A circulating sub having an elongate outer member and an elongate inner member positioned within the outer member. Locking members releasably maintain the inner and outer members in a longitudinally fixed relationship. The sub may be activated by a single ball. The ball engages with the locking members and unlocks the inner member from the outer member. The increase of fluid pressure within the sub causes the inner member to move downward within the outer member. Downward movement of the inner member opens exit ports on the outer member to allow fluid to flow into a wellbore surrounding the sub. The decrease of fluid pressure within the sub causes the inner member to move upward within the outer member. Upward movement of the inner member seals the exit ports and deactivates the sub. Once the sub is deactivated, the ball may be expelled from the sub.

A drill rod for assembly with other drill rods to form a drillstring used for fluid reverse circulation drilling comprising: an outer drill rod comprising a lightweight drill rod used in core drilling with a bore, an inner drill rod comprising a bore, a first coupling member removably coupled to one end of the inner drill rod, a second coupling member removably coupled to a second end of the inner drill rod, wherein the first and second coupling members centre the inner drill rod within the outer drill rod.

A system includes an outer completion string, an inner service string configured to connect within the outer completion string, and an upper completion. The outer completion string includes at least one isolation packer, a sand control assembly and a gravel pack extension disposed uphole of a washdown shoe in a bottom-most well zone. In a top well zone, the outer completion string includes a latch profile, a female inductive coupler, a gravel pack packer, and a sand control assembly and a gravel pack extension disposed downhole of the gravel pack packer. The inner service string includes, among other components, an inner concentric string that is concentrically arranged within a workstring creating an inner-annulus between the workstring and the inner concentric string. The upper completion includes a male inductive coupler that is configured to connect with the female inductive coupler of the outer completion string.

A system includes an outer completion string, an inner service string configured to connect within the outer completion string, and an upper completion. The outer completion string includes at least one isolation packer, a sand control assembly and a gravel pack extension disposed uphole of a washdown shoe in a bottom-most well zone. In a top well zone, the outer completion string includes a latch profile, a female inductive coupler, a gravel pack packer, and a sand control assembly and a gravel pack extension disposed downhole of the gravel pack packer. The inner service string includes, among other components, an inner concentric string that is concentrically arranged within a workstring creating an inner-annulus between the workstring and the inner concentric string. The upper completion includes a male inductive coupler that is configured to connect with the female inductive coupler of the outer completion string.

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 multi-impeller passive-rotating-stirring-type rotary drilling rig for open caissons includes a hollow main drill pipe, a drill bit, four cutting edges, four impeller shafts, four passive impellers and a rotation bracket. Through being uniformly distributed at a peripheral of the drilling rig, four passive impellers contact with a hole wall of a borehole during the drilling process for passively generating relative rotation opposite to the rotation direction of the drill bit, so as to accelerate sufficient mixing of silt and water for forming mud during the drilling process.

In one aspect the present invention may be said to comprise a drill rod for assembly with other drill rods to form a drillstring used for fluid reverse circulation drilling comprising: an outer drill rod comprising a bore that is tapered at each end, an inner drill rod within the outer drill rod, and a retention member removably coupled to each end of the inner drill rod to retain the inner drill rod between the tapered ends of the outer drill rod.

In one aspect the present invention may be said to comprise a drill rod for assembly with other drill rods to form a drillstring used for fluid reverse circulation drilling comprising: an outer drill rod comprising a bore that is tapered at each end, an inner drill rod within the outer drill rod, and a retention member removably coupled to each end of the inner drill rod to retain the inner drill rod between the tapered ends of the outer drill rod.

During a drilling operation, drilling mud is degaussed to remove magnetic interference that may disrupt measurements.

During a drilling operation, drilling mud is degaussed to remove magnetic interference that may disrupt measurements.