Anisotropic Porochemoelectroelastic Solution for an Inclined Wellbore Drilled in Shale

Abstract

The porochemoelectroelastic analytical models have been used to describe the response of chemically active and electrically charged saturated porous media such as clay soils, shales, and biological tissues. However, existing studies have ignored the anisotropic nature commonly observed on these porous media. In this work, the anisotropic porochemoelectroelastic theoiy is presented. Then, the solution for an inclined wellbore drilled in transversely isotropic shale formations subjected to anisotropic far-field stresses with time-dependent down-hole fluid pressure and fluid activity is derived. Numerical examples illustrating the combined effects of porochemoelectroelastic behavior and anisotropy on wellbore responses are also included. The analysis shows that ignoring either the porochemoelectroelastic effects or the formation anisotropy leads to inaccurate prediction of the near-wellbore pore pressure and effective stress distributions. Finally, wellbore responses during a leak-off test conducted soon after drilling are analyzed to demonstrate the versatility of the solution in simulating complex down-hole conditions.

Numerical Simulation Analysis of Wellbore Stability in Weak Interlayer of Igneous Rock

“…To investigate wellbore stability in weak interlayer igneous formation, the following fundamental assumptions were made: the igneous rock behaves as an isotropic elasticplastic material; he presence of weak planes are taken into account as transverse isotropy in terms of strength and deformability; the fluid within the borehole is considered incompressible; changes in formation and drilling fluid temperature do not affect the direction of the borehole [16][17][18]; and the stress distribution near the borehole adheres to Saint-Venant's principle.…”

Large‐scale experiments of the borehole instability on shale formation influenced by drill pipe rotation

“…Both isotropic and anisotropic of shale rock were considered. Based on the basic theories established a long time before, researches now focus on borehole stability under dynamic loading conditions, and the influence of anisotropic strata, including anisotropy of sedimentary tectonics, strength parameters, and elastic parameters . Using these contributions, more accurate predictions were achieved.…”