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Title: Brittleness evaluation of the shale reservoirs in Wufeng and Longmaxi formation in the DS Area, southeast Sichuan, China
Authors: Luo, Zhenhua
Qin, Qirong
Li, Hu
Zhong, Cheng
Dai, Xiaojun
Keywords: Shale reservoirs;Brittleness;Mineral composition;Elasticity parameters;The Wufeng and Longmaxi Formations;DS area
Issue Date: Oct-2018
Publisher: NISCAIR-CSIR, India
Abstract: Present study analyzed the brittleness of shales in the Wufeng and Longmaxi Formations based on mineral composition and elasticity parameters, using a combination of core samples, well logging, X-ray diffraction, and mechanical tests. Fracturability of the two formations was then assessed. The results show that, from the perspective of mineral composition, the brittleness of shales in the Wufeng and Longmaxi Formations is affected mainly by brittle minerals like quartz, feldspar, and pyrite. Shale samples ranged from 36.2% to 62.7% in brittleness index (BRIT) based on mineral composition, with an average of 48.6%. Mechanical tests under different confining pressures revealed three failure modes of the shale samples: splitting, bidirectional shear, and unidirectional shear. Their values of BRIT based on elasticity parameters were between 40.7% and 61.6%, averaging 52.6%. Compared to other gas-producing shale formations, the Wufeng-Longmaxi shales in the study area have above-average BRIT levels and high fracturability. There are good correlations between their brittle mineral content, BI, and total organic carbon (TOC). At well DY1, the strata at depths of 2027 to 2054.2m show high brittleness with BRIT values exceeding 50%.
Page(s): 1959-1968
ISSN: 0975-1033 (Online); 0379-5136 (Print)
Appears in Collections:IJMS Vol.47(10) [October 2018]

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