Abstract: A method of sealing a subsurface bore comprises: locating a volume of thermite in the bore; locating a volume of alloy in the bore with the thermite; initiating reaction of the thermite to heat the alloy; and bringing the alloy to above the melting point of the alloy whereby the alloy flows and occludes the bore. The thermite may retain its initial form during or following reaction or may partially fluidise. The thermite may react to provide a platform that at least partially occludes the bore. The alloy may flow over a surface of the thermite.

Abstract: A downhole tool comprises a heater including a container enclosing a volume of compacted thermite. A volume of flowable alloy is provided above the heater. A fusible bulkhead may be provided between the heater and the alloy and provides for direct conduction of heat from the heater to the alloy. A housing containing the alloy may be separated from the heater by heating a fusible socket that anchors an end of a tensioned support member. The thermite may define an internal volume adapted to receive alloy. The heater may be activated to melt the alloy and the alloy may then solidify to form a bore-sealing plug.

Abstract: A method of sealing an annulus between first and second bore-lining tubulars comprises providing a first bore-lining tubular having a first volume of alloy thereon and running the first bore-lining tubular into a bore provided with a second bore-lining tubular. The alloy is fluidised and then allowed to solidify in an annulus between the bore-lining tubulars and bond the tubulars together. The alloy may be fluidised in the presence of flux.

Abstract: A method of retaining material in a bore comprises running a tool comprising a retainer member and a fusible part into a bore with the retainer member in a retracted configuration. The tool is positioned at a desired location in the bore and the fusible part is heated to reconfigure the retainer member to an extended configuration in which the retainer member engages the bore wall.

Abstract: A downhole method comprises expanding a patch member. The patch member may be employed in a method of sealing a wall of a bore. The sealing method may comprise: providing the patch member with a sealing material on an exterior surface; running the patch member into the bore in a smaller diameter first configuration; heating the sealing material to render the sealing material flowable; reconfiguring the patch member to a larger diameter second configuration; and hardening the sealing material to provide a seal between the exterior surface of the patch member and an inner surface of the bore.

Abstract: A method of sealing a subsurface bore comprises: locating a volume of thermite in the bore; locating a volume of alloy in the bore with the thermite; initiating reaction of the thermite to heat the alloy; and bringing the alloy to above the melting point of the alloy whereby the alloy flows and occludes the bore. The thermite may retain its initial form during or following reaction or may partially fluidise. The thermite may react to provide a platform that at least partially occludes the bore. The alloy may flow over a surface of the thermite.

Abstract: A downhole system (10) comprises a tool (16) suspended on a reelable support (18). The support (18) has an optical fibre and the tool communicates with a surface controller via the fibre. The tool (16) has a number of units (24,16a,16b,16c), the unit (24) functioning as a router to transmit and receive signals to and from the other units (16a,16b,16c) and the surface controller via the optical fibre. Each of the units (24,16a,16b,16c) is assigned a unique address which permits secure communication between each unit (24,16a,16b,16c) and the controller over the fibre.