Case History: Extended-Stroke Downhole Power Unit Successfully Pulls Subsea Wellhead Plugs

Abstract As exploration continues to venture into more challenging environments, service companies have had to increase their scope of capabilities to meet the challenges brought about by the new environments into which the oil and gas industry has ventured. One of these areas has been the deepwater subsea arena. This paper will focus on one of the slickline innovations — an extended-stroke electro mechanical device — that enables performance of deepwater subsea well interventions more cost-effectively than other service alternatives. Today's needs to provide deepwater subsea well servicing has created many new challenges for the industry. For example, pulling a deepwater subsea wellhead or crown plug can require an extreme pulling force. The difficulties experienced can be compounded by conditions that occur when the plug has been in place for extended periods of time as well as the more demanding deepwater conditions, such as high differential forces and settlement on top of the plug that contribute to the need for the higher pulling forces. These conditions often exceed the capabilities of conventional slickline services. An option that has met other challenges in difficult scenarios is a slickline-deployed electro-mechanical device that produces a high linear pulling force directly at the wellhead plug without jarring. This tool does not require explosives or hydrostatic setting tools because it is operated by batteries. Since first being introduced, the electro-mechanical device has undergone several changes that have increased its capabilities and functionality. For example, it has recently been configured for pulling subsea wellhead plugs. This paper will present a case history that details the first use of the ‘extended stroke’ electro mechanical device in the Gulf of Mexico in which it was capable of pulling plugs at a water depth of 5,339 feet. Using the electro-mechanical device with slickline instead of coiled-tubing resulted in a substantial savings in both the cost of deployment and rig time.