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Brittleness Index Evaluation Based on Micromechanics Model for Longmaxi ShaleNormal access

Authors: L. Wang, Y. Zhang, W. Wu, N. Zhang and C. Zhao
Event name: 81st EAGE Conference and Exhibition 2019
Session: Poster: Unconventional A
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201901108
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 524.29Kb )
Price: € 20

Summary:
Shale gas reservoir is tight with very low permeability. In order to commercially develop shale gas, hydraulic fracturing is essential to improve the permeability. Evaluation of the brittleness index for shale gas is significant in choosing the available zone for hydraulic fracturing. In this paper, multi-scale micromechanics model (Mori-Tanaka) is used to calculate the effective elastic parameter for the evaluation of the brittleness index Ba. Then Ba is compared with the brittleness index Ba_d and Bm, which are based on the dynamic mechanical parameters and mineral content, respectively. Finally, Partial least squares regression (PLS) is used to study the relationship between Ba and mineral components. Results show that Bm increases from the top to the bottom of the interval. Besides, Ba has the same trend with Bm, but Ba_d does not. Compared with Bm, Ba can highlight the ductile and brittle areas, which makes the evaluation of brittleness index effective. Analysis shows that only Quartz and pyrite have positive correlation with Ba among all minerals. Quartz and clay mineral are the most important factors to increase and reduce the brittleness index of shale, respectively.


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