Implementation of Dual Gradient Drilling

摘要

RMR - Riserless Mud Recovery technology is a “first out” commercial Dual Gradient Drilling (DGD)technology. The technology has to date been deployed on more than 200 wells. The majority of wells arein less than 2000ft water depth, and the maximum water depth to date is close to 5000ft.Initially the development was driven by a zero-discharge demand, but early on the benefits related toDualGradient Drilling became the main drivers for the Operators to select the technology. In fact, for onlya few of the 200 wells to date, zero-discharge has been the driver. The technology allows weighted andengineered drilling fluid to be used on the top-hole sections and volume control is enabled throughcirculation of fluid to surface - same as post-Blow Out Preventer (BOP). Borehole quality is significantlyimproved and planned Total Depth (TD) can be reached without the risk of running out of fluid.The Managed Pressure Cementing (MPC) technology has been developed as an add-on to RMR. Thistechnology has been used for more than 20 wells to date. Combined with the improved hole quality RMRcan deliver, MPC improves the chances of circulating the cements slurry around the well without losses.The pressure is managed and controlled during the circulation time, and monitored during the setting time.A third development of the core RMR technology has been EC-Drill. EC-Drill has been deployed on6 jack-up wells and 3 deep water wells drilled from a Semisubmersible rig (SEMI). North Sea and Gulfof Mexico (GOM) deployments are under ways. EC-Drill enables precise control of Bottom-holePressure(BHP) through manipulation of the fluid column within the Drilling Riser. Pressure build up dueto circulating friction is eliminated and flow rate / Rate of Penetration (ROP) can be increased. Bymanaging Equivalent Circulating Density (ECD), drilling through tight drilling window is enabled.Depleted / low pressure reservoirs can be drilled with conventional / low mud weights. EC-Drill in itspresent form delivers primarily ECD control and only partial - not full DGD capability.