A bit saver assembly having an inner valve sleeve that actuates upon the weight-on-bit (WOB) of the drill bit exceeding a threshold value to overcome the countervailing force provided by a spring contained within the bit saver assembly and the internal flow pressure of the drilling fluid at the area of the inner valve sleeve. Actuation of the inner valve sleeve opens a fluid passage to the wellbore annulus resulting in a reduction of drilling fluid flow pressure and the stretch of the drill string thereby reducing WOB of the drill bit without operator assistance.

A bit saver assembly having an inner valve sleeve that actuates upon the weight-on-bit (WOB) of the drill bit exceeding a threshold value to overcome the countervailing force provided by a spring contained within the bit saver assembly and the internal flow pressure of the drilling fluid at the area of the inner valve sleeve. Actuation of the inner valve sleeve opens a fluid passage to the wellbore annulus resulting in a reduction of drilling fluid flow pressure and the stretch of the drill string thereby reducing WOB of the drill bit without operator assistance.

A flow measurement apparatus can include a main flow passage, a variable flow restrictor, a bypass flow passage having an inlet connected with the main flow passage upstream of the variable flow restrictor and an outlet connected with the main flow passage downstream of the variable flow restrictor, and a mass flowmeter connected in the bypass flow passage between the inlet and the outlet. A method can include connecting a flow measurement apparatus, so that a fluid flow in a well also flows through the flow measurement apparatus, and varying a restriction to the fluid flow through the variable flow restrictor in response to a change in a flow rate of the fluid flow.

A flow measurement apparatus can include a main flow passage, a variable flow restrictor, a bypass flow passage having an inlet connected with the main flow passage upstream of the variable flow restrictor and an outlet connected with the main flow passage downstream of the variable flow restrictor, and a mass flowmeter connected in the bypass flow passage between the inlet and the outlet. A method can include connecting a flow measurement apparatus, so that a fluid flow in a well also flows through the flow measurement apparatus, and varying a restriction to the fluid flow through the variable flow restrictor in response to a change in a flow rate of the fluid flow.

The present invention refers to a method of drilling a marine wellbore with fluid reverse circulation without using drilling riser tubulars. In reverse circulation drilling, the fluid return with gravels occurs inside the drill string (17) and the injection of clean fluid is done through the annular of the well, so that, having a rotating head over the BOP (19), or inside it, the use of riser tubulars as a flow line for the fluid return with gravels is disposed, using instead the drill string (17). For the kill and choke lines, as well as for fluid injection, rigid or flexible lines can be used, eliminating the need to use drilling risers, thus releasing large load capacity and space on the probe. The method of this invention also eliminates the need for large volumes of fluid to fill entire riser tubulars. The entire operation can be done without the need for subsea pumps or concentric columns. Additionally, the invention makes the operation of lowering the drilling riser tubulars unnecessary, which lasts for days and has a high cost. Finally, for dual activity probes, the arrangement allows the use of the two towers even after connecting the BOP (19), something that is not possible with the use of drilling riser tubulars. Therefore, operations such as mounting and lowering the casing in the water depth can be carried out in parallel with the drilling of the phase, allowing a significant additional gain of time.

The present invention refers to a method of drilling a marine wellbore with fluid reverse circulation without using drilling riser tubulars. In reverse circulation drilling, the fluid return with gravels occurs inside the drill string (17) and the injection of clean fluid is done through the annular of the well, so that, having a rotating head over the BOP (19), or inside it, the use of riser tubulars as a flow line for the fluid return with gravels is disposed, using instead the drill string (17). For the kill and choke lines, as well as for fluid injection, rigid or flexible lines can be used, eliminating the need to use drilling risers, thus releasing large load capacity and space on the probe. The method of this invention also eliminates the need for large volumes of fluid to fill entire riser tubulars. The entire operation can be done without the need for subsea pumps or concentric columns. Additionally, the invention makes the operation of lowering the drilling riser tubulars unnecessary, which lasts for days and has a high cost. Finally, for dual activity probes, the arrangement allows the use of the two towers even after connecting the BOP (19), something that is not possible with the use of drilling riser tubulars. Therefore, operations such as mounting and lowering the casing in the water depth can be carried out in parallel with the drilling of the phase, allowing a significant additional gain of time.

A managed Pressure Drilling manifold provides accurate back pressure control of a well head when drilling. The MPD system provides two paths for the drilling fluid to flow from the RCD to the flowline. The drilling fluid flows along an MPD path sending the drilling fluids through at least one sensor, preferably three sensors, a flow control device, and a flowmeter. The MPD system also provides a bypass path that isolates the flow control device and flowmeter while direct the drilling fluid from the RCD to the bypass to avoid the flow control device and flowmeter. The MPD system provides three valves that direct the drilling fluid in the bypass path or the MPD path.

A managed Pressure Drilling manifold provides accurate back pressure control of a well head when drilling. The MPD system provides two paths for the drilling fluid to flow from the RCD to the flowline. The drilling fluid flows along an MPD path sending the drilling fluids through at least one sensor, preferably three sensors, a flow control device, and a flowmeter. The MPD system also provides a bypass path that isolates the flow control device and flowmeter while direct the drilling fluid from the RCD to the bypass to avoid the flow control device and flowmeter. The MPD system provides three valves that direct the drilling fluid in the bypass path or the MPD path.

A rupture disc assembly and a float tool incorporating the rupture disc assembly is disclosed. The rupture disc assembly may include a rupture disc assembly comprising a rupture disc, an upper tubular portion and a lower tubular portion, and a securing mechanism for holding the rupture disc between the upper and lower tubular portions. A float tool for creating a buoyant chamber in a casing string may include the rupture disc assembly and a sealing device for sealing the lower end of the casing string, the buoyant, sealed chamber may be created there between. In operation, applied fluid pressure causes the rupture disc to move downward. The rupture disc may be shattered by contact with a surface on the lower tubular portion. Full casing internal diameter may be restored in the region where the rupture disc formerly sealed the casing.

A rupture disc assembly and a float tool incorporating the rupture disc assembly is disclosed. The rupture disc assembly may include a rupture disc assembly comprising a rupture disc, an upper tubular portion and a lower tubular portion, and a securing mechanism for holding the rupture disc between the upper and lower tubular portions. A float tool for creating a buoyant chamber in a casing string may include the rupture disc assembly and a sealing device for sealing the lower end of the casing string, the buoyant, sealed chamber may be created there between. In operation, applied fluid pressure causes the rupture disc to move downward. The rupture disc may be shattered by contact with a surface on the lower tubular portion. Full casing internal diameter may be restored in the region where the rupture disc formerly sealed the casing.