Abstract: A system for sealing the intersection between a primary borehole and a branch borehole comprises a primary casing section located in the primary borehole in the region of the branchpoint, and a branch casing section located in the branch borehole and secured to the primary casing section. The primary casing section is tubular and defines a slant surface which intersects a central axis of the primary casing section at an acute angle, so that the primary casing section can be pressed towards the branchpoint by means of a hollow whipstock or other wedge-shaped element.

Abstract: A method for joining well and other oilfield tubulars by amorphous bonding comprises the steps of positioning a body of amorphous material (16) between adjacent and surfaces of a pair of oilfield tubulars (3, 4) that are to be joined and using induction heating to melt the amorphous material and create on cooling a metallurgical bond between the tubulars (3, 4). Throughout the heating and bonding process the tubulars (3, 4) are fixed in axial alignment with each other using clamp means which include a mandrel (1) which is inserted into the interior of the tubulars (3, 4) so that the bonding process can be performed in a sealed chamber (17, 18) which is filled with an inert gas.

Abstract: A method is provided for creating zonal isolation between the exterior and interior of an uncased section of an underground well system which is located adjacent to a well section in which a well casing is present. The method includes inserting an expandable tubular through the existing well casing into an uncased section, such as a lateral branch, of the underground well system and subsequently expanding the expandable tubular such that the one end is pressed towards the wall of the uncased section of the well system and the outer surface of the other end is pressed against the inner surface of the well casing thereby creating an interference fit capable of achieving a shear bond and a hydraulic seal between the surrounding surfaces.