A significant problem confronting Operators in modern field development and production is that created by loss of functionality of the surface controlled subsurface safety valve (SCSSV) due to blockage of, or damage to, the hydraulic control line. The consequent loss of hydraulic pressure to the valve means its closure, the resultant loss of production and the need to provide an alternative safety system in order to continue exploiting the wells reserves Currently two alternatives are available:○A full scale workover to pull tubing, replace the inoperable control line and restore functionality to the SCSSV.○Installation of a velocity or dome charged subsurface controlled subsurface safety valve (SSCSSV). The former approach requires a major expense, which may not be justifiable in a mature well, while the reliability offered by the latter approach typically does not meet well integrity requirements and can sometimes lead to reduced production. Nederlandse Aardolie Maatschappij (NAM) has been faced with this problem in many onshore and offshore wells and was determined to find an alternative solution. Based on the successful completion of a previous development project, NAM asked Weatherford to jointly develop a solution to this problem, which would allow the installation of an alternative control line without the expense of a workover. In this paper the authors will review the problems associated with loss of control line functionality and consequent SCSSV malfunction. They will go on to describe in detail the joint project which led to the development, testing, and eventual field deployment of the Weatherford Damaged Control Line (WDCL) Safety Valve featuring surface control, which can be installed using wireline and capillary string techniques. Introduction In any and all field developments which incorporate surface controlled subsurface safety valves a significant potential problem exists with the hydraulic access conduit. When a control line is used to provide hydraulic power to the safety valve, the danger is ever present that it could become blocked or damaged thus rendering the safety valve inoperable. When such a situation occurs there are normally two possible alternatives to be considered in order to restore safety valve control to the well and thereby facilitate continued safe production:○The well can be worked over to pull the tubing, replace the damaged control line and recomplete the well with a functioning safety system. This approach involves major expenditure which, in more mature wells, can often be financially unjustifiable because the remaining reserves may be insufficient. In the case of NAM operations the approximate cost of such a workover is in the range 6 - 8 million Euros which makes it a fiscally unattractive approach.

As gas wells mature, the problem of liquid loading and the resultant intermittent flow can reduce production to rates below the anticipated decline curve. It has been demonstrated that the introduction of surfactants such as foamers can mitigate the problems caused by liquid loading, and experience has shown that the introduction of these production enhancing chemicals in a continuous stream at the perforations can significantly reduce critical velocity and extend the productive life of gas wells. At the same time, especially in offshore wells, Operators must maintain a fully functional safety system including the downhole safety valve and the surface master valves and actuators which are controlled by an operating panel and are an integral part of the emergency shutdown system. This is especially true for operators in the North Sea who must adhere to some of the most rigid safety requirements in the industry. Clearly a new system was needed to allow the continuous injection of production enhancing chemicals through the safety systems in the well while maintaining their full integrity. This paper will detail the conception and development of a new downhole safety valve and wellhead penetration system, incorporating a capillary string, to allow an operator to inject production enhancing chemicals through the safety valve while maintaining full control of the surface and subsurface safety equipment. The new system, the deployment of which is also detailed in this paper, is installed by means of slick line and capillary string using a combination of proven intervention methods thus eliminating the need for a major rig operation and saving the operator substantial workover cost.