Tandem Downhole-Isolation-Valve System Eliminates Snubbing

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 173043, “First Ever North Sea Deployment of Tandem DIV System Eliminates Snubbing—A Case Study,” by Gary Mueller, Weatherford, prepared for the 2015 SPE/IADC Drilling Conference and Exhibition, London, 17–19 March. The paper has not been peer reviewed. The operator of an offshore jackup rig in the North Sea required safe and efficient deployment of the completion string without killing the well during tripping. A solution other than a snubbing unit was needed because of the length of the completion string, which included 12 swellable packers for 13 zones. To provide for a safer, less-expensive, and efficient method of tripping pipe, the operator chose a downhole-isolation-valve (DIV) solution that allowed for the process to be performed in a conventional manner under conditions of complete well control. Introduction During the past decade or so, the industry has developed drilling methods to address more-complex and - challenging prospects such as ultradeep prospects, deepwater applications, and high-pressure/ high-temperature wells in order to continue meeting the worlds’ demand for energy. This seemingly insatiable demand has led to the development and widespread use of unconventional techniques such as underbalanced drilling (UBD) or near-balanced drilling and various forms of managed-pressure drilling, including pressurized-mud-cap drilling (PMCD) and constant- bottomhole-pressure drilling with their attendant well-control and safety challenges. Some of these challenges are Moderate to severe lost-circulation conditions and consequent nonproductive time (NPT) Formation damage as a result of having to kill the well before tripping pipe Pore-pressure and fracture-gradient similarity leading to kick and loss cycles and well-control problems A necessity for snubbing techniques to trip the pipe in and out of the hole above the “pipe light” depth, with the attendant added cost and risk Overall operational safety and environmental issues Operational economics and the effect of resulting NPT As a result of these challenges, mitigating drilling hazards has become an extremely important facet of drilling operations and has prompted the development of procedures and equipment designs to address them, one of which is the DIV.