Experimental Model for the Determination of Hydration Potential of Niger-Delta Shales for Drilling Mud Design

Abstract

Maintaining stability between shale-mud interaction is a key factor towards improving safety and drilling efficiency while minimizing costs associated with drilling and production operations. The use of conventional Water Base Mud in drilling shale formation results in the adsorption of water associated with the drilling mud by the shale. Depending on the shale type, water adsorption may lead to various reactions such as swelling, cuttings dispersion, and increase in pore pressure creating wellbore instability to varying degrees. This research provides information on shale characterization of two Wells, A and B in Niger/delta region Nigeria and proposes the development of inhibitive Water based drilling fluids for the shale samples. It also provide results of the shale mineralogy, native moisture content, total organic carbon content, cation exchange capacity and the adsorption isotherm of the shale samples. From the analysis, the X-Ray Diffraction (XRD) results indicate that the shales are dominant of kaolinite. The result of the CEC falls within the Kaolinites group of 3 Meq/100g -10 Meq/100g according to Boulding and Ginn (2003). Polymeric fluids composed of varying Polymer/salt (KCl, NaCl and CaCl 2 ) concentrations was prepared and evaluated for the shales samples using dispersion test. The result of the analysis was used to design a mud selection template for drilling through shales. Recommendations for improving shale stability were described, based on the current understanding of shale stability.