A pipe segment having an insulated electrical conductor includes a first electrical contact disposed at one end of an electrical conductor on an interior of the pipe segment from a male threaded connection on one end to a female threaded connection on the other end of the pipe segment. A second electrical contact is on the other end of the insulated electrical conductor. The first contact makes electrical connection with the second contact in an adjacent segment when the male connection on one segment is engaged to the female connection on the adjacent segment. A seal disposed on an interior of an insulating layer on an interior wall of each respective pipe segment provides a space beyond the end of the seal to enable inward flexure of the seal under pressure such that lubricant extruded by connecting the male threaded end and the female threaded end is pressure relieved.

A gap sub comprises at least one electrically isolating threaded joint in a conductive tubular collar. The threads of the joints are isolated by a non-conductive coating. The shoulders of the joints are separated by an isolating ring. Annular faces on the ring make contact with the shoulders in the joints. The ring is made of conductive material with a non-conductive coating deployed on (1) at least one of the ring's annular faces, and (2) the interior surface of the ring. An annular recess in the collar prevents electrical contact between collar sections nearby the ring on either side of at least one threaded joint.

An electrical isolator comprising: a first fluid-carrying member and a second fluid-carrying member spaced apart from said first fluid-carrying member; wherein said first fluid-carrying member has a first toothed surface and said second fluid-carrying member has a second toothed surface; wherein the electrical isolator further comprises: a fibre-reinforced polymer tube that overlaps both the first fluid-carrying member and the second fluid-carrying member and which contacts the first toothed surface in a first interface region of the fibre-reinforced polymer tube and which contacts the second toothed surface in a second interface region of the fibre-reinforced polymer tube; and a compression fitting arranged to bias the first interface region and the first toothed surface together.

A central body for a hydraulic system for fluid, including a frame having a first tubular end for connecting an upstream hydraulic circuit including a first fitting, and a second tubular end for connecting a downstream hydraulic circuit including a second fitting, the central body including a passage passing through the frame in order to convey the fluid coming from the upstream hydraulic circuit to the downstream hydraulic circuit, the frame being produced from an electrically insulating material, the central body including a printed circuit having controlled electrical properties in order to conduct a part of the electrical charges flowing in the upstream hydraulic circuit and the downstream hydraulic circuit.

A tubular member for threadably engaging another tubular member to form a tubular string includes a first end including a helical female thread formed in an outer surface of the tubular member, wherein the female thread includes a slot extending radially inwards from the outer surface, and a root extending radially inwards from the slot, wherein the root has a maximum width that is greater than a maximum width of the slot, a second end opposite the first end and including a helical male thread formed on an inner surface of the tubular member, wherein the male thread includes a shank extending radially outwards from the inner surface, and a notch extending radially outwards from the shank, wherein the notch has a maximum width that is greater than a maximum width of the shank.

A pipe segment having an insulated electrical conductor includes a first electrical contact disposed at one end of an electrical conductor on an interior of the pipe segment from a male threaded connection on one end to a female threaded connection on the other end of the pipe segment. A second electrical contact is on the other end of the insulated electrical conductor. The first contact makes electrical connection with the second contact in an adjacent segment when the male connection on one segment is engaged to the female connection on the adjacent segment. A seal disposed on an interior of an insulating layer on an interior wall of each respective pipe segment provides a space beyond the end of the seal to enable inward flexure of the seal under pressure such that lubricant extruded by connecting the male threaded end and the female threaded end is pressure relieved.

One or more seals may be provided in a gap sub to prevent the ingress of drilling fluid into an insulating gap between a male member of the gap sub and a female member of the gap sub. A first seal may comprise an internal gap sub seal provided near the tip of the male member of the gap sub. A second seal may comprise an external gap sub seal provided near the tip of the female member of the gap sub. The first and second seals may comprise non-conductive materials. The first and second seals may each comprise one or more O-rings. The first and second seals may comprise one or more lips, protrusions or flanges to engage the male and/or female members of the gap sub for maintaining contact with the male and/or female members during deformation of the gap sub.

A dielectric fitting includes a nut having inner threads and an axial compression surface, and a hole having a first diameter. A mating component includes outer threads that engage with the inner threads including a second axial compression surface. A first fitting includes a circumferential flange captured between the first axial compression surface and the second axial compression surface, the first fitting having a first wall that extends axially and passes through the first hole and includes first fitting threads. A second fitting includes second fitting threads that engage with the first fitting threads, the second fitting having a second wall and a bulge portion that radially projects to a second diameter and includes an O-ring. The nut and the mating component are dielectrically isolated from the first fitting and the second fitting, and the second diameter is larger than the first diameter.

An apparatus includes first and second electrically conductive tubes, first and second electrical isolators, and a nut. The first electrical isolator has a central passageway. The first electrically conductive tube has a flared end disposed around the first electrical isolator. The flared end includes external threads. The second electrically conductive tube has an outer flange. The second electrical isolator is disposed around the second electrically conductive tube and engages the outer flange. The nut is disposed around the second electrically conductive tube and engages the second electrical isolator. The nut includes internal threads corresponding to the external threads of the flared end of the first electrically conductive tube.

An electrical isolator comprising: a first fluid-carrying member and a second fluid-carrying member spaced apart from said first fluid-carrying member; wherein said first fluid-carrying member has a first toothed surface and said second fluid-carrying member has a second toothed surface; wherein the electrical isolator further comprises: a fibre-reinforced polymer tube that overlaps both the first fluid-carrying member and the second fluid-carrying member and which contacts the first toothed surface in a first interface region of the fibre-reinforced polymer tube and which contacts the second toothed surface in a second interface region of the fibre-reinforced polymer tube; and a compression fitting arranged to bias the first interface region and the first toothed surface together.