Managed-Pressure Drilling: Beyond the Conventional Limit in a Deepwater HP/HT Well

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This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 142312, ’Managed-Pressure Drilling Enables Drilling Beyond the Conventional Limit in a Deepwater HP/HT Well,’ by F. Kernche, D. Hannegan, SPE, E. Sammat, and M. Arnone, SPE, Weatherford, prepared for the 2011 SPE Offshore Europe Oil and Gas Conference and Exhibition, Aberdeen, 6-8 September. The paper has not been peer reviewed. Managed-pressure drilling (MPD) was used successfully on an offshore high-pressure/high-temperature (HP/HT) well. Wells in this field and other offset wells in the area had faced many problems including inadequate mud management resulting from depleted or overpressured zones, influxes, mud losses, and differential sticking. This well was drilled with a proprietary MPD system that is a closed-loop method of monitoring and controlling flow and pressure. Introduction MPD uses a closed and pressurized drilling-fluid (mud) circulating system that facilitates drilling with precise management of the wellbore-pressure profile. The primary objective of MPD is to optimize drilling processes by decreasing nonproductive time (NPT), mitigating drilling hazards, and enabling the drilling of otherwise technically or economically undrillable highly complex prospects. Because MPD addresses NPT, the technology is of greatest potential benefit to expensive offshore-drilling programs. Although MPD was been practiced safely and efficiently from all types of offshore rigs, yielding the desired results, it still is considered a relatively new technology to many offshore drillers. The uptake in offshore MPD applications is, in part, because drilling is taking place in greater water depths, through depleted zones or reservoirs, and into narrow or relatively unknown equivalent-mud-weight (EMW) drilling windows. Technical Justification The application of MPD technology can optimize the drilling process by decreasing NPT and mitigating drilling hazards associated with conventional drilling techniques. Most importantly, the MPD system reduces drilling costs and limits drilling-cost uncertainty by: Avoiding conventional-drilling NPT problems, such as lost circulation, shale instability, kicks, nuisance-gas zones, and differential sticking. Increasing the rate of penetration, increasing bit life, and decreasing trip frequency. Enabling access to potential assets/reservoirs previously believed to be undrillable by improving health, safety, and environmental (HSE) conditions. MPD System The MPD system used in this specific application consisted of a proprietary control algorithm to identify influxes and losses on a real-time basis and a choke at surface to apply backpressure to maintain well control. The system allows making drilling decisions on the basis of actual pressure and flow data rather than by use of predicted downhole parameters based on hydraulic models, and it provides real-time monitoring of the well-bore parameters while drilling.