Abstract
Abstract Traditionally it has been quite a daunting task to place high-performance cement in tophole sections of many subsea wells, where tight-formation pressure windows pose problems for operators. Cement jobs have reportedly been unsuccessful in numerous cases under such challenging conditions. Losing cement to the formation, plus the added problems of shallow gas and water influx, have been common elements in such cement-job failures. AGR has developed a cementing method that mitigates the risk of losses in tophole sections during circulation and early gas migration in the dormant and transient-gelation periods. This subsea Managed Pressure Cementing (MPC) method was implemented successfully first time in early 2010 on a subsea well in the Caspian Sea, isolating unconsolidated, overpressurized sand stratum with well-bonded cement. This meant drilling could continue to the next hole section with the desired integrity at the shoe. Proven Riserless Mud Recovery (RMR) equipment, which includes the Subsea Pump Module (SPM) as the key component of the system, is used for subsea MPC operation. A closed-loop circulation system is established facilitating an excellent level of control over the wellbore pressure gradient, so wellbore pressure falls inside the pressure window of the formation during all stages of the cement job. Any small amount of loss is detected immediately and cured by the subsea pump inlet pressure. Great potential was seen with this subsea MPC method. Indeed it has not shown any problems that would prevent its use in similar situations. This paper examines details of this method and its successful applications in one of the most challenging areas in offshore.
Published Version
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