Operators continue to explore new techniques in order to optimize well productivity and, at the same time, decrease drilling and completion costs. The goal is for the net result to be a quicker return on investment. Formation damage caused by kill fluid can have a negative impact on well productivity. Damage cleanup operations are generally both expensive and time consuming, thereby extending time to payback. Live well deployment of tubing conveyed perforating guns addresses the need to perforate and complete without killing the well after perforating allowing the well to be brought on production immediately.
With the increased use of underbalanced drilling and completion techniques using coiled tubing and snubbing, wells can now be brought on production without subjecting the formation to kill weight fluids. In addition to cost savings benefits related to lower fluid costs, time sensitive expenses relating to fluid change out and clean up may be realized. The operator may also reduce the possibility for near wellbore damage, possibly caused by the kill weight fluids, thereby improving productivity.
Safely perforating long intervals when utilizing coiled tubing or snubbing presents challenges when attempting to run and/or retrieve the guns in a live well condition. Sub surface safety valves may be used as a shut in device during perforating gun deployment. However, most operators would prefer to activate the safety valve only in emergency situations. When perforating initial completions or recompletions, the sub surface valve can present a well bore restriction (WRSCSSV) or it (TRSCSSV) may not be positioned at a sufficient depth to allow lubrication of the entire gun length in a single trip. Valves, or possibly plugs, may be positioned at sufficient depths to accommodate the entire gun length and isolate the formation from the surface. But these methods have yet to be proven worthy of full operator confidence such that a surface mounted, shut in method would not also be required as a means for emergency back-up. Therefore a perforating gun deployment system, or live well deployment system (LWDS), is necessary to safely deploy perforating guns.
Utilizing an LWDS to safely snub or strip perforating guns into and out of a live well in a timely manner requires coordination of surface BOP stack, riser assembly and a specially designed perforating gun connector system. The system utilizes conventional BOP equipment positioned at surface, and a gun connector system which allows for quick gun assembly and provides for safety during all phases of the deployment and perforating operation.
With any perforating operation, the primary objective must be safety. Perforating in live well situations requires complex safety consideration for handling both pressure and explosives at the same time. The surface equipment must be designed for the complexity of safely handling pressure without at any time affecting the explosives. At the same time the perforating equipment must be capable of safely containing the explosives during run-in and provide for pressure isolation while both running and retrieval.
Emergency shut-in while deploying the perforating guns must also be a consideration. Closing shear rams on perforating guns containing explosives is an extremely dangerous situation. Accidental surface detonation may be possible if the shear rams are closed while containing the guns or firing head assembly. The system must be designed such that the shear rams can be safely closed without crushing the explosives. Live Well Deployment System (LWDS) Operation In a conventional tubing conveyed perforating operation, gun lengths varying from 3 to 28 feet in length are picked up and assembled to each other via threaded connections.