Differences and development patterns of karst reservoirs in Majiagou Formation, northern Ordos Basin

被引：0

作者：

Zhang, Juntao ^{[1
]}

Jin, Xiaohui ^{[1
]}

Gu, Ning ^{[1
]}

Bian, Changrong ^{[1
]}

Yang, Jiaqi ^{[1
,2
]}

He, Zhiliang ^{[1
,3
]}

机构：

[1] Key Laboratory of Deep Geology and Resources, SINOPEC, Beijing,102206, China

[2] School of Energy Resources, China University of Geosciences (Beijing), Beijing,100083, China

[3] Ministry of Science & Technology, SINOPEC, Beijing,100728, China

来源：

Oil and Gas Geology | 2021年 / 42卷 / 05期

关键词：

Catchments - Lime - Metamorphic rocks - Cracks - Landforms - Dolomite - Molds - Grading - Gypsum - Seepage - Dissolution;

D O I：

暂无

中图分类号：

学科分类号：

摘要：

Karst reservoirs are widely developed in the Majiagou Formation, northern Ordos Basin, though they are markedly different from the classic karst model.An integrated analysis of petrology and geochemistry functions to identify 3 types of karst reservoirs related in genesis and affected by gypsum-bearing strata, and a karst model of strata bearing evaporite minerals in the Majiagou Formation is established.The results show that the gypsum-bearing dolomite reservoirs with gypsum mold pores are formed under sabkha-associated dolomitization, featuring richness in evaporate minerals, sedimentary setting of gypsum-bearing dolomite flat, and reservoir space of dissolved gypsum mold pores.Dolomite reservoirs with dissolved-intercrystalline (dissolved) pores are generated under seepage-reflux dolomitization, with the fluid coming from overlying strata bearing gypsum, and mainly occur in dolomite of shallow shoal facies with reservoir space dominated by dissolved pores and intercrystalline (dissolved) pores.Fractured-vuggy limestone reservoirs are mainly developed in (dolomitic) limestone formations, which originally are deposited in limestone flat, with cracks and dissolved-intercrystalline (dissolved) pores as dominant reservoir space, and the development of primary cracks within is associated with the dissolution and deformation of underlying gypsum-bearing rocks.In terms of spatial distribution in the study area, reservoirs of the 3 types are all discovered in the central and eastern parts of northern Ordos Basin; while dolomite reservoirs with dissolved-intercrystalline (dissolved) pores are popular in the western part, and the fractured-vuggy limestone reservoirs dominate the northern part.The reservoirs of the same type also exhibit different petrological and geochemical characteristics in different paleo-geomorphic units, which could be in turn subdivided into seepage zones of the high and catchment zones of the low.The former rarely impacted by atmospheric precipitation, is characterized by well-preserved reservoirs filled with a small amount of dolomite and of low impurity level (Al, K, and Sr, etc.).The latter under the significant impact of atmospheric precipitation, features seriously-damaged reservoirs filled with a large amount of calcite, and of high impurity level and generally negative δ18O. © 2021, OIL & GAS GEOLOGY Editorial Board. All right reserved.

引用

页码：1159 / 1168