement strata of the Jurassic and Cretaceous.
State Key Laboratory, Sinopec
China University of Geosciences