Novel Method to Drift and Pressure Test a Casing String without Intervention

Abstract This paper describes the first practical application, to the authors’ knowledge, of using longstring casing wiper plugs to interventionlessly drift, wipe and pressure test a casing string during installation, and then subsequently cementing the casing string in place. While installing certain critical wells the completion casing string must be examined for leaks and internal obstructions that could compromise future operations. Up until now the casing string has been drifted and pressure tested during installation by using multiple slickline and retrievable bridge plugs runs. This current practice has certain limitations, primarily the capability of the slick line, which is negatively affected by high mud weight, the slick line maximum over-pull load rating, and the well trajectory. This was a 17,986 ft long/deep vertical well with a bottom hole temperature of 340°F. This new system eliminated the need for multiple slickline, and retrievable bridge plug runs, reduced the entire shoetrack length to less than 6 feet, and included a new type of high-performance one-way check valve in the float equipment. The new system saved more than 24 hours of rig time compared to the previous method. Three rupture disk longstring wiper plugs were used, each having drift gauge outer diameter to drift and pressure test the casing to 5,000 psi in three separate intervals. A fourth wiper plug with solid core was dropped behind the cement to wipe the casing clean during the cement job. All four longstring wiper plugs landed (bumped) as expected in the integrated shoetrack tool at the bottom of the casing string. The integrated shoetrack tool had four one-way backpressure valves, each rated to 15,000 psi differential backpressure qualified according to API-10F. Once the last wiper plug landed (bumped), 893 bbls of fluid had been circulated through the integrated shoetrack tool, and the floats were confirmed to hold. This paper presents a new and novel method to drift, and pressure test a casing string using rupture disk longstring wiper plugs to drift and wipe the casing. The plugs were circulated down the casing string until they land at the end of the completion string, into a profile in a unique integrated shoetrack tool, at which point the casing string was pressure tested. After achieving a successful pressure test, pressure was further increased until the rupture disk in the rupture disk longstring wiper plug burst, at which point circulation was restored. Once the entire casing string had been run in hole and it had been drifted and pressure tested, the cement job was performed. The cement was displaced by a solid core longstring wiper plug. The solid core wiper plug latched and sealed on the last previous longstring rupture disk wiper plug at the end of the cement displacement operation.