沁水盆地晋中地区上古生界致密砂岩气勘探潜力

Exploration potential of tight sandstone gas in upper Paleozoic in Jinzhong area of Qinshui basin

沁水盆地晋中地区勘探程度较低,为了探究晋中地区上古生界致密砂岩气的成藏地质条件,明确其勘探前景,在前人研究的基础上,利用地震、测录井、岩心、测试分析及相关地质资料,对晋中地区上古生界成藏地质要素进行综合研究。结果表明:上古生界储层分布主要受石炭系-二叠系近海平原三角洲沉积河道砂体的控制,单层砂岩厚度为1.0~10.0 m,平均为7.1 m,储层平均孔隙度为3.6%,平均渗透率为0.21×10-3μm 2,属于特低孔特低渗致密储层;石炭系-二叠系至三叠系泥岩发育,平均泥地比大于0.7,是良好的盖层,但三叠纪末-新生代的挤压隆起、抬升剥蚀作用导致保存条件差。针对本地区成藏主控因素,结合近年的勘探成果及地震资料,预测出晋中地区榆社缓坡和武乡背斜带是致密砂岩气发育的有利区带,勘探潜力良好。

The exploration degree in Jinzhong area of Qinshui basin is low.In order to explore the geological conditions of upper Paleozoic tight sandstone gas accumulation in Jinzhong area and clarify the exploration prospect,based on previous studies,the geological elements of upper Paleozoic reservoir formation in Jinzhong area are comprehensively studied by using seismic,logging,core,test analysis and relevant geological data.The results show that the distribution of upper Paleozoic reservoir is mainly controlled by the sedimentary channel sand body of Carboniferous-Permian offshore plain delta.The thickness of single-layer sandstone is 1.0~10.0 m,with an average of 7.1 m,the average porosity of reservoir is 3.6%,and the average permeability is 0.21×10-3μm 2,belonging to ultra-low porosity and ultra-low permeability tight reservoir.From Carboniferous-Permian to Triassic,mudstone is developed,with an average mud to ground ratio greater than 0.7,which is a good cap rock.However,the compression uplift,uplift and denudation from the end of Triassic to Cenozoic developed faults,resulting in poor preservation conditions.According to the main controlling factors of reservoir formation in this area,combined with the exploration results and seismic data in recent years,it is predicted that Yushe gentle slope and Wuxiang anticline in Jinzhong area are favorable areas for the development of tight sandstone gas and both have a good exploration potential.