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.

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.

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.

An insulating collar for a gap sub assembly for electromagnetic (EM) telemetry used in downhole drilling is disclosed. The gap sub assembly comprises a female member comprising a female mating section and a male member comprising a male mating section and a gap section. The male mating section is matingly received within the female mating section and electrically isolated therefrom. The insulating collar is positioned on the gap section. The collar is made up of a framework with a plurality of discrete bodies spaced about the framework and a portion of each of the discrete bodies protrudes above the framework. Either the framework or the discrete bodies are made of an electrical insulator material to electrically isolate one end of the collar from the other end of the collar. The collar therefore electrically isolates the male member from the female member and the male member, female member and insulating collar function as the gap sub for EM telemetry.

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.

An electrical insulated threaded connection includes a conductive box with a plurality of internal threads, a conductive pin with a plurality of external threads, and a double-threaded electrical insulator sleeve disposed between the conductive pin and box. The double-threaded electrical insulator sleeve comprises a plurality of external threads that mate with the plurality of internal threads of the conductive box and a plurality of internal threads that mate with the plurality of external threads of the conductive pin. In certain embodiments, the double-threaded electrical insulator sleeve fills a full volume between the plurality of internal threads of the conductive box and the plurality of external threads of the conductive pin, and there are no voids or pockets between any of the mating threads.

An electrical insulated threaded connection includes a conductive box with a plurality of internal threads, a conductive pin with a plurality of external threads, and a double-threaded electrical insulator sleeve disposed between the conductive pin and box. The double-threaded electrical insulator sleeve comprises a plurality of external threads that mate with the plurality of internal threads of the conductive box and a plurality of internal threads that mate with the plurality of external threads of the conductive pin. In certain embodiments, the double-threaded electrical insulator sleeve fills a full volume between the plurality of internal threads of the conductive box and the plurality of external threads of the conductive pin, and there are no voids or pockets between any of the mating threads.

A gap sub assembly and methods for using the gap sub provide an electrical isolating joint that is mechanically strong enough to withstand the rigors of drilling environments, resistant to environmental effects (heat, corrosive liquids and gases, and high pressures), and maintainable. The gap sub assembly provides a male member and a female member that may be connected together, wherein a non-conductive material is applied between the two at the attachment points. A locking ring or collar affixes to both male and female members to prevent back off while drilling and preserving the electrical isolation of the gap joint. Non-conductive material may be injected between the locking ring and one or more of the male or female members.

An insulating collar for a gap sub assembly for electromagnetic (EM) telemetry used in downhole drilling is disclosed. The gap sub assembly comprises a female member comprising a female mating section and a male member comprising a male mating section and a gap section. The male mating section is matingly received within the female mating section and electrically isolated therefrom. The insulating collar is positioned on the gap section. The collar is made up of a framework with a plurality of discrete bodies spaced about the framework and a portion of each of the discrete bodies protrudes above the framework. Either the framework or the discrete bodies are made of an electrical insulator material to electrically isolate one end of the collar from the other end of the collar. The collar therefore electrically isolates the male member from the female member and the male member, female member and insulating collar function as the gap sub for EM telemetry.