--> The Effects of Reservoir Heterogeneity on Shale Gas Accumulation and Production – Case Study From Ordovician Wufeng-Silurian Longmaxi Marine Shale in the Sichuan Basin, China

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The Effects of Reservoir Heterogeneity on Shale Gas Accumulation and Production – Case Study From Ordovician Wufeng-Silurian Longmaxi Marine Shale in the Sichuan Basin, China

Shu Jiang1, Xianglu Tang2, Zhenxue Jiang2, Lei Chen3, Shengxiang Long4 and Zhiliang He4

1 Energy & Geoscience Institute, University of Utah, Salt Lake City, Utah, United States
2 Unconventional Natural Gas Research Institute, China University of Petroleum, Beijing, China
3 Southwest Petroleum University, Chengdu, China
4 Sinopec Petroleum Exploration and Production Research Institute, Beijing, China

April 3, 2017 Monday 9:05 A.M. AAPG Annual Convention and Exhibition, Houston, Texas

Abstract

Heterogeneous nature of the Ordovician Wufeng-Silurian Longmaxi shale reservoir in the Sichuan Basin in China is characterized through the analysis organic matter content (TOC), mineral content, porosity, permeability, in situ gas content, natural fractures, and beddings based on the detailed core description and lab measurements. The qualitative and quantitative methods for heterogeneity characterization are proposed to systematically study the shale heterogeneity within the sequence stratigraphic framework. The normalized shale heterogeneity index (SHI) is employed to quantitatively characterize the variations of key shale properties in time and space and the shale resource index (SRI) is adopted to gauge the shale gas accumulation. Statistics of the tested data indicates that the TOC plays the most important role in the SHI among the geochemistry, mineralogy, petrophsyics, sedimentation, and structure properties. Pearson Correlation statistics reveals the positive relationship between in situ gas content and TOC, porosity, and permeability and negative relationship between in situ gas content and clay content and bedding frequency. The moderate density of natural fractures will be favorable for shale gas accumulation, while the absence of natural fractures and abundant natural fractures will be unfavorable for shale gas accumulation. The TOC has the highest weigh value among they key reservoir properties influencing the shale gas accumulation. The transgressive systems tract (TST) with high TOC, high biogenic quartz content, high porosity and permeability is more favorable for gas accumulation. The SHII, SRI, and shale gas production rate generally have positive relationships and they all decrease from the tectonically stable area inside the Sichuan Basin to tectonically active area outside the basin, which implies that the heterogeneity has positive effects on shale gas accumulation and production and tectonic activities result in the disruptions of shale gas accumulation and decrease in production.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017