Experimental studies of physicochemical reactions between water-based drilling fluids and argillaceous rock formations

摘要

This thesis relates to wellbore stability problems in shale formations. Two test methods were investigated comprising the dynamic pellet test (DPT) and the shale membrane test (SMT). These methods focus on borehole instability induced through physicochemical reactions between shale and water-based drilling fluids. The main emphasis was put on the methods, and aspects of shale/fluid interactions were also investigated in order to evaluate the inhibiting effects of fluid additives. The calculation procedure for DPT-index parameters has been based on modified test procedure. The original indices have been redefined. Two new indices, the Adsorption Index and the Alteration Index, have been introduced and broaden the evaluation potential of the test method. The repeatability of the DPT has been improved. The SMT is aimed to estimate the ion-selective properties of a shale and the influence of osmotic flow on the transport of mud filtrate. For these purposes, a theoretical model based on Irreversible Thermodynamics has been derived and test equipment has been designed and built. Ion transport processes in shale were investigated by means of this method.