3D Modeling of Fracture Propagation Using Coupled Variational Phase Field and Porous Media Multiphysics
Authors: Almetwally A. G. , Wheeler M. 
Published: September 2023

ABSTRACT
Hydraulic fracturing is a vital tool in enhancing oil and gas production and geothermal energy. The fracturing process entitles the effects of the multiphysics on the final fracture configuration. It is important to characterize the fracture attributes including width, height, and conductivity to accurately predict the recovery response to the exploitation activities. Finite element simulation is used to quantify the multiphysics effects of the fracturing operational parameters. Coupling these physics is computationally expensive and lacks experimental and analytical validation. There is a need for efficient coupling algorithms and discretization schemes that reduce computational costs and ensure simulation accuracy. Therefore, in this paper, we extend the fixed stress split approach for simulating the fully coupled fracturing multiphysics to accelerate their simulation. The Enriched Galerkin discretization scheme is used as a mass/energy conservative scheme that can capture the abrupt jump in pressure and temperature at the matrix-fracture interface. The variational phase field was used to simulate fracture initiation, propagation, and fracture width estimation. Two analytical problems are simulated along with a 3D triaxial geothermal experiment capturing the pressure-induced fracture propagation tracked by micro-seismic events. The matching results show the proposed fracture simulation framework's capabilities and suitability for field-scale applications.

INTRODUCTION
Hydraulic fracturing is a technique used in the petroleum and geothermal industries to extract oil and natural gas from shale and other tight rock formations, as well as to enhance the production of geothermal energy. This technique has enabled the extraction of previously inaccessible reserves, significantly increasing global energy production. The process involves injecting a mixture of water, proppant, and chemicals into a wellbore to create fractures in the rock formations. These fractures, also known as "proppant-laden fractures," allow for the easier flow of oil and natural gas from the rock to the wellbore, thereby increasing production (King, 2010, 2012). In the geothermal industry, hydraulic fracturing is used to create pathways for water to circulate and absorb heat, thus increasing the amount of geothermal energy that can be produced (Jia et al., 2022). Studies have examined the economic and environmental impacts of hydraulic fracturing in the petroleum industry, with one finding that the widespread adoption of this technique in the United States has contributed to a significant increase in domestic oil and gas production, leading to lower energy prices and increased economic activity (Aguilera et al., 2014; Lum et al., 2001). In the geothermal industry, hydraulic fracturing has been demonstrated to be an effective method for increasing the production of geothermal energy from a given reservoir (Kumari et al., 2019). However, the long-term effects of hydraulic fracturing on geothermal reservoirs are not fully understood and require further research.