GB2141237A - Method and apparatus for reducing Groeningen effect errors in resistivity measurements of an earth formation - Google Patents
Method and apparatus for reducing Groeningen effect errors in resistivity measurements of an earth formation Download PDFInfo
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- GB2141237A GB2141237A GB08413679A GB8413679A GB2141237A GB 2141237 A GB2141237 A GB 2141237A GB 08413679 A GB08413679 A GB 08413679A GB 8413679 A GB8413679 A GB 8413679A GB 2141237 A GB2141237 A GB 2141237A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
- G01V3/20—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with propagation of electric current
- G01V3/24—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with propagation of electric current using AC
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Abstract
In a method and apparatus for reducing "Groeningen" effect and other anomaly induced errors in resistivity measurements of an earth formation, a sonde 12 having a plurality of voltage measuring electrodes M1l--- and current emitting electrodes A1l--- suspended in a borehole by a conductive cable 16 to which the sonde is attached by a length of insulated cable 32; and two reference electrodes N,N1 are disposed above the sonde 12. A survey current and at least two focusing currents are emitted from the sonde at different respective frequencies; and various voltages induced by each current are measured and utilized to calculate a corresponding set of transfer impedances for that current, and hence the relationships of focusing currents to survey current which is necessary to properly focus the sonde. With these relationships thus defined, the apparent resistivity of the formation may be expressed as a function of the transfer impedances and the currents without the necessity of actually altering the amount of focusing current. One of the focusing currents is operated at a very low frequency to minimise the effect of a resistive anomaly and, by measuring the voltages induced by that current between widely spaced electrodes, the sonde may be operated at a faster rate than would otherwise be possible. <IMAGE>
Description
SPECIFICATION
Method and apparatus for reducing Groeningen effect errors in resistivity measurements of an earth formation
This invention relates to geological formation exploration in general and in particular to the utilization of resistivity measurements in the exploration of geological formations. More particularly, this invention relates to a method and apparatus for reducing anomaly induced errors in such resistivity measurements of geological formations.
It is well known in the prior art that the sedimentary portion of the earth's surface is generally comprised of successive layers or beds which generally do not have a constant thickness. Each of these beds will typically exhibit a certain resistivity characteristic which can be highly useful in the evaluation of a particular borehole with regard to the presence of hydrocarbon deposits. The resistivity characteristics of a particular formation are generally investigated by introducing a resistivity measurement sonde into the borehole. Such sondes are generally lowered into a borehole on a cable utilizing a section of insulated cable generally known as the "bridle" which is generally disposed between the cable and the sonde.
While disposed in the borehole, the resistivity measuring sonde is utilized to generate a survey current and generally one or more focusing or "bucking" currents which are utilized to obtain deeper lateral penetration of the formation by the survey current. In previously known resistivity measurement sondes, voltage measurements taken between electrodes disposed on the sonde are utilized to constantly adjust the amount of focusing current necessary to optimize the penetration of the survey current into the formation. A return electrode is utilized at the surface to provide a return for the various currents and permit the current measurements necessary to determine formation resistivity. A voltage reference electrode is also generally utilized and is generally located at a point between the lower part of the conductive cable and the sonde.
While this system has worked well for many years, certain field conditions have been encountered which cause errors in the calculated or apparent resistivity of the formation. One such error is induced due to an anomaly in the resistance of a formation above the sonde which causes variations in the return path of the survey and focusing currents to the return electrode. When attempting resistivity measurements in a low resistance earth formation below a highly resistive bed, the survey and focusing currents tend to return along the well casing or cable and induce a greater than normal voltage at the reference electrode disposed above the sonde.This results in an error in calculation due to the fact that the voltage differential between the sonde and the reference electrode will not be equal to the voltage differential between the sonde and the theoretical point at infinity utilized in these calculations.
This particular error, sometimes referred to as the "Groeningen" effect or casing effect is particularly distressing in that the resultant resistivity measurements are similar in nature to those associated with petrochemical deposits when such deposits are not present. The expense associated with drilling and testing these wellbores makes it desirable that a method and apparatus be defined to correct for or reduce the errors induced by such resistive anomalies. One method of correcting for this error involves the utilization of very low frequency currents; however, since several cycles of current are necessary to complete a single resistivity measurement, the speed at which the sonde must be operated in this method is quite slow.The expense associated with these wells and equipment dictates that these measurements be taken as rapidly as possible, thereby eliminating this approach as a viable alternative.
It is therefore one object of the present invention to provide an improved apparatus for reducing anomaly induced errors in resistivity measurements of earth formations.
It is another object of the present invention to provide an improved method for reducing anomaly induced errors in resistivity measurements of earth formations.
It is yet another object of the present invention to provide an improved method for reducing anomaly induced errors in resistivity measurements of earth formations which permits the resistivity measurement device to be operated at normal speeds.
It is another object of the present invention to provide an improved method for reducing anomaly induced errors in resistivity measurements of earth formations which can be utilized in conjunction with known resistivity measurement sondes.
The present invention provides a method for reducing anomaly induced errors in resistivity measurements of an earth formation traversed by a borehole in which the resistivity measurement is accomplished utilizing a sonde suspended in said borehole from a conductive cable in the borehole, said sonde having a plurality of voltage measuring electrodes and current emitting electrodes dispsed thereon and a first reference electrode disposed above said sonde, comprising.
emitting a survey current from a selected one of said plurality of current emitting electrodes and measuring the voltage induced by said survey current at at least a selected one of said voltage measuring electrodes;
disposing a second reference electrode between said first reference voltage electrode and said sonde;
emitting a first focusing current at a first selected frequency from a selected one of said plurality of current emitting electrodes and measuring the voltage induced by said first focusing current between said sonde and said second reference electrode;
emitting a second focusing current at a frequency substantially below said first selected frequency from a selected one of said plurality of current emitting electrodes and measuring the voltage induced by said second focusing current between said second reference electrode and said first reference electrode; and
combining the voltage induced by said first focusing current and the voltage induced by said second focusing current to obtain a resultant total voltage measurement between said sonde and said first reference
electrode wherein said resultant total voltage measurement has a reduced anomaly induced error.
The various voltages induced by the survey and focusing currents may be utilized to calculate a
corresponding set of transfer impedances for that current. By utilizing the calculated transfer impedances, the relationships of focusing currents to survey current which is necessary to properly focus the sonde may
be calculated. With the relationship of the survey current and focusing currents thus defined, the apparent
resistivity of the formation may be expressed as a function of the transfer impedances and the currents
without the necessity of actually altering the amounts of focusing current.
In an embodiment of the invention, one of the focusing currents is operated at a very low frequency to
minimize the effect of a resistive anomaly and, by measuring the voltages induced by that current between
widely spaced electrodes, the sonde may be operated at a faster rate than would otherwise be possible.
The present invention further provides apparatus for correcting anomaly induced errors in resistivity
measurements of an earth formation traversed by a borehole in which the resistivity measurement is
accomplished utilizing voltage measurements between a sonde suspended in said borehole from a
conductive cable and a first reference electrode disposed above said sonde, comprising::
means for emitting a first focusing current from said sonde at a selected frequency;
a second reference electrode disposed between said first reference electrode and said sonde;
means for measuring a first voltage induced by said first focusing current between said sonde and said
second reference electrode;
means for emitting a second focusing current from said sonde at a frequency substantially below said
selected frequency;
means for measuring a second voltage induced by said second focusing current between said second
reference electrode and said first reference electrode; and
means for combining said first voltage and said second voltage wherein said resultant voltage is a
corrected measurement of the voltage measurement between said sonde and said first reference electrode.
By way of example, an embodiment of the invention will now be described with reference to the
accompanying drawings, wherein:
Figure lisa partially schematic, partially diagrammatic view of resistivity measuring apparatus of the
present invention; and
Figure 2 is a block diagram of the circuitry of resistivity measuring apparatus of the present invention.
With reference nowtothe Figures, and in particularwith referenceto Figure 1,thereisdepicteda partially
schematic, partially diagrammatic view of the resistivity measuring apparatus of the present invention.
The method and apparatus disclosed herein will find application with many different types of resistivity
measuring devices; however, for purposes of explanation, the embodiment disclosed herein is described
with respect to a so-called "deep laterolog". The "deep laterolog" is designed to measure formation
resistivities at greater distances from the borehole and, in particular, beyond the "invaded zone" where the
presence of drilling fluids may alter the formation resistivity.
As in most typical installations of this type, the system includes a sonde 12 suspended in a borehole 14 by
means of a wireline cable 16. Electrical conductors (not shown) disposed within wireline cable 16 are
coupled to various electronic processing devices contained in van 18. Sonde 12 includes a plurality of
voltage measuring electrodes M and Miu, M2L and M2U, and A*lL and Aau which are disposed on the surface
of sonde 12 on either side of a survey current emitting electrode Ao. The subscripts U and L signify the upper
and lower of each pair of a pair of symmetrical electrodes.Sonde 12 also includes a plurality of focus current
emitting electrodes A1L, Aiu, A2L and A2u.
Also depicted in Figure lisa voltage reference electrode or torpedo N which is separated from sonde 12
by a length of insulated cable 32, typically referred to as a "bridle." Located between sonde 12 and torpedo N
is an additional voltage measuring electrode N1. Electrode N1 is particularly useful in the method disclosed
herein for reducing errors in the formation resistivity measurements which may be caused by resistive
anomalies such as zone 36.
As is depicted in Figure 1, a typical path of return for survey current 38 is altered by the highly resistive
nature of zone 36. Rather than proceeding radially outward to return electrode B, the path of survey current is
altered by the presence ofwireline cable 16 and well casing 40. Those skilled in the art will appreciate that the
electromagnetic phenomena known as "skin effect" will enhance this alteration of return path and induce a ,greaterthan normal voltage at electrode N. This error may be minimized by utilizing very low frequency
currents (typically less than one hertz); however, since it is generally acknowledged that three cycles of
current are necessary for each resistivity reading, a resistivity log of several thousand feet of borehole could
become very time consuming.
Fortunately, the "Groeningen" effect varies very slowly with depth and may be compensated for by
utilizing this novel technique of independent voltage and current measurements which permits sonde 12 to
be operated at normal logging speeds while simultaneously measuring and computing a "focused"
condition which is corrected for the errors induced by the effect.
In order to understand the novel . method and apparatus being described it is necessary to understand the operation of a conventional deep laterolog system.
Generally, a survey current lo is emitted by the central electrode Ao and a plurality of focusing currents are emitted from electrodes AlL, Alu, A2 and A2U. The ratios between focusing currents and survey current are constantly adjusted to maintain a zero or null voltage gradient between electrode pairs M1 and M2 and A and A2 In order to simplify the notation utilized herein, the average voltage of symmetrical electrode pairs, without U and L subscripts, is written utilizing the rule expressed in equation (1):: VM, = VMIU + VM!L 2 (1)
Similarly, the sum of currents flowing from (or to) symmetrical electrodes will be written without the U and
L subscript as follows: Ii = (11U + IlL) (2)
When the aforementioned zero voltage gradient is achieved and the sonde is "focused," the apparent resistivity of a formation can be expressed by: R ~ K [VM VN]
Ra = K [VM - VN
lo (3) Where No is a remote electrode which is ideally at electrical infinity. In actual practice, the voltage measurement is taken with respect to torpedo N. In general, torpedo N is far enough away from sonde 12 that no error occurs.However, as depicted in Figure 1, measurements taken beneath a zone of high resistivity can be perturbed by the presence of the current flowing down wireline cable 16 to sonde 12.
The method of the present invention utilizes four nominal value currents which are emitted from sonde 12.
A survey current lo is emitted from electrode Ao. Three separate focusing currents are also utilized. Current I, is emitted from electrodes Aiu and A1L; current 12 is emitted from electrodes A2U and A2L; and, current 1*2 is also emitted from electrodes A2U and A2L.
Each of these currents is emitted independently which, as those skilled in the art will appreciate, can be accomplished by alternately emitting each current or by continuously emitting all currents at various different frequencies. No attempt is made during this process to alter the amount of focusing current being emitted to actually balance sonde 12. In the preferred mode of the present invention, currents lo and Il are alternately emitted at several hundreds of hertz, current 12 is emitted at less than 100 hertz and current 1*2 at a very low frequency (less than one hertz).
Preferably, during the period of time that each current is emitted, a series of five voltage potentials are measured:
Voltage Measuring Point
V1 between M1 and N
V2 between M1 and M2
V3 between A1 and A2
V4 between M1 and N1 V5 between N1 and N Each of these voltages is utilized in conjunction with each currentto generate five transfer impedances for sonde 12 for each current source. In this manner, the principle of superposition in linear circuitry permits the amounts of various currents necessary to achieve a desired voltage level to be simply and easily computed utilizing the transfer impedances.The matrix of thus calculated transfer impedances is as follows:
V1 V2 V3 V4 V5 o aO1 a02 a03 a04 a05 Il a11 a12 a13 a14 a15
12 a21 a22 a23 a24 a25 1*2 a31 a32 a33 a34 a35 (4)
By now setting lo equal to unity and writing the conditions necessary to balance sonde 12, the theoretical amount of focusing currents necessary to balance the tool may be derived.The balance conditions are:
lo = 1 (5)
V2 = VM1 - VM2 = at210 + a1211 + a2212 = 0 (6) V3 = VA* - VA2 = at310 + a1311 + a2312 = (7) By solving equations (5), (6) and (7) we can determine the exact amount of focusing current necessary to balance sonde 12 without the limitations generally imposed by physical constraints in existing systems.
Io = 1 (8) 17 = aO2a23 - a03a33
a22a13 - a13a23 (9)
12 = a02a13 - a03a12
a12a23 - a22a13 (10) Given the precise amount of focusing current needed to balance sonde 12, the apparent resistivity of sonde 12 can be expressed as follows:
Ra = K (apollo + as + a212) 11 (11)
As those skilled in the art will appreciate, by substituting equations (9) and (10) into equation (11) the apparent resistivity of the formation may be expressed as a function of transfer impedances with lo being constrained to unity.
This expression of the apparent resistivity of the formation is not corrected for the resistive anomaly of zone 36. This error can be seen to be an error in transfer impedance a21 due to the spurious voltage induced between electrodes M1 and N by the altered current path. In order to reduce this error it is only necessary to replace transfer impedance a21 by a combination of two different transfer impedances, only one of which can be measured at a very low frequency.Indeed, since the voltage difference between electrodes M1 and N is equal to the voltage difference between electrodes M1 and N1 plus the voltage difference between electrodes
N1 and M, transfer impedance a21 can be replaced by a combination of transfer impedances a24 and a35, where a24 is measured at a less than one hundred hertz and a35 is measured at a very low frequency.By having measured the voltage induced between electrodes N1 and N at a very low frequency, this measurement can be combined with the voltage induced between electrodes M1 and N1 at normal survey frequencies to generate a corrected voltage measurement as expressed in equation (12):
Ra = K[a01l0 + a11l1 + (a24 + a35)l2] 11o (12)
Those ordinarily skilled in the art will appreciate that the physical distances between electrodes M1, N1 and N are much greater than the distances between electrodes disposed on sonde 12, and this physical separation will permit the measurement ofthe voltage between electrode N1 and N to be accomplished at a very low frequency.
A block diagram of the circuitry necessary to perform this method is depicted in Figure 2. As can be seen, the voltages at each electrode on sonde 12 are coupled to appropriate band pass filters 50,52,54, 56 and 58, in those embodiments in which differing frequencies are utilized. The outputs of each band pass filter are then amplified by amplifiers 60, 62, 64, 66 and 68 and coupled to analog-to-digital converters 70,72,74,76 and 78. Similarly, the amount of current emitted from each electrode is coupled to an appropriate analog-to-digital converter 80, 82, 84 and 86. The outputs of each analog-to-digital converter are then coupled to an appropriately programmed digital processing device 88 which is utilized, in a preferred embodiment of the present invention, to calculate the necessary transfer impedances and to control the selective application of various survey and focusing currents in a manner well known in the art.
Claims (13)
1. A method for reducing anomaly induced errors in resistivity measurements of an earth formation traversed by a borehole in which the resistivity measurement is accomplished utilizing a sonde suspended in said borehole from a conductive cable in the borehole, said sonde having a plurality of voltage measuring electrodes and current emitting electrodes disposed thereon and a first reference electrode disposed above said sonde, comprising::
emitting a survey current from a selected one of said plurality of current emitting electrodes and measuring the voltage induced by said survey current at at least a selected one of said voltage measuring electrodes;
disposing a second reference electrode between said first reference voltage electrode and said sonde;
emitting a first focusing current at a first selected frequency from a selected one of said plurality of current emitting electrodes and measuring the voltage induced by said first focusing current between said sonde and said second reference electrode;
emitting a second focusing current at a frequency substantially below said first selected frequency from a selected one of said plurality of current emitting electrodes and measuring the voltage induced by said second focusing current between said second reference electrode and said first reference electrode; and
combining the voltage induced by said first focusing current and the voltage induced by said second focusing current to obtain a resultant total voltage measurement between said sonde and said first reference electrode wherein said resultant total voltage measurement has a reduced anomaly induced error.
2. The method for reducing anomaly induced errors in resistivity measurements of an earth formation according to Claim 1 further including the step of calculating a first set of transfer impedances for said sonde by means of measuring said survey current and said voltage induced by said survey current.
3. The method for reducing anomaly induced errors in resistivity measurements of an earth formation according to Claim 2 further including the step of calculating a second set of transfer impedances for said sonde by means of measuring said first focusing current and said voltage induced by said first focusing current.
4. The method for reducing anomaly induced errors in resistivity measurements of an earth formation according to Claim 3 further including the step of calculating a third set of transfer impedances for said sonde by means of measuring said second focusing current and the voltage induced by said second focusing current.
5. The method for reducing anomaly induced errors in resistivity measurements of an earth formation according to Claim 4 further including the step of calcuating the amount of focusing current needed to properly focus said sonde by utilizing said first, second and third sets of transfer impedances.
6. The method for reducing anomaly induced errors in resistivity measurements of an earth formation according to Claim 5 further including the step of calculating the resistivity of an earth formation transversed by said sonde as a function of said survey current, said first focusing current, said second focusing current and said first, second and third sets of transfer impedances.
7. Apparatus for correcting anomaly induced errors in resistivity measurements of an earth formation traversed by a borehole in which the resistivity measurement is accomplished utilizing voltage measurements between a sonde suspended in said borehole from a conductive cable and a first reference electrode disposed above said sonde, comprising::
means for emitting a first focusing current from said sonde at a selected frequency;
a second reference electrode disposed between said first reference electrode and said sonde;
means for measuring a first voltage induced by said first focusing current between said sonde and said second reference electrode;
means for emitting a second focusing current from said sonde at a frequency substantially below said selected frequency;
means for measuring a second voltage induced by said second focusing current between said second
reference electrode and said first reference electrode; and
means for combining said first voltage and said second voltage wherein said resultant voltage is a corrected measurement of the voltage measurement between said sonde and said first reference electrode.
8. The apparatus for correcting anomaly induced errors in resistivity measurements of an earth formation according to Claim 7 further including an elongate insulated cable disposed between said sonde
and said first reference electrode.
9. The apparatus for correcting anomaly induced errors in resistivity measurements of an earth formation according to Claim 8 wherein said second reference electrode is disposed on said elongated
insulated cable.
10. The apparatus for correcting anomaly induced errors in resistivity measurements of an earth formation according to Claim 7 wherein said sonde includes a plurality of current emitting electrodes and wherein said survey current is emitted from a first selected current emitting electrodes and wherein said first
and second focusing currents are emitted from a second selected current emitting electrode.
11. A method for reducing anomaly induced errors in resistivity measurements of an earth formation traversed by a borehole, in which the resistivity measurement is accomplished utilizing a sonde suspended
in said borehole from a conductive cable in said borehole, said sonde having a plurality of voltage measuring electrodes and current emitting electrodes disposed thereon, comprising::
suspending said sonde from said conductive cable utilizing a length of insulated cable;
disposing a first reference electrode above said sonde;
disposing a second reference electrode on said insulated cable at a point between said first reference electrode and said sonde;
emitting a survey current from a selected one of said current emitting electrodes;
measuring the voltages induced by said survey current at at least one of said voltage measuring electrodes;
computing at least a first set of transfer impedances utilizing said voltages induced at at least one of said voltage measuring electrodes and said survey current;
emitting a first focusing current from a selected one of said current emitting electrodes;
measuring the voltages induced by said first focusing current between said sonde and said second reference electrode;;
computing at least a second set oftransfer impedances utilizing said voltages induced between said sonde and said second reference electrode and said first focusing current;
emitting a second focusing current from a selected one of said current emitting electrodes at a frequency substantially below the frequency of said first focusing current;
measuring the voltages induced by said second focusing current between said second reference electrode and said first reference electrode;
computing at least a third set of transfer impedances utilizing said voltages induced between said second reference electrode and said first reference electrode and said second focusing current; and
determining the resistivity of the earth formation as a function of said first, second and third sets of transfer impedances.
12. A method according to any one of claims 1 to 6 and 11, substantially as described herein with reference to the accompanying drawings.
13. Apparatus for correcting anomaly induced errors in resistivity measurements of an earth formation traversed by a borehole, the apparatus being substantially as described herein with reference to, and as illustrated by the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49927383A | 1983-05-31 | 1983-05-31 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8413679D0 GB8413679D0 (en) | 1984-07-04 |
| GB2141237A true GB2141237A (en) | 1984-12-12 |
| GB2141237B GB2141237B (en) | 1986-10-22 |
Family
ID=23984591
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08413679A Expired GB2141237B (en) | 1983-05-31 | 1984-05-29 | Method and apparatus for reducing groeningen effect errors in resistivity measurements of an earth formation |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1216025A (en) |
| FR (1) | FR2547063B1 (en) |
| GB (1) | GB2141237B (en) |
| NO (1) | NO159322C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991006854A1 (en) * | 1989-11-04 | 1991-05-16 | Natural Environment Research Council | Method for use in assessing the physical state of ground materials and apparatus for use therein |
| WO2014011186A1 (en) * | 2012-07-13 | 2014-01-16 | Halliburton Energy Services, Inc. | System and method of focusing an array laterolog |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2653294A (en) * | 1949-04-21 | 1953-09-22 | Phillips Petroleum Co | Apparatus for electrical well logging |
| US4335353A (en) * | 1979-06-18 | 1982-06-15 | Schlumberger Technology Corporation | Method and apparatus for detecting an anomaly in a resistivity measurement of an earth formation |
-
1984
- 1984-05-23 CA CA000454930A patent/CA1216025A/en not_active Expired
- 1984-05-29 GB GB08413679A patent/GB2141237B/en not_active Expired
- 1984-05-29 FR FR8408401A patent/FR2547063B1/en not_active Expired - Fee Related
- 1984-05-30 NO NO842169A patent/NO159322C/en unknown
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991006854A1 (en) * | 1989-11-04 | 1991-05-16 | Natural Environment Research Council | Method for use in assessing the physical state of ground materials and apparatus for use therein |
| GB2253912A (en) * | 1989-11-04 | 1992-09-23 | Natural Environment Res | Method for use in assessing the physical state of ground materials and apparatus for use therein |
| GB2253912B (en) * | 1989-11-04 | 1994-04-06 | Natural Environment Res | Method for use in assessing the physical state of ground materials |
| WO2014011186A1 (en) * | 2012-07-13 | 2014-01-16 | Halliburton Energy Services, Inc. | System and method of focusing an array laterolog |
| US10175378B2 (en) | 2012-07-13 | 2019-01-08 | Halliburton Energy Services, Inc. | System and method of focusing an array laterolog |
Also Published As
| Publication number | Publication date |
|---|---|
| CA1216025A (en) | 1986-12-30 |
| GB2141237B (en) | 1986-10-22 |
| FR2547063A1 (en) | 1984-12-07 |
| FR2547063B1 (en) | 1993-04-30 |
| GB8413679D0 (en) | 1984-07-04 |
| NO159322C (en) | 1988-12-14 |
| NO842169L (en) | 1984-12-03 |
| NO159322B (en) | 1988-09-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |