鄂尔多斯盆地延安地区下古生界天然气成藏过程和机理  

Accumulation process and mechanism of Lower Paleozoic gas reservoir in Yan'an area,Ordos Basin

作　　者：王震亮[1,2] 魏丽[1,2] 王香增 王念喜 范昌育[1,2] 李彦婧[2,4] 赵雪娇[2,5] 赵晓东[1,2] 任来义 曹红霞 

机构地区：[1]西北大学大陆动力学国家重点实验室,陕西西安710069 [2]西北大学地质学系,陕西西安710069 [3]陕西延长石油(集团)有限责任公司研究院,陕西西安710075 [4]中国石油化工股份有限公司华东分公司勘探开发研究院,江苏南京210000 [5]陕西煤田地质勘查研究院有限公司,陕西西安710014

出　　处：《石油学报》2016年第B11期99-110,共12页Acta Petrolei Sinica

基　　金：国家自然科学基金项目"延安地区下古生界碳酸盐岩天然气的成藏过程和机理"(No.41172122);陕西延长石油(集团)有限责任公司研究院项目(陕研11-8)资助

摘　　要：延安地区下古生界碳酸盐岩主体位于古岩溶斜坡,勘探证实含气性良好,但天然气的成藏过程和机理研究相对薄弱。主要采用盆地数值模拟技术,恢复出关键地质时期的古流体动力特征,分析天然气运移方向,总结上、下古生界输导体系的配置关系,根据马家沟组微观流体活动记录,如包裹体的均一温度、盐度反映的成岩环境和活动期次,及与上古生界储层的对比,探讨了下古生界天然气的成藏过程和机理。研究认为,下古生界天然气主要来自上古生界。三叠纪末,山西组发生第一期油气充注,因规模较小且向下运移动力不足,未能在马家沟组充注。中、晚侏罗世,山西组发生第二期油气充注,在向下运移动力的驱动下,沿着砂体-裂缝输导体向下运移到风化壳,由古沟槽处和岩溶高地铝土岩缺失部位进入马家沟组,在储集性能较好的古地貌构造高点以及沟槽附近聚集成藏。早白垩世,上古生界烃源岩进入生、排烃高峰期,山西组发生第三期油气充注,是天然气向下运移的主要时期,除在第二期油气充注的区域外,在东部酸性流体活动形成的次生孔隙中也可聚集成藏。晚白垩世,烃源岩生气能力降低,天然气进入运聚调整阶段。总体上,延安地区西部、中部,因长期接受上古生界天然气的运移而发生充注,并在马家沟组内发生侧向运移,容易形成较大规模聚集。The main part of Paleozoic carbonate in Yan＇an area is located at the paleokarst slope,and exploration has confirmed that it has good gas-bearing properties.However,there are few researches on the accumulation process and mechanism of gas.Numerical simulation technique was mainly used to reconstruct the dynamic characteristics of paleo-fluid in key geological periods,conducting an analysis on the gas migration direction,and make a summarization on the allocation relations of the Upper and Lower Paleozoic carrier system.According to the records of microfluidic activity,such as the homogenization temperature,salinity,its diagenetic environments and active stages of inclusions in Majiagou Formation,and in comparison with Upper Paleozoic reservoirs,the accumulation process and mechanism of Lower Paleozoic gas were explored in this study.Studies suggest that Lower Paleozoic natural gas is mainly originated from the Upper Paleozoic source rocks.At the end of Triassic,the first stage of hydrocarbon chargting occurred in the Shanxi Formation,but did not occur in the Majiagou Formation due to its small scale and insufficient downward migration force.In the Middle and Late Jurassic,the second stage of hydrocarbon charging occurred in the Shanxi Formation.Driven by the downward migration force,hydrocarbons migrated downward to weathering crust along the sand body-fracture conductor department,then entered into Majiagou Formation by means of ancient valley troughs and the missing parts of bauxite in karst highland,and accumulated in the palaeogeomorphic structural highs with good reservoir properties and areas adjacent to the troughs.In the Early Cretaceous,Upper Paleozoic source rocks entered into the peak of hydrocarbon generation and expulsion,and the third stage of hydrocarbon charging occurred in the Shanxi Formation,which is the main period of downward gas migration.In addition to the hydrocarbon charging areas in the second stage,hydrocarbon also accumulatedin the secondary pores formed by the activity of acidic flu

关 键 词：碳酸盐岩 古流体动力 输导体系 流体包裹体 成藏模式 延安地区 鄂尔多斯盆地 

分 类 号：TE122.14[石油与天然气工程—油气勘探]