鄂尔多斯盆地青石峁气田成藏条件及勘探开发关键技术

Accumulation conditions and key technologies of exploration and development for Qingshimao gas field in Ordos Basin

2022年探明的青石峁气田,其探明区域的面积为2 151 km^(2),探明储量为1 459×10^(8)m^(3),是长庆油田第8个千亿立方米大气田。通过回顾青石峁气田的勘探历程,总结了其天然气成藏的地质特征,研究结果表明:青石峁气田的主力含气层为二叠系下石盒子组8段;主要烃源岩为石炭系本溪组、二叠系太原组和山西组的煤层和暗色泥岩,具有广覆式生烃的特点;发育三角洲前缘亚相沉积体系,其中,多物源、多水系、强供给、多期河道控制了砂体的展布特征;储层为水下分流河道砂体,平均孔隙度为7.9%,平均渗透率为0.363 mD,储层致密,砂体的连通性受控于砂体的展布方向;气藏压力系数为0.78~0.90,属于低压气藏;低生烃强度背景下的长期连续充注、断裂系统对致密储层的调整改造、较高的源-储压差造就了岩性-构造控制下的改造型气藏;三维地震勘探技术、砂体精细刻画技术和复杂气水关系下的井位优选技术是青石峁气田勘探开发的关键技术。

Qingshimao gas field was explored in 2022,which has the proved area of 2151 km^(2)and proved reserves of 1459 ×10^(8)m^(3),making it the eighth gas field of hundred billion cubic meters in Changqing oilfield.By reviewing the exploration history of Qingshimao gas field,the geological characteristics of natural gas accumulation are summarized as follows.The main gas-bearing stratum of Qingshimao fas field is the Member 8 of the Permian Xiashihezi Formation;the main source rocks are coal seams and dark mudstones in Carboniferous Benxi Formation,Permian Taiyuan Formation and Shanxi Formation,characterized by widespread hydrocarbon generation.Delta front subfacies sedimentary system is developed,where the distributions of sand bodies are controlled by multiple provenances,multiple drainage systems,strong supply and multiple channel.The reservoir is dominated by fluvial channel sandstones with an average porosity of 7.9%and an average permeability of 0.363 mD,indicating a tight reservoir,and the connectivity of sand bodies is controlled by their distribution.The pressure coefficients of gas reservoir range from 0.78 to 0.90,demonstrating a low pressure gas reservoir.The reconstructed gas reservoir under the control of lithology and structure was formed due to longterm continuous charging under low hydrocarbon generation intensity,adjustment and transformation of tight reservoirs by fault systems,and high source-reservoir pressure difference.The three-dimensional seismic exploration,sand body fine characterization,and well location selection under complex gas-water relationships are key technologies for exploration and development of Qingshimao gas field.