Advances in Mud Design and Challenges in HPHT Wells

Abstract

Abstract The world's energy demand is rising and favourable economics has allowed oil companies prospect and drill for oil in deeper, more challenging frontiers (which are prone to high pressures and high temperatures) than ever before. There are vast reserves of hydrocarbons in these remote locations that promise to bridge the gap between demand and supply for energy. However HPHT prospects can be a formidable challenge. The mud weight (which is higher for HPHT wells) must be accurately controlled because of the very narrow mud weight windows. This high mud weight requirement leads to problems of high solid loading and barite sag. Technology to effectively monitor downhole pressure and temperature conditions is not well developed. Rig crews need to be adequately trained to adopt best practices in HPHT drilling to minimize the risk of well control issues. In this study, the conventional practices and procedures in mud design were studied and analyzed. Advances in mud design were highlighted and case studies of some HPHT wells in regions around the world were reviewed to learn the lessons and best practices that led to their success. Many of the conventional practices were found to be inadequate for HPHT drilling. Rigorous laboratory testing is necessary to generate detailed engineering guidelines for HPHT drilling fluids. Furthermore, a standard temperature concept used for controlling the surface mud weight was defined. The results of the new approaches to mud design and practices have been phenomenal. The importance of a stable mud system, detailed drilling program, best practices and correct field execution are fundamental. With the new approaches, many HPHT wells have been successfully completed in a cost effective manner and with no well control incidents recorded.