Abstract: A drilling method in which a rotary drill bit is mounted on a tubular drillstring extending through a bore comprises: drilling through a formation containing fluid at a predetermined pressure; circulating drilling fluid down through the drill string to exit the string at or adjacent the bit, and then upwards through an annulus between the string and bore wall; and adding energy to the drilling fluid in the annulus at a location above the formation. The addition of energy to the fluid in the annulus has the effect that the pressure of the drilling fluid above the formation may be higher than the pressure of the drilling fluid in communication with the formation and that predetermined differential may be created between the pressure of the formation fluid and the pressure of the drilling fluid in communication with the formation.

Abstract: A deformable member can be used in a well tool for use in downhole oil/gas wells. In one embodiment, a deformable member (46) is described which is deformable between undeformed and deformed positions, and comprises a generally hollow cylindrical body (48) defining a wall (50). The wall (50) includes three circumferential lines of weakness in the form of grooves, with two grooves (52, 54) provided in an outer surface (56) of the member wall (50), and the other groove (58) provided in an inner surface (60). The member (46) is deformed outwardly by folding about the lines of weakness (52, 54, 56) and is used in particular to obtain sealing contact with a tube in which the member (46) is located.

Abstract: The present invention relates methods and apparatus for lining a wellbore. In one aspect, a drilling assembly having an earth removal member and a wellbore lining conduit is manipulated to advance into the earth. The drilling assembly includes a first fluid flow path and a second fluid flow path. Fluid is flowed through the first fluid flow path, and at least a portion of which may return through the second fluid flow path. In one embodiment, the drilling assembly is provided with a third fluid flow path. After drilling has been completed, wellbore lining conduit may be cemented in the wellbore.

Abstract: A drilling method in which a rotary drill bit is mounted on a tubular drillstring extending through a bore comprises: drilling through a formation containing fluid at a predetermined pressure; circulating drilling fluid down through the drill string to exit the string at or adjacent the bit, and then upwards through an annulus between the string and bore wall; and adding energy to the drilling fluid in the annulus at a location above the formation. The addition of energy to the fluid in the annulus has the effect that the pressure of the drilling fluid above the formation may be higher than the pressure of the drilling fluid in communication with the formation and that predetermined differential may be created between the pressure of the formation fluid and the pressure of the drilling fluid in communication with the formation.

Abstract: A drilling method in which a rotary drill bit is mounted on a tubular drillstring extending through a bore comprises: drilling through a formation containing fluid at a predetermined pressure; circulating drilling fluid down through the drill string to exit the string at or adjacent the bit, and then upwards through an annulus between the string and bore wall; and adding energy to the drilling fluid in the annulus location above the formation. The addition of energy to the fluid in the annulus has the effect that the pressure of the drilling fluid above the formation may be higher than the pressure of the drilling fluid in communication with the formation and that predetermined differential may be created between the pressure of the formation fluid and the pressure of the drilling fluid in communication with the formation.

Abstract: A deformable member can be used in a well tool for use in downhole oil/gas wells. In one embodiment, a deformable member (46) is described which is deformable between undeformed and deformed positions, and comprises a generally hollow cylindrical body (48) defining a wall (50). The wall (50) includes three circumferential lines of weakness in the form of grooves, with two grooves (52, 54) provided in an outer surface (56) of the member wall (50), and the other groove (58) provided in an inner surface (60). The member (46) is deformed outwardly by folding about the lines of weakness (52, 54, 56) and is used in particular to obtain sealing contact with a tube in which the member (46) is located.

Abstract: A downhole ball-valve (20) comprises a body (22) defining a bore (32), a valve ball (34) defining a through passage (36) such that the ball (34) may be positioned to permit flow through the body bore (32) or to close the bore, and a sealing assembly (44) located to one side of the ball and defining a valve seat (50, 53) for forming a sealing contact with the ball (34) and a seal between the body and the assembly. A fluid pressure force applied at one side of the ball (34) tends to urge the valve seat (50, 53) towards the ball (34) and a fluid pressure force applied at the other side of the ball tends to urge the ball towards the valve seat. The sealing assembly forms part of a ball carriage which is axially movable in the bore, axial movement of the carriage inducing rotation of the ball between the open and closed positions.

Abstract: A downhole check valve includes a body (32) defining a flow passage and a valve assembly (34, 42, 44) mounted in the body, the valve assembly including a valve member (34) movable from a first configuration to a second configuration. In the first configuration the valve member prevents flow in one direction through the passage, and in the second configuration the valve member is retained in an open position. A valve member retaining sleeve (48) is normally restrained in a first configuration and biassed for movement to a second configuration. The retainer is held in the first configuration while the valve member (34) is in the first configuration and is releasable from the first configuration to move the valve member to the open position and retain the valve member in the open position.