RU2611204C1 - Electromagnetic logging method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes the operations of probing electromagnetic field excitation in control zones and measuring of controlled borehole environment reaction signals with via respectively transmitting and receiving antennas placed inside a metal casing with slits. Transmit antennas are excited simultaneously with a high-frequency harmonic signal with different frequencies f₁…f_n. Signals accepted by receiving antennas are amplified and subjected to a multi-channel narrowband filtration with subsequent readings accumulation and isolating the amplitude and phase information.

EFFECT: increased reliability and accuracy in determining electrical conductivity of drilled formations and as a result, increased efficiency of drilling tool control during drilling of deviated and horizontal wells.

3 cl, 3 dwg

Description

The proposed method relates to the field of well research during drilling and can be used for logging and geo-navigation of oil and gas wells during drilling as part of MWD systems.

When drilling oil and gas wells, information on the geological properties of the section is necessary for the operational optimization of the trajectory of wells, especially horizontal ones, in order to bring the drilled well into the most productive oil or gas formations.

A known method of electromagnetic well logging, which consists in the excitation in the control zone of an alternating two-frequency electric field by connecting a logging system to an electric separator of a telemetry system with an electromagnetic communication channel. To measure the reaction signals of the controlled medium, the indicated electric separator, a metal bracket and the dielectric body of the instrument container, in which the downhole logging equipment is located, are used. The method is implemented using a device containing a telemetry system with a wireless electromagnetic communication channel, current sensors and voltage converters, three electronic keys, a two-channel digital-to-analog converter, a multi-channel analog-to-digital converter, a command memory, a memory for storing results, an input-output device and a digital signal processor with a switching control port and a serial port as electrodes for creating and measuring a probe electric field using tsya electric separator, the metal bracket, the housing point of the well logging equipment and instrumentation dielectric housing container, which accommodates the logging apparatus [Russian Patent 2199008, cl. ЕВВ 47/12, G01V 3/30, priority 16.08.2000].

The disadvantage of this method is the reduced reliability associated with the use of dielectric inserts that perform the function of an electrical splitter.

The closest in technical implementation is [RF Patent 2392644, cl. G01V 3/30, priority 05.21.2009], which includes the operation of exciting a probe electromagnetic field in the control zone using transmitting antennas and measuring the reaction signals of the controlled near-wellbore environment using receiving antennas located inside the metal casing with slots, while the parameters of the received signal are measured sequentially in time from each of the transmitting antennas. The method is implemented by a compensated electromagnetic logging tool in the process of drilling small diameter wells, containing a metal pipe on which at least two receiving and two transmitting antenna assemblies are located, each of which contains an antenna wire forming at least one turn, ferrite inserts and a resonant capacitor, as well as an electronics unit, each antenna assembly consists of a groove on the outer surface of a metal pipe to accommodate a split sleeve, consisting of two identical parts, on each part of the split sleeve has through narrow longitudinal slots made, a triangular ring groove is made on the inner surface of each part of the split sleeve, a triangular ring groove is made in the center of the groove on the outer surface of the metal pipe serving to accommodate the split sleeve, the dimensions of which correspond to a triangular ring groove made on a split sleeve, in the groove on the outer surface of the metal pipe narrow longitudinal slots are also made, in which are located Erritic inserts, in the center of the antenna channel formed by triangular annular grooves, an antenna wire is placed, isolated from a metal pipe and centered in the antenna channel by plasma sprayed onto the surface of the triangular annular grooves with a ceramic layer based on a mixture of aluminum oxide and titanium dioxide, the antenna wire is connected via pressure glands with resonant capacitor located in the cavity of a metal pipe in the immediate vicinity of the antenna assembly, the cavity is protected from external hydraulic pressure cap, sleeve and o-rings, the resonant capacitor is electrically connected via a coaxial cable to an electronics unit located in a pressure-resistant protective casing, which is located inside a metal pipe and is attached to it with bolts and o-rings, a split sleeve is attached to the bolts by a metal pipe, wherein the electrical contact between the split sleeve and the metal pipe is by soldering.

The disadvantage of this method of electromagnetic logging is the impossibility of simultaneously determining the electrical conductivity of the drilling formation for all the probes used during drilling, which significantly reduces the information content of the logging.

The objective of the invention is to increase the reliability and accuracy of determining the electrical conductivity of the drilled formations and, as a result, the efficiency of controlling the drilling tool during drilling of deviated and horizontal wells.

This task is achieved by exciting a probe electromagnetic field in the control zone and measuring the reaction signals of the controlled near-wellbore environment using respectively transmitting and receiving antennas located inside a metal casing with slots, the transmitting antennas are excited simultaneously by a harmonic high-frequency signal with different frequencies f ₁ ... f _n , the signals received by the receiving antennas are amplified and subjected to multi-channel narrow-band filtering with subsequent accumulation iem samples and isolating the amplitude and phase information.

In FIG. 1 shows a simplified block diagram of an information processing process, FIG. 2 is a construction, and in FIG. 3 is a diagram of a device that implements the proposed method.

,The transmitters 1 ₁ ... 1 _n irradiate the near-wellbore space with high-frequency signals with frequencies respectively f ₁ ... f _n . The reaction signals of the controlled environment are recorded by receivers 2 and 3. The signals from the outputs of receivers 2 and 3 are fed to the inputs of the digital filters 4 ₁ ... 4 _n and 5 ₁ ... 5 _n, respectively. Filters 4 _i and 5 _{i are} tuned to the frequency f _1i . The signals from the outputs of the filters 4 _i and 5 _i are fed to the inputs of the processing unit 6 _i and characterize the parameters of the medium according to the results of irradiation with its transmitter 1 _i . Digital filtering by filters 4 ₁ ... 4 _n , 5 ₁ ... 5 _{n is} carried out by transferring the spectrum of the high-frequency signal to the low-frequency region and then averaging it over the time interval t _arr . To effectively separate the signals from the near-wellbore medium as a result of high-frequency irradiation by its transmitters, the frequency difference Δf should be at least 5 / t _avg , where t _avg is the duration of the averaging interval. Considering that the base research frequency f ₀ for electromagnetic logging is at least 400 kHz, and Δf is equal to units of hertz at t _{arr. Of the} order of 1 s, the channel spacing does not introduce significant errors in the measurement process. Wherein

,

Where

f ₀ - base measurement frequency,

i = 1 ... n is the number of the transmitter,

[] is the operator of taking the integer part of a number,

n is the total number of transmitters.

Structurally, the device that implements the method of electromagnetic logging during drilling, comprises a housing 7, on which receiving 8 and 9 and transmitting 10 ₁ ... 10 _n antenna assemblies are located, including at least one turn of wire wound on an insulating strip, and a split sleeve with slots.

A device that implements the method of electromagnetic logging during drilling, contains transmitters 11 ₁ ... 11 _n , generating high-frequency signals for transmitting antennas 12 ₁ ... 12 _n , irradiating the near-wellbore, receiving antennas 13 and 14, recording reaction signals of the controlled medium that are received at the inputs receivers 15 and 16, from their output to the processing unit 17 and from its output to the information transfer unit to the surface 18.

The device operates as follows.

The processing unit 17 transmits via a common bus to the transmitters information defining the operating modes of the transmitters corresponding to the radiation frequencies f ₁ ... f _n . The synchronization of high-frequency oscillations of all transmitters 11 ₁ ... 11 _n is a single clock sequence, also formed by the processing unit 17.

The reaction signals of the controlled medium from the outputs of the receiving antennas 13 and 14 are recorded by the receivers 15 and 16, from the outputs of which they enter the processing unit 17, in which they are multi-channel filtered with frequencies f ₁ ... f _n , the selection of amplitude and phase information characterizing the conductive properties of the near-wellbore space and the transmission of this information to the surface by block 18.

Using a distributed control and processing system, introducing elements of digital frequency synthesis into the composition of transmitters increases the functional stability of devices that implement this method. Digital filters can be made on the basis of FPGAs, DSP even 32-bit microprocessors, the processing power of which is enough to implement 4-6 filters of the proposed structure.

Thus, the proposed method allows for electromagnetic well logging directly during drilling.

The use of multi-frequency processing with electromagnetic logging allows to increase the spatial accuracy of determining the electrical conductivity of the reservoirs.

The proposed method is easily implemented using a modern elemental base, its application can improve the competitiveness of domestic systems for researching wells during drilling.

The proposed device was implemented in the development and production of integrated downhole equipment and tested in the conditions of deposits in Western Siberia, which allows us to conclude that “Industrial applicability”.

Claims (8)

1. The method of electromagnetic logging of wells during drilling, including the operation of exciting a probing electromagnetic field in the control zone and measuring the reaction signals of the controlled near-wellbore environment using respectively transmitting and receiving antennas located inside a metal casing with slots, characterized in that the transmitting antennas are excited simultaneously a harmonic high-frequency signal with different frequencies f ₁ ... f _n , the signals received by the receiving antennas are amplified and multichannel narrow-band filtering followed by the accumulation of samples and the allocation of amplitude and phase information. 2. The method of electromagnetic well logging during drilling according to claim 1, characterized in that the frequencies f ₁ ... f _{n are} determined by the formula

, where f ₀ is the base measurement frequency, i = 1 ... n is the number of the transmitter, [] is the operator of taking the integer part of a number, n is the total number of transmitters. 3. The method of electromagnetic well logging during drilling according to claim 2, characterized in that Δf> = 5 / t _ycp , where t _ycp is the duration of the averaging interval.

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