Increasing the Wellbore Pressure Containment in Gulf of Mexico HP/HT Wells

Abstract

This article discusses the application of two wellbore pressure-containment integrity (WPCI) treatments that substantially increased the pressure-containment integrity in 852 ft of open hole in the last sidetrack for a production hole section. These treatments ultimately made it unnecessary to set pipe early, which could have jeopardized the commercial discovery of the lower gas sand. Earlier sidetracks attempted unsuccessfully to bypass the loss/flow problems that would not allow drilling ahead and increasing the 18.0-lb/gal mud weight (MW) to drill into a high-pressure zone on a deep, high-pressure/high-temperature (HP/HT) well in the western Gulf of Mexico shelf in offshore Louisiana. Various conventional lost-circulation material (LCM) treatments were used without success, increasing the hole's pressure containment. The WPCI treatments raised the leakoff test (LOT) across the entire 852 ft of open hole to 19.1 pounds per gallon equivalent (ppge) vs. the lower LOT of 18.26 ppge before the first WPCI job. LOTs were performed before and after each of the two WPCI treatments to measure improvement in the open hole's pressurecontainment integrity. This LOT data indicated that apparent fracture gradients can be simultaneously increased in multiple rock layers with various types of weak formations exposed in long, open holes by inducing near-wellbore stress fields created from WPCI treatments (Webb et al. 2001; Kelley Sweatman and Heathman 2001; Sweatman et al. 2001; Sanad and Waheed 2003). This approach can then allow use of increased mud weights (MW) and drilling pressures to prevent excessive gas influx from high-pressure sands without lost circulation (LC) in adjacent weak zones. Also discussed are the WPCI treatment design and job procedures, including treatment optimization by the analysis of data from openhole wireline/logging while drilling (OHWL/LWD) logs, cuttings lithology, fracture-seal location indicators (torque on bit [TOB]/weight on bit [WOB]), and before/after LOT pressures. Real-time operations (Kulakofsky et al. 2002) (also described) enabled remote expert analysis and support so that wellsite personnel could: (1) interpret formation characteristics for optimized treatment design, and (2) analyze treatment pressure/rate data for selective placement of WPCI sealants.