Innovative Process to Set Record Length of Cement Plug in an Offshore ERD Well

Abstract

From an operator’s standpoint, well abandonment is viewed as a costly, but necessary, process that does not typically add value. The service company is tasked with performing the abandonment operations safely, efficiently, and economically without issues. This paper presents a technique for the placement of an extremely long, single cement plug using sacrificial pipe and a special release tool under conditions that significantly exceeded the limits attempted by the industry previously. The plug and abandonment (P&A) process with conventional balanced-plug methods presents many challenges, particularly in the case of multiple cement plugs in a long, extended-reach drilling (ERD) section covering several permeable intervals. The most common issue is cement contamination, which results in poor zonal isolation caused by insufficient slurry strength. A special downhole tool was used for this operation, which provided a reliable solution for placing one long cement plug instead of placing up to 10 balanced plugs, thereby decreasing operational risks and saving rig time. This fit-for-purpose tool is torque-capable, which enabled running sacrificial pipe in a wellbore with high inclination, where right-hand torque up to 30,000 lbf-ft was necessary to reach TD. Equipment could be drillable or nondrillable; in this case, a nondrillable solution consisting of 7-in., 26-ppf steel casing used as the sacrificial pipe. A dart was used for the displacement of cement through the pipes and activation of the releasing mechanism to place the sacrificial pipe in the hole. The P&A operation was performed on a 9750-m MD ERD well with an inclination of 78 to 84° in the abandonment interval of an offshore drilling rig in Russia. One cement plug covered 2550 m of sacrificial pipe, isolated several zones, and saved two days of rig time. This procedure did not require pulling pipe out of cement. The risk of cement contamination was significantly diminished, and further operations could be performed immediately after the release. An added benefit was the reduction in contaminated mud that would require treatment and disposal compared to the multiple conventional balanced-cement plug techniques. Tool manufacturers are challenged to continue developing higher torque capacity tools to meet the demands of future ERD P&A activity.