In high cost, high risk deepwater exploration and production, operators are seeking technologies and methods that reliably accelerate the well completion process while reducing risks to operational safety and the marine environment.
The bi-directional hydromechanical valve, or "disappearing plug," is one of these technologies. The disappearig plug is used to set hydraulically actuated completion packers, test tubing, isolate zones, and provide a barrier for temporary abandonment of subsea wells.
This paper shows how disappearing plug technology helped simplify and accelerate several well completion operations in deep water.
Wells completed in over 1,000 feet of water usually require purpose-built drillships or semi-submersible drilling rigs for operations. The spread cost of activities on deepwater wells ranges from $150,000 to $450,000 per day, depending on the region of the world, the capabilities of vessel, and the availability of equipment at the time. In this high-cost environment, operators pursue new technologies that can improve operational reliability, flexibility and cost effectiveness.
One historically proven technology that has found broader application recently is the bi-directional hydromechanical valve, or "disappearing plug." Unlike simple wireline plugs which must be set and removed using conventional intervention methods, disappearing plug devices typically operate by pressure cycles down the tubing, so many time and risk sensitive well completion operations can be simplified and accelerated. This paper discusses several of these enhanced well completion operations.
The "best practices" approach to well completion in deepwater wells includes the placement of a completion packer at or near the bottom of the production tubing to isolate and control pressure and fluids from the producing zone. Though sometimes a two-trip system is employed, conventional completion practice requires running wireline or a coiled tubing string into the well to set a packer in a one-trip hydraulic system. The tubing is plugged by landing a wireline or coiled tubing-conveyed blanking plug or check valve into a seating nipple below the packer. The packer is then set using hydraulic tubing pressure. The one-trip hydraulic system requires well intervention, which can consume from 12 hours to two days of rig time, and introduces the risk of losing the wireline or coiled tubing and associated tools in the well.
A more fit-for-purpose setting system would include all the features of the existing one-trip hydraulic system, while eliminating the associated well intervention. Disappearing plugs, run as part of the completion tailpipe, provide a method of actuating completion packers without intervention with coil tubing or wireline. These devices typically operate by pressure cycles down the tubing.
When run in hole, the device has a ball or flapper obstruction in the tubing and a by-pass to self-fill the completion as it is run. Once at depth, pressure cycles may be required to close the auto-fill device. Further pressure cycles are applied to set the completion packer. Additional pressure cycles down the tubing are required to open the obstruction. Usually, these tools leave a full-open internal diameter. Uni-directional and bi-directional devices are available. (See Figure 1.)
There are two other well documented, completely interventionless, methods for setting hydraulic completion packers: absolute well pressure activation and pressure pulse telemetry activation.