Jinchang Sheng

Stress Analysis of a Borehole in Saturated Rocks Under in situ Mechanical, Hydrological and Thermal Interactions

Abstract A novel approach is developed to represent coupled thermal-hydraulic-mechanical (THM) behavior of porous systems that incorporates the non-isothermal free and forced convection of a single component fluid in a non-boiling thermoelastic medium. The three-way simultaneous coupling between the THM triplet is currently linear, but no restriction is placed on incorporating material nonlinearities. The coupled PDEs are solved in space by grid-adaptive finite elements. The model is validated against solutions for linear non-isothermal consolidation of a column. We demonstrate the utility of the model by analyzing the behavior of a deep wellbore in a themoelastic medium circulated by a pressurized, but chilled fluid. Model results illustrate the significant importance of the cross-couplings between individual THM processes for the evaluation of wellbore stability.

Simulation of Progressive Borehole Failure at Multi-Lateral Junctions

Abstract Multi-lateral junction failure, one of the challenges introduced by employing multi-lateral technology to improve production of oil and gas wells, has imposed significant impacts on the employment of this new technology. Therefore, a powerful computer simulator is required for analyzing the issues of both fracturing and collapse at the multi-lateral junction. In this study, we present such a simulator, Rock Failure Process Analysis (RFPA2D), in which rock is assumed to be heterogeneous at a mesoscopic level and an elastic-damage based constitutive law is used to describe the constitutive law of elements. The applicability of RFPA2D to simulate progressive borehole failure processes at junction locations is demonstrated through (1) successful comparisons of the simulated distribution of stress concentration factors with the known analytical solutions for the elastic case; (2) successful comparisons of the simulated borehole failure patterns with experimental observations reported in previous studies; and (3) simulations of progressive borehole failure processes under a variety of geometrical and loading conditions.