Integrated rock mechanics and drilling fluid design approach to manage shale instability

摘要

In recognising the petroleum industry's need for a technology to design optimal drilling fluid (weight, type and chemistry) to solve and manage shale instability problems, a collaborative project has been underatken to develop the technology which will provide the basis for state-of-the-art drilling fluid design criteria. The key drilling fluid-shale interaction mechanisms included in the study are mud pressure penetration, chemical potential and swelling-hydrational stress. Fundamental condepts, processes, models and a range of novel test equipment and procedures for laboratory simulation of the mechanisms were develoepd. The laboratory test results were used in the refinement and verification of the models. The verified models, which have been integrated in a wellbore stability analysis software, were used to conduct analyses to demonstrate the effects of shale and drilling fluid properties on time-dependent wellobre (in) stability. The understanding of the drilling fluid-shale interaction mechanisms and the development of the capacity to model them enabled the development of drilling fluid design charts. These charts, together with a shale property database and property correlations, provide a pragmatic and effective approach for deisgning optimal drilling fluids to manage shale instability efficiently.