An offshore well-processing system includes a mobile offshore drilling unit and a remote well-processing device configured to be positioned on an offshore platform different from the mobile offshore drilling unit, the mobile offshore drilling unit defining at least one well centre and comprising at least one primary drill rig including at least one drill floor and at least one hoisting system for raising and lowering tubular equipment through the at least one well centre from/into a well in the seafloor. The mobile offshore drilling unit and the remote well-processing device are configured to be operationally coupled to each other; and the mobile offshore drilling unit is configured to assist in performing concurrent well-processing tasks on respective wells, including the first well processing task performed by the remote well-processing device on a first well and a second well-processing task concurrently performed by the offshore well-processing system on a second well.

An offshore well-processing system includes a mobile offshore drilling unit and a remote well-processing device configured to be positioned on an offshore platform different from the mobile offshore drilling unit, the mobile offshore drilling unit defining at least one well centre and comprising at least one primary drill rig including at least one drill floor and at least one hoisting system for raising and lowering tubular equipment through the at least one well centre from/into a well in the seafloor. The mobile offshore drilling unit and the remote well-processing device are configured to be operationally coupled to each other; and the mobile offshore drilling unit is configured to assist in performing concurrent well-processing tasks on respective wells, including the first well processing task performed by the remote well-processing device on a first well and a second well-processing task concurrently performed by the offshore well-processing system on a second well.

A process is described for milling a window in the casing (2) of an oil or gas producing well, for example in order to drill a lateral well branching off from the main well. A wireline milling tool is first used, in a relatively low cost operation, to create a small window (14) or notch in the casing (2). Provided a small window (14) or notch can be created successfully, an expensive heavy duty coil tubing milling operation can then be conducted to create the full window, some 4-6 feet in length. Previous attempts to create a full window using wireline tools have encountered difficulties due to there being no circulating drilling fluid to remove metal swarf and due to the need for the tool to be supported by casing during the milling operation, when the integrity of the casing is being compromised by drilling the window. The proposed wireline tool has an actuator (4) with relatively small stroke length and a relatively small container (8) to manage the swarf produced by the milling process. (FIG. 2).

A process is described for milling a window in the casing (2) of an oil or gas producing well, for example in order to drill a lateral well branching off from the main well. A wireline milling tool is first used, in a relatively low cost operation, to create a small window (14) or notch in the casing (2). Provided a small window (14) or notch can be created successfully, an expensive heavy duty coil tubing milling operation can then be conducted to create the full window, some 4-6 feet in length. Previous attempts to create a full window using wireline tools have encountered difficulties due to there being no circulating drilling fluid to remove metal swarf and due to the need for the tool to be supported by casing during the milling operation, when the integrity of the casing is being compromised by drilling the window. The proposed wireline tool has an actuator (4) with relatively small stroke length and a relatively small container (8) to manage the swarf produced by the milling process. (FIG. 2).

An abrasive suspension eroding system has an eroding unit (11), which can be lowered into an existing drilled hole (1), in order to generate a high-pressure erosion jet for the abrasive suspension eroding of material (6, 20) in an existing drilled hole (1). The eroding unit (11) can be connected to a drilling fluid line (9) and is configured to generate a high-pressure erosion jet from a drilling fluid abrasive suspension device.

An abrasive suspension eroding system has an eroding unit (11), which can be lowered into an existing drilled hole (1), in order to generate a high-pressure erosion jet for the abrasive suspension eroding of material (6, 20) in an existing drilled hole (1). The eroding unit (11) can be connected to a drilling fluid line (9) and is configured to generate a high-pressure erosion jet from a drilling fluid abrasive suspension device.

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 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 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 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.