For exploration and development drilling of deepwater prospects in the Gulf of Mexico, operators have primarily utilized a high salt (20 percent w/w), partially hydrolyzed Polyacrylamide (PHPA) mud system. This system has been used for many years as one of the most inhibitive water-based mud systems commercially available to the industry. Observations from both the laboratory and the field indicate that shale is stabilized by the presence of PHPA. In this report, laboratory evidence is presented which investigates possible mechanisms by which PHPA influences cuttings as well as wellbore stability. In addition, results are presented which dictate requirements for maintaining an effective concentration of PHPA for shale stabilization and the impact of thinners on shale stabilization.

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