The Effect of Stress-Dependent Permeability on Gas Production and Well Testing

Abstract

The effect of stress-dependent permeability on gas production and well testing in tight gas sands was studied by use of a modified pseudopressure that included stress dependence. This work assumes that information on cores is applicable to reservoir behavior. Because microcracks are the primary path for flow through tight-gas-sand cores, average stress-dependent permeabilities were found as an average over all crack orientations in a nonuniform stress field, with a horizontal stress only 0.6 times the vertical one. Initial in-situ permeabilities are found to be two to five times the values obtained from uniformly restressed cores. Stress de-. pendence decreases initial gas production by at most 30 %, with the loss increasing with reservoir depletion.Buildup tests yield reliable results for the properties at average reservoir pressure. Drawdown tests are more sensitive to stress effects and are much less reliable.

A fully coupled method to model fracture permeability change in naturally fractured reservoirs

“…The pressure dependence of matrix permeability occurs as the porosity and connectivity of pores decrease with the increase in effective stress. But the permeability change in tight gas reservoirs mainly results from the closure of microcracks with the increase of effective stress [13].…”

Impact of Stress-Dependent Matrix and Fracture Properties on Shale Gas Production

“…The dependence of matrix permeability on effective stress can be described as a poro-elastic effect which has an exponential form [11,12]: …”

“…The dependence of matrix permeability on effective stress can be described as a poro-elastic effect which has an exponential form [11,12]: We assume that the pore space in shale matrix consists of a series of parallel tubes with varying radii as shown in Figure 2. The intrinsic permeability, , of a cylinder tube with the radius of is given by [14]: Based on Equation (2), the apparent permeability (permeability measured by total flux) of the shale matrix system shown in Figure 2 can then be expressed by: Based on Equation (2), the apparent permeability (permeability measured by total flux) of the shale matrix system shown in Figure 2 can then be expressed by:…”

Transient thermo-poroelastic analysis of drilling-induced mechanical damage in nonfractured rocks

“…Zimmerman (1991) defined four types of compressibilities to relate pore and rock compressibilities to stress and pore pressure. These equations along with various stress-compressibility correlations (Ostensen 1986;Jones 1998;Liu et al 2009) are used to examine the variations of pore volume with effective stress changes. Moosavi et al (2012) utilized the compressibility correlation developed by Liu et al (2009) and introduced an equation for the changes of rock porosity with stress as follows…”