WO2012142692A1

WO2012142692A1 - Probe for collecting geophysical logging data

Info

Publication number: WO2012142692A1
Application number: PCT/CA2012/000213
Authority: WO
Inventors: Blaine R. WEBSTER; Alex JELENIC; Mony AMIEL; Djordje Mihajlovic; Tony SVIRGA
Original assignee: Jvx Ltd.
Priority date: 2011-04-20
Filing date: 2012-03-07
Publication date: 2012-10-26

Abstract

The present invention related to a probe for use in collecting geophysical logging data for subterranean strata. The probe includes a charging assembly having a current input wire and current electrode for transmitting an electrical charging current to the strata to form an electrically charged strata and a signal reception assembly including a plurality of potential wires and associated potential electrodes for transmitting electrical potential readings from the electrically charged strata. The probe including an outermost insulating jacket substantially encasing the charging assembly and the signal reception assembly, wherein the current wire is electromagnetically insulated from the plurality of potential wires.

Description

PROBE FOR COLLECTING GEOPHYSICAL LOGGING DATA

Related Application

The application claims the benefit of 35 USC 119(e) to United States Provisional Application Serial No. 61/457,553 filed April 20, 2011 (20.04.201 1).

Scope of the Invention

The present invention relates to geophysical logging and more particularly to a probe for simultaneously collecting multiple dipole geophysical log data, including chargeability and resistivity data.

Background of the Invention

Geophysical borehole logging involves gradually lowering a probe down a borehole while the probe measures a physical property of the surrounding rock or soil. Probes can be designed to measure any one of a variety of physical properties. Since the measured physical property is related to the composition of the surrounding rocks and soils, borehole logs can be used to map or model the subsurface strata.

Many measurement probes are known in the art and are designed to measure different properties, enabling borehole logging to be used in a wide variety of applications.

Conductivity logs measure the electrical conductivity of the soil or rock

surrounding a borehole. They provide a detailed measure of changes in conductivity with depth. The electrical conductivity of soil or rock (and its' reciprocal, electrical resistivity) depends on the porosity, groundwater conductivity, degree of saturation, clay content, and other bulk soil properties. Hence it is a useful tool in determining the changes with depth of any of these properties.

Computer analysis or computer modeling of geophysical borehole logging data is now widely used, and if done properly, can contribute significantly to results from log interpretation. The very large amount of data in a suite of borehole logs cannot easily be collated or condensed in the human mind so that all interrelations can be isolated and used; computer analysis makes this possible. The quality of log interpretation is, however, limited to the quality of geophysical borehole logs recorded. Therefore an effort is made to reduce the electrical interference (electrical noise) while measurements are recorded, as for example, produced from the current inputs when collecting logging data. Furthermore, computer analysis or computer modeling of geophysical borehole logs would be significantly improved if a single probe was capable of collecting multiple dipole geophysical log data for both chargeability and resistivity measurements. However no such probe is available on the market to date.

Accordingly, there remains a need for an improved subsurface probe for use in geophysical logging capable of simultaneously collecting multiple dipole chargeability and resistivity log data.

Summary of Invention

The present invention has been developed in view of the difficulties in the art noted and described above.

To at least partially overcome these disadvantages, in a first aspect, the present invention provides a probe for use in geophysical logging and which allows for the simultaneous collection of multiple dipole chargeability and resistivity log data. In a first aspect of the invention, there is provided a probe for use in collecting geophysical logging data for subterranean strata, the probe extending longitudinally from a first end to a second end, comprising: a charging assembly for transmitting an electrical charging current to the strata to form an electrically charged strata, the charging assembly comprising: a current wire having a primary insulating jacket and extending from a proximal end to a distal end, the proximal end being configured to receive the charging current, and a current electrode for transmitting the charging current to the strata, the current electrode being in electrical communication with the distal end of the current wire; a signal reception assembly for transmitting electrical potential readings from the electrically charged strata, the signal reception assembly comprising: a plurality of potential electrodes spaced longitudinally apart along the probe relative to the current electrode, each said potential electrode being configured to receive an associated one of the electrical potential readings, and a plurality of potential wires, each said potential wire having an associated secondary insulating jacket and extending from a proximal end to a distal end, wherein each distal end of the plurality of potential wires is in electrical communication with an associated one of the potential electrodes, and each proximal end of the plurality of potential wires being configured to transmit the associated one of the electrical potential readings as an output; and an outermost insulating jacket substantially encasing the current wire and the plurality of potential wires, wherein the current wire is electromagnetically insulated from the plurality of potential wires.

In a further aspect of the invention, the charging assembly further comprises: a conductive shielding wire having a length substantially corresponding to a length of the primary insulating jacket; and a conductive foil, wherein the foil being wrapped circumferentially about substantially the length of the shielding wire and the length of the primary insulting jacket.

In a further aspect of the invention, the current electrode is arranged at the second end of the probe, and the first end of the probe is provided with a coupling member having a first set of electrical contacts, the first set of electrical contacts being in communication with the proximal end of said current wire, each of said proximal ends of the plurality of potential wires and the shielding wire.

In a further aspect of the invention, the probe further comprises a material strand for providing mechanical pulling strength to the probe, the material strand extending from the first end of the probe to the second end of the probe and being arranged within the outermost insulating jacket.

In a further aspect of the invention, at least one of the plurality of potential electrodes comprises a tubular body composed of a conductable material, the at least one potential electrode being arranged coaxially in-line with said outermost insulating jacket, the tubular body being potted with a polymer based material to provide a water tight seal under pressure.

In a further aspect of the invention, the current electrode comprises a tubular body composed of a conductable material, the tubular body being configured to receive the distal end of the current wire so that the current electrode is arranged coaxially in-line with said outermost insulating jacket, the tubular body being potted with a polymer based material to provide a water tight seal under pressure. In a further aspect of the invention, the shielding wire has a diameter ranging from 0.2 mm to 0.4 mm.

In a further aspect of the invention, the foil comprises an aluminum foil having a thickness ranging from 25 to 35 microns.

In a further aspect of the invention, the outermost insulating jacket comprises a polymer based material having properties selected from the group consisting of having an insulating resistance greater than 999 M Ω at 500 volts direct current, a breaking strength greater than 100 Kgf @ 50 mm/min and an operating temperature range from -20° C to 70° C.

In a further aspect of the invention, the outermost insulating jacket comprises a thickness ranging from 0.5 mm to 2.0 mm and a diameter ranging from 5 mm to 7 mm.

In a further aspect of the invention, the current wire has an electrical resistance less then 14 OHM/KM at 20° C and a diameter ranging from 1.2 mm to 1.7 mm.

In a further aspect of the invention the primary insulating jacket comprises a polypropylene material having a thickness ranging from 0.2 mm to 0.4 mm.

In a further aspect of the invention, the secondary insulating jacket comprises a polyurethane material having a thickness ranging from 0.1 mm to 0.2 mm.

Further aspects of the invention will become apparent upon reading the following detailed description and drawings, which illustrate exemplary embodiments of this invention. Brief Description of the Drawings

Reference may now be had to the following detailed description taken together with the accompanying drawings in which:

Figure 1 shows a schematic illustration of the probe in accordance with the present invention.

Figure 2 shows a cross sectional view of the cable take at line A - - A in Figure 1.

Figure 3 shows a perspective view of a potential electrode shown in Figure 1.

Figure 4 shows a front elevation view the potential electrode shown in Figure 1.

Figure 5 shows a potential electrode being connected to a potential wire in accordance with the present invention.

Figure 6 shows a potential electrode integrally formed with the cable in accordance with the present invention.

Figure 7 shows a current electrode integrally formed with the cable in accordance with the present invention.

Figure 8 shows a connecting assembly integrally formed with the cable in accordance with the present invention.

Figure 9 shows the connecting assembly and corresponding female connecting assembly in accordance with the present invention.

Detailed Description of the Invention

Reference may now be made to Figure 1 which shows a schematic illustration of the probe 100 of the present invention. The probe includes a cable 10 which extends from a first end 1 OA to a second end 10B, a connecting assembly 2 positioned at the first end 10A of the cable 10, a plurality of in-line potential electrodes PI to P6 spaced apart along a length of the cable 10, and a current electrode CI positioned at the second end 10B of the cable 10.

A cross-sectional view of the cable 10 is shown in Figure 2. The cable 10 includes an outer jacket 12 made from an electrically insulating material which forms an internal cavity 14. An internal surface of the outer jacket 12 includes a tape lining 16, preferably being a polyester tape lining. The insulating material preferably has an insulation resistance greater than 999 M Ω at 500 VDC (volts direct current), a breaking strength greater than 100 Kgf @ 50 mm/min, and an operating temperature range from - 20° C to 70° C. Suitable insulating materials for the jacket 12 include polymer based materials, and most preferably a polyurethane material. The outer jacket 12 has a thickness and diameter selected to optimize the cable's insulating properties while limiting the overall diameter of the cable 10. Preferably the outer jacket 12 has a thickness ranging from 0.5 mm to 2.0 mm, most preferably from 1.0 mm to 1.5 mm and a diameter ranging from 5.0 mm to 7.0 mm, more preferably 6.0 mm to 6.5 mm.

Within the cavity 14 formed by the outer jacket 12 there is provided a current input/charging assembly 18 which extends from the first end 10A of the cable 10 to the current electrode CI . The assembly 18 includes a conductive current wire 20 having an insulating material 22 formed about the current wire 20. A conductive shielding wire 24 runs longitudinally along an outer surface of the insulating material 22 and a conductive outer foil wrapping 26 is wrapped circumferentially about the outer surface of the insulating material 22 and the shielding wire 24 enclosing the assembly 18. The insulating material 22, conductive shielding wire 24 and conductive foil wrapping 26 function/assist to insulate the electrical interference (electrical noise) produced by current flowing through the current input/charging assembly 18 from the remainder of the probe 10, as more fully detailed below. Electrical insulation of the input/charging assembly 18 allows for the accurate measurement of data to be taken at the potential electrodes PI to P6, as for example resistivity well log data which is highly sensitive to electromagnetic interference.

The current wire 20 is preferably made from wire strands of a conductive material, such as wire strands of a tinned copper alloy material, which exhibit good conductive properties. Preferably the current wire has an electrical resistance being less then 14 OHM/KM at 20° C and a diameter ranging from 1.2 mm to 1.7 mm and more preferably about 1.5 mm. The insulating material 22 surrounds the current wire 20 and has a thickness ranging from about 0.2 mm to 0.4 mm and more preferably about 0.35 mm. Suitable material for the insulating material 22 include polymer based materials, preferably being a polypropylene material.

The conductive shielding wire 24 runs longitudinally along an outer surface of the insulating material 22 of the current wire 20. Preferably the shielding wire 24 is made from wire strands of a tinned copper alloy material and has a diameter ranging from 0.2 mm to 0.4 mm. The outer foil wrapping 26 is wrapped circumferentially about the shielding wire 24 and the outer surface of the insulating material 22. The foil wrapping preferably is an aluminum foil having a 10 mm width and a 30 micron thickness, with an outer side of the aluminum foil being insulated, preferably by a thin polypropylene film. The shielding wire 24 and outer foil wrapping 26 function to ground any electrical noise produced by the input/charging assembly 18. Within the cavity 14 there is also provided a material strand 28 which extends from and the first end 10A to the second end 10B of the cable 10. The material strand 28 increases the mechanical pulling strength of the probe 100, and preferably is formed from strands of Kevlar.

A plurality of conductive potential wires, namely a first potential wire 30, a second potential wire 32, a third potential wire 34, a fourth potential wire 36, a fifth potential wire 38 and a sixth potential wire 40 are also provided within the cavity 14. Each potential wire 30, 32, 34, 36, 38 and 40 extend from the first end 10A of the cable 10 to an associated one of the potential electrodes PI to P6. For example, the first potential wire 30 extends from the first end 10A and is in electrical contact with the potential electrode PI, the second potential wire 32 extends from the first end 10A and is in electrical contact with the potential electrode P2, and the third, fourth, fifth and sixth potential wires 34 to 40 extend from the first end 10A and are each in electrical contact with their associated potential electrode P3 to P6, respectively.

The following more detailed description will be restricted to the first potential wire 30 which should be understood as being equally applicable to the second 32, third

34, fourth 36, fifth 38 and sixth 40 potential wires, respectively. The first potential wire

30 includes a conductive material/wire 30a which preferably is made from separate strands of wire material. Preferably the conductive material/wire 30a includes six separate copper wire strands and a single stainless steel wire strand which are intertwined together, as is known in the art. The conductive material/wire 30a preferably has a diameter ranging from 0.25 mm to 0.5 mm. The first potential wire 30 also includes a relatively flexible insulating material 30b formed about the conductive material/wire 30a.

The insulating material 30b has a thickness ranging from 0.1 mm to 0.2 mm and is preferably made from a polyurethane material which exhibits good electrical resistance properties and mechanical flexibility.

The following more detailed description will be restricted to the first potential electrode PI which should be understood as being equally applicable to the second, third, fourth, fifth and sixth potential electrodes P2 to P6.

Figures 3 to and 4 show the first potential electrode PI in accordance with the present invention. The potential electrode PI has a cylindrical tubular shape extending longitudinally from one open end 52 to an opposing open end 54. A connecting wire 56 is provided within the hollow cavity of the first potential electrode PI . One end of the connecting wire 56 is secured and in electrical communication with an inner surface of the first potential electrode PI (not shown) and the other opposing end of the connecting wire 56 is connected to and in electrical communication with the distal end of the conductive material/wire 30a of the first potential wire 30 as more fully detailed hereafter.

Figures 5 and 6 illustrate the manner in which the potential electrodes are connected to respective potential wires. To connect the potential electrode PI to the conductive material/wire 30a of the first potential wire 30, the cable 10 is threaded lengthwise through the first potential electrode PI to a position along a length of the probe 100. The outer jacket 12 is then sliced/cut to expose the first potential wire 30. The connecting wire 56 is connected to the conductive material/wire 30a of the first potential wire 30 and thereafter brazed with silver to ensure a tight connection between the wires. Once connected, the connecting wire 56 and the first potential wire 30 are positioned at about a longitudinal center of the first potential electrode PI by further threading the probe 100 through the first potential electrode PI . In this manner, the first potential electrode PI is provided in-line (coaxially) with the cable 10 which facilitates the positioning of the probe 100 within a borehole and reduces the likelihood of the potential electrodes PI to P6 from being caught on something when removing the probe from a borehole.

Each end 52 and 54 are provided with a number of groves as illustrated in Figures 3 and 4 so that the first electrode PI and the cable 10 can be potted/joined together in a water tight seal, even under elevated pressures typical within the borehole. To pot or otherwise couple the first potential electrode PI and cable 10 together in a sealed manner, a polyurethane mold (not shown) having corresponding groves is fitted over and about one end 52 of the first potential electrode PI and a portion of the cable 10 proximal to the end 52. A polyurethane material is injected through the mold to form a sealed joint 58 around and between the end 52 of the first potential electrode PI and the cable 10. The potential electrode PI is also filled with the polyurethane material. To prevent leakage between the electrode and the mold during polyurethane injection, a seal 50 is provided on the ends 52 and 54. The other end 54 of the first electrode PI is likewise joined to the cable 10 to form a water tight sealed connection as shown in Figure 6.

Similarly, each of the second, third, fourth, fifth and six electrodes P2 to P6 are joined to the cable 10 in spaced apart relation in a manner similar to that described above. Potting of the potential electrodes PI to P6 with the cable 10 provides a unified pressure tight structure for the probe 100 which ensures good electrical connectively.

Preferably the potential electrodes are spaced apart between 5 m to 25 m, and more preferably between 10 m to 20 m. The length of each potential electrode PI to P6 is also not particularly restricted, but preferably has a length ranging from about 5 inch to about 24 inches. Any suitable material may be selected for the potential electrode, but preferably a stainless steel material is selected due to its electrical properties and durability.

The current electrode CI is arranged at the distal end of the cable 10 and is in electrical communication with the current wire 20 of the input/charging assembly 18. The current electrode CI includes a closed end tubular body 60 having one open end 62 for receiving the cable 10. Once the cable 10 is inserted through the opening 62, the current wire 20 of the input/charging assembly 18 is electrically connected to an internal surface of the electrode CI . Similarly the material strand 28 is fixed to the current electrode CI to provide mechanical pulling strength to the probe 100. In a preferred aspect of the invention, the current electrode may be provided as two separate pieces which can be threaded together to facilitate access to connecting the current wire 20 and material strand 28 to the current electrode CI .

The first end 10A (proximal end) of the probe 100 is provided with the connecting assembly 2. The connecting assembly 2 facilitates the connection of the probe 100 to a current transceiver/receiver (not shown) in a simple manner. In this regard, each proximal end of the potential wires 30 to 40, the proximal end of the current wire 20 and shielding wire 24 are electrically connected to the connecting assembly 2. The connecting assembly 2 is provided with a number of pins 4 being in electrical contact with a corresponding one of the potential wires 30 to 40 and the current wire 20. A corresponding female assembly 3 is provided on a wench cable or directly to the current transceiver/receiver cable. The connecting assembly is provided with a collar having internal threads to threadably couple the connecting assembly 2 to the corresponding assembly 3. The corresponding assembly 3 is provided with a number of sockets corresponding to associated one of the pins 4 thereby allowing electrical communication between each potential wire PI to P6 and the current electrode CI with the current transceiver/receiver connected to the assembly 3.

The probe 100 in accordance with the present invention allows for the

simultaneous collection of a multiple array of dipoles resistivity and chargeability data. The uses of the cable are not limited, but are particularly suited for radial detection log surveys, gradient surveys (directional survey) and cross hole surveys.

The purpose of the detection log is to measure chargeability and primary voltage data from the potential electrodes PI to P6. The 6 potential electrodes PI to P6 in accordance with the preferred embodiment of the present invention produce 5 dipoles of data. In this case, each dipole is measuring chargeability and apparent resistivity in concentric cylinders about an axis of the borehole where the probe 100 has been arranged. The potential electrodes closest to the current source, namely the current electrode CI, provide near hole information and the further potential electrodes measure larger off hole radii. The unique capability of the probe 100 in accordance with the present invention is that 5 dipoles can be collected simultaneously, and larger radii measurements are possible. Industry standard instrumentation such as the "IFG" probe use a single dipole, which is very small, thus it is only sensitive to near hole. Also the combined use of near hole, and off hole data can be combined to determine if anomalies are: only near hole, in-hole with off-hole extent, only off-hole, and that the zone is not near hole. All three of these pieces of information can be used to determine what was actually intersected by the borehole, and if there are any zones that were missed by the borehole. Non-quantitative interpretation of the logging data can then be processed in 2D or 3D.

The purpose of the directional log is to measure chargeability and primary voltage data from the potential electrodes. The probe in 100 allows for 7 potential electrodes PI to P6 and CI to produce 6 dipoles of data. In this case, each dipole is a measuring chargeability and apparent resistivity in a directional sensitive matter. The use of the probe 100 facilitates multiple dipoles to be read at once, which improves data quality and guarantees consistent spacing and depth locations/depth relocations.

The purpose of the cross hole array is to measure chargeability and primary voltage data from the potential electrodes. In cross hole measurements, a first probe 100 in lowered into a first borehole with a second probe being lowered into a second coaxial borehole spaced away from the first bore hole. The boreholes can be very far apart such as 300 meters or more, or the borehole can within a few meters of each other. Since the probes 100 each have 6 potential electrodes, there are 36 unique dipoles that can be selected. Typical receivers can handle between 8 and 30 dipoles. So an operator will need to decide which dipoles are of most importance to select. In this case, each dipole is a measuring chargeability and apparent resistivity in a cross hole tomographic manner. Typically the array is sensitive in a 2D region (plane) between two boreholes. Although the use of tomography for seismic and resistivity surveys is well established, the probe 100 in accordance is used for borehole IP and resistivity measurements simultaneously.

To the extent that a patentee may act as its own lexicographer under applicable law, it is hereby further directed that all words appearing in the claims section, except for the above defined words, shall take on their ordinary, plain and accustomed meanings (as generally evidenced, inter alia, by dictionaries and/or technical lexicons), and shall not be considered to be specially defined in this specification. Notwithstanding this limitation on the inference of "special definitions," the specification may be used to evidence the appropriate, ordinary, plain and accustomed meanings (as generally evidenced, inter alia, by dictionaries and/or technical lexicons), in the situation where a word or term used in the claims has more than one pre-established meaning and the specification is helpful in choosing between the alternatives.

It will be understood that, although various features of the invention have been described with respect to one or another of the embodiments of the invention, the various features and embodiments of the invention may be combined or used in conjunction with other features and embodiments of the invention as described and illustrated herein.

Although this disclosure has described and illustrated certain preferred

embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. Rather, the invention includes all embodiments, which are functional, electrical or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein.

Claims

We claim:

1. A probe for use in collecting geophysical logging data for subterranean strata, the probe extending longitudinally from a first end to a second end, comprising:

a charging assembly for transmitting an electrical charging current to the strata to form an electrically charged strata, the charging assembly comprising:

a current wire having a primary insulating jacket and extending from a proximal end to a distal end, the proximal end being configured to receive the charging current, and

a current electrode for transmitting the charging current to the strata, the current electrode being in electrical communication with the distal end of the current wire; a signal reception assembly for transmitting electrical potential readings from the electrically charged strata, the signal reception assembly comprising:

a plurality of potential electrodes spaced longitudinally apart along the probe relative to the current electrode, each said potential electrode being configured to receive an associated one of the electrical potential readings, and

a plurality of potential wires, each said potential wire having an associated secondary insulating jacket and extending from a proximal end to a distal end, wherein each distal end of the plurality of potential wires is in electrical communication with an associated one of the potential electrodes, and each proximal end of the plurality of potential wires being configured to transmit the associated one of the electrical potential readings as an output; and

an outermost insulating jacket substantially encasing the current wire and the plurality of potential wires, wherein the current wire is electromagnetically insulated from the plurality of potential wires.

2. The probe according to claim 1, wherein the charging assembly further comprises:

a conductive shielding wire having a length substantially corresponding to a length of the primary insulating jacket; and a conductive foil, wherein the foil being wrapped circumferentially about substantially the length of the shielding wire and the length of the primary insulting jacket.

3. The probe according to claim 1 or claim 2, wherein the current electrode is arranged at the second end of the probe, and the first end of the probe being provided with a coupling member having a first set of electrical contacts, the first set of electrical contacts being in communication with the proximal end of said current wire, each of said proximal ends of the plurality of potential wires and the shielding wire.

4. The probe according to any one of claims 1 to 3, further comprising:

a material strand for providing mechanical pulling strength to the probe, the material strand extending from the first end of the probe to the second end of the probe and being arranged within the outermost insulating jacket.

5. The probe according to any one of claims 1 to 4, wherein at least one of the plurality of potential electrodes comprises a tubular body composed of a conductable material, the at least one potential electrode being arranged coaxially in-line with said outermost insulating jacket, the tubular body being potted with a polymer based material to provide a water tight seal under pressure.

6. The probe according to any one of claims 1 to 5, wherein the current electrode comprises a tubular body composed of a conductable material, the tubular body being configured to receive the distal end of the current wire so that the current electrode is arranged coaxially in-line with said outermost insulating jacket, the tubular body being potted with a polymer based material to provide a water tight seal under pressure.

7. The probe according to claim 3, wherein the shielding wire has a diameter ranging from 0.2 mm to 0.4 mm.

8. The probe according to claim 3 or claim 7, wherein the foil comprises an aluminum foil having a thickness ranging from 25 to 35 microns.

9. The probe according to any one of claims 1 to 8, wherein the outermost insulating jacket comprises a polymer based material having properties selected from the group consisting of having an insulating resistance greater than 999 M Ω at 500 volts direct current, a breaking strength greater than 100 Kgf @ 50 mm/min and an operating temperature range from -20° C to 70° C.

10. The probe according to any one of claims 1 to 9, wherein the outermost insulating jacket comprises a thickness ranging from 0.5 mm to 2.0 mm and a diameter ranging from 5 mm to 7 mm.

11. The probe according to any one of claims 1 to 10, wherein the current wire has an electrical resistance less then 14 OHM/KM at 20° C and a diameter ranging from 1.2 mm to 1.7 mm.

12. The probe according to any one of claims 1 to 1 1, wherein the primary insulating jacket comprises a polypropylene material having a thickness ranging from 0.2 mm to 0.4 mm.

13. The probe according to any one of claims 1 to 12, wherein the secondary insulating jacket comprises a polyurethane material having a thickness ranging from 0.1 mm to 0.2 mm.

14. The probe according to any one of claims 1 to 13, wherein the geophysical logging data comprises chargeability and resistivity log data.