Multiphase Flow in Highly Fractured Shale Gas Reservoirs: Review of Fundamental Concepts for Numerical Simulation

Abstract

Conventional hydrocarbon reservoirs, from an engineering and economic standpoint, are the easiest and most cost-efficient deposits to develop and produce. However, as economic deposits of conventional oil/gas become scarce, hydrocarbon recovered from tight sands and shale deposits will likely fill the void created by diminished conventional oil and gas sources. The purpose of this paper is to review the numerical methods available for simulating multiphase flow in highly fractured reservoirs and present a concise method to implement a fully implicit, two-phase numerical model for simulating multiphase flow, and predicting fluid recovery in highly fractured tight gas and shale gas reservoirs. The paper covers the five primary numerical modeling categories. It addresses the physical and theoretical concepts that support the development of numerical reservoir models and sequentially presents the stages of model development starting with mass balance fundamentals, Darcy’s law and the continuity equations. The paper shows how to develop and reduce the fluid transport equations. It also addresses equation discretization and linearization, model validation and typical model outputs. More advanced topics such as compositional models, reactive transport models, and artificial neural network models are also briefly discussed. The paper concludes with a discussion of field-scale model implementation challenges and constraints. The paper focuses on concisely and clearly presenting fundamental methods available to the novice petroleum engineer with the goal of improving their understanding of the inner workings of commercially available black box reservoir simulators. The paper assumes the reader has a working understanding of flow a porous media, Darcy’s law, and reservoir rock and fluid properties such as porosity, permeability, saturation, formation volume factor, viscosity, and capillary pressure. The paper does not explain these physical concepts neither are the laboratory tests needed to quantify these physical phenomena addressed. However, the paper briefly addresses these concepts in the context of sampling, uncertainty, upscaling, field-scale distribution, and the impact they have on field-scale numerical models.

Semi-Analytical Modeling of Fractured Horizontal Wells in Heterogeneous Formations Considering the Interference between Hydraulic Fractures

“…However, incorporating heterogeneity into numerical simulations of multistage fractured horizontal wells increases computational costs and raises the possibility such as nonconvergence and significant computational errors. These greatly limit the applicability of numerical simulations in real-time monitoring and quick production analysis (Seales, 2020). Semi-analytical modeling technique which integrates the advantages of analytical models and numerical simulations can offer production modeling at enough accuracy but with less computational cost and strong applicability to complex reservoir conditions (Ning et al, 2020;Yao et al, 2013)…”

From fluid flow to coupled processes in fractured rock: recent advances and new frontiers

“…Wang, 1991). Some more recent reviews deal with specific technical issues in fractured systems (Babadagli, 2020;Berkowitz, 2002;Berre et al, 2019;Dietrich et al, 2005;Seales, 2020). Other reviews touch, but do not focus on, flow and transport in fractured rock (Bense et al, 2013;Bonnet et al, 2001;Laubach et al, 2019;Ma, 2015;Meakin & Tartakovsky, 2009;Molz et al, 2004;Tsang & Neretnieks, 1998).…”

Investigation of the Effect of Fracturing Fluids on Shale Pore Structure by Nuclear Magnetic Resonance

“…Shale oil and gas, as the most potential strategic replacement resources, are also hot spots for exploration and development in the global oil field in recent years [1][2][3][4][5] fracturing technology has become an essential method to develop shale oil and gas effectively [6][7][8]. Hydraulic fracturing forms artificial fractures in the shale, accompanied by the intrusion of fracturing fluids into the shale matrix.…”