Effective Zonal Isolation Straddle Deployment in a Slim Deviated Well using Electric Line Tractor / Stroker Combination

Abstract

Due to sand production coming from the upper zone of a multizone monobore gas well completion, the well production had to be choked back to a flow rate below the well's maximum sand free rate (MSFR). This resulted in suboptimal production. A straddle packer assembly was installed across this upper zone, which isolated the sand production and, therefore, enabled the choke to be removed and the well production to be increased to its true, optimal capacity. Several previous attempts to deploy and install the straddle components at their required depth using the prescribed slickline deployment method proved unsuccessful, because of hold ups that occurred while running in hole—due to a well trajectory of 72 degrees deviation and 4.579 deg/100 ft dog leg severity, coupled with the small tubing inside diameter (ID) associated with the slim 3 ½ in. completion. Furthermore, it was found that insufficient forces were available via slickline deployment to execute the related stabbing, setting and release actions required during in-well straddle component installation, because of the limited jar down weight available and safe working load limits on the slickline at the setting depth. As a result, a slim 2 ⅛ in. electric line tractor was utilised, in combination with a 2 ½ in. electrohydraulic linear actuator (stroker). The tractor conveyed the various straddle packer and spacer elements (straddle tubes) to depth and the stroker installed these components in the well to confirm their engagement and to ensure their controlled and confirmed release. Being bi-directional by design, the stroker provided both the upward and downward forces required for component installation—stabbing, setting, and pin shearing to release. The stroker was also available in the toolstring in case of any inadvertent tool sticking encountered while running in hole due to the well trajectory and produced sand debris. A system integration test (SIT) was meticulously planned and executed by the relevant operator and service company representatives before the operation. It was used to confirm the stroker's capability to stab and set the straddle tube into the lower packer and to shear the running tool used to install the straddle tubes and upper packer. This included the installation of straddle tubes into the lower packer section, done in a horizontal configuration and completed using higher setting and pulling forces than those expected during the actual job to ensure more than adequate forces would be available. The operation was executed successfully following the newly defined program, applying the lessons learned from the SIT. A total of four runs were carried out using the combined tractor/stroker deployment string configuration without any in-well deployment issues—the straddle component installation completed with 100% operational efficiency. Following this, the well was put back onto production and the production rate increased from approximately 1 million standard cubic feet per day (MMscf/D) to 3 MMscf/D, with no sand production observed at surface. Having not been done before, this methodology proved to be a successful option for the operator for straddle packer assembly deployment in deviated slim wells.