Downhole cables are used to simultaneously power downhole instrumentation from the surface and transmit data back to surface. GCDT offers a full range of cables for downhole applications. These cables are available in numerous configurations, materials and dimensions. We have several standard products, and we also custom design cables for customer specified applications.
GCDT's cables can be split into the following broad categories:
In the permanent monitoring downhole gauge industry the downhole cable is commonly referred to as TEC (Tubing Encased Conductor). TEC has to be of a robust design to function in an extreme environment both during installation of the gauge system and over the life of the well during which time it will be subjected to pressure and temperature. GCDT offers a full range of downhole cables for that are available in numerous configurations, materials, and dimensions. The cables can be provided with encapsulation including flatpacks with bumper bars, chemical injection, and control lines. Encapsulated products are available with Safety-Strip�
The most common multi-conductor cable uses twisted pair conductors. The twisted pair cables are often frequently used where there is a requirement to reduce noise on the return signal or where a dedicated return path is required.
Multi-conductor cables with more than two conductors are often manufactured for downhole tools that have unique communication protocols. A wide range of conductor combinations are available, these include high temperature multi-conductor designs in side 5/16" heavy wall tube.
Return Serve and Shielded Cable
Typically downhole instrumentation systems use the tube as the electrical return path to surface. GCDT's return serve cable can be used to significantly improve the conductivity of this return path. The return serve cable design is comprised of a central mono conductor with an extruded insulation and secondary extruded jacket. A copper serve (or braid) is wound over the secondary extruded jacket and is in direct contact with the outer metal tube.
The shielded cable uses a similar construction to the braided return cable. In the shielded deign a jacket is extruded over the braid to insulate it from the outer tube.
Fiber Optic Cable
Fiber optic cables are used for a wide range of applications The most common use for downhole fiber cables is to provide distributed temperature sensing (DTS) in the well. However, fiber sensing technology also includes single point pressure and temperature measurement, flow measurement and acoustic sensing. The broad range of fiber applications results in a number of unique cable requirements. These include fiber type, make of fiber, the number of fibers, filler gels and temperature requirements.
GCDT offers a range of downhole fiber optic cables. Typically the designs are customized to meet customer requirements. The standard 1/4" design has the fibers contained with a protective microtube, which is jacketed and installed into a larger heavy wall tube. Several different constructions of 1/8" fiber optic cables are also available.
Hybrid Electro/Fiber Cable
In applications where electrical and fiber optic devises are installed downhole, the hybrid cables combine both of these data transmission mediums into a single package. Many hybrid designs are custom built to meet a customer's specific requirement. There are three main construction methods.
The flatpack design has separate fiber optic and electrical cables which encapsulated in a thermoplastic jacket create a hybrid flatpack.
The conductive microtube design has the fibers encased in a microtube. An insulated copper braid on the outside of the microtube acts the electrical conductor. A secondary extrusion centralizes and supports the conductor / fiber assembly in the outer tube.
With the insulated wire and microtube design the fibers are encased in a microtube. Insulated wires are wrapped around the central microtube with a binding layer centralizing and supporting the electrical wire/microtube assembly in the outer tube.