Performance Comparison of Vertical and Horizontal Hydraulic Fractures and Horizontal Boreholes in Low Permeability Reservoirs: A Numerical Study

Abstract

ABSTRACT A single/two-phase, multi-dimensional, finite-difference numerical reservoir simulator, which had been validated through history matches against field data, was used to investigate and compare the production performances of horizontal wells and hydraulically stimulated vertical wells. In the case of vertical wells performance characteristics of vertically and horizontally fractured systems were studied. In the mathematical formulation of the transport problem a multi-mechanistic flow mechanism which is obtained by superposition of the Darcian and Fickian flow components is implemented to describe the flow of gas in tight porous media. The non-linear system of equations resulting from the finite-difference approximation are solved by using fully implicit generalized Newton-Raphson procedure. In order to verify the accuracy of the hydraulically stimulated vertical well formulations, the results generated by the numerical model were compared against the existing analytical solutions in the literature. These comparisons exhibited excellent agreements between the numerical and analytical solutions. Low permeability, single-phase and two-phase (gas-water) natural gas reservoirs have been selected as the target of this study. A series of numerical exercises in a systematic manner were conducted by sifting through the parameters associated with the reservoir characteristics and stimulation strategies in order to understand those which most significantly affect the production from low permeability gas reservoirs. These parameters are reservoir thickness, permeability, isotropicity of the formation, penetration lengths of horizontal boreholes and hydraulic fractures.