Experimental Study On Effective Stress Of Permeability Of Zhenjing Sandstone Reservoir

Effective stress for permeability of reservoirs is still not a definite expression. In the present study, based on the previous theoretical and experimental study, tests of effective stress coefficient for permeability are carried out on low-permeability clayey-sandstones from ZhenJing reservoir. Major work and conclusions achieved are as follows:(1) Models of effective stress coefficient for permeability for fractured rock and matrix rock are investigated, and ranges of effective stress coefficient for permeability in clay-free rocks and clayey rocks are gained;(2) Five analysis methods for experimental data from the test of effective stress for permeability are summarized, and application conditions and advantages for each method are analyzed;(3) Scanning Electron Micrograph, Rock Slice Micrograph, X-ray diffraction and Mercury injection experiments are performed on eight low-permeability sandstones from ZhenJing reservoir to research on microscopic features;(4) Permeability measurements are performed on eight samples with transient pulse technique, when confining pressure is constant and pore pressure is changed, and nitrogen is the pore fluid;(5) Tests of effective stress for permeability are carried on two fractured samples with nitrogen, distilled water and salt water as pore fluid, respectively;(6) The effective stress coefficient for permeability is obtained with Bernabe’s method, two element linear regression and response-surface method, and the reasonable values are chose with the consideration of microscopic features and testing principle;(7) The study of stress sensitivity for permeability is evaluated with three methods on the basis of seasoning process, constant confining pressure cycles and effective stress tests for permeability;The effect of different fluid on the effective stress coefficient for permeability is mainly discussed in this study. The understanding for the mechanism of rock deformation is further, and provides a scientific guide for the evaluation of stress sensitivity for permeability, wellbore stability and rational exploitation in low-permeability reservoirs.