One-Trip Perforate and Gravel Pack System

Abstract A downhole tool system has been developed that makes it possible to perforate well casing with all the advantages of a TCP (Tubing Conveyed Perforating) gun and to gravel pack that well using proven techniques, all on the same trip in the hole. The system has been operated successfully in 7-5/8″, 7″ and 5″ casing, and is also available for 5-1/2″ and 9-5/8″ casing. The system has been in development for about 2 years in the Texas and Louisiana Gulf Coast area, in cooperation with several different operators and under varying well conditions. The main components of the system are a casing sized TCP gun, a hookwall packer which is multiple acting and operated by reciprocation of the workstring only, screen and blank pipe common to gravel packed completions, and a hydraulically set seal bore packer. The operation of the system is as follows: –– As the system is run in the hole, a radioactive tag is installed in the workstring at a known distance from the TCP gun. With the gun at approximate perforating depth based on pipe measurements, a gamma ray logging tool is used to locate the tag and correlate its position back to previous logs. Knowing the exact location of the tag, the gun is re-positioned precisely for perforating. –– The hookwall packer, just above the gun in the assembly, is set and tested, then a bypass is opened allowing circulation through the packer. Lightweight fluid is then circulated down the workstring and the packer bypass is closed, creating an underbalanced pressure in the wellbore compared to reservoir pressure. –– The gun is then detonated by dropping a detonating bar or pressuring the workstring-casing annulus, depending on whether a mechanical or hydraulic firing head is used. The well can be flowed as necessary for clean up and testing. –– The well is killed by unsetting the hookwall packer and reverse circulating kill weight fluid into the workstring. –– The entire assembly is moved downhole and the hookwall packer is reset below the just-perforated interval. The seal bore packer is then hydraulically set by dropping a ball into the workstring and pressuring against the ball. This setting operation also converts a tool inside the packer to a dual flow path crossover tool, crossing over tubing flow above the seal bore packer to annular flow below it. –– After rotating the crossover tool free from the seal bore packer, upward movement of the crossover tool unseals a concentric string (washpipe) inside the screen from the hookwall packer. Fluid treatments such as acids, clay stabilizers, and the gravel slurry itself can then be circulated down and circulated through the screen or squeezed into formation similar to common industry practices. –– After the gravel pack is complete, the crossover tool and concentric string are removed, and a seal assembly is run inside the seal bore packer for production. The chief limitation of the system is the amount of rathole available in the well. The area below the producing zone must be long enough to accept the spent TCP gun assembly.