Tight oil sandstones in Upper Triassic Yanchang Formation, Ordos Basin, N. China : reservoir quality destruction in a closed diagenetic system.
- Liu, Mingjie
- Gluyas, Jon
- Wang, Weibin
- Liu, Zhen
- Liu, Junbang
- Tan, Xiucheng
- Zeng, Wei
- Xiong, Yi
DOIAbstract
An investigation of the Triassic Yanchang Formation, Ordos Basin, N. China, revealed that the diagenesis and quality of tight oil sandstone reservoirs (with an average porosity of 9.83% and an average permeability of 0.96 mD) were controlled by a closed diagenetic system. The carbonate cements observed in the sandstone were derived from decarboxylation of organic matter that occurred in the adjacent mudstones. These reactions supplied CO32−, which reacted with cations derived from grain dissolution in the sandstones. The average size of the diagenetic geochemical system with respect to carbonate cements was small (<6 × 10−2 m3), comprising sandstone and its adjacent mudstone(s). The carbonate cements tend to concentrate in the marginal sand...
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