Pesca Pubblicazione scientifica Improving the Performance of Coiled Tubing Underbalanced Horizontal Drilling Operations FILONE TECNOLOGICO TEMA produzione e cattura RIASSUNTO AbstractThe paper will address the specific issues associated with underbalance horizontal drilling using two phase flow. Firstly, the challenges that were overcome in devising a ""safe"" method of deploying a directional drilling BHA into a live well will be presented together with a review of the deployment performance results from over a 100 different horizontal drilling operations.Secondly, BHA performance issues associated with two-phase flow will be reviewed and results presented. This will include such issues as un-constrained vibration (encountered when the hole is not liquid full) and such effects as explosive decompression and the consequent reduction of elastomer performance.Perhaps most important will be a discussion of the issues associated with cuttings transport in two phase flow and the methodology devised to reduce (and in many cases eliminate) wiper trips by varying the circulating conditions using a circulating valve incorporated into the BHA. Data from actual jobs will be presented to demonstrate how effective the process has become in regular field operations.Lost time statistics for coiled tubing underbalanced drilling operations will be summarised and performance improvements highlighted.IntroductionIncreasing demand for continuous underbalanced conditions when drilling horizontal wells has allowed coiled tubing to compete effectively with conventional drilling rigs which by their very nature can only offer intermittent underbalanced operations. Under the right conditions effective underbalanced drilling allows Operators the best return for their investment dollar by maximizing results from their drilling programs. Important issues that have been addressed for drilling with two-phase fluids are:Safety and Deployment for a true under-balanced drilling operation.Benefits of using a circulating valve for improved hole cleaning.Unconstrained vibration and its effect on BHA reliability.Elastomer performance and the effect on performance and costs.Communication on location and into the office.Safety and BHA DeploymentThe capability to safely drill in a true underbalanced condition with coiled tubing equipment has been established as a common practice in the Canadian Oil and Gas Sector. This has become common practice due to the inherent ability of the coiled tubing to deploy and run bottom hole assemblies (BHA) in a safe and efficient manner, under flowing well conditions.Keeping the well in an under-balanced condition through every operation within the drilling project is the key to a successful operation. True underbalanced drilling dictates that the well never be killed or over pressured during the drilling or completion stage. Therefore it becomes necessary to retrieve and deploy the entire BHA under live conditions. The current tool string is approximately 20 m in length (which considers a standard length mud motor and bit). A unique deployment system was developed to safely enable this length of tool to be deployed and retrieved from live wells. DATA Data di pubblicazione: 04/04/2013 AUTORI RPT RG FRASER RAVENSBERGEN J ENTE DI AFFERENZA BJ SRVC CO CANADA RIVISTA SPE/ICoTA Coiled Tubing Conference and Exhibition, 9-10 April, Houston, Texas