Fractured Wellbore Stress Analysis: Sealing Cracks To Strengthen a Wellbore

Abstract

TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractWellbore pressure containment, the maximum pressure that a wellbore can withstand before whole drilling mud begins to leak off into formations, defines the upper bound of the mud weight window. Drilling costs are heavily associated with this mud weight window in terms of expensive casing programs or nonproductive time because of narrow mud weight windows.Although various methods have been developed using different materials for curing mud losses, the performance has been poor as a result of the lack of engineering design for the materials and placement techniques. The commonly used "trial and error" approach reveals inadequate understanding of the challenge, although a number of advances have been accomplished in recent years.In this paper, results are reported from a fundamental study aimed at revealing the basic physics that control the success of treatments strengthening wellbores or widening the mud weight window. It first focuses on reviewing and identifying factors that can reduce the upper bound of this mud weight window, followed by analysis of wellbore strengthening that can increase this upper bound of mud weight window, especially by sealing hydraulically conductive cracks at the wellbore.