鄂尔多斯盆地上古生界天然气运移特征及成藏过程分析  

ANALYSIS OF CHARACTERISTICS OF GAS MIGRATION AND RESERVOIR-FORMING IN THE UPPER PALEOZOIC OF NORTHERN ORDOS BASIN

作　　者：李仲东[1] 惠宽洋[2] 李良[2] 周文[1] 张哨楠[1] 过敏[1] 

机构地区：[1]成都理工大学'油气藏地质及开发工程'国家重点实验室,四川成都610059 [2]中国石油化工股份有限公司华北分公司,河南郑州450006

出　　处：《矿物岩石》2008年第3期77-83,共7页Mineralogy and Petrology

基　　金：国家973煤层气项目(2002CB211705)

摘　　要：运用石油地质动态分析及综合研究方法,以鄂尔多斯盆地上古生界砂泥岩压实特征、古压力恢复、包裹体、成岩作用资料为基础,对上古生界天然气运移的地质背景、天然气运移特征进行详细分析,对储层致密化、古高压异常对天然气运移、成藏的影响等方面进行研究,认为上古生界砂岩致密化发生于中三叠世—晚三叠世,早于大规模油气运移时期,天然气呈连续相运移需要的临界气柱高度远大于砂岩的单层厚度,受压力封存箱的封闭以及封存箱内不均匀分布的高压泥质岩阻隔,天然气难以沿构造上倾方向作大规模运移,主要为就近垂向运移聚集成藏;成藏特征研究显示,只有毛管中值压力平均值小于6.21 MPa、厚度大于4 m以上的优质储层段能够允许天然气成藏,而且气水分布主要受构造部位、储层非均质控制。故此,上古生界气藏主要为致密储层条件下的岩性和构造-岩性气藏类型;根据各时期、各地区、各层段不同的天然气运移、成藏特征,将上古生界压力封存箱划分为非烃源岩和烃源岩两个成藏子系统,前者具自生自储、短距离运移、早期(J2—K1)源内成藏特点,形成原生气藏,而后者属近-远距离运移、晚期(K1—K2,K2末—Q)源外成藏特点。On the basis of synthetic data,such as compaction of sand mud rocks, restoration of paleo-pressure, fluid inclusions and diagenesis,the geological background of natural gas migration and characteristics of gas migration in the Paleozoic strata of the Ordos basin are analyzed comprehensively. The main focus is put on the effect of tight reservoir and abnormal pressure on the migration and accumulation of gas. The study reveals that the Paleozoic sandstone became tight during middle-late Triassic period, prior to the large scale migration of gas and oil. Continuous phase of gas migration requests critical gas column height higher than the thickness of single sandstone layer. Since the closure of pressure compartment and the obstruction of high pressure mudstone unevenly distributed in the compartment, it is difficult for gas to move upwards in the dip direction, instead, it mainly migrates vertically to form gas accumulation. It is showed that only the mean capillary pressure is less than 6.21 MPa and only the thickness of reservoir is over 4 m, can the gas accumulation be formed. And the distribution of water and gas is mainly controlled by the heterogeneity of reservoirs and tectonic position. Therefore, the Paleozoic gas reservoir is lithologic gas reservoir and tectonic lothologic gas reservoir under the condition of tight reservoir. Based on the characteristics of gas migration and accumulation in different stages, different regions and different segments,the Paleozoic pressure compartment is divided into 2 subsystems of non hydrocarbon source rocks and hydrocarbon source rocks. The former is characterized by nearfar distance migration and formed in K1-K2,late K2- Q. And the latter is characterized by selfgenerating and self preserving reservoir, near distance migration, autogenic accumulation formed in J2- K1.

关 键 词：鄂尔多斯盆地北部 上古生界 天然气运移 成藏特征 成藏过程分析 

分 类 号：TE122.3[石油与天然气工程—油气勘探]