Step changes in design are overcoming earlier prototype difficulties.

Completion isolation valves (CIVs) were developed in the mid-1990s as a solution to problems associated with high-angle sand-face completion operations. Specifically, they were designed to curb fluid loss and formation damage that can result in overall well productivity impairment and increased well cleanup times. In addition, the requirement for high-integrity suspension and test barriers could be removed with no need for well intervention.
However, although the first valves performed well, particularly given the immaturity of the interventionless technology, debris within the well, especially in high-pressure, high-temperature (HP/HT) applications, continued to adversely affect the valve's full capabilities. To improve its performance and reliability, many valuable lessons regarding the valve's application have been continually fed back into the design. As a result, CIV technology is improving well cleanup and productivity, especially in more complex applications that are significantly different from the earlier prototype installations.
Background
After drilling relatively deep, high-angle wells, operators often suspend each well using some form of reservoir isolation device to protect the formation from fluid losses below the barrier while allowing installation and testing of the upper production completion, tubing hangers and packers above it. Drilling and completion activity timings may require a long-term suspension of the sand-face completion prior to installation of the upper completion and Christmas tree.
The traditional approach to fluid loss prevention is to install a simple flapper valve, and the traditional approach to well suspension is to install some form of retrievable plug run on drill pipe or coiled tubing. The disadvantage to these methods is that the flapper will only hold pressure from above. Additionally, a complete sand-face suspension requires a time-consuming intervention to set a plug on drill pipe or coiled tubing followed by additional runs to retrieve the plug.
Operators recognized that advantages could be accrued by incorporating a purpose-designed isolation valve within the sand-face completion. This would not only minimize operational time and expense of rigging up coiled tubing at the suspension and completion phase but also benefit safety by reducing personnel exposure to risk.
The subsequent concept involved a bidirectional ball valve below a liner hanger packer assembly. The valve was run in the open position such that all required sand screen placement operations could be conducted normally. The ball valve then could be closed to form a suspension barrier, allowing the drilling rig to move to the next well location and continue drilling operations. Months later, the rig could return and open the valve hydraulically without intervention. When used with a hydraulic setting valve to set the production packer, the CIV allowed the wells' flow control objectives to be achieved with no coiled tubing or slickline intervention below the tubing hanger. In combination, these two valves can give improved long-term well performance and significant cost savings during initial completion installation.
To ensure maximum integrity, the valve included a single-seat, nonelastomeric, bidirectional ball-sealing unit capable of withstanding extremely high differential pressure ratings of up to 7,500 psi from above and below. It was designed to ensure a minimal bearing force between ball and seat during rotation yet guarantee that the ball and seat would not part company when direction of pressure loading was reversed. Features were included to allow sand-face service tools such as those associated with inflating annulus casing packers to be run through the CIV without interfering with the CIV operation. Lastly, the valve was to be activated mechanically with a shifting tool or remotely with tubing pressure cycles applied from surface.
Lessons learned
The initial CIV installations confirmed a desire within the operator community for the value-adding benefits of interventionless tools. While the bulk of the early installations were successful, it also was apparent that there was room for improvement. Particularly in the more challenging near-HP/HT applications, the overlap between the CIV operating envelope and the level of cleanliness achievable in well cleanup was not sufficient. This resulted in debris impacting operational success. It also was apparent that a need existed for the CIV that could not be met with the original design specification and functionality.
For instance, other operators began to look at the tool for application in their near-HP/HT wells. Here the CIV allowed safe underbalanced completion installation. These high-pressure wells were completed with heavy mud and brine fluid systems necessary to control the downhole pressures. Therefore, the CIV had to be installed under conditions of extreme high debris potential and withstand severe bidirectional pressure differentials.
However, in some cases the debris within the well had an adverse effect on the valve. Heavy barite-weighted muds were required at valve installation to balance the downhole pressures. In one application, this resulted in up to 200 ft (61 m) of barite accumulating above the valve and making it difficult to operate, although the valve was in good working order when retrieved.
The lessons from this work directed a strict application of rigorous operational hole-cleaning techniques to minimize the effect of the deposition of external debris.
Solution
The two major tasks faced by the designers were increasing reliability and extending operability. The lessons of operating in high-debris environments resulted in an enhanced debris management system, including internal filter mechanism improvements and pressure-cycle ratchet enhancements.
Feedback from the operators suggested the desirability of extending the initial CIV/ratchet single open-and-close functionality to a design that could be subjected to any number of open-and-close cycles. The output of this was the CIV/ratchet mechanical variant, manufactured in 7-in. and 95/8-in. sizes. A step change for the valve design, the ratchet mechanical version enhanced operational flexibility and included significant design improvements to overcome the problems identified in the early installations.
A mechanical tool introduced in 5-in., 7-in. and 95/8-in. sizes was aimed at bottomhole assembly deployment applications. A further design project resulted in the development of a 7-in. and 95/8-in. stinger version, which recently was selected by the Ocean Petroleum Development Co. of Shengli Petroleum Administration Bureau in China for the Shengli field development. In this application, the valve will be operated by a stinger on the upper completion tail pipe as opposed to being activated by shifting tools.
Case history
The improved ratchet mechanical design has been applied in numerous wells worldwide. In recent operations for a major North Sea operator, the 95/8-in. tool is being run as part of a horizontal screen placement sand-control completion. After setting of the screen hanger packer, the CIVs are closed with a shifting tool. This tool was introduced, along with the ratchet mechanical version of the valve, to address problems experienced with the shifting tools used with the original prototype CIV. The main advantage is a simpler and more reliable shifting tool system. The tool is less complex to assemble and operate downhole, and it maintains the essential positive indication at surface of the CIV being closed.
Once closed, the screen running string is retrieved to surface. The shut CIV stems fluid losses to the formation and acts as a suspension barrier prior to upper completion installation. The upper completion is run and tested against the closed CIV. Once the surface tree is installed, the CIV is pressure-cycled open from surface. The end result is that the fluid- loss control, suspension and upper completion test requirements of the well have been achieved with no intervention runs.