Significant discovery and significance of oil and gas exploration Well Yetan1 of Kekeya peripheral in the Front Mountain of Southwest area of Tarim Basin

doi:10.3969/j.issn.1672-7703.2024.04.001

Abstract

Abstract: The Yetan1 well in Kedong tectonic belt, west Kunlun thrust belt in the front mountain of southwest area of Tarim Basin, has made a major breakthrough in the Permian Pusige Formation, marking the discovery of an important exploration successor system in southwest area of Tarim Basin. Based on the regional geological data and the field outcrop, drilling and seismic research, the reservoir-forming conditions of the Permian Pusige Formation sandstone around Kekeya are reunderstood. A new round of research holds that the upper member of Permian Pusige Formation has a semi-deep lacustrine facies source rock with an area of 1.0×10⁴km² and a maximum thickness of 800m. The organic matter abundance is 0.89%~1.5%. The source of organic matter is mainly bacteria and algae, and the type of organic matter is mainly type II. Hydrocarbon generation potential S₁+S₂ is 1.47-2.78mg/g. Due to the tectonic uplift of the Kunlun Mountains, the lower member of the Permian Pusige Formation in the periphery of Kekeya subdivision entered the continental sedimentary system, and the delta front and shoal shallow lake sand bar high-quality sandstone reservoirs developed in the lower submember II, withsand body thickness of 42.5-63m and sand-land ratio of 27%-47%, which are a set of widely distributed reservoirs. It is a high quality reservoir-cap association with lower submember I of Pusige Formation and upper mudstone member of Pusige Formation. According to the structural pattern analysis after drilling of Yetan 1 well, it is concluded that the Kekeya subperipheral developed two phases of Indosinian and Alpine tectonic deformation, Palaeozoic imbricated thrust, strong overthrust, trap rows and belts, and the further extrusion and uplift in the Alpine period were partially complicated, and the imbricated thrust belt formed is a favorable exploration area. According to the analysis of natural gas dryness coefficient of the Pusige Formation, the R_o is 1.31%-1.42%, which is similar to the maturity phase of the source rock, indicating that the oil and gas come from the foote overlying source rock and have undergone the accumulation process of early oil and late gas, and the accumulation has the characteristics of "hydrocarbon supply by the overlying foote, new layers produce and ancient layers storage, lower layers produce and upper layers storage, transport by fault ". Through re-comprehensive analysis, it is believed that the Permian Pusige Formation traps in this area are distributed in rows, and 9 traps are found, covering an area of 307.7km², with 286 billion square meters of natural gas resources and 143 million tons of condensate oil. Meanwhile, several favorable exploration targets such as PT1 well, PS1 well and PS2 well are selected and have great exploration prospects. It is expected to become an important replacement field for large-scale natural gas storage and production.

Key words: front Mountain of Southwest area of Tarim Basin;Kekeya peripheral, Permian Pusige Formation, YeTan 1 well, Reservoir forming conditions

CLC Number:

TE112.1

Wang Qinghua, Yang Haijun, Li Yong, Cai Zhenzhong, Yang Xianzhang, Xie Huiwen, Chen Cai, Sun Chunyan. Significant discovery and significance of oil and gas exploration Well Yetan1 of Kekeya peripheral in the Front Mountain of Southwest area of Tarim Basin[J]. China Petroleum Exploration, 2024, 29(4): 1-17.

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