Systems and methods for casing drilling riserless sections of a subsea bore may include casing drilling a section of a bore for a casing of the subsea bore to a predetermined depth. The method also may include, while casing drilling the section of the bore, obtaining information indicative of pore pressure and fracture pressure of a geological formation through which the section is casing drilled, and determining a pressure range based at least in part on the pore pressure, the fracture pressure, and a modification to mechanical properties of the geological formation due to the casing drilling of the section. The method further may include selecting, based at least in part on the pressure range and the predetermined depth, a pressure of the bore for casing drilling the section.

Systems and methods for casing drilling riserless sections of a subsea bore may include casing drilling a section of a bore for a casing of the subsea bore to a predetermined depth. The method also may include, while casing drilling the section of the bore, obtaining information indicative of pore pressure and fracture pressure of a geological formation through which the section is casing drilled, and determining a pressure range based at least in part on the pore pressure, the fracture pressure, and a modification to mechanical properties of the geological formation due to the casing drilling of the section. The method further may include selecting, based at least in part on the pressure range and the predetermined depth, a pressure of the bore for casing drilling the section.

A subsea vertical drilling machine is disclosed, having: a drill assembly formed by: a riser pipe having a first end, a second end, and a length extending between the first and second ends; and a drilling machine body, including a drilling head, coupled to the first end of the riser pipe;
and a vertical feed system configured for advancing the drill assembly in a vertical direction.

The riser pipe is provided with at least one rack extending along at least a part of the length of the riser pipe, and the vertical feed system comprises a motor coupled to a pinion, the pinion arranged for engaging with the rack for advancing the drill assembly.

The invention concerns a bend stiffener (10, 32) for locally protecting an elongate flexible member (14) from excessive curvature when the elongate flexible member is deployed in water. The bend stiffener comprises an elongate stiffener body (34) which has a root end, a free end, and a passage (36) extending through the stiffener body from the root end to the free end for receiving and embracing the flexible member. A coupling (16) at or toward the root end of the stiffener body serves to mount the stiffener body. The stiffener body is sufficiently flexible to curve somewhat along with the flexible member when the flexible member suffers a bending load and carries a sensor module which is located proximate the free end of the bend stiffener and is configured to sense inclination and/or orientation and/or movement of the free end of the bend stiffener.

A method is for performing work in a well and on a vessel. A wellbore assembly such as a tool string is suspended on a first flexible elongate member from the vessel. The wellbore assembly is used to perform work in the well. The wellbore assembly such as a tool string is suspended on a second flexible elongate member from the vessel. The wellbore assembly on the first flexible elongate member is removed from the well, and after the removal, the wellbore assembly on the second flexible elongate member is inserted into the well. The inserted wellbore assembly in the well can then be used to perform further work. The wellbore assemblies may be deployed and retrieved on independently operable wirelines. A related vessel and apparatus is also described.

A method is for performing work in a well and on a vessel. A wellbore assembly such as a tool string is suspended on a first flexible elongate member from the vessel. The wellbore assembly is used to perform work in the well. The wellbore assembly such as a tool string is suspended on a second flexible elongate member from the vessel. The wellbore assembly on the first flexible elongate member is removed from the well, and after the removal, the wellbore assembly on the second flexible elongate member is inserted into the well. The inserted wellbore assembly in the well can then be used to perform further work. The wellbore assemblies may be deployed and retrieved on independently operable wirelines. A related vessel and apparatus is also described.

A double-layer coiled tubing double-gradient drilling system, on the basis of conventional drilling equipment, includes a double-layer coiled tubing system, spacer fluid, a downhole lifting pump system, throttling control systems and a data monitoring system. Power fluid enters an annular space of the tubing through an adapter, passes through a downhole lifting pump, enters an inner pipe through a bridge channel, and enters the bottom hole through the drill bit. Return fluid enters an annular channel of the tubing through a recovery hole, then enters the inner pipe through the bridge channel and enters the lifting pump, and then enters a solid control system through the adapter and the control systems in sequence. Gradient control of the bottom hole pressure is realized through monitoring of the spacer fluid and control of the drilling pump unit and throttling control systems. The problem of narrow safe drilling density window is solved.

A double-layer coiled tubing double-gradient drilling system, on the basis of conventional drilling equipment, includes a double-layer coiled tubing system, spacer fluid, a downhole lifting pump system, throttling control systems and a data monitoring system. Power fluid enters an annular space of the tubing through an adapter, passes through a downhole lifting pump, enters an inner pipe through a bridge channel, and enters the bottom hole through the drill bit. Return fluid enters an annular channel of the tubing through a recovery hole, then enters the inner pipe through the bridge channel and enters the lifting pump, and then enters a solid control system through the adapter and the control systems in sequence. Gradient control of the bottom hole pressure is realized through monitoring of the spacer fluid and control of the drilling pump unit and throttling control systems. The problem of narrow safe drilling density window is solved.

What is provided is a method and apparatus which can be detachably connected to an annular blowout preventer thereby separating the drilling fluid or mud into upper and lower sections and allowing the fluid to be displaced in two stages, such as while the drill string is being rotated and/or reciprocated. In one embodiment the sleeve can be rotatably and sealably connected to a mandrel. The swivel can be incorporated into a drill or well string and enabling string sections both above and below the sleeve to be rotated in relation to the sleeve. In one embodiment the drill or well string does not move in a longitudinal direction relative to the swivel. In one embodiment, the drill or well string does move longitudinally relative to the sleeve of the swivel.

What is provided is a method and apparatus which can be detachably connected to an annular blowout preventer thereby separating the drilling fluid or mud into upper and lower sections and allowing the fluid to be displaced in two stages, such as while the drill string is being rotated and/or reciprocated. In one embodiment the sleeve can be rotatably and sealably connected to a mandrel. The swivel can be incorporated into a drill or well string and enabling string sections both above and below the sleeve to be rotated in relation to the sleeve. In one embodiment the drill or well string does not move in a longitudinal direction relative to the swivel. In one embodiment, the drill or well string does move longitudinally relative to the sleeve of the swivel.