Sensitivity Analysis of Near-Wellbore Fracture Curving in Horizontal Well
A three-dimensional (3D) model is presented for initiation and propagation of hydraulic fracture in near-wellbore region of horizontal well, investigating the sensitivity of fracture curving to relevant mechanical and reservoir properties, far-field stress conditions, operating data and azimuth angle of horizontal wellbore. The new model is based on a fully coupled pressure/deformation extended finite element method (XFEM) capable of activating arbitrarily oriented discontinuities in both displacements and pore pressure, considering the flow of the fracturing fluid that enters and leaks through the fracture surfaces, the flow of the pore fluid within the pores, the rock deformation, and the fracture evolution. Also, the corresponding governing equations for each of the coupled processes, details of 3D model setup, and assumptions involved in near-wellbore hydraulic fracture curving within Abaqus are provided in this paper. Compared to other analytical or 2D numerical solutions, this methodology described here provides a way to quantify the magnitude of fracture radius of curvature and width variation along the turning fracture correlated to controlling parameters. Our results demonstrate that fracture initiates from non-ideal orientation may extends outwards and turns toward its preferred direction relative to the far-field stress as previously published experimental results. It is shown that both maximum horizontal in situ stress contrast and leakoff coefficient of fracture surfaces are negatively correlated to the radius of fracture curvature that as either of them increases, the radius of curvature will decrease. On the contrary, Young’s modulus, fluid viscosity, injection rate, and azimuth angle of horizontal wellbore are positively correlated to the radius of fracture curvature. Among these key parameters, the maximum horizontal in situ stress contrast plays the most important role and compared to viscous fluid, fracture curving is more sensitive to injection rate. The sensitivity of fracture curving radius to various properties obtained in this numerical procedure would allow operators to optimize the treatment design for proper fracture tortuosity remedy in the near-wellbore region of horizontal well in tight oil and gas reservoirs.
KeywordsSensitivity Near-wellbore Fracture tortuosity Fracture curvature Horizontal well
The author would like to acknowledge the financial support provided by State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development.
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