Hydrocarbon Distribution Characteristics And Main Controlling Factors Of Accumulation In South Konys Oilfield In South Turgay Basin, Kazakhstan

The South Konys oilfield, one of the most important oilfields in the South Turgay basin, Kazakhstan, is a combination of structural and lithostratigraphic reservoir. The study on hydrocarbon accumulation, influenced by strike-slip faults, is of great importance on oil and gas exploration and development, enrichment of hydrocarbon accumulation theory of strike-slip basin.This study, based on the current status of exploration and development of the oilfield,with fine interpretation of the 3D seismic, drilling, well test and production data, is conducted to focus on the comprehensive research of fine stratigraphic correlation,sedimentary structure, reservoir bed, structure and reservoir, etc., to implement the faults system and trap types, to describe the regional sedimentary system, and to clarify the reservoir distribution. Furthermore, with fine dissection of the reservoir,this study also aims to summarize the accumulation model and fluid distribution pattern, to make a guidance for optimization of the favorable oil and gas accumulation zones and local tectonic traps around the reservoir, to provide the basis for expansion of the exploration and development area of the oilfield and location selection of the exploration and evaluation wells.On the basis of the analysis of petroleum geology of the South Konys oilfield, the author summarized the oil and gas distribution characteristics. The results show that the oil and gas distribution in M-II layers in K1 ln Formation was controlled by both structural and lithologic changes. The oil and gas distribution was characterized by:(1)the reservoir has a gas cap;(2) Oil column is controlled by the thickness and porosity of sandstones.(3) The South Konys oilfield is a combination of structural and lithostratigraphic reservoir. The Jurassic reservoir is mainly controlled by lithology,and the reservoir lithology, physical property and thickness change greatly, and the reservoir continuity is relatively poor. Sandstones in the Jurassic J-0-1, J-0-2 layers show great lateral changes in thickness and oil and gas reservoirs are distributed in lenticular.Combining with the analysis of structural evolution and fault features, main controlling factors of hydrocarbon accumulation were discussed. The results show that:(1) hydrocarbon accumulation of plays in K1 ln and K1 un Formation is controlled by faulting activities. The hydrocarbon generated from the Middle Jurassic source rocks was communicated to the reservoir of M-II and M-0-2 through the Eastern Karatau strike-slip fault, then adjusted and finalized along the associated feather-shaped faults in the structure, forming the anticlinal reservoirs and fault-trapped reservoir.(2) Lateral Distribution of the Jurassic lithostratigraphic reservoirs is controlled by lithologic pinch-out belts. In the layers of Jurassic Akshabulak group J-0-1 and J-0-2, the hydrocarbon is mainly distributed as the shape of thin-layered lens, and formed lithologic stratigraphic reservoirs mainly controlled by phase transition and deposition pinch-out belts.(3) Vertical distribution of the Jurassic lithostratigraphic reservoirs is controlled by regional unconformities. The hydrocarbon migrated through the vertical faults to the unconformity surface, then horizontally migrated along the unconformity and connected sand bodies, and then accumulated in the sand bodies under and above the unconformity surface, thus a Jurassic unconformity-blocked reservoir formed.