Origin of Calcite Cements in Tight Sandstone Reservoirs of Chang 8 Member of the Yanchang Formation in Zhijing-Ansai Area, Ordos Basin, China

Zehan Zhang, Kelai Xi (), Honggang Xin, Chunming Yang, Hui Zhao, Youcheng Wang, Weidong Dan and Bin Luo
Additional contact information
Zehan Zhang: Key Laboratory of Deep Oil and Gas, China University of Petroleum, Qingdao 266580, China
Kelai Xi: Key Laboratory of Deep Oil and Gas, China University of Petroleum, Qingdao 266580, China
Honggang Xin: Research Institute of Petroleum Exploration & Development, PetroChina Changqing Oilfield Company, Xi’an 710065, China
Chunming Yang: Xi’an Changqing Chemical Group Co., Ltd., Xi’an 710018, China
Hui Zhao: Key Laboratory of Deep Oil and Gas, China University of Petroleum, Qingdao 266580, China
Youcheng Wang: Key Laboratory of Deep Oil and Gas, China University of Petroleum, Qingdao 266580, China
Weidong Dan: Research Institute of Petroleum Exploration & Development, PetroChina Changqing Oilfield Company, Xi’an 710065, China
Bin Luo: Research Institute of Petroleum Exploration & Development, PetroChina Changqing Oilfield Company, Xi’an 710065, China

Energies, 2022, vol. 15, issue 24, 1-21

Abstract: Calcite cement is a common type of cementation in tight sandstone reservoirs of the Upper Triassic Yanchang Formation Chang 8 Member in the Zhijing-Ansai area of the Ordos Basin, which has significant influence on reservoir densification and heterogeneity. Calcite cements affect the quality of the reservoir conspicuously. The characteristics and origins of calcite were investigated using a series of approaches from the perspective of petrography and geochemistry, including thin section observation and identification, cathode luminescence, scanning electron microscopy, AMICS analysis, LA-ICP-MS elements analysis, and carbon and oxygen isotopes analysis. The results of all analytical tests indicated that calcite cements can be divided into two types according to their occurrence and origins. Type-I calcite cements mainly occur in sandstone reservoirs near the sandstone–mudstone interface or the sandstone layers adjacent to mudstone. Generally, there is no chlorite coating around them, and they appear dark orange under cathode luminescence. The carbon source of Type-I calcite cements may be related to the compaction and drainage of mudstone. Type-II calcite cements are formed in the early stage, and their carbon source may be related to the compaction and drainage of the adjacent mudstone. Type-II calcite cements are surrounded by chlorite coating primarily present in the interior of fine-grained sandstone, showing as bright yellow under cathode luminescence. Decarboxylation of organic matter in the source rocks may provide a crucial source of carbon for Type-II calcite cements.

Keywords: calcite cements; reservoir heterogeneity; tight sandstone reservoir; Yanchang Formation; Ordos Basin (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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