Patent CA-2168311-A1 (CA)
Title: Well completion system with well control valve
Inventor: CROW ROBERT W
IPC: E21B34/14
Filed: 1996-01-29
Abstract: A system for selective production from, and stimulation of, subterranean production zones while improving productivity and enhancing control of the well. Portions of a production tubing string and an internal stimulation/shifter string are assembled and run together as completion segments. Consecutive completion segments, with each segment including packers that surround sleeves and terminate at the upper end in a well control valve, are run into the cased wellbore so that the acid flow ports operated by sleeve valve assemblies are placed proximate the perforations of prospective production zones. The production zones are then stimulated as the stimulation/shifter string is moved progressively outward placing acid at each consecutive zone. The stimulation/shifter string is then removed from the production tubing string, mechanically closing the well control valve assembly by tubing manipulation. A well control valve assembly prevents flow from or to completion segments further downhole from the well control valve assembly once the stimulation/shifter string has been removed from the production tubing string. The well control valve assembly features a shaped flapper plate which, when opened, conforms closely to the shape and size of the production tubing string's interior diameter. The flapper plate is biased toward a closed position by a compression spring arrangement that includes an arm which levers the plate upward toward a seating surface. The valve assembly's closure is mechanically induced and is not responsive to a sensed well condition.     Reopening of the valve assembly is accomplished by insertion into the assembly of a tubular member, or "stinger", which is incorporated into a running arrangement. The stinger is described in relation to a seal assembly which is capable of reopening the well control valve and securing it in the open position. The seal assembly is incorporated into a running arrangement and inserted into the valve assembly to open the valve assembly and seal the connection between the seal assembly and the well control valve assembly. In one application, the seal assembly is incorporated onto the mating end of an adjacent completion segment. In this embodiment, a method of production becomes possible whereby completion segments are run into the borehole sequentially. As the running operation for each segment is completed, packers are set and the stimulation string is withdrawn, closing the well control valve and leaving the well control valve assembly of the emplaced segment closed against fluid flow out of the well. As adjoining segments are run into the borehole, the seal assembly on its lower end will secure the well control valve of the adjacent emplaced segment into an open position. In another application, the seal assembly is incorporated into a contingency reentry tool. The reentry tool is introduced by a running arrangement into the production tubing string of an emplaced completion segment to reopen the segment's well control valve assembly. Stimulation tools may then be introduced into the emplaced completion segment to accomplish further stimulation. When the contingency reentry tool removed from the segment, the well control valve assembly is reclosed.     The utility of the well control valve, stacked completion segments, and other features make the system of the present invention desirable for use in horizontal and deviated wellbores where fluid balancing may be a problem. The system is also beneficial in situations where there are numerous potential producing sections in a single zone since each of the sections can be completed in a single run.