Shale experiment and numerical investigation of casing deformation during volume fracturing
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ICCESEN 2017
Shale experiment and numerical investigation of casing deformation during volume fracturing Xueli Guo 1 & Jun Li 1 & Gonghui Liu 1,2 & Wei Lian 1 & Yijin Zeng 3 & Qian Tao 3 & Xuefeng Song 1 Received: 2 January 2018 / Accepted: 16 November 2018 / Published online: 26 November 2018 # Saudi Society for Geosciences 2018
Abstract The casing deformation issues have occurred widely in Changning-Weiyuan National Shale Gas Demonstration Area. During multi-stage volume fracturing process, a large amount of fracturing fluid is injected into the formation, leading to tremendous change of stratum property and formation stress field. To assess the influence of shale formation on casing deformation, the acoustic velocity is measured to obtain the shale rock elastic modulus after saturation with water for different times. Then, the three-dimensional physical and finite element models are established using the stage finite element method considering transient thermal-pressure coupling. Shale anisotropy, shale stiffness degradation, and formation slip are taken into account to investigate the influences on casing deformation. Experiment results indicate that shale stiffness degrades dramatically after saturation with water for 24 h. Numerical simulations indicate that the shale modulus degradation mainly leads to large casing stress. Formation slipping not only causes excessive casing stress, but also causes large casing displacement. When slipping distance is larger than 15 mm, casing stress can reach up to the yield stress for P110 grade casing. Meanwhile, the casing deformation will be 14.95 mm, blocking the fracturing tools into the well bottom. Shale anisotropy has a minor influence on casing deformation. Keywords Casing integrity . Stage finite element method . Volume fracturing . Formation slipping . Stiffness degradation . Anisotropy PACS 89.30.aj 89.30.an
Introduction Horizontal well drilling and multi-stage stimulated reservoir volume are two key techniques for the development of shale gas
This article is part of the Topical Collection on Geo-Resources-EarthEnvironmental Sciences * Xueli Guo [email protected] * Jun Li [email protected] 1
College of Petroleum Engineering, China University of Petroleum– Beijing, Beijing 102249, China
2
Beijing University of Technology, Beijing 100124, China
3
Sinopec Engineering and Technology Research Institute, Beijing 100101, China
(Sugden et al. 2012). During multi-stage fracturing process, a large amount of fracturing fluid is injected into the borehole with high pump rate and pressure (Zhou et al. 2015). High pressure and complex downhole conditions will increase the risk of casing deformation (Davies et al. 2014; Rocha-Valadez et al. 2014). From 2009 to 2016, Petro-China has completed 101 fracturing wells in the Changning-Weiyuan National Shale Gas Demonstration Area, including 90 horizontal wells. The number of casing deformation well is 32 with 47 deformation points, accounting for 31% of all the fracturing wells (Yan et al. 2017). When a large amou
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