Reservoir Compaction Damage Evaluation in Hydraulically Fractured Oil Wells Incorporating Geomechanics

Abstract

ABSTRACT: The interaction between reservoir Biot's effective stress and pore pressure change is significant in stress-sensitive reservoirs. Consequently, coupling geomechanics and fluid flow to analyze pressure transient problems for stress-sensitive reservoirs may be necessary. Effective permeability loss monitoring in fractured oil wells is essential in maintaining economic reservoir productivity. This paper proposes a new analytical solution for the nonlinear hydraulic diffusivity equation (NHDE) in Biot's effective stress-sensitive reservoir fully penetrated by a fractured oil well. The proposed modeling considers the hydraulic fracture infinite and crosses the whole reservoir net pay. A new permeability stress-sensitive pseudo-pressure m(σ′) is presented, and the solution of the NHDE is derived in terms of this function. NHDE is expanded in a first-order asymptotic series, and an integro-differential solution coupled to a Green's function (GF) is used to represent the source/sink term. A set of pressure and permeability data from geomechanical literature is used and transformed into effective stress through Biot's equation. The effects of overburden, source/sink term, deviation factor, and Biot's coefficient are investigated to prevent severe permeability losses. Model calibration is performed using a numerical oil flow simulator named IMEX®, widely used in formation evaluation literature. The accuracy, ease of implementation, and low computational costs constitute the main advantages of the model addressed in this paper. Hence, it may be a valuable and attractive mathematical tool to identify flow regimes, providing permeability loss control and supporting well-reservoir management. 1 INTRODUCTION The production of petroleum reservoirs results in a decrease fluid pressure and an increase in effective overburden stress (Fernandes, 2022). As fluid production proceeds, the progressive increase in effective overburden load will, in turn, compact the reservoir rock and change its stress state (Soares and Ferreira, 2002; Soares et al., 2003). For reservoir rocks that are mechanically stable with fluid-flow properties e.g. the ones that permeability are not influenced by effective stress changes or are solely dependent upon fluid pressure change under a constant overburden load, pressure transient problems can be properly analyzed by conventional methods. Nonetheless, for stress-sensitive formations, coupling geomechanics with flow equations become the modeling more realistic. The economic production of either wells completed in low permeability reservoirs, e.g. shales or damaged wells has been possible because of hydraulic fracturing. In this scenario, estimating hydraulic fracture's geometric parameters and flow characteristics represents useful information for the calibration of fracture design methods and permits forecasting well flow behavior (Miskimins and Barree, 2003; Miskimins, 2019).