Brittleness Evaluation in Shale Gas Reservoirs and Its Influence on Fracability

Yapei Ye, Shuheng Tang and Zhaodong Xi
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Yapei Ye: School of Energy Resources, China University of Geosciences, Beijing 100083, China
Shuheng Tang: School of Energy Resources, China University of Geosciences, Beijing 100083, China
Zhaodong Xi: School of Energy Resources, China University of Geosciences, Beijing 100083, China

Energies, 2020, vol. 13, issue 2, 1-22

Abstract: The brittleness index ( BI ) is a key parameter used to identify the desirable fracturing intervals of shale gas reservoirs. Its correlation with fracability is still controversial. There have been a variety of methods proposed that can estimate BI. The brittleness evaluation method based on stress-strain curves according to the energy-balanced law is the most suitable and reliable in this study. Triaxial compression test, optical microscopy and scanning electron microscopy (SEM) observation, and X-ray diffraction analysis (XRD) were performed on nine drill core samples from well SY3 located in the peripheral regions of Sichuan Basin, China. These tests further evaluated several commonly used methods (brittleness indices based on rock elastic parameters, rock mineral compositions) and determined the relationship between brittleness, rock elastic parameters, and the content of minerals. The results obtained indicate that for sedimentary rocks, a higher Young’s modulus reduces the brittleness of rock, and Poisson’s ratio weakly correlates with brittleness. Excessive amounts of quartz or carbonate minerals can increase the cohesiveness of rock, leading to poor brittleness. Furthermore, the most suitable fracturing layers possess a high brittleness index and low minimum horizontal stress.

Keywords: brittleness; brittle minerals; Young’s modulus; Poisson’s ratio; fracability; in-situ stress (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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