CN111119851A

CN111119851A - Asymmetric far detection logging method

Info

Publication number: CN111119851A
Application number: CN201811265490.2A
Authority: CN
Inventors: 许孝凯; 张晋言; 翟勇; 晁永胜; 纪祝华; 刘美杰; 王志美; 韩晓梅; 蒋红娜; 周朋飞; 于宁宁
Original assignee: Sinopec Oilfield Service Corp; Sinopec Shengli Petroleum Engineering Corp; Logging Co of Sinopec Shengli Petroleum Engineering Corp
Current assignee: Shengli Logging Co Of Sinopec Jingwei Co ltd; China Petrochemical Corp; Sinopec Oilfield Service Corp; Sinopec Shengli Petroleum Engineering Corp; Sinopec Jingwei Co Ltd
Priority date: 2018-10-29
Filing date: 2018-10-29
Publication date: 2020-05-08
Anticipated expiration: 2038-10-29
Also published as: CN111119851B

Abstract

The invention belongs to the technical field of acoustic logging data processing and interpretation methods, and particularly relates to an asymmetric remote detection logging method. By utilizing the remote detection logging method, the transverse wave can be effectively detected, the sensitive distinguishing of the reflection signals of the geological abnormal bodies in different directions is finally realized, and a new thought is provided for the imaging of the whole-direction reflection transverse wave around the well. A remote detection well logging method for asymmetric measurement adopts a symmetric dipole array as a transmitting combination, n receiving electrodes are matched and arranged for each emitting electrode, and n is a natural number greater than or equal to 1; the plane of the receiver and the plane of the emitter are arranged in parallel, and an included angle different from 0 exists between any emitter and the receiver arranged in a matched mode.

Description

Asymmetric far detection logging method

Technical Field

The invention belongs to the technical field of acoustic logging data processing and interpretation methods, and particularly relates to an asymmetric remote detection logging method.

Background

As a well logging method, acoustic logging is a commonly used method, which utilizes the changes of acoustic characteristics such as speed, amplitude, frequency and the like when acoustic waves propagate in rock strata with different properties to determine the characteristics of a drilling geological profile, and finally judges the well cementation quality.

For example, as shown in FIGS. 1-3, based on the fundamental principles of borehole acoustics, one can determine to obtain the solution of the wave equation and its displacement:

(λ+μ)▽(▽·u)+μ▽²u+ρω²u (1)

wherein phi is a longitudinal wave displacement potential function;

is a unit vector in the z direction; gamma is an SV shear wave displacement potential function; χ is a function of SH shear wave displacement potential. The SV transverse wave is polarized in a vertical plane, and the SH transverse wave is polarized in a horizontal plane. The wavelengths of the longitudinal wave, the SV transverse wave and the SH transverse wave respectively satisfy one of the following equations:

wherein k is_pω/α and k_sω/β represents the wave number of the longitudinal wave and the wave number of the transverse wave, α and β represent the velocity of the longitudinal wave and the transverse wave, and the solution of each potential function in the wave number domain is:

wherein

And

longitudinal wave radial wavenumber and transverse wave radial wavenumber.

Reflection coefficient A_n、B_n、C_n、D_n、E_n、F_nMay be continuously determined from the following wellbore fluids and formation stress displacements.

Wherein, tau_ijThe pore formation is subjected to the total stress, and the inside and outside of the well are distinguished by (1) and (2) in the superscript. And substituting the relevant expressions, and solving the reflection coefficient to further obtain the waveform obtained in the well hole. The acoustic pressure time domain waveform function of the acoustic logging response is:

and further from the fundamental principles of reflected acoustics:

acoustic reflection detection, the recorded reflected wave signal is controlled by several important factors:

wherein RWV represents the received reflected wave; s is the system transfer function of the sonic instrument, which includes signal generation and recording; RD is the borehole radiation directivity; RC is a receive azimuth mode; RF is the reflector reflection coefficient. Both of which can vary with angular frequency omega as shown in figure 1. Wherein the parameters S, RD, RC are closely related to the borehole acoustics, and the reflection acoustics determine the parameter RF.

In addition to these factors, the reflected wave is dominated by propagation losses along the wave path. The propagation loss consists of two parts: geometric diffusion 1/D, where D is the total distance traveled to and back from the reflector; the amplitude of the path attenuates exp (- ω T/2Q), where T is the travel along path D and Q is the quality factor. Equation (10) shows that if T, which travels to a distant reflector and reflects back, is within the recording time and the formation attenuation 1/D does not attenuate the reflected wave amplitude to a noise level, the recorded data can image the reflector under appropriate radiation and reception conditions.

① emission part

Another important factor in the theoretical model of equation (10) is the acoustic source radiation characteristic RD. Although the radiation characteristics of monopole sound sources have been studied in detail (Meredith,1990), further analysis is required for the radiation characteristics of dipole S-wave reflection detection.

The radiation of a dipole source in a fluid-filled borehole is directional. Dipole sonic logging is often used to measure formation S-wave velocity and S-wave azimuthal anisotropy. One very useful characteristic of a dipole source or receiver system is directivity: the amplitude of the excited or received sound wave depends on the angle phi between the direction of the particle motion of the sound wave (polarization direction) and the direction of the sound source or receiver. Assuming a vertical well, the orientation of SV and SH waves excited by a dipole source is determined (Schmitt, 1988):

where φ is the azimuth, θ is the angle of intersection with the vertical; u. of_φAnd u_θSH and SV wave displacements, respectively. Fig. 2 shows examples of SH and SV wave polarization directions.

The greatest advantage of a dipole source is that the excited SH and SV waves are sensitive to the orientation of cos phi and sin phi, respectively, which provides the basis for determining the orientation of the reflector using a dipole source.

② orientation reception

An important factor in the theoretical model is the response of the borehole to the reflected wave, i.e., the RC of equation (10). Although this effect has been studied in detail by Schoenberg (1986) and Peng (1993), its importance for reflected shear wave detection has only recently been realized. FIG. 3 shows the SH and SV wave reception patterns for a liquid filled borehole having a borehole diameter of 0.2m in a fast formation. The SH wave response shows a wide pattern at all angles of incidence in the plane of incidence, indicating that the borehole can receive SH waves from all directions. In contrast, when the angle of incidence approaches 90 °, the SV wave mode approaches 0 °, which means that SV waves incident normally to the borehole cannot be detected. This response characteristic of SH and SV waves is used below for S-wave imaging analysis and field data interpretation.

Therefore, the inventor finds that the existing remote detection well logging process still has the following defects: when the transverse wave reflection signals are used for imaging geological abnormal bodies in different directions (when dipoles and receiving dipoles which are symmetrically arranged as shown in fig. 4 are used), a technician cannot solve the problem that the left and right resolution of the dipole reflection transverse wave far detection is unclear.

Disclosure of Invention

The invention provides an asymmetric far detection logging method, which can be used for effectively detecting transverse waves, finally realizing sensitive distinguishing of reflection signals of geological abnormal bodies in different directions and providing a new thought for well circumference all-direction reflection transverse wave imaging.

In order to solve the technical problems, the invention adopts the following technical scheme:

a remote detection well logging method for asymmetric measurement adopts a symmetric dipole array as a transmitting combination, n receiving electrodes are matched and arranged for each emitting electrode, and n is a natural number greater than or equal to 1;

the plane of the receiver and the plane of the emitter are arranged in parallel, and an included angle different from 0 exists between any emitter and the receiver arranged in a matched mode.

Preferably, the application scenario of the asymmetric far detection logging method is a horizontal well or a highly deviated well.

The invention provides an asymmetric far detection well logging method, wherein a symmetric dipole array is used as a transmitting combination, each emitting electrode is provided with n receiving electrodes in a matching mode, and an included angle different from 0 exists between any emitting electrode and any receiving electrode arranged in a matching mode. According to the asymmetric far detection well logging method, by adopting a technical means of arranging the emitting electrodes and the receiving electrodes in a staggered mode, an asymmetric eccentric effect can be generated during transverse wave detection, and therefore reflected signals of geological abnormal bodies in different directions can be acquired more sensitively.

Drawings

FIG. 1 is a schematic representation of a prior art technique for shear wave imaging using a multicomponent dipole tool;

FIG. 2 is a diagram of prior art dipole S-wave reflection detection x-direction dipole source far-field directivity;

FIG. 3 is a borehole reception azimuth map of incident waves of fast formations SH and SV;

FIG. 4 is a schematic diagram of a symmetrical arrangement of a prior art transmitter dipole and receiver dipole structure;

FIG. 5 is a schematic view of a first embodiment of the present invention;

FIG. 6 is a model according to an embodiment;

FIG. 7 shows an emitter state of the embodiment;

FIG. 8 illustrates a receiver state according to one embodiment;

FIG. 9 shows the state of the transmitter according to the second embodiment;

FIG. 10 is a graph of the relative positions of stress state points for the second study of example two;

FIG. 11 is a full wave waveform of the embodiment;

FIG. 12 is an enlarged waveform of a reflected wave according to an embodiment;

FIG. 13 is a diagram illustrating a formation-corresponding location waveform according to an embodiment.

Detailed Description

Specifically, the asymmetric far detection well logging method adopts a symmetric dipole array as a transmitting combination, and n receiving electrodes are matched and arranged for each emitting electrode, wherein n is a natural number which is more than or equal to 1; the plane of the receiver and the plane of the emitter are arranged in parallel, and an included angle different from 0 exists between any emitter and the receiver arranged in a matched mode. Particularly preferably, the application scenario of the asymmetric far detection logging method is a horizontal well or a highly deviated well.

It should be noted that there are many different applications of the asymmetric far-detection logging method in practical use, and the following specific embodiments are exemplified as examples.

The application scene one: symmetric pole transmission, multi-component asymmetric pole reception

Referring to fig. 5, a symmetric dipole array is taken as a transmitting combination, and a group of receiving electrodes is arranged for matching each group of the transmitting electrodes, specifically, X and X are taken as a group of the transmitting electrodes, Y and Y are taken as another group of the transmitting electrodes, and correspondingly, (a, a) and (a) are taken as a receiving electrode combination, and planes (X, Y) where the receiving electrodes are located are arranged in parallel with planes (a, a) where the transmitting electrodes are located, defining an axis point in the instrument as an O point, then A1OX is A3OY is A2OX is A4OY is theta, where theta is an angle different from 0.

Taking the model of fig. 6 as an example, the formation in which the model of fig. 6 is located is a hard formation, a fracture is located outside the well, the dipole transmitting sound source generates shear wave information as shown in fig. 7, and the receivers n2, n4, n6 and n8 are used for receiving pressure information of well bore fluid (see fig. 8), and the receivers (n2, n8) and (n4, n6) can form eccentric dipole receivers (as shown in fig. 11); the foremost part is the direct wave, and reflected wave information begins to appear near 0.0018 s. Since the receiver is located at different distances from the slit, and there is a difference in arrival time, n28 arrives earlier than n46 (as shown in FIG. 12). Therefore, the orientation of the geological abnormal body on the instrument can be distinguished in sequence by the arrival time, and the multi-solution of the imaging orientation can be eliminated. When the size of the instrument cannot be ignored relative to the wavelength, the blocking effect of the reflected wave signal by the instrument is larger, the amplitude of the reflected signal which is directly opposite to the reflector is strong, the amplitude of the reflected signal which is far away from the reflector is weak, and the orientation of the geological abnormal body can also be judged through the amplitude of the reflected signal. When the orientation of the geological abnormal body is unknown, the received waveforms of the corresponding orientations can be formed by synthesizing pairwise orthogonal components.

Application scenario two: eccentric pole transmission, orthogonal component pole reception

Referring also to fig. 5, an eccentric emitter is used as a transmitting combination, and a set of receiving electrodes is matched with each set of emitters, specifically, a combination of (Y, X), (X, Y), (Y, X), (X, Y) are used as transmitting electrodes, and correspondingly, (a, a) and (a, a) are used as receiving electrode combinations, and planes (X, Y) where the receiving electrodes are located and planes (a, a) where the emitters are located are arranged in parallel, defining the axis point in the apparatus as an O point, and A1OX A3OY A2OX A4OY θ, where θ is a non-0 angle.

Here, taking the model of fig. 9 as an example, the stratum in which the model of fig. 9 is located is a hard stratum, and the transmitting sound source is an eccentric dipole sound source (see fig. 9). In order to research the condition that the energy emitted by the instrument enters the stratum, n1-n8 shear strain detection points are arranged at 4m outside the well; the waveforms corresponding to n1 and n5 are shown in fig. 13, where n1 is closer to the eccentric emitter and is significantly earlier in time than n 5; from the reflector to the receiver, because of the symmetrical arrangement, the changes of two sides in the transmission process of the reflected signal are consistent; and because the propagation distance of the side close to the abnormal body is small during eccentric emission, and the propagation distance of the waveform of the side far away from the abnormal body is small, the orientation of the geological abnormal body can be distinguished by using the arrival time of the reflected signal. Meanwhile, when the size of the instrument while drilling and the like is not negligible compared with a wave field, a signal of the same position of the near transmitting end reaching the stratum is strong, and a signal of the same position of the far transmitting end reaching the stratum is relatively weak. Thus, the orientation of the anomaly may also be determined by comparing the arrival time and the amplitude. In addition, if the direction of the abnormal body is inconsistent with the transmitting direction, synthesis can be carried out through corresponding direction orthogonal components.

It should be noted that, the space is limited, the staggered arrangement manner of the emitters and the receivers and the specific included angle cannot be listed one by one, and those skilled in the art can arrange the emitters and the receivers as needed according to actual situations, which is not described herein again.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. An asymmetric far detection well logging method is characterized in that a symmetric dipole array is used as a transmitting combination, n receiving electrodes are matched and arranged for each emitting electrode, and n is a natural number which is more than or equal to 1;

2. The asymmetric far detection logging method according to claim 1, wherein the asymmetric far detection logging method is applied in a horizontal well or a highly deviated well.