A method of extracting the underground resources by pressurizing a fluid filled in an ore chute in which cracks are formed and by, further, forming or growing the cracks, the underground resources being extracted through the cracks, wherein a hydrolysis-blocking agent is introduced with pressure into the fluid to block a diverting agent that works to temporarily close the cracks.

A diverter assembly includes a tubing segment and one or more sleeve members disposed therein. The tubing segment includes apertures that are selectively alignable with apertures of an inner sleeve disposed within the tubing segment. The tubing segment includes a series of stops (e.g., shear pins) to arrest movement of the first sleeve within the bore of the tubing segment. A first one or more ball seats are included in the first sleeve such that deployment of a first ball and pressurization of the well above the first ball causes a first set of shear pins to fail, thereby allowing the first sleeve to slide downhole to cause apertures of the sleeve to align with apertures of the tubing segment, thereby causing fluid to flow to an annulus between the tubing segment and wellbore wall.

A wellbore is plugged using a bismuth alloy. The wellbore is arranged so that a liquid bismuth alloy sets with an excess pressure of the plug relative to the borehole fluid pressure along a desired seal height distance.

A portion of a wellbore is drilled in a subterranean formation, using a drilling string (140) disposed within a casing string (130) and extending through a cement retainer (150) disposed within the casing string. The drilling string can be retracted into the casing string to a location fully above the cement retainer, and subsequently the casing string can be cemented in the wellbore whereby maintaining the drilling string inside the casing in the wellbore.

A method for forming an offshore well comprises forming a well structure (1) which includes a lower well portion extending below a seabed and an upper well portion (2) extending upwardly between the seabed (18) and a terminating upper end (3) of the well structure, wherein the well structure comprises a plurality of concentrically arranged tubular strings (22) and at least one annulus (48) defined therebetween. The method includes steps for minimising the bending stiffness of the upper well portion. In one example minimising the bending stiffness of the upper well portion may comprise partially filling at least one annulus with cement (52) to a height which: is intermediate the seabed and the terminating upper end of the well structure. In another example minimising the bending stiffness of the upper well portion may comprise providing a cement disruptor within at least one annulus and locating cement within said at least one annulus to define a cement sheath, wherein the cement disruptor, for example sleeve (122), reduces resistance of at least a portion of the cement sheath to bending of the upper well portion. In a further example minimising the bending stiffness of the upper well portion may comprise locating a flexible material within at least one annulus; and In a further example minimising the bending stiffness of the upper well portion may comprise varying the bending stiffness along at least one of the plurality of tubular strings.

A wellbore system includes a lock ring forming at least a portion of a sealing assembly, the lock ring being coupled to and axially lower than one or more components of the sealing assembly to be positioned within an annulus. The wellbore system also includes a pedestal coupled to the lock ring, the pedestal arranged axially lower than at least a portion of the lock ring, the pedestal to be installed within the annulus. The wellbore system further includes a shoulder formed on at least a portion of a hanger. The wellbore system also includes a debris pocket formed within the annulus, the debris pocket arranged axially lower than both the shoulder and a lock ring groove.

A method of locating bore-lining tubing, such as a liner (120), in a drilled bore (106) comprises selecting a buoyant material, such as air (138), having a density lower than the density of an ambient fluid, such as well fluid (180, 182). The buoyant material (138) and an inner tubing (140) are located within the bore-lining tubing (120) with the inner tubing (140) extending from a distal end of the bore-lining tubing to a proximal end of the bore-lining tubing. The inner tubing (140) is sealed to the distal end of the bore-lining tubing (120) and to a portion of the bore-lining tubing (120) spaced from the distal end to define an inner annulus (152) between the inner tubing (140) and the bore-lining tubing (120). A volume of the buoyant material (138) is retained within the inner annulus (152). An assembly (168) comprising the inner tubing (140) and the bore-lining tubing (120) and containing the volume of buoyant material (138) is run into a drilled bore (106). Fluid (126a) may be flowed through the inner tubing (140) and into an outer annulus (124) surrounding the bore-lining tubing (120).

An apparatus for flowing and mixing cement within a subterranean formation includes a housing, a flow control device, and baffles. The housing is configured to contain a cement additive. The housing includes a first end and a second end. The first end is configured to couple to a cement retainer. The flow control device is disposed at the second end of the housing. The baffles are disposed within the housing.

A method for cementing a tubular string into a wellbore includes: running the tubular string into the wellbore using a workstring having a deployment assembly; delivering an opener activator through the workstring to the deployment assembly, thereby launching an opener plug from the deployment assembly; pumping the opener activator and plug to a stage valve of the tubular string, thereby opening the stage valve; pumping cement slurry into the workstring; pumping a closer activator through the workstring behind the cement slurry, thereby launching a closer plug from the deployment assembly; and pumping the closer activator and plug to the open stage valve, thereby driving the cement slurry into an annulus between the tubular string and the wellbore and closing the stage valve.

Methods and systems including a wellbore having a pipe string extending through a wellhead and into the wellbore, wherein an annulus is formed between the pipe string and the wellbore, an isolation device that closes the wellbore in a closed pressure loop, a choke line in fluid communication with an interior of the pipe string through an outlet port of the wellhead, a choke valve fluidly coupled to the outlet port of the wellhead, wherein the choke valve is manipulable to control fluid flow through the choke line, and a crossover tool in the wellbore to divert incoming fluid from the interior of the pipe string to the annulus.