WO2006111111A1

WO2006111111A1 - Cable for geophysical measuring and exploration purposes

Info

Publication number: WO2006111111A1
Application number: PCT/DE2005/000749
Authority: WO
Inventors: Werner Führer
Original assignee: Warschau, Katrin
Priority date: 2005-04-19
Filing date: 2005-04-19
Publication date: 2006-10-26

Abstract

The invention relates to a cable for geophysical measuring and exploration purposes with a high axial rigidity, which is particularly used in the petroleum and natural gas industry. The invention is characterized in that the cable comprised of a outer sheath (2), which is provided as a reinforcement, and of a core (3), which is enclosed by this reinforcement and which has a measuring and supply cable with a number of conductors (3.2) that are insulated from one another, has the following basic construction. The reinforcement consists of at least one ply (2.1) of Z wires that, while forming a media-tight smooth outer surface (2.2) of the running surface of the Z wires, are laid in a helical line-shaped manner around the core (3) over a longitudinal section, namely the length of lay L, of the cable (1), each of the respectively adjacent Z wires adjoining one another in a positive and/or non-positive manner and engaging with one another. The measuring and supply cable comprises at least two current-carrying conductors (4, 5) and at least one measuring or control line (6, 7, 8) insulated therefrom for at least one measuring head placed at the distal end of the cable (1) and, optionally, a mobile cable pull device. The conductors (4 8) are combined to form a bundle (3.2) of conductors, and this bundle of conductors is surrounded by a special sheath (3.1) made of glass fibers embedded in plastic in order to increase the torsional rigidity of the cable (1).

Description

Cable for geophysical measurement and reconnaissance purposes

The invention relates to a cable for geophysical measurement and reconnaissance purposes with high axial stiffness, which is used in particular in the petroleum and natural gas production industry.

In order to obtain useful information on the presence and the yield as well as possibilities of developing the oil and natural gas deposits, geophysical measurements are carried out by means of measuring cables and associated measuring heads or probes in vertical and partly also horizontally inclined boreholes.

Geophysical measurements are carried out both at the open borehole and after lowering a production pipe under production conditions, respectively at the closed borehole. The probes are either lowered to the measuring cable or they are already placed before the introduction of the cable into the well at a distal end of the cable. However, this presupposes that the measuring and exploration cables with associated measuring technology are designed for the pressures, temperatures and humidities inherent in the depths.

So far unresolved is the introduction of the measuring devices in horizontal holes with longer lengths.

To ensure the cable insertion in horizontally drilled holes, an axial force is required due to the contacting of the measuring and reconnaissance cable with the borehole wall, with which the fretting and braking resistances caused by contacting must be overcome. This can only be achieved with a cable that can absorb shear forces. The associated prior art is represented by a measuring and exploration cable, the core of which is enclosed by a reinforcement consisting of two layers of high-strength steel wires with 0.8-1.3 mm diameter. These cables can only absorb tensile forces.

Furthermore, such trained cable penetration of partially aggressive media such. As fluids or solids, not effectively prevent. The water that does not escape from the reinforcement increases the risk of corrosion or the risk of decomposition of the cable core. In summary, it can be stated that the measurement and exploration cables known from the prior art due to their lack of axial rigidity and their non media-tight closed armor are not suitable for larger depths and the measurement of long horizontal boreholes with low inclination.

In addition, the round wires used for the reinforcement must be stretched to achieve a uniform fit or a uniform alignment over the circumference of the cable.

The object of the invention is now to develop a cable for measurement and reconnaissance purposes, which has a high axial rigidity and reliably prevents the passage of media through its outer shell and thus for larger depths and the measurement of long horizontal wells with low inclination can be used ,

This object is achieved in that the cable for geophysical measurement and reconnaissance purposes from a formed as a media-tight reinforcement outer shell and a trapped by this reinforcement core, which has a measuring and supply cable with a plurality of mutually insulated conductors constructed. The media-tight reinforcement consists of at least one layer of Z-wires, which are helically struck around the core over a length of length with the lay length L. The measuring and supply cable includes at least two current-carrying conductors and at least one measuring line insulated therefrom for a measuring head arranged at the distal end of the cable and optionally a mobile advancing device. The high axial stiffness of the cable to be achieved, expressed by the buckling length λ, is hereby dimensioned as a function of the breaking strength δ β of the Z-wires, the lay length L and the geometry of the Z-wires.

The measuring head comprises a plurality of probes, in particular probes for detecting physical parameters, such. As temperature, pressure or specific resistances of the rock formations, or the location of the inflow of the natural gas and oil to be exploited. Furthermore, the measuring head can serve to control the spatial position of the drill bit or the quality of the attachment of a conveyor pipe.

By using Z-wires as external single-layer reinforcement, a very high axial rigidity of the cable can be achieved. In contrast to the multi-layered round wires used in the prior art as a reinforcement, adjacent Z-wires of the cable according to the invention form and optionally non-positively engage each other and thus ensure an axial force introduction and forwarding in the direction of the longitudinal extent of the cable.

Usually, the cross section of the vertical borehole is dimensioned only so large that the inserted or retracted cable can be easily lowered therein, at least in the opening region of the borehole, due to the effect of gravity. The further retraction or the further propulsion of the cable in the borehole is ensured by the application of an axial thrust force on the outer end side of the cable by means of a cable thruster. In this case, the cable alternately strikes against the oppositely spaced inner sides of the borehole, with inevitably a frictional force during further cable propulsion is generated between the outer jacket of the cable and the wall of the borehole. This distance of the attachment points is defined as the buckling length λ of the cable, with naturally introduced with a large lay length L cable produces a greater buckling length λ and thus lower frictional forces, with the result that the applied axial force can be reduced to the cable.

The Z wires are made of shaped steel wire. The number of Z-wires used is measured depending on the thickness of the core of the cable described later, in order to form a closed running surface of the reinforcement or lateral surface of the cable in the stranded state of the Z-wires.

As a material for the Z-wires steel with a high breaking strength δ _{B is} provided. In a particularly preferred embodiment of the invention, the Z-wires have a coating which counteracts corrosion and promotes the tightness of the outer jacket against the passage of media. The coating can be applied to the entire lateral surface of each individual Z-wire or only on the tread of the Z-wires after stranding. For special applications, the Z-wires consist of an alloyed and treated steel, which is optionally surface-treated with a zinc layer.

Another advantage of the relatively soft zinc layer of the Z-wires is that when the cable is stranded by the force of the stranding machine, adjacent Z-wires in fact "fuse" with each other, thereby metallically sealing the contact points between the Z-wires.

The production of the cable according to the invention requires unspecified special stranding machines. The stranding of the individual Z wires to an external reinforcement of the cable takes place in Dependence on cross section and structure of the core and a desired lay length L of the cable.

The Z wires used for the reinforcement are shaped and stranded with one another in such a way that, in cross-section, they enclose the measurement and supply cable designed as a core in a mechanically and media-tight manner. The closed running surface of the armor or lateral surface of the cable can effectively prevent the penetration of fluids and dust into the core region of the cable during the insertion of the cable into the borehole and during operation. Dusts contain very small solid particles that destroy the measuring and power cables placed in the core by erosion.

The core of the cable, which is completely enveloped by the reinforcement or outer sheath, may be designed differently in relation to the measuring conductor. According to the concept of the invention, metallic conductors or preferably also optical fiber conductors are used. Using optical fiber cables, interference caused by magnetic fields and galvanic currents in the passing rock formations or earth strata can be eliminated, especially at large depths of 3000 m. As a result, the quality of the measurement results to be evaluated and the measurement speed can be considerably increased.

The measurement and supply cable enclosed by a special sheath, which in its structure is made of plastic encapsulated glass fibers, contains, in addition to the actual measuring conductors, further conductors, at least a pair of current-carrying conductors for a measuring head arranged at the distal end of the cable and optionally another pair current carrying conductor in the event that a propulsion device of the cable (Kabelzugeinrichtung) used within the borehole to be connected. The special sheath is flexurally elastic but torsionally rigid, so that residual stresses from the stranding of the steel reinforcement are compensated and thus a rotation of the cable in the borehole is largely prevented.

When reaching large depths of the cable, the temperature of the rock formation rises, whereby the measuring and supply cable is exposed to a high undesired heat load. The special sheath of the core and the completely closed outer sheath of the cable act as a good heat insulator.

The propulsion device, which can be used for propulsion of the measuring and supply cable in horizontal boreholes, is not the subject of this invention and is therefore not described in detail.

In exemplary embodiments, the measuring and supply cable can have one or more metallic measuring leads for the measuring heads, two current-carrying metallic conductors for the advancing device and the measuring heads, and one optical fiber cable designed as an optical measuring lead.

The significant advantages and features of the invention over the prior art are essentially:

■ very high axial rigidity of the cable by using Z-wires as external reinforcement and thus ensuring the necessary axial rigidity,

■ The special sheath made of plastic embedded glass fibers increases the torsional stability of the cable and thus counteracts a twisting movement of the cable (caused by residual stresses of the stranded outer sheath). ^■ The closed running surface of the Z-wires effectively prevents ingress of sometimes aggressive media into the core.

^■ This dense, smooth outer surface continues to provide ideal sealing of the cable in high pressure oil wells, especially gas; in sealing measures of the cable along its circumferential line, for example in the lock in front of the borehole mouth, the remaining outflow surface is practically zero.

^■ Reduction of surface abrasion of the outer sheath, as the large buckling length λ minimizes the frictional forces μ between the outer sheath of the cable and the borehole wall when entering the borehole

^■ virtually lossless information transmission by using a fiber optic cable as a measuring cable.

Various solutions and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment with reference to the accompanying drawings; in this show:

Fig. 1 shows a cross section of an embodiment of the invention

Cable and

Fig. 2 is a perspective view of the new measuring and

Supply cable.

1 illustrates a cross section of the cable 1 according to the invention using an optical measuring conductor 8, the cable 1 essentially consisting of a core 3 and an outer casing 2 which completely surrounds this core 3. The core 3 consists of measuring and supply wires with eg 10 mutually insulated conductors 3.2 and the Special jacket 3.1 made of plastic embedded in glass fibers, which surrounds these conductors 3.2. As a plastic, for example, a polyester resin is used.

A cable pulling device (not shown) placed in the borehole at the distal end of the cable 1 is supplied by means of two current-carrying metallic conductors 4. Another pair of metallic conductors 5 is provided to electrically supply an optical measuring technique, also not shown, at the distal end of the cable 1. An optical information transmission takes place through a fiber optic cable 8 as a measuring conductor with 8 multimode fibers. Furthermore, three signal wires 6 are provided as control lines for cable pulling device and measuring technology as well as three signal wires 7 for the wired measured value transmission.

In this embodiment, an 18 mm cable is used, in which the core 3 measures 9 mm in diameter. The outer shell 2 comprising the core 3 consists here of sixteen galvanized Z wires 2.1 (with δ _B = 1760 N / mm ² ) which are stranded together in a layer radially around the core 3. The Z-wires 2.1 are shaped and stranded together so that they enclose the core 3 mechanically and media-tight. Here, each adjacent Z wires 2.1 are positively connected to each other, wherein the right inner edge of a Z-wire 2.1 contacts the left inner edge of the adjacent Z-wire 2.1 almost over its entire length. Each individual Z-wire 2.1 abuts with its foot on the outer surface of the core 3. As can be seen, form the facing away from the core 3 of the cable 1 end faces, respectively, the running surface 2.2 of each Z-wire 2.1, a media-tight closed armor.

For the Z-wires 2.1 shaped steel wire is provided with a standard leg dimension of eg 4.5 mm. Thickness is understood to mean the distance between the surface of the core 3 and the foot region of the Z-wire 2.1 and the running surface 2.2 of the Z-wire 2.1. To improve the positive and non-positive bond of the Z-wires 2.1 with the special sheath 3.1 of the core 3, the foot resting on the special sheath 3.1 of the Z-wires 2.1 can be made profiled or it has claw-like formations 2.3 in the longitudinal extent of the Z-wires 2.1 on. As a result, the torsional stability is further increased.

The total diameter of the cable 1 is thus 18 mm in the example chosen. Every single Z-wire 2.1 made of steel is completely galvanized. Optionally stainless steel can also be used. All Z wires 2.1 extend basically in the direction of the longitudinal axis of the core 3, but are stranded together and thereby hit the core 3 of the cable 1. A complete transfer of the Z wires 2.1 around the core, ie a 360 ° spiral, by definition corresponds to a lay length L of the cable 1. The lay length L of the reinforcement or the outer jacket 2 is proportional to the buckling length λ of the cable 1, which is a measure for the axial rigidity of the cable 1. With changing the lay length L, the number and geometry of the Z wires used 2.1 and depending on the material properties of the Z wires 2.1 thus the desired axial stiffness of the cable 1 can be achieved.

From the perspective view in Fig. 2, the basic structure of the new measuring and supply cable 1 is made clear again.

The outer sheath 2 consisting of Z wires 2.1 encloses the core 3 of the cable with smooth and media-free running surface 2.2, this core 3 being constructed from the special sheath 3.1 and the sheaths 3.1 enclosed by this sheath 3.1, comprising the lines 4 to 8. LIST OF REFERENCE SIGNS

1 cable

2 outer jacket

2.1 Z wires

2.2 Tread of the Z wires, outer surface of the cable

2.3 Formations in the foot area of the Z-wires

3 core

3.1 Special coat

3.2 internal wires, conductors

4 Power supply cable feed device

5 power supply measurement technology

6 control cables, cable pulling device, measuring technology

7 signal wires measuring technology

8 multimode fiber optic cable (for measured value transmission)

Claims

1. cable (1) for geophysical measurement and reconnaissance purposes, in particular for use in the oil and gas extraction industry, consisting of an armored outer sheath (2) and a core enclosed by this reinforcement (3), a measuring and supply cable Having a plurality of mutually insulated conductors (3.2), characterized in that

a. the reinforcement is constructed of at least one layer of Z-wires (2.1) helically over a portion of length, namely the lay length L, of the cable (1) around the to form a media-tight smooth outer surface (2.2), the tread of the Z-wires Core (3) are beaten, in each case adjacent Z-wires form and possibly non-positively connect to each other and interlock and

b. the measuring and supply cable comprises at least two current-carrying conductors (4, 5) and at least one measuring or control line (6, 7, 8) insulated therefrom for at least one measuring head arranged at the distal end of the cable (1) and possibly a mobile cable pulling device, in which

c. the conductors (4 - 8) are combined to form a conductor bundle (3.2) and this conductor bundle is surrounded by a special sheath (3.1) of plastic embedded glass fibers to increase the torsional rigidity of the cable (1) and the axial stiffness of the cable (1), expressed by the buckling length λ, depending on the breaking strength δ _{B of} the Z-wires (2.1), the lay length L and the geometry of the Z-wires (2.1) measured.

2. Cable (1) according to claim 1, characterized in that the measuring and supply cable one or more metallic measuring or

Control leads (6, 7) for the measuring heads and two current-carrying metallic conductors (5) for the power supply of the measuring technology.

3. Cable (1) according to claim 1 or 2, characterized in that the measuring and supply cable each have two current-carrying metallic

Having conductor (4, 5) for the propulsion device and the measuring heads and additionally as a optical measuring line (8) formed fiber optic cable.

4. Cable (1) according to one of claims 1 to 3, characterized in that the Z-wires (2.1) used for the reinforcement are shaped and stranded in such a way that they form in cross-section as the core (3) formed measuring and supply cable mechanically and media-tight enclosure and form a closed tread (2.2)

5. cable (1) according to one of claims 1 to 4, characterized in that the Z-wires (2.1) one of the corrosion counteracting and the

Tightness of the outer jacket (2) against the passage of media-promoting coating, e.g. Zinc layer.

6. Cable (1) according to one of claims 1 to 5, characterized in that the outer jacket (2) of the cable, for example, comprises sixteen Z-wires (2.1) with a Z-leg dimension of 4.5 mm, and that of the Outer jacket (2) enclosed core (3) has a diameter of 9 mm.

Cable (1) according to one of claims 1 to 6, characterized in that to improve the positive and non-positive bond of the Z-wires (2.1) with the special sheath (3.1) of the core (3) of the special sheath (3.1) seated Has foot portion of the Z-wires (2.1) is profiled or claw-like formations (2.3) in the longitudinal extent of the Z-wires (2.1).