A bidirectional disappearing plug member (102) and plug assembly is capable of blocking pressurized fluid flow from opposing axial directions in a flowbore (116). In one embodiment, the plug member (102), which blocks flow through the flowbore (116), may be readily and at least partially dissolved through the application of at least one pressurization and depressurization within a tubing string above the plug assembly. Construction of the plug assembly permits the plug member to be conveniently emplaced in a fluid-filled wellbore by permitting fluid flow (210) around the plug member (102) during the emplacement process. The plug member may then be secured within the plug assembly to block fluid flow from either axial direction. Operation of a plug rupture sleeve (220) or mandrel, for at least partially dissolving the plug member, may be controlled by a ratchet assembly or linear indexing apparatus requiring multiple pressurizations and depressurizations before the plug member is exposed to wellbore fluids and thereby at least partially dissolved.

A plug provided with a holding device for releasably attaching said plug to a support having a shoulder, characterised in that said holding device comprises a tubular sleeve to which said plug is secured, said tubular sleeve having an external ring which, in use, rests on said shoulder and supports said plug, the arrangement being such that when said sleeve is subject to sufficient force said external ring will shear and thus release said plug from said support.

A well completion tool (10) operatively positionable within a subterranean well (12). The tool (10) comprises a fluid delivery flowpath (56) configured for delivering fluid into the well (12), a fluid return flowpath (62) configured for returning fluid from the well (12) and a pressure relief device (64) in fluid communication with the fluid delivery and fluid return flowpaths (56,62). The pressure relief device (66) is operative to provide fluid communication between the fluid delivery and fluid return flowpaths (56,62) upon application of a first predetermined fluid pressure differential between the fluid delivery flowpath (56) and the fluid return flowpath (62).

A method of stimulating a subterranean well permits each desired location within a portion of a well to be isolated from other portions of the well during stimulation operations therein, but does not require lining a portion of the well with casing and cement, and does not require the use of sealing devices, such as inflatable packers, in the well portion. In an embodiment, a stimulation method includes the steps of depositing a barrier fluid (32) in a portion of a well, forming a radially extending opening (56) through the fluid, and flowing stimulation fluids through the opening and into a formation surrounding the portion of the well.

A method of stimulating a portion of a subterranean well (12) at axially spaced apart desired stimulation locations therein, the well portion intersecting a formation (38), comprising: disposing a viscous fluid (32) within the well portion; forming an opening (56) through the viscous fluid (32) at a first one of the desired stimulation locations; and flowing stimulation fluids through the opening and into the formation (38) at the first desired stimulation location, whereby the viscous fluid (32) substantially prevents flow of the stimulation fluids into any portion of the formation (38) other than at the first desired stimulation location.

A method of stimulating a portion of a subterranean well (12) at axially spaced apart desired stimulation locations therein, the well portion intersecting a formation (38), comprising: disposing a viscous fluid (32) within the well portion; forming an opening (56) through the viscous fluid (32) at a first one of the desired stimulation locations; and flowing stimulation fluids through the opening and into the formation (38) at the first desired stimulation location, whereby the viscous fluid (32) substantially prevents flow of the stimulation fluids into any portion of the formation (38) other than at the first desired stimulation location.

A method and apparatus for temporarily closing a subterranean conduit wherein a tubular housing (52) is disposed in the well, a temporary plug (70) is positioned in the housing to block fluid flow therethrough, mechanical fracturing means (72) is provided for breaking the plug (70); and the plug is formed at least partially of material dissolvable in the well fluid.

Method and apparatus for actuating one or more downhole well tools carried by a production or work string conduit (12) having an imperforate wall (19) and for blocking fluid communication between an activating fluid body and a second fluid source within said well across dynamic seals between actuating members of the well tool, by producing selective signals through the conduit wall detectable by a member (183) to produce an activating signal for actuating the downhole well tool by a downhole energy source.

A casing valve for use in a well comprises an outer housing (50) having a longitudinal passageway (52) defined therethrough and having a housing wall (54) with a housing communication port (56) defined through said housing wall, said housing including a first disintegratable plug (96) initially blocking said housing communication port; and a sliding sleeve (66) slidably disposed in said longitudinal passageway, said sleeve having a longitudinal sleeve bore (90) defined therethrough and having a sleeve wall (92) with a sleeve communication port (94) defined through said sleeve wall, said sleeve including a second disintegratable plug (98) initially blocking said sleeve communication port, said sleeve being selectively movable relative to said housing between a first position wherein said housing communication port and said sleeve communication port are out of registry with each other and a second position wherein said ports are in registry with each other.