Diagenesis and its controls on reservoir properties and hydrocarbon potential in tight sandstone: a case study from the
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ORIGINAL PAPER
Diagenesis and its controls on reservoir properties and hydrocarbon potential in tight sandstone: a case study from the Upper Triassic Chang 7 oil group of Yanchang Formation, Ordos Basin, China Yunlong Zhang 1,2 & Zhidong Bao 1,2 & Yan Zhao 3 & Li Jiang 1,2 & Fanhao Gong 4
Received: 12 January 2015 / Accepted: 11 May 2017 # Saudi Society for Geosciences 2017
Abstract The sandstones in the Chang 7 oil group are typically recognized as unconventional tight clastic rock reservoirs. These sandstones are fine-grained and have low permeability and porosity and low textural and compositional maturity. In the present study, optical microscopy, SEM, cathodoluminescence, and wireline log, core analysis permeability and porosity, and production test data are applied to analyze the diagenesis and its controls on hydrocarbon potential in these tight sandstones. The results indicate that the sedimentary environment and diagenesis controlled the physical properties of the reservoir. Three different diagenesis processes were likely occurred in these sandstones. Early strong carbonate cementation is a key factor for other subsequent alterations and the final reservoir properties. The sandstones dominated by dissolution and compaction have more capacity for hydrocarbon preservation.
Keywords Diagenesis . Physical properties . Tight sandstone . Hydrocarbon potential . Ordos Basin
* Yunlong Zhang [email protected] * Zhidong Bao [email protected]
1
College of Geosciences, China University of Petroleum-Beijing, No. 18 Fuxue Road, Changping, Beijing 102249, China
2
State Key Laboratory of Petroleum Resource and Prospecting, Beijing 102249, China
3
Department of Exploration and Development, Oil and Gas Company, China Huadian Engineering Co. Ltd, Beijing 100035, China
4
Shenyang Center of China Geological Survey, Shenyang 110034, China
Introduction Tight oil, as an important unconventional hydrocarbon resource, has attracted more and more attention recently (Lai et al. 2016; Li et al. 2015b; Wang et al. 2015; Zhao et al. 2016). With the development of exploitation techniques, some of the reservoirs, which were under the economic threshold, are now effective exploitation objectives. Tight reservoirs undergo more complex diagenetic processes than conventional reservoir, which control on the hydrocarbon potential of the reservoir. In these processes, physical effects, including compaction, decrease the porosity persistently. Chemical effects, including alteration of the minerals, precipitation of cements, and dissolution, have an impact on the reservoir quality in different ways. For instance, carbonate cements decrease the porosity. Kaolinite occupied original pores but create micro intercrystalline pores. Dissolution builds secondary pores or makes the redistribution of the original pores (Remy 1994; Worden and Burley 2003; Zhong et al. 2013). These factors impact on hydrocarbon potential directly with the controls on reservoir quality, particularly in the reservoir that is adjacent to source rocks, such as
