Abstract
The tight sandstone reservoirs of the Lower Silurian Kepingtage Formation are important exploratory targets for tight gas resources in the Shuntuoguole Low Uplift of Tarim Basin. How to evaluate tight sandstone reservoir is an urgent problem to be solved. In this study, we investigated the effects of diagenesis on the heterogeneity of tight sandstone deposits in similar sedimentary facies and established the relationship between the diagenetic facies and reservoir quality. Cores of the tight sandstone reservoirs of Lower Silurian Kepingtage Formation in Shuntuoguole Low Uplift are studied with thin section observation, SEM, XRD, and mercury injection. Quantification of diagenesis influencing porosity suggests that sandstone densification is mainly controlled by compaction, cementation, and hydrocarbon charging (bitumen charging), and the reservoir properties are effectively improved by dissolution, based on which 6 types of diagenetic facies are classified. Interpretation of the log data from individual wells with “K nearest neighbor” algorithm concludes that top and base of the upper member of Kepingtage Formation are believed to have favorably diagenetic reservoirs mainly falling in Type V; favorably diagenetic facies develop best in the lower member of Kepingtage Formation predominated by Types V and VI which mainly distribute in its top. Composite analysis of diagenetic facies, sedimentary facies, and porosity distribution shows that the favorable area of further exploration and development is east of Well SH903 and north of Well SH10. The quantitative identification of diagenetic facies based on logging information can provide reasonable results for the evolution of the tight sandstone reservoirs for a similar area in the Tarim Basin.
Highlights
The evaluation and prediction of the tight sandstone reservoirs have been hotspots for the petroleum industry (Guo et al, 2019; Ren et al, 2019; Xiao et al, 2019; Li et al, 2020)
Kepingtage Formation mainly consists of fine sandstone which contains litharenite
The quantitative calculation shows that the Kepingtage Formation is densified due to compaction, cementation, and hydrocarbon charging whereas its reservoir porosity is enhanced due to dissolution
Summary
The evaluation and prediction of the tight sandstone reservoirs have been hotspots for the petroleum industry (Guo et al, 2019; Ren et al, 2019; Xiao et al, 2019; Li et al, 2020). Diagenetic facies study focusing on the effects of diagenesis process on reservoir properties and pore configuration (Ochoa, 2010; Cui et al, 2017; Lai et al, 2018) is to effectively help hydrocarbon exploration and development by determining the spatial distribution of high-quality reservoir to provide reliable evidence for reservoir prediction (Maast et al, 2011; Meng et al, 2015; Li et al, 2019). Gray mudstone developed in the middle member (S1k2) and upper part of upper member (S1k3), constitutes a good cap layer in the region, forming several sets of favorable reservoir-cap assemblages in the study area (Figure 1B) They are the major exploration targets for Paleozoic clastic rock hydrocarbon exploration in the Shuntuoguole region (Xiong et al, 2013; Cai et al, 2014; Peng et al, 2018; Wang et al, 2020). The original porosity of the sandstone is restored through particle size analyzer (SFY-D Acoustic Screener and CG-1 Centrifugal Settling Particle Size Distribution Analyzer)
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