Structure Characteristics of Karatau Strike-Slip Faults and their Control on Hydrocarbons in South Turgay Basin
The South Turgay Basin is one of the most prolific petroliferous basins in Central Asia which was greatly influenced by the movement of Karatau Fault (the north part of Talas-Fergana Fault). And the Karatau Fault vertically cut through the central section of Aryskum Graben. High-resolution seismic data and drilling data have been used to interpret the Karatau Fault. The structure features, evolutionary process, as well as its control on the petroleum accumulation were researched. According to the interpretation, the Karatau Fault cut all the covering strata in the graben with typical features of strike-slip faults, such as flower structures, Dolphin’s effect and steep fault plane vertically, multi-fault segments, and minor feather faults in the horizontal slices. There are lots of alternating anticlines and synclines along the main strike-slip fault. The structure evolution study shows that three periods of strike-slip movements occurred from the Early Jurassic or Late Triassic epoch. The first tensile movements in Early Jurassic result in the formation of rift basin, and the second compressional movements in Late Jurassic generated lots of anticlines and positive flower structure; the third strike-slip movements generated negative flower structure which is a disadvantage for the formation of oil reservoir. The multi-periodic activities of Karatau Fault accelerate the migration of oil and gas from the deep source kitchen along the vertical and flower faults. The fault-related anticlines and feather fault blocks are the best entrapments for hydrocarbons. And multi-layer reservoirs have been found along the strike-slip fault. Otherwise, the multi-stage movements lead to the hydrocarbon losses in the Aryskum sag. So, the overlying cap rocks and the fault sealing are critical for the oil entrapment. Most of oils were found in the reservoirs below the three maximum flooding surfaces.
KeywordsKaratau strike-slip fault Tectonic evolutionary Petroleum entrapment South Turgay Basin
This study was supported by science and technology projects of CNPC (NO. 2013D-0901). The authors also thank the CNODC for publication authorization.
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