Major oil and gas discovery and significance of Well Yetan 1 in the peripheral Kekeya area in the piedmont of the southwestern Tarim Basin
A major breakthrough has been made in the Permian Pusige Formation in Well Yetan 1 in Kedong structural zone in West Kunlun Thrust Belt,marking a major exploration replacement field in the piedmont of the southwest Tarim Basin.Based on regional geological data,field outcrop,well drilling and seismic data,the comprehensive study has been conducted to re understand the hydrocarbon accumulation conditions in the Permian Pusige Formation in the peripheral Kekeya area.The study results show that the continental lacustrine-delta sedimentary system was developed in the Permian Pusige Formation,and the semi-deep to deep lake facies source rock was deposited in the upper member,with an area of 1.0×104 km2,a maximum thickness of 800 m,high organic matter abundance of 0.92％-1.16％in the concentration section,mainly bacteria and algae organic matter source,and mainly Type Ⅱ organic matter;The high-quality sandstone reservoirs of delta front and shallow shoal lake sand bar facies were developed in the lower member,with sand body thickness of 42.5-63 m and sand to formation ratio of 27％-47％,which served as the regional reservoir with a wide distribution area,and formed high-quality reservoir and cap rock combination with mudstone in the upper member of Pusige Formation;Affected by two stages of tectonic deformation in the peripheral Kekeya area during the Indosinian and Himalayan periods,the imbricated thrusts and strong overthrusts were superimposed in the Paleozoic,forming traps in rows and belts,and the traps were locally complicated by further compression and uplift in the Himalayan period,developing imbricated thrust belts,which are favorable exploration areas.The analysis of natural gas dryness coefficient indicates that Ro is 1.31％-1.42％,which is similar to the maturity of source rock in the foot wall,indicating that the hydrocarbon was supplied by the overthrust and superimposed source rock and experienced hydrocarbon accumulation process of early oil and late gas,with hydrocarbon accumulation characteristics of"hydrocarbon supply by the overthrust and superimposed source rock in the foot wall,lower source rock and upper reservoir,and hydrocarbon transport by faults".The comprehensive study results indicate that traps of the Permian Pusige Formation are distributed in rows and belts,and nine traps have been identified,with an area of 301 km2,gas resources of 2930×108m3 and condensate oil resources of 2×108t,showing broad exploration prospects.
万方数据
维普
