Main types and formation mechanisms of marine carbonate reservoirs in the Ordos Basin

被引：0
|
作者：
Zhou J. [1 ,2 ]
Fu J. [3 ]
Yu Z. [1 ]
Wu D. [1 ]
Ding Z. [1 ]
Li W. [1 ]
Tang J. [4 ]
机构：
[1] PetroChina Hangzhou Research Institute of Geology, Hangzhou
[2] CNPC Key Laboratory of Carbonate Reservoirs, Hangzhou
[3] PetroChina Changqing Oilfield Company, Xi'an
[4] China University of Petroleum, Beijing, Beijing
来源：
Natural Gas Industry | 2020年 / 40卷 / 11期
关键词：
Cambrian-Ordovician; Favorable exploration zone; Formation mechanism; Marine carbonate rock; Ordos Basin; Reservoir distribution; Reservoir type;
D O I：
10.3787/j.issn.1000-0976.2020.11.003
中图分类号：
学科分类号：
摘要：
The macroscopic distribution laws and favorable distribution zones of marine carbonate reservoirs in the Ordos Basin have not been understood clearly, so it is difficult to meet the needs of zone evaluation and target selection. To this end, this paper discusses deeply the characteristics, formation mechanisms and distribution laws of marine carbonate reservoirs in the Ordos Basin based on outcrop, drilling and geophysical data, combined with experimental analysis data, and then accordingly points out the direction of the next natural gas exploration. And the following research results were obtained. First, two types of dolomite reservoirs are mainly developed in the marine carbonate rocks of the Ordos Basin, i.e., karst dolomite reservoirs and grain beach dolomite reservoirs. Karst dolomite reservoirs are developed in the gypsum-bearing dolomite and gypseous dolomite flat microfacies of evaporative platform, and it is mainly distributed in the upper assemblage of the fifth Member of Lower Ordovician Majiagou Formation (O1M5), the O1M1 and the O1M3. Grain beach dolomite reservoirs are mainly developed in the marginal platform grain beach microfacies and the intra-platformgrain beach microfacies, and it is distributed in the Zhangxia Formation of Middle Cambrian, the Sanshanzi Formation of Upper Cambrian, the O1M4 and the middle assemblage of O1M5. Second, the lithology of grain beach reservoirs is oolitic dolomite, doloarenite, crystalline dolomite and microbial dolomite. Its reservoir space is mainly acted by residual intergranular (dissolved) pores, microbial framework (dissolved) pores, intercrystalline(dissolved) pores and karst caves with a small number of fractures, and the porosity ranges from 2.00% to 18.03%, averaging 6.16%. Mechanical sedimentation and microbial mounding are the important formation mechanisms of primary pores, penecontemporaneous dissolution and weathering crust karstification in the exposure period are the main factors controlling the formation of dissolved pores and karst caves, and the early dolomitization and sealing system are favorable for the preservation of pores. Third, the lithology of karst reservoirs is fine-silt crystalline dolomite containing anhydrite moldic pores and silt crystalline dolomite. Its reservoir space is mainly acted by anhydrite moldic pores, karst caves and micro-fractures, and the porosity ranges from 2.00% to 16.36%, averaging 5.98%. Inter-layer karstification in the syngenetic period and weathering crust karstification in the exposure period are the main formation mechanisms of anhydrite moldic pores, and the mineral filling and sealing system are two major factors controlling the preservation of anhydrite moldic pores. In conclusion, the favorable reservoirs are mainly distributed in the areas of Eketuoqianqi-Dingbian-Shanghan, Taolimiao-Wuqi and Yulin-Zhidan, and Taolimiao-Wuqi and Yulin-Zhidan areas are the most favorable zones for deep carbonate gas exploration. © 2020, Natural Gas Industry Journal Agency. All right reserved.
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页码：20 / 30
页数：10
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