The present invention provides a downhole heating tool with an increased heating capacity for use in setting alloy plugs/seal in downhole target regions of wellbores, such as oil/gas wells. The increased heating capacity enables greater quantities of alloy to be melted in one operation. It also enables alloys with higher melting points to be melted in the downhole environment. To this end the heating tool comprises a plurality of discrete tubular heating units linked together by connection means that permit the movement of the tubular heating units relative to one another. The relative freedom of movement between the heating units facilitates a transition between a deployment configuration, in which the heating tool is optimised for deployment downhole, and a heating configuration, in which the heating tool adopts an expanded heating footprint within a downhole target region.

A system for supporting a borehole junction includes a device configured to deploy a material in a solid state to a downhole location proximate to the borehole junction, and a heat source configured to apply heat to the material to a temperature sufficient to liquefy the material. The liquified material is configured to flow into a formation region adjacent to the borehole junction and consolidate the formation region.

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 method of conveying materials or tools into a well, the well including a plurality of lengths of concentric tubing, comprising the step of permitting at least one cartridge to free-fall under gravity into the well. No line may be connected to the cartridge. The cartridge is selected from a group of cartridges which may comprise, a cartridge including thermite, hermetically sealed from well fluids, a cartridge including low temperature alloy, hermetically sealed from well fluids, a cartridge formed from low temperature alloy, a cartridge including a detonator triggered by impact, a cartridge including a detonator triggered by an electronic or mechanical clock, a cartridge formed from tungsten carbide, a bridge plug cartridge including slips to retain the bridge plug in a position against the wall of well tubing, a thermal barrier material, or a shock absorber that absorbs energy from subsequent cartridges being dropped.

A well cleanup process involves removing an impermeable filter cake from a formation face with thermochemical and chelating agents to allow formation fluids to flow from a reservoir to a wellbore. The method may be used with oil and water-based drilling fluids with varied weighting agents, e.g., bentonite, calcium carbonate, or barite. Such thermochemical agents may involve two salts, e.g., NO.sub.2.sup.− and NH.sub.4.sup.+, which, when mixed together, can generate pressure and heat, in addition to hot H.sub.2O and/or N.sub.2. For example, the thermochemical agents may comprise Na.sup.+, K.sup.+, Li.sup.+, Cs.sup.+, Mg.sup.2+, Ca.sup.2+, and/or Ba.sup.2+ with NO.sub.2.sup.− and NH.sub.4.sup.+ with F.sup.−, Cl.sup.−, Br.sup.−, I.sup.−, CO.sub.3.sup.2−, NO.sub.3.sup.−, ClO.sub.4.sup.−, and/or .sup.−OH. The thermochemical agents in combination with a chelator such as EDTA can removed the filter cake after 6 hours with a removal efficiency of 89 wt % for the barite filter cake in water based drilling fluid, exploiting the generation of a pressure pulse and heat which may disturb the filter cake and/or enhance barite dissolution and polymer degradation.

A well abandonment tool for deployment in a well tubing, comprising an upper section, including a connector to allow the tool to be deployed on slickline or wireline a housing including a chamber containing bismuth a receiver and processor, capable of receiving a signal from the surface to actuate a permanent sealing process a lower section, including a release means capable of releasing the upper section of the tool from a lower section of the tool a tubing cup seal capable to making a seal against the inside of the well tubing to contain moltenbismuth until it solidifies a tubing bridge plug or anchor capable of securing the tool inside the well tubing the tool also including a heat source capable of melting the bismuth to a flowable state, actuated by the receiver and processor such that when the tool has been secured in the well tubing, the bismuth melting process can be initiated, and the upper housing released from the lower housing to recover the upper housing, and bismuth being melted by the heating means and caused to flow into the well tubing above the tubing cup seal to form a plug.

Disclosed herein are compositions and methods for reducing fluid loss in a well bore, methods for wellbore strengthening and increasing the integrity of the borehole of an oil or gas well. Also disclosed are methods for artificially increasing the temperature of a subsurface formation in the wellbore to increase the apparent wellbore strength. The mechanism for accomplishing this revolves around increasing fracture propagation pressure by actively manipulating thermal wellbore stresses.

A chemical reaction heat source for use in heaters used in down-hole applications is provided. The heat source has a fuel composition that comprises thermite and a damping agent. The use of the thermite mix enables the heaters of the present invention to generate hotter temperatures down wells. This in turn allows the use of Bismuth/Germanium alloys, which have higher melting points, to enable the production of plugs for the abandonment of deeper wells where subterranean temperatures are higher.

A method for repairing a leak in a cement sheath of a casing of a well. A portion of the inner casing and the cement sheath is removed to create an opening that extends through the inner casing and the cement sheath. A tool is inserted within the inner casing to a location adjacent to the opening and one or more segments of a heat-deforming material that are part of the tool is heated to cause melting of the heat-deforming material. The tool is configured to direct the melted heat-deforming material radially outward into the opening. Once cooled, the heat-deforming material plugs the opening, thereby repairing the leak within the cement sheath.

A method and apparatus are provided for removably plugging a wellbore. The wellbore leads to a reservoir having a reservoir temperature. The method includes: selecting a melting point of a metal alloy based on the reservoir temperature; sealing the metal alloy against an interior wall of a tubing, while the tubing is above a ground in which the wellbore is drilled, such that the metal alloy defines a fluid barrier plug against flow of any portion of the reservoir through the tubing when the tubing is disposed within the wellbore; and heating the metal alloy above the melting point while the tubing is disposed within the wellbore such that the metal alloy flows from the tubing and the fluid barrier plug is eliminated.