鄂尔多斯盆地中部地区马家沟组断裂控制天然气运移方向的流体包裹体证据  

Migration of Natural Gas Controlled by Faults of Majiagou Formation in Central Ordos Basin:Evidence from Fluid Inclusions

作　　者：冯艳伟 陈勇 赵振宇 刘听雨 雷静 钟升 王淼 李冠华 裴仰文 Feng Yanwei;Chen Yong;Zhao Zhenyu;Liu Tingyu;Lei Jing;Zhong Sheng;Wang Miao;Li Guanhua;Pei Yangwen(School of Geosciences,China University of Petroleum,Qingdao 266580,China;Institute of Science and Technology Co.,Ltd.,China National Petroleum Corporation,Beijing 100083,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China)

机构地区：[1]中国石油大学地球科学与技术学院,山东青岛266580 [2]中国石油集团科学技术研究院有限公司,北京100083 [3]中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《地球科学》2021年第10期3601-3614,共14页Earth Science

基　　金：国家自然科学基金-石油化工联合基金(A类)培育项目(No.U1762108);国家自然科学基金面上基金项目(No.41873070);国家重大科技专项(No.2016ZX05004)。

摘　　要：为研究鄂尔多斯盆地中部地区马家沟组成藏期次和天然气运移方向与断裂活动的相关性,利用流体包裹体岩相学观察、激光拉曼光谱分析、均一温度和冰点温度的测定以及热力学PVT模拟方法对奥陶系马家沟组马五段储层的岩心样品进行了成分、温度和压力的测定与恢复.结果表明:构造裂缝脉体中充填的矿物为方解石、白云石和菱镁矿;脉体中共有4类流体包裹体,分别为富甲烷气体包裹体、含CO_(2)富甲烷气体包裹体、含甲烷盐水包裹体和盐水包裹体,这4类流体包裹体均存在于方解石脉体中;构造裂缝脉体和溶孔中含甲烷流体包裹体的均一温度在130.1~179.6℃之间,与含甲烷流体包裹体同期的盐水包裹体的均一温度范围为112.3~173.3℃.结合生排烃史和埋藏史,证明早白垩世是马家沟组天然气的主要成藏期.沿断裂分布的各井的捕获压力和压力系数呈现由西南向东北递减的趋势,早白垩世的构造运动在北东向的断层中产生大量构造裂缝,为天然气的运移提供了通道,证明含甲烷的流体沿北东向断裂运移并充注成藏.Taking the Member-5 of Ordovician Majiagou Formation in the central Ordos basin as an example, the relationship between migration direction of natural gas and faulting activities was investigated based on integrated observations of fluid inclusion petrology, laser-Raman spectroscopy, homogenization and ice melting temperature measurements, thermodynamic PVT simulation. The results indicate that the minerals in the veins of structural fractures are calcite, dolomite and magnesite. There are four types of fluid inclusions found in the veins, including methane-rich gas inclusions, CO_(2)-bearing and methane-rich gas inclusions, methane-bearing aqueous inclusions and brine aqueous inclusions. The homogenization temperatures of the methanebearing fluid inclusions range from 130.1 to 179.6 ℃, while the homogenization temperatures of the brine aqueous inclusions at the same time as the methane-bearing fluid inclusions range from 112.3 to 173.3 ℃. Combined with the history of hydrocarbon generation and strata burial, the Early Cretaceous is the important period of natural gas accumulation for the Majiagou Formation in studied area. While, Early Cretaceous tectonic movement produced a large number of structural fractures by the northeastoriented faults. As the fluid inclusions in veins recorded the fluids of natural gas migration, experimental results prove that structural fractures had been channels for the migration of natural gas. The trapping pressures of fluid inclusions and pressure coefficients show a decreasing trend from SW to NE along the faults, which implies that the methane-bearing fluids migrated along the NE-trending fault.

关 键 词：鄂尔多斯盆地 流体包裹体 断裂活动 天然气运移 马家沟组 天然气 

分 类 号：P618.13[天文地球—矿床学]