Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
2000-05-19
2001-10-02
Dinkins, Anthony (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
C174S036000
Reexamination Certificate
active
06297455
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to multi-conductor electrical cables of the type used in oilfield wireline logging cables.
Once an oil well is drilled, it is common to log certain sections of the well with electrical instruments. These instruments are referred to as “wireline” instruments, as they communicate with the logging unit at the surface of the well through an electrical wire or cable with which they are deployed. Such cables are used for transmitting power and for telemetry. Since down hole temperatures and pressures can reach, for example, 500° F. and sometimes up to 25,000 psi, the cables must be designed to withstand extreme environmental conditions.
2. Description of the Related Art
A standard cable in the oilfield industry is a seven-conductor design called a “heptacable.” As shown in
FIG. 1
, the heptacable
2
, generally 0.38-0.55 inches in diameter, includes six conductors
4
symmetrically wrapped around a center conductor
6
. These types of heptacables are used extensively in the oilfield wireline logging industry, for the purpose of lowering and retrieving sensors and instruments capable of measuring acoustic, nuclear, resistivity, and nuclear magnetic resonance (NMR) properties of freshly drilled downhole rock formations and their fluid content. Other uses of the heptacable include cement analysis, perforating, PVT and fluid sampling, and other electro-mechanical services that may be required in oil and gas wells.
BRIEF SUMMARY OF THE INVENTION
We have developed an improved wireline cable construction that, while enabling a high degree of backwards compatibility with prior heptacables and the instruments they service, can provide an advantageously high current-carrying capacity while maintaining standard voltage ratings, leading to a substantial increase in the power delivery capacity of the cable, without any increase in its nominal diameter.
The wireline cable of the invention can provide high power delivery capacity during operation while maintaining good data transmission, e.g., high signal-to-noise ratio and low attenuation. By using heavy gauge (i.e., large diameter) primary conductors, more conductive material, e.g., copper, can be packed into a given cross-sectional area of the cable. Thus, the cable can provide increased power delivery capacity and improved data transmission characteristics when compared to a standard heptacable. The cable includes secondary conductors that allow it to be backward compatible with existing standard heptacables. The improved power capacity is especially advantageous for current and future downhole applications requiring higher power, while still meeting environmental, packaging, and flexibility requirements.
In one aspect, the invention features a flexible electrical wireline cable defining a longitudinal axis and having four insulated primary conductors, at least one insulated secondary conductor of a wire gauge smaller than the primary conductors, and an armor shield. The primary conductors extend along the cable and define interstices between adjacent primary conductors. The secondary conductor extends about the longitudinal axis of the cable and is at least partially nested in one of the interstices. The armor shield surrounds the primary and secondary conductors.
Embodiments of the invention may include one or more of the following. The primary conductors are arranged in a cross pattern about the longitudinal axis. The cable has at least three secondary conductors for a total number of at least seven conductors. The cable has an overall diameter, including the armor shield, of less than about 0.55 inch. The cable has a minimum bending radius of about 4 inches. The cable has five secondary conductors. The secondary conductor extends along the longitudinal axis of the cable. The primary conductors are twisted together about the secondary conductor. The cable further includes a non-conductive filler rod extending about the longitudinal axis of the cable and at least partially nested in the interstices formed by the primary conductors. The cable further includes a non-conductive filler rod extending along the longitudinal axis. The primary conductors are twisted together about the filler rod, e.g., made of a fluoropolymer.
The cable further includes a plurality of secondary conductors arranged symmetrically about the longitudinal axis. The primary conductors, the secondary conductor, and the armor shield define interstitial voids, and the cable further includes a semi- or non-conductive material, such as a cross-linked polymer, disposed in the voids. The secondary conductor has a wire gauge of between 24 AWG and 20 AWG.
The cable further includes a bedding layer, e.g., a binder tape and an extruded material, surrounding the primary and secondary conductors. The armor shield includes two layers of contrahelically wound fibers. The armor fibers include a material selected from a group consisting of steel, metals, and non-metals.
In another aspect, the invention features a flexible electrical cable defining a longitudinal axis and having four insulated primary conductors of a common wire gauge twisted together and extending along the cable, five insulated secondary conductor of a wire gauge larger than the wire gauge of the primary conductors, a bedding layer surrounding the primary and secondary conductors, and an armor shield surrounding the bedding layer. The primary conductors are arranged in a cross pattern about the longitudinal axis and define interstices between adjacent primary conductors. Four of the secondary conductors are each at least partially nested in one of said interstices, and the other secondary conductor extends along the longitudinal axis of the cable. The cable has an outer diameter of less than about 0.55 inch.
As used herein, the “longitudinal axis” of a cable is an imaginary axis that extends through the cross-sectional center of the cable and along the length of the cable from one end of the cable to another end of the cable.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
REFERENCES:
patent: 2927954 (1960-03-01), Ellsworth
patent: 3602632 (1971-08-01), Ollis
patent: 3784732 (1974-01-01), Whitfill, Jr.
patent: 4440974 (1984-04-01), Naudet
patent: 4654476 (1987-03-01), Barnicol-Ottler et al.
patent: 4657342 (1987-04-01), Baiier
patent: 4658089 (1987-04-01), Guzy et al.
Hernandez-Marti Ramon
Howard Pete
Wijnberg Willem A.
Dinkins Anthony
Jeffery Brigitte
Mayo III William H.
Ryberg John
Schkumberger Technology Corporation
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