Current capabilities with coiled tubing and slickline are insufficient to provide complete well intervention support to deep, high-pressure wells drilled from a floating vessel in a deepwater Gulf of Mexico (GOM) field. These intervention technologies limit the allowable departure of proposed wells to 8,500 ft and often restrict intervention scope to “dead well” operations. A hydraulic workover (HWO) system is being developed to support a deepwater GOM field. The system will be located under the rig floor with heave compensation provided by the rig’s riser tensioning system. HWO control will be achieved using a remote panel and operations will be observed from the driller’s cabin on closed-circuit television (CCTV). To keep the stack-up height as short as possible, the surface pressure control equipment (PCE) will utilize special unitized body valves. The PCE will be stored on a purpose-built fixture where it can be pressure and function tested prior to rig up. The surface and subsea PCE will include shearing and sealing capability for the largest diameter pipe to be used. The HWO solution provides a high-strength conveyance method to intervene and operate under pressure from a floating vessel in deep, high-pressure reservoirs. The customized HWO extends intervention capabilities to a departure of 15,000 ft (28,800 ft MD) under 8,800-psi wellhead pressure. The HWO provides features that enhance personnel safety and economic efficiency. The advantages of a sub-floor HWO include: (1) improved safety by removing personnel from an elevated workbasket exposed to pressure and erratic movement, (2) more efficient operation through use of the rig’s regular hoisting equipment, (3) elimination of the need to pull production tubing when extending existing wells, and (4) complete reservoir accessability without the need for satellite wells.
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