CN112034522A - Method for measuring formation resistivity by using six-subarray coil system - Google Patents
Method for measuring formation resistivity by using six-subarray coil system Download PDFInfo
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- CN112034522A CN112034522A CN202010850715.1A CN202010850715A CN112034522A CN 112034522 A CN112034522 A CN 112034522A CN 202010850715 A CN202010850715 A CN 202010850715A CN 112034522 A CN112034522 A CN 112034522A
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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
- G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
- G01V3/28—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device using induction coils
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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
- G01V3/38—Processing data, e.g. for analysis, for interpretation, for correction
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
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Abstract
The invention discloses a method for measuring formation resistivity by a six-subarray coil system, which is characterized by calculating and drawing a relation chain table of the original apparent conductivity ratio of a subarray 6A6B farthest from a transmitting coil to an adjacent subarray 5A5B of the subarray 6A6B and the original apparent conductivity of the subarray 5A5B by a traditional seven-subarray coil system, measuring the apparent conductivity of the farthest subarray 5A5B by using a six-subarray coil system induction logging instrument, and inquiring the relation chain table to obtain the conversion coefficients of the subarray 5A5B and the subarray 6A6B, so that the original apparent conductivity information of the farthest subarray 6A6B of the traditional coil system is the conversion coefficient multiplied by the apparent conductivity of the subarray 5A5B measured by the six-subarray coil. The method reduces a pair of receiving coils, optimizes the structural length of the system, makes the whole instrument compact in structure and convenient to operate, and enhances the tensile strength and the compressive strength of the measuring instrument.
Description
Technical Field
The invention belongs to the technical field of geophysical logging, relates to an induction logging technology, and particularly relates to a method for measuring formation resistivity by a six-subarray coil system.
Background
Induction logging tools are logging tools that measure formation resistivity using the principle of electromagnetic induction. After the transmitting coil generates an alternating electromagnetic field in a stratum medium, an induced current can be generated in the stratum unit ring with the shaft as the axis, and the magnitude of the induced current is in direct proportion to the conductivity of the stratum unit ring. The electromagnetic fields generated by these current loops are called secondary fields. The secondary field can generate induced electromotive force in the receiving coil, and the size of the induced electromotive force reflects the conductivity of the stratum, so that the resistivity of the stratum can be indirectly measured by measuring the induced electromotive force caused by the secondary field in the receiving coil.
The underground part of the array induction logging instrument consists of three parts, namely an electronic instrument short section, a coil system and a transmitting short section, wherein the coil system is a key component of the array induction instrument. The array induction logging instrument coil system is an array coil system formed by a plurality of sub-arrays. Each subarray consists of a transmitting coil and two receiving coils; the receiving coil close to the transmitting coil is a compensation receiving coil, and the receiving coil far away from the transmitting coil is a main receiving coil. The compensation receiving coil and the main receiving coil are connected in series but opposite in winding direction, and form a mutual inductance balanced three-coil system sub-array with the transmitting coil. By reasonably selecting the distance between the main receiving coil and the compensation receiving coil and the distance between the transmitting coil and the receiving coil, the array coil system with different radial detection depths, different longitudinal resolutions and balanced mutual inductance can be obtained.
The conventional array induction logging tool coil system is composed of 7 sub-arrays, such as the array induction logging coil system (200910235768.6) for measuring the formation resistivity, which is disclosed in the invention patent, has the disadvantage that the whole structure is long, thereby having certain structural risks. Therefore, the improved design of the coil system on the premise of ensuring the accuracy of the measurement result is a good structure optimization scheme. Meanwhile, convenience can be brought to production, installation, transportation and logging operation of the instrument.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for measuring the resistivity of a stratum by using a six-subarray coil system, which measures the conductivity of the stratum by reducing one subarray on an original induction logging instrument with seven subarrays, and simultaneously adopts a scientific algorithm aiming at the structure of the six subarray coil systems to ensure that an accurate measurement result can be obtained after a pair of coils is reduced, so that the structural risk caused by the overlong length of the traditional array induction coil system is solved.
The technical purpose of the invention is realized by the following technical scheme:
a method for measuring formation resistivity by a six-subarray coil system is characterized by calculating and drawing a relation chain table of an original apparent conductivity ratio of a subarray 6A6B farthest from a transmitting coil and an adjacent subarray 5A5B of the subarray 6A6B and an original apparent conductivity of the subarray 5A5B through a traditional seven-subarray coil system, measuring by using an induction logging instrument of the six-subarray coil system to obtain the apparent conductivity of the farthest subarray 5A5B, inquiring the relation chain table to obtain the apparent conductivity conversion coefficients of the subarray 5A5B and the subarray 6A6B, and multiplying the apparent conductivity of the farthest subarray 6A6B of the traditional coil system by the apparent conductivity of the subarray 5A5B obtained by measuring the six-subarray coil system.
The conventional seven-subarray coil system is a six-subarray coil system except for the subarray 6A6B farthest away from the transmitting coil.
The relation linked list is obtained by the following method: obtaining a subarray original apparent conductivity response curve along with the change of the stratum conductivity through the calculation of a traditional seven-subarray coil system, calculating an original apparent conductivity ratio of the subarray 6A6B to 5A5B, and drawing a relation chain table of the original apparent conductivity of the subarray 5A5B and the original apparent conductivity ratio of the adjacent subarray 6A6B to the subarray 5A 5B.
The calculation formula of the apparent conductivity of the subarray is as follows:
where ω denotes angular frequency and μ denotes magnetic permeability, and μ ═ 4 pi × 10 is taken for calculation-7Where k denotes the wave number of the formation medium, i ω μ σ denotes the conductivity, i denotes the imaginary symbol, σ denotes the conductivityaRAnd the apparent conductivity corresponding to the real part signal is represented, beta represents a proportionality coefficient between the distances of the transmitting coil, the receiving coil and the shielding coil of the subarray, and beta is less than 1, namely, the distances are L and beta L respectively.
The value range of the stratum conductivity sigma is 0.001-10.0S/m.
The invention has the beneficial effects that:
through the six array induction coil systems of new design, effectively shortened the length of whole structure, the shortening of structure length makes the resistance to compression and the tensile strength of instrument promote greatly. Meanwhile, a scientific algorithm aiming at a novel coil system structure is adopted, so that the influence on a measurement result caused by reducing coils is avoided, and an accurate measurement curve can still be obtained. Meanwhile, the novel coil system has the characteristics of simple structure and convenience in maintenance and replacement, and the use cost and the maintenance cost of related equipment are reduced. In addition, the instrument belongs to a long rod type, and the effective shortening of the length can also bring convenience to the transportation process and the logging operation.
Drawings
FIG. 1 is a schematic diagram of a conventional coil architecture of the present invention;
FIG. 2 is a schematic diagram of the coil architecture of the method of the present invention;
FIG. 3 is a graph of the apparent conductivity response of different subarrays in accordance with the present invention;
FIG. 4 is a chart of the conversion chain of the apparent conductivity ratio of adjacent subarrays in accordance with the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a novel six-subarray coil system aiming at the defects of the traditional array induction coil system structure, and the novel six-subarray coil system has a unique coil system structure. The coil is made up of 6 sub-arrays, which share a single transmit coil. All receiving coils are axially arranged on one side of the receiving coil, and the coil system in the form is simple in structure and easy to manufacture and debug; compared with 7 sub-arrays of the traditional coil, the coil system structure has the advantages that each sub-array shares one transmitting coil, so that on the basis of effectively shortening the length of the instrument, one sub-array is further reduced, namely a pair of receiving coils are reduced, the length of the instrument is further shortened, the structural performance of the system is greatly optimized, the structure of the whole instrument is compact, and the operation is convenient; in addition, because the coil system adopts the reinforced metal mandrel, the overall mechanical performance of the instrument is greatly improved, and a reliable path is provided for the through wire, so that the through wire can be conveniently combined with other instruments for logging, and the use flexibility of the instrument is greatly improved. Meanwhile, a scientific algorithm aiming at a new coil system structure is adopted, so that accurate measurement results can be obtained after a pair of coils is reduced.
As shown in fig. 1, the conventional coil system structure is composed of 7 sub-arrays, each of which is composed of one transmitting coil and two receiving coils. They share a transmitter coil, and all receiver coils are arranged on one side of the receiver coil along the axial direction, and can be numbered as 0A0B, 1A1B, 2A2B, 3A3B, 4A4B, 5A5B and 6A6B according to the figure, wherein the 6A6B coil group is composed of two coils, namely A6A coil and A6B coil. The 6A coil and the 6B coil are separated by the glass fiber reinforced plastic sleeve, and the schematic diagrams can be used for understanding that the 6A coil and the 6B coil are connected to form a large total size, so that the installation difficulty and the transportation difficulty are improved to a certain extent, the integral structure of the instrument is overlong, and the system risk is increased. Therefore, if the coil system can be perfected on the basis of not influencing the measurement result, the improvement of the performance of the whole structure is strongly necessary. As shown in fig. 2, the whole coil system is composed of 6 sub-arrays, compared with the original coil system, a pair of coils, namely 6A and 6B, and a glass fiber reinforced plastic sleeve are reduced, the length is shortened by nearly one meter, the overall size is greatly shortened, and the tensile and compressive indexes of the instrument are greatly improved.
On the basis of optimizing the instrument structure, a scientific processing algorithm aiming at the novel coil system measurement data is adopted, and the acquisition and the accuracy of the apparent conductivity information of 7 sub-arrays of the traditional coil system are ensured. The array induction logging can realize formation information measurement under various frequencies and various source distances, and a novel coil system measurement data processing method is specifically described by taking 26.256KHz working frequency as an example. Constant alternating current is applied to the transmitting coil, and different receiving coils are utilized to receive the secondary induction field of the stratum so as to generate induced electromotive force, wherein the signal is an original measuring signal. In order to not lose the measurement information of the longest source distance of the original coil system, the longest source distance measurement signal of the novel coil system is compensated by adopting a mathematical method to obtain the 7 th measurement signal of the longest source distance sub array of the original coil system.
The array induction subarray consists of a transmitting coil and two receiving coils and is divided into two double-coil systems,
respectively representing the distances between the transmitting coils and the receiving coils and between the transmitting coils and the shielding coils of different sub-arrays.
Single set of transmit and receive dual coil system apparent conductivity σaThe calculation formula of (2):
in the formula: ω represents angular frequency, μ represents magnetic permeability, and μ ═ 4 pi × 10 is taken for calculation-7K denotes the wave number of the formation medium, i ω μ σ denotes the conductivity, and i denotes the imaginary symbol.
On the basis of the above, the subarray three-coil system is according to the calculation formula of the conductivity:
in the formula: sigmaaRAnd the apparent conductivity corresponding to the real part signal is represented, beta represents a proportionality coefficient between the distances of the transmitting coil, the receiving coil and the shielding coil of the subarray, and beta is less than 1, namely, the distances are L and beta L respectively.
Through the above-mentioned subarray three-coil system apparent conductivity calculation formula, the stratum conductivity value range is 0.001-10.0S/m, 7 subarray original apparent conductivity response curves along with stratum conductivity change curves are obtained by calculation, as shown in fig. 3, on the basis, subarray 6A6B and subarray 6A6 are further calculatedThe original apparent conductivity ratio of the subarray 5A5B is obtained as a linked list of the relationship between the original apparent conductivity of the subarray 5A5B and the original apparent conductivity ratio of the adjacent subarray 6A6B and the subarray 5A5B, as shown in fig. 4, the relationship is (σ) in paira(5)，σa(6)/σa(5)). Under the novel six-subarray coil system structure, the original apparent conductivity information of the subarray 6A6B cannot be directly measured, and by using a relationship linked list, the corresponding abscissa is found in fig. 4 by using the measured original apparent conductivity information of the subarray 5A5B, taking 1.0S/m as an example, so that the ordinate value corresponding to the abscissa is 0.44, namely, the ordinate value is a conversion coefficient, and therefore, the original conductivity information of the subarray 6A6B can be multiplied by the coefficient by the original conductivity of the subarray 5 A5B.
σa(6)＝(array(6)/array(5))*σa(5)
On the basis of the novel six-array coil system probe structure, the data relation linked list conversion method is adopted, and the acquisition and accuracy of the apparent conductivity information of the 7 th sub-array of the traditional coil system structure are ensured.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. A method for measuring formation resistivity by a six-subarray coil system is characterized in that a relation chain table of original apparent conductivity ratio of a subarray 6A6B farthest from a transmitting coil and an adjacent subarray 5A5B of the subarray 6A6B and subarray 5A5B is calculated and drawn through a traditional seven-subarray coil system, the apparent conductivity of the farthest subarray 5A5B is obtained by measuring with a six-subarray coil system induction logging instrument, conversion coefficients of subarray 5A5B and subarray 6A6B are obtained by inquiring on the relation chain table, and then original apparent conductivity information of the farthest subarray 6A6B of the traditional coil system is obtained by multiplying the apparent conductivity of the subarray 5A5B obtained by measuring with the six-subarray coil system by the conversion coefficients.
2. The method of claim 1, wherein the six-subarray coil system is a six-subarray coil system except for the subarray 6A6B farthest from the transmitter coils.
3. The method of claim 1, wherein the relationship list is obtained by: obtaining a subarray original apparent conductivity response curve along with the change of the stratum conductivity through the calculation of a traditional seven-subarray coil system, calculating an original apparent conductivity ratio of the subarray 6A6B to 5A5B, and drawing a relation chain table of the original apparent conductivity of the subarray 5A5B and the original apparent conductivity ratio of the adjacent subarray 6A6B to the subarray 5A 5B.
4. The method of claim 3 in which the subarray apparent conductivity calculation formula is:
where ω denotes angular frequency and μ denotes magnetic permeability, and μ ═ 4 pi × 10 is taken for calculation-7Where k denotes the wave number of the formation medium, i ω μ σ denotes the conductivity, i denotes the imaginary symbol, σ denotes the conductivityaRAnd the apparent conductivity corresponding to the real part signal is represented, beta represents a proportionality coefficient between the distances of the transmitting coil, the receiving coil and the shielding coil of the subarray, and beta is less than 1, namely, the distances are L and beta L respectively.
5. The method for measuring the formation resistivity by using the six-subarray coil system according to claim 4, wherein the value of the formation conductivity σ ranges from 0.001 to 10.0S/m.
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Effective date of registration: 20220127 Address after: 100029 Chaoyang District, Beijing Hui Xin Street six, Twelfth level. Applicant after: SINOPEC OILFIELD SERVICE Corp. Applicant after: Sinopec Jingwei Co.,Ltd. Applicant after: Southwest measurement and control company of Sinopec Jingwei Co.,Ltd. Address before: 100029 Chaoyang District, Beijing Hui Xin Street six, Twelfth level. Applicant before: SINOPEC OILFIELD SERVICE Corp. Applicant before: LOGGING BRANCH, SINOPEC SOUTHWEST PETROLEUM ENGINEERING CO.,LTD. |
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