An Experimental Study on Shale-Fluid Interactions to Help Drill Stable Shale Formations

Abstract

AbstracDrilling stable boreholes in shale formations is a challenging task due to the potential interactions of clay-rich shales with aqueous phase of drilling fluids. The objective of this paper is to look into some testing techniques utilized to characterize shale rock samples and assess the reactivity, recommend a strategy and best practices to overcome the wellbore instability problems when drilling shale formations.Wellbore instability associated with drilling shale formations is a major source of non-productive time in drilling operations. Inhibiting shale-fluid interactions and minimizing the scope of time-dependent shale problems are essential to mitigate this challenge. The solution is of two-fold: mechanical and chemical. This paper addresses the chemical aspects of the problem and recommends a novel type and combination of shale inhibitors to use in drilling.Different testing techniques were employed to assess the shale reactivity with different types of drilling fluids. After characterizing the shale samples in terms of mineralogy, petrography and inhibition testing has been carried out to reveal the reactivity extent of the shales. Dispersion test predict the shale-fluid interactions to help in optimizing the drilling fluid formulations to drill those shale formations. Two shale inhibitor combinations were tested against shale samples with different characteristics and clay mineralogy to develop a semi-universal type of inhibitive drilling fluid formulation.