A well system includes a drilling vessel, a concentric drillstring extending from the vessel into a subterranean wellbore disposed beneath a mudline, wherein the concentric drillstring is configured to circulate a drilling fluid from the drilling vessel into the wellbore along a first passage, and to circulate the drilling fluid from the wellbore to the drilling vessel along a second passage, and a subsea pump in fluid communication with the wellbore, wherein the subsea pump is configured to manage fluid pressure in the wellbore by controlling a height of a column of hydrostatic fluid disposed in the wellbore.

A cementing tool and a method for cementing a casing string using the cementing tool is provided. The cementing tool comprises threaded top and bottom openings for attaching to a casing string, a plurality of ports, and a plurality of shear plugs shaped to fit within the ports. In the method, a casing string comprising the cementing tool is run into a well and the cementing process of the casing string is initiated. When the casing shoe of the casing string becomes plugged, the cementing tool is activated without removing the casing string from the well. Activation of the cementing tool releases pressure trapped in the cementing tool, thereby releasing the shear plugs from the ports and opening the ports to create alternative passages for the cement to complete the cementing process.

A wellbore assembly includes a wellbore string configured to be disposed within a wellbore. The wellbore assembly also includes a float collar coupled to a downhole end of the wellbore string. The float collar includes a housing, a check valve, and a sleeve. The housing includes a fluid outlet. The housing defines a fluid port that extends through a wall of the housing. The check valve is disposed within the housing between the fluid port and the fluid outlet. The sleeve is coupled to the wall of the housing uphole of the check valve. The sleeve moves, based on pressure changes of the fluid in the float collar, with respect to the wall of the housing thereby either exposing the fluid port and opening a fluid pathway from the bore to an annulus of the wellbore, or covering the fluid port and blocking the fluid pathway.

A return exhaust assembly (50) for a reverse circulation hammer H comprises return tube (52) having first and second ends and a seat (56) at or near the first end (54). An exhaust sleeve (58) has: a section (60) seated and resiliently supported on the seat (56); and, a portion (62) that extends to and includes an end (64) of the exhaust sleeve (58) distal the section (60). The portion (60) surrounds a length of the return tube (52) with an annular clearance 66 formed between the return tube (52) and the sleeve (58) from a down hole end of the seat (56) to the distal end (64) of the exhaust sleeve (58). This arrangement allows relative movement, and therefore a degree of misalignment between the exhaust sleeve (58) and the return tube.

A circulating downhole tool utilising a variable fluid pressure regulated cycle valve device that can be attached to the borehole assembly BHA of a coiled tubing and used down an offshore or onshore wellbore is disclosed. The circulating downhole tool utilising a variable fluid pressure regulated cycle valve device can be remotely operated by an operator on the surface as many times as required in either the through-flow, intermediary or circulatory modes-of-operation, by simply varying the drilling fluid flow rate and pressure being supplied from the pump located on the surface and interconnected to the coiled tubing and the BHA that will include the circulating downhole tool utilising a variable fluid pressure regulated cycle valve device.

Gravity driven reverse circulator tools are provided and methods of using same. One tool has nested pipes that when fully nested close a hole in one of the pipes, but when the drillstring is lifted, the pipes partially separate under the force of gravity to expose the hole. The other embodiment is similar, but the hole is hook shaped (hook on top as in a walking cane) and a protrusion from the other pipe fits in the hole. Thus, both lifting and rotation are needed open the tool.

A downhole cleaning tool (40) adapted for location in bore-lining tubing (22). The tool (40) comprises a tubular body (42) defining an internal bore (48), at least one radially extending cleaning blade (92), and an external axially extending bypass flute (96, 98, 100, 102). The body further defines a fluid flow path from the internal bore (48) to at least one elongated jetting slot (94) extending along an outer surface of the blade (92).

A system for controlling surge pressure and deployed into a wellbore drilled using a managed pressure drilling technique includes auto-fill float equipment allowing flow into a liner casing string, a drillpipe diverter providing a flow path between a drillpipe landing string and an annulus, and a drillpipe flow restrictor selectively blocking the flow path from the top of the drillpipe landing string while allowing fluid to be displaced up the liner casing string and into the annulus. The drillpipe flow restrictor and the drillpipe diverter are convertible to provide a flow path from the wellbore through the auto-fill float equipment to a top surface while blocking flow through the diverter into the annulus. The auto-fill float equipment is convertible to block the flow path from the wellbore into the liner casing string, while allowing fluid to flow from the liner casing string into the wellbore.

A body defines a central flow passage. A check valve is located within the central flow passage. The check valve is supported by the body. The check valve is arranged such that a fluid flow travels in a downhole direction during operation of the float collar. An auxiliary flow passage is substantially parallel to the central flow passage and is defined by the body. The auxiliary flow passage includes an inlet upstream of the check valve and an outlet at a downhole end of the float collar. A rupture disk seals the inlet of the auxiliary flow passage. The rupture disk is configured to burst at a specified pressure differential.

A casing removal system includes a flow diversion valve. The flow diversion valve includes a flow switch that engages an upper end of an inner casing. When the flow switch engages the upper end of the inner casing, the flow diversion valve opens and at least a portion of the fluid flow through the casing removal system exhausts to the annulus. The remaining fluid flow below the flow diversion valve is insufficient to operate a mud motor that drives a casing cutter. In other embodiments, when the flow switch is not engaged with the inner wall of casing, the flow diversion valve prevents fluid flow to components that are downhole of the valve and when the flow switch is engaged with the inner wall of casing, the flow diversion valve allows for fluid flow to components that are downhole of the valve.