鄂尔多斯盆地神木气田二叠系太原组天然气成藏条件

Gas accumulation conditions of the Permian Taiyuan Formation in Shenmu gas field,Ordos Basin

为了进一步揭示鄂尔多斯盆地神木气田天然气成藏条件与主要控制因素,利用石油地质学理论和油气成藏原理,结合地球化学特征,对太原组生烃条件和储集层特征、储盖条件和生储盖组合进行了系统剖析,同时探讨了成藏主控因素。研究认为:本溪组、太原组和山西组二段煤系地层是太原组气藏的优质烃源岩,有机质丰度高,生烃条件优越;山西组二段泥岩有机质丰度高,生烃能力强,同时具有物性封闭和烃浓度封闭双重封盖能力,具备良好的储盖条件;受物源和沉积作用双重控制,太原组储集层岩性以岩屑石英砂岩和石英砂岩为主,物性总体呈现低孔、低-特低渗特征,但由于石英砂岩储层的发育,局部仍存在富集高产层段。储集岩物性是影响该区太原组天然气成藏的主要控制因素,平面上追踪石英砂岩储层展布是今后降低钻井风险、确保气井高产的重点。

In order to further reveal natural gas reservoir forming conditions and its main controlling factors in Shenmu gas field, Ordos Basin, this paper systematically analyzed the hydrocarbon generation conditions, reser- voir characteristics, reservoir and seal conditions, source-reservoir-cap assemblage and key controlling factors of gas accumulation in the Taiyuan Formation by using theories of petroleum geology and hydrocarbon accumulation in combination with geochemical characteristics. The results indicate that Benxi Formation, Taiyuan Formation and coal seams in the 2na member of Shanxi Formation are high quality source rocks for the Taiyuan Formation reservoir, and have high organic content which is favorable for hydrocarbon generation. The shale in the 2no mem- ber of Shanxi Formation has dual sealing mechanisms （ i. e. capillary seal and hydrocarbon concentration seal） with strong sealing capacity, which are favorable for hydrocarbon preservation. The reservoir lithology of the Taiyuan Formation is dominated by quartz sandstone and lithic quartz sandstone with low porosity and low to ex- tra-low permeability due to the control of both provenance and sedimentation. However, local high-yield pay zones still exist due to the development of quartz sandstone reservoirs. Physical properties are the main factors controlling hydrocarbon accumulation of the Taiyuan Formation in this area. Mapping quartz sandstone distribu- tion is the key to reduce drilling risk and to ensure high yield of gas wells.