Creep Strain and Permeability Evolution in Cracked Granite Subjected to Triaxial Stress and Reactive Flow

Abstract

Fluid flow and fluid-rock interaction mainly take place in fracture network, consequently resulting in deformation and permeability variation of rock and deterioration of the wellbore performance. Mechanical-reactive flow coupling creep tests are performed on cracked granite under various confining pressures and acid and alkaline solution flows. The testing results show that the confining pressure and solution pH significantly influence the creep deformation, creep strain rate, and permeability. A primary creep stage and secondary creep stage are observed in all creep tests in this study; notably, the sample under a confining pressure of 10 MPa and acid solution injection undergoes creep failure for over 2700 hours. The acid solution has a more obvious influence on the creep behavior than that of the alkaline solution. With an increase in confining pressure, the total creep strain and creep strain rate in the samples gradually decrease during the injection of either solution. The permeability of the samples injected with either solution gradually deceases during the testing process, and this deceasing rate increases with the confining pressure. The scanning electron microscopy observations on the crack surfaces after the creep tests show that the surfaces of the fractures injected with the acid solution are smooth due to the dissolution of the matrix, while those injected with the alkaline solution include voids due to the dissolution of quartz. These experimental results could improve the understanding of the long-term transport and mechanical behaviors of wellbore.

Experimental Study on Influence of Chemical Corrosion on Mechanical Property of Fissured Granite

“…The contents of mica and potassium feldspar show a downward trend during the immersion process, and the decreasing rates of mass percentage are, respectively, 43.55% and 62.96% after chemical corrosion for 90 days. This phenomenon is attributed to the reaction of mica and potassium feldspar in an acidic environment (Equations (2) and (3)) [36,37]. However, the content of quartz and sodium feldspar slightly ascends with the increase of the immersed time, and the content of chlorite appears to fluctuate.…”

Investigation of Damage and Creep for Bedding’s Carbonaceous Slate with Chemical Erosion Effect

“…There has been considerable research on rock behavior under chemical erosion environments for rock specimens. For example, Zhang et al [ 19 ] conducted creep tests on cracked granite under various confining pressures and different chemical solutions, and they found that an acid solution has a more obvious influence on the creep behavior than that of an alkaline solution. Hu et al [ 20 ] proposed constitutive models to describe the mechanical responses of cement-based material subjected to a long-term chemo-mechanical coupling effect.…”