During oil extraction, the permeability of reservoir changes due to the decrease in the pressure of reservoir and the increase in effective stress. Many researchers have studied the stress sensitivity of reservoir, and reservoir models taking it into account.
Previous researchers considered the influence of stress sensitivity and elastic outer boundary on the flow characteristics of fluids in reservoirs, and solved problems by considering stress sensitivity and elastic outer boundary conditions when analyzing the flow characteristics. However, they failed to analyze the stress sensitivity and elastic outer boundary conditions at the same time, so there are still errors in well test analyses.
Han Song Guk, a researcher at the Faculty of Earth Science and Technology, has developed a well test analysis model of a dual-porosity reservoir with stress sensitivity and elastic outer boundary conditions in simultaneous consideration, and obtained its solution.
Based on the consideration of stress sensitivity and elastic outer boundary conditions, he first formulated a seepage differential equation in the dual-porosity reservoir considering wellbore storage and skin factor, and defined dimensionless variables to facilitate the derivation of the solution. This mathematical model is strong in nonlinearity, so he applied the Pedrosa’s transformation and perturbation transformation to eliminate the nonlinearity of the model. Then, he performed the Laplace transformation to obtain an analytical solution of the well test model in the dual-porosity reservoir considering elastic outer boundary and stress sensitivity in the Laplace space, and applied the Laplace numerical inversion to obtain dimensionless pressure and pressure derivative model curve in the wellbore.
For more details, please refer to his paper “Analysis of Fluid Flow Characteristics for Stress-Sensitivity Dual-Porosity Reservoir considering Elastic Outer Boundary” in “Journal of Clinical Research and Reports” (SCI).