Cost-Effective Bidirectional Barrier Technology Improves Interventionless Applications

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 34885, “Cost-Effective Innovation Qualified as Bidirectional Barrier To Support Well-Cost Reduction, Eliminate Slickline Operation, and Improve Robustness of Interventionless Systems Application in the Market,” by Asba M.B. Abu Bakar, Fadzil Yahaya, SPE, and Mohd S. Abd Shukor, Petronas, et al. The paper has not been peer reviewed. _ A barrier-rated tubing-hanger valve has been invented to eliminate slickline intervention and minimize associated risks and operation time. Based on pilot installation performance, projected cost savings for one well from operation simplification and rig-time reduction are expected to be approximately 86% compared with conventional slickline run for 3½-in. tubing sizes, with up to approximately 10 hours of rig-time savings. Introduction Conventional backpressure valves (BPVs) are used commonly in current applications but are not certified as well barriers and are only used in a debris-catching capacity. The well design should include a minimum of two independent and tested barriers during any operation to prevent uncontrolled flow from the well into the environment. In the past, common practice was to deploy a deep-set plug by slickline as the first barrier and a tubing-retrievable surface-controlled subsurface safety valve as a second barrier before nippling down the blowout preventer (BOP). Occasionally, the operator has experienced nonproductive-time and operational difficulties related to slickline operations in which a slickline fish was left in hole. BPVs and two-way check valves (TWCV) are not accepted by the operator as well-barrier elements because they do not meet the operator’s barrier-verification requirements. To overcome operational issues related to slickline and limitations of BPVs and TWCVs, the operator considered various interventionless options. The bidirectional barrier-rated tubing-hanger valve was invented to eliminate slickline runs, minimize risks, and realize significant cost savings from reduced rig-operation time. The presented valve is a well-barrier element qualified per API 6A that also passes leak-acceptance criteria in API 19V. The valve also provides isolation to nipple down the BOP and nipple up the tree and incorporates equalization features that relieve pressure surges during removal from conventional H-type tubing-hanger profiles. Use of this type of tubing-hanger valve enables the operator to use a nonbarrier-rated tubing-conveyed downhole plug to set a production packer, which is relatively cheaper than the barrier-rated type. In this configuration, two independent and verified well-barrier elements are available in the well for safe BOP removal. Methodology and Design Features To resolve challenges related to slickline operation and limitation of existing BPVs and TWCVs, changes were implemented to conventional BPV design. The presented valve still features a threaded profile that allows it to be set at the standard H-type tubing hanger profile and is set at the tubing hanger using a dry rod connected to a designated setting tool. The internal part of the tubing-hanger valve body is equipped with an inner plug that replaces the spring and plunger valve in BPVs and TWCVs, respectively. The outer part of the inner plug features a thread connection that allows it to be screwed inside the plug body. The inner plug has double O-rings to seal the valve body against upstream and downstream pressure. Insertion of the inner plug into the tubing-hanger valve body can be performed offline on the deck before running in hole. Integrity of the inner plug can be verified by a negative-pressure test through the test port at the bottom of the valve body.