Horizontal Bedding Shale Geostress Calculation Method
Zhang Ligang*, Qu Sining, Yan Tie, Guan Bing
Identifiers and Pagination:Year: 2017
First Page: 143
Last Page: 151
Publisher Id: TOPEJ-10-143
Article History:Received Date: 15/08/2016
Revision Received Date: 11/01/2017
Acceptance Date: 14/02/2017
Electronic publication date: 31/05/2017
Collection year: 2017
open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Since the fragile anisotropy of shale, it is difficult to carry out laboratory experiments of geostress by shale cores. The existing geostress calculation model that is based on the homogeneous hypothesis also cannot meet the accuracy requirement. Therefore, it is necessary to establish the new geostress calculation model and test methods which are suitable for shale and provide the effective guidance for drilling and fracturing.
Firstly, the triaxial stress experiments were carried out. It showed that the mechanical parameters had strong difference between parallel and vertical bedding direction. The characteristics of transversely isotropic were shown obviously. Then, the geostress calculation model which considers the mechanical parameters of anisotropy in different direction was established by the constitutive relation of transversely isotropic materials. Finally, it was assumed that there is no relative displacement between formations in the process of deposition and the late tectonic movement; the prediction method for the shale geostress was established by the adjacent homogeneous formation. The sensitivity factors and influence laws were analyzed for the horizontal bedding shale geostress.
The results showed that the shale geostress was controlled by the elastic parameters of its own and the adjacent beds’.
The research can provide the theoretical basis and easy way for calculating the shale geosterss.