摘要
勘探实践表明,鄂尔多斯盆地东部奥陶系风化壳蕴含了丰富的天然气资源,是重要的勘探领域,深入分析盆地东部奥陶系风化壳岩溶储层的孔隙充填特征,对储层平面分布预测及提高钻探成功率具有重要意义。早奥陶世,鄂尔多斯盆地处于稳定的碳酸盐台地沉积环境,马家沟期发育广泛的碳酸盐岩地层,其中马家沟组马五1亚段和马五2亚段发育典型的含硬石膏结核白云岩坪沉积,至中晚奥陶世,受构造抬升后遭受长达1.3亿年的风化溶蚀,形成风化壳膏模孔型岩溶储层。在岩心及薄片观察基础上,重点通过激光碳氧同位素、电子探针、阴极发光等微区多参数实验分析,研究表明奥陶系风化壳岩溶储层膏模孔中的充填物,包括渗流白云石粉砂、(含铁)方解石、(含铁)白云石、石英、萤石、黄铁矿、高岭石、硬石膏、残余泥质及有机质等12种,常见8种充填矿物组合类型。结合成岩演化分析,奥陶系风化壳岩溶储层膏模孔经历了早表生期、晚表生期、浅埋藏期和深埋藏期等4期充填。盆地东部膏模孔的充填程度明显高于盆地中部的靖边气田,充填程度主要受风化壳古岩溶地貌的控制,在盆地东部奥陶系风化壳二级古岩溶地貌中的平台、残丘、坡地及古沟槽两侧,膏模孔充填弱,储集空间大,储集性能更好。
The exploration shows that the natural gas resources in the Ordovician weathered crust at the eastern part of Ordos Basin is rich.An in-depth analysis for the pore-filling characteristics of the reservoirs is of great significance to the prediction of reservoir distribution and to the improvement of drilling success.Located in a stable carbonate platform in Majiagou period(Early Ordovician),there developed a wide range of carbonate rocks,among which anhydrite concretion-bearing dolomite flat developed in Majiagou Submember-51-2.Under the weathering and erosion(about 130 Ma)in the Late Ordovician,weathered crust karst reservoir developed mainly with anhydrite moldic pores.Based on cores,thin sections,and microstructure analysis by many experiments including carbon and oxygen isotopes,electron probe,and cathodoluminescence,there are 12 kinds of minerals such as calcite,dolomite,quartz,fluorite,pyrite,etc.filled in the pores,which usually formed 8 types of mineral assemblages.According to the diagenetic evolution of the Ordovician weathered crust karst reservoir,there are 4 filling stages including sea water,meteoric water,shallow burial,and deep burial.Mainly controlled by Ordovician paleokarst geomorphology,the anhydrite moldic pores are weakly filled at the platforms,mounds,slopes,and both sides of ancient trenches in the eastern part of the basin,with relatively high porosity.
作者
沈扬
吴兴宁
王少依
吴东旭
丁振纯
于洲
SHEN Yang;WU Xingning;WANG Shaoyi;WU Dongxu;DING Zhenchun;YU Zhou
出处
《海相油气地质》
CSCD
北大核心
2018年第3期21-31,共11页
Marine Origin Petroleum Geology
基金
国家科技重大专项"大型油气田及煤层气开发"(编号:2016ZX05004-002)
国家"十三五"油气专项"深层古老含油气系统成藏规律与目标评价"(2017ZX05008005)资助
关键词
鄂尔多斯盆地
奥陶纪
马家沟组
风化壳
岩溶储层
膏模孔
充填特征
Ordos Basin
Ordovician
Majiagou Formation
weathered crust
karst reservoir
anhydrite moldic pores
pore-filling characteristics