otc16051

OTC 16051Wash Pipe Or No Wash Pipe? That is The QuestionFrancisco Pineda, SPE, Bryce Traweek, and James Curtis, SPE, BJ Services CompanyCopyright 2004, Offshore Technology ConferenceThis paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, U.S.A., 3–6 May 2004.This paper was selected for presentation by an OTC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Offshore Technology Conference or officers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented.AbstractConventional gravel pack or frac pack completions typically require the use of wash pipe to act as a conduit for fluid returns as well to carry a shifting mechanism to open or close a return port. Using properly sized wash pipe can enhance the placement of the gravel across the entire annular space and the formation. It can be used in conjunction with a shifting mechanism and a sliding sleeve to force the fluid returns to pass through the bottom of the screen. It can allow a wash-down capability while running the assembly into hole. In specialty systems, it can even act as a pumping conduit for post-gravel pack stimulation.However, the use of wash pipe, especially in long horizontal wells, means the loss of valuable rig time due to make up and break up of the wash pipe, or recovery if the wash pipe is stuck. Economic considerations, along with completion efficiencies, are especially important on deepwater completions. Not using wash pipe reduces rig time, generating significant cost savings, and also eliminates the risk of sticking it.This paper reviews conventional wash pipe applications and describes new systems that accomplish the same goal with a minimum amount of wash pipe or no wash pipe at all.Uses of Wash PipeThe production of formation sand into a well is one of the oldest problems plaguing the oil and gas industry because its adverse effects on well productivity and equipment.1Gravel packing and frac packing are the methods of choice for sand control. In combination with sand screens they provide downhole filters to prevent production of formation sand. During the execution of these methods, a properly sized sand or proppant has to be placed in the formation as well as the annulus of the screen-casing or screen-open hole using a gravel pack packer assembly with a gravel pack service tool and wash pipe inside the sand screen, with its bottom hanging as close as possible to the end of the screen. Thisconfiguration aids the placement of the sand or proppant by allowing the gravel pack fluids to travel down the tubing, through and out the ports of the gravel pack service tool and assembly, down the blank/screen-casing or open hole annulus, into the perforations or open hole, through the screen, up the wash pipe and gravel pack service tool, and into the gravel pack packer-casing annulus.Wash pipe can also be use as a conduit to allow wash-down capabilities when installing screens or liners. In isolation systems, wash pipe is used to run shifting tools to activate sliding sleeves in order to achieve returns during gravel packing.There are also other economic factors to consider when using wash pipe, such as the valuable rig time necessary for making up, running in and breaking up, especially in horizontal wells, and also in the unfortunate case of fishing if the wash pipe becomes stuck.Wash Pipe Selection CriteriaProper selection criteria include strength, material, connection type, and diameter. Strength must exceed the maximum expected tensile load, however the internal diameter should also be maximized in order to minimize flow friction and facilitate fluid returns. The preferred connection type is a flush joint to prevent sticking and to allow downward flow in the wash pipe – screen annulus near the end of the treatment. Properly sized wash pipe is as important as properly sized sand screen. The generally accepted optimum ratio of the ID of the screen to the OD of the wash pipe is 0.8 or greater, in order to facilitate return flow up the wash pipe.2 This also results in a narrow wash pipe – screen annulus, which favors fluid flow on the outside rather than the inside of the screen, due to the higher friction pressure in the inner annulus. Premature bridging and a possible screen out is discouraged. This could occur when the fluid enters the screen/wash pipe annulus, depositing gravel in the outer annulus and possibly causing premature bridging. The most common screen/wash pipe configurations are shown in Table 1.2 OTC 16051subs in the washpipe assembly to the annulus above the packer. Once a sand-out is achieved the service tool is positioned in the reverse position changing the fluid path direction. After excess slurry is reversed from the workstring, a secondary ball is dropped and converts the tool from gravel packing mode to stimulation mode.Standard Gravel Pack Assembly w/ Retrievable Isolation AssemblyIn this system the isolation assembly serves as a conduit to aid circulation of the gravel pack fluids to the bottom of the annulus of the screen/casing or screen/open hole, obtaining fluid returns through the screen and lower sliding sleeve. The wash pipe serves as shifting tool carrier to open or close lower sliding sleeve, as shown in Fig. 2. Isolation tubing OD - screen ID ratio should optimally be 0.8.The stimulation mode relies on the bullplugged washpipe incorporating polished stingers and ported subs that seal between screen sections to allow for selective stimulation placement. The fluid path is thus changed to exit the workstring through the service tool and directly enter the inside of the washpipe.This system has shown to be effective for controlling fluid losses and for zonal isolation in stacked multi-zonal completions, yet still requires rig time for wash pipe handling, especially in longer intervals.The service tool is then picked up in order to position the straddled polished stingers across the inverted molded seals placed between screen joints. Between the polished stingers, at the end of the washpipe, the ported subs that were previously used to take returns during the gravel pack now create flow path for the stimulation treatment to be squeezed into selected intervals. Once the first screen joint/open hole section has been stimulated, the service tool and washpipe are picked up to straddle the next screen section and pumping resumes. This can be repeated as many times as necessary to selectively stimulate the entire open hole section.At the time of writing, for standard offshore as well as deep-water applications, 636 systems with 431 sliding sleeves had been run since 1995 in the United States. For deep-water application in South America, 55 systems with 134 sliding sleeves had been run since 2000.After the stimulation treatment is complete, the service tool is pulled from the wellbore until the polished stinger trips the double flapper valve isolating the formation from fluid losses.3Gravel Pack Systems with out Wash PipeIn areas of the world where transportation, access, availability, and maintenance of equipment are difficult, utilizing a gravel pack system that requires no wash pipe is advantageous.The need for such “washpipeless” systems has been increasing due to high rig rates in the event of fishing operations. In a frac pack operation, one of the most common problems is stuck wash pipe, soon after screen out or reverse out is accomplished. Utilizing a gravel pack system that requires no wash pipe eliminates that unforeseen event in addition to reducing costs.The following systems incorporate the previously mentioned isolation assemblies to obtain zonal isolation and to control fluid losses.Standard Gravel Pack Assembly w/ High Pressure Retrievable Isolation AssemblyThis system is mechanically actuated and hydraulically powered, and is shown in Fig. 4. The isolation assembly serves as a conduit to aid circulation of the gravel pack fluids to the bottom of the screen/casing annulus, where fluid returns are obtained through the screen. The fluid enters the isolation tubing through a screen-wrapped port on the bottom of the assembly, which later becomes isolated after system actuation. The isolation tubing OD – screen ID ratio should optimally be 0.8.The system uses a short actuation string section, less than 20 feet, which is composed of flush joint tubing and an Retrievable Isolation AssemblyStandard Gravel Pack Assembly w/ Ball Drop Retrievable Isolation AssemblyThis system is hydraulically actuated and powered, and is shown in Fig. 5. The isolation assembly serves as a conduit to aid circulation of the gravel pack fluids to the bottom of the screen/casing annulus. Fluid returns are obtained through the screen and a multi-service valve (MSV) on the bottom of the isolation tubing. The MSV is closed after system actuation. The isolation tubing OD – screen ID optimum ratio should be 0.8. This system does not use any wash pipe or actuation string.This system has been developed and tested and at the time of writing, was ready to go in the field. This kind of system has particular application in deep-water, sand control environments, where minimization of rig time and risk mitigation are of paramount importance.4 OTC16051Isolation AssemblyConclusions1. In gravel packing, a conduit is needed to ensurecirculation to the bottom of the screen. The conduitmay be retrievable (wash pipe) or permanent/retrievable (isolation assembly).2. In frac packing, taking returns through the bottom ofthe screen is not as important, but having a conduit isnecessary in the event that gravel packing thescreen/casing annulus is required afterwards.3. Especially in deep-water environments, and wells withlong intervals, the trend is to reduce or eliminate theusage of washpipe.4. “Washpipeless” systems can save rig time and preventfishing operations.5. When possible, choose a “washpipeless” gravel packor frac pack system that accomplishes the samefunctions as systems that use washpipe.AcknowledgmentsThe authors of this paper would like to express theappreciation of the members of their respective engineeringand operations staff. Without their combined efforts, thisaccomplishment would not be possible. We also thank BJServices for the permission to publish this paper.NomenclaturepackGravelGPdiameterIDInternalvalveMulti-serviceMSVdiameterODOutsideSHGPSS system = Single trip horizontal gravel pack andselective stimulation system。