阅读说明：本技术 一种各向异性矢量波场井地联合定位方法 (Well-ground combined positioning method for anisotropic vector wave field ) 是由 余波 于 2018-07-27 设计创作，主要内容包括：本发明提供一种各向异性矢量波场井地联合定位方法。该方法包括：利用地面矢量检波器采集井下微地震信号,对微地震事件进行初步定位,估算出微地震事件初始定位结果；建立各向异性矢量波场井地联合定位目标方程OPJ；拾取井中观测到的射孔纵横波走时,结合已知的射孔空间位置和声波测井纵横波速度,利用所述目标方程OPJ对射孔开展定位分析,反演出射孔各向异性参数；将反演出的射孔各向异性参数作为微地震事件初始各向异性参数,以微地震事件初始各向异性参数为参数约束,以微地震事件初始定位结果为空间约束,在扰动范围内,利用所述目标方程OPJ对微地震事件做进一步的层析定位处理,获得定位精度更高的微地震事件最终定位结果。(The invention provides an anisotropic vector wave field well-ground combined positioning method. The method comprises the following steps: acquiring underground micro-seismic signals by using a ground vector detector, carrying out primary positioning on the micro-seismic events, and estimating initial positioning results of the micro-seismic events; establishing an anisotropic vector wave field well-ground combined positioning target equation OPJ; picking up the longitudinal and transverse wave travel time of the perforation observed in the well, combining the known perforation space position and the acoustic wave logging longitudinal and transverse wave speed, carrying out positioning analysis on the perforation by using the target equation OPJ, and inverting perforation anisotropy parameters; and taking the inverted perforation anisotropy parameters as initial anisotropy parameters of the micro-seismic event, taking the initial anisotropy parameters of the micro-seismic event as parameter constraints, taking the initial positioning result of the micro-seismic event as space constraints, and performing further chromatography positioning processing on the micro-seismic event by using the target equation OPJ in a disturbance range to obtain a final positioning result of the micro-seismic event with higher positioning precision.)

1. An anisotropic vector wave field well-ground combined positioning method comprises the following steps:

s1, collecting underground micro seismic signals by using a ground vector detector, carrying out primary positioning on the micro seismic events based on the instantaneous amplitude of longitudinal and transverse waves of the micro seismic signals, and estimating the initial positioning result RT of the micro seismic events_event＝{L_event,Z_eventIn which L is_event、Z_eventRespectively describing radial coordinates and depth coordinates of the space position of the microseism event;

s2 equation OPJ for the location of longitudinal wave travel time of anisotropic microseismic_PAnisotropic microseism transverse wave time-of-flight positioning equation OPJ_SAnd the anisotropic microseism longitudinal and transverse wave travel time difference positioning equation OPJ_PSPerforming linear combination to establish a target equation OPJ;

s3, picking up perforation longitudinal and transverse wave travel time in a well, carrying out positioning analysis on the perforation by using the target equation OPJ in combination with the known perforation space position and the known acoustic wave logging longitudinal and transverse wave speed, and inverting an anisotropy parameter delta of the perforation as { epsilon, delta }, wherein epsilon and delta are two parameters for describing perforation anisotropy;

and S4, taking inverted perforation anisotropy parameter delta ({ epsilon, delta } as a microseism event initial anisotropy parameter, taking the microseism event initial anisotropy parameter as parameter constraint, taking a microseism event initial positioning result as space constraint, and performing further chromatography positioning processing on the microseism event by using the target equation OPJ in a disturbance range to obtain a microseism event final positioning result with higher positioning precision.

2. The positioning method according to claim 1, wherein the step S1 includes the steps of:

s11, collecting underground micro seismic signals by using a ground vector detector, picking up the instantaneous amplitude of longitudinal and transverse waves of a micro seismic, and establishing a micro seismic amplitude cross-correlation function f (n) of the 1 st detector on the ground and other detectors on the ground;

s12, performing curve fitting on the cross-correlation function f (n), searching the serial numbers N, N +1 of two adjacent detectors when the cross-correlation function f (n) crosses zero, and estimating the initial positioning result RT of the microseism event according to the known radial coordinates and the longitudinal and transverse wave travel time of the two detectors by combining the sound wave speed_event＝{L_event,Z_event}。

3. The positioning method according to claim 2, wherein the step S11 includes the steps of:

acquiring underground micro-seismic signals by using a ground vector detector, picking up micro-seismic longitudinal and transverse wave instantaneous amplitudes from a micro-seismic signal vector wave field by taking the maximum value of the absolute value of the longitudinal and transverse wave amplitudes as the center and adding a time window with the same width, and performing cross-correlation on the micro-seismic instantaneous amplitudes of the ground 1 st detector and other ground detectors to establish a cross-correlation function f (n):

wherein M is the width of the time window, n is the serial number of the ground detector, A_1,P(i)、A_1,S(i) Respectively is the instantaneous amplitude value of the longitudinal and transverse waves of the 1 st ground detector in the time window, A_n,P(i)、A_n,S(i) The instantaneous amplitude values of longitudinal and transverse waves of the nth ground detector in the time window are respectively.

4. The positioning method according to claim 2, wherein the step S12 includes the steps of:

performing curve fitting on the cross-correlation function f (n), searching the serial numbers of adjacent detectors at the zero-crossing point, assuming that the serial numbers are N, N +1, and picking up the longitudinal and transverse wave travel time t of the ground microseismic detector N, N +1_N,P、t_N,S、t_N+1,P、t_N+1,SEstimating the initial positioning result RT of the microseism event according to the following formula according to a known acoustic logging speed model_event＝{L_event,Z_event}：

L_event＝(L_N,receiver+L_N+1,receiver)/2

Wherein L is_N,receiver、L_N+1,receiverRespectively are the radial coordinates of the Nth and the (N + 1) th ground detectors,

Z_event＝(Z_P,event+Z_S,event)/2

wherein Z is_P,evevt、Z_S,evevtVertical self-excited self-receiving depth H of longitudinal and transverse wave ground detector of microseism event_model,j、V_Pj、V_SjRespectively the j-th layer thickness, the longitudinal wave velocity and the transverse wave velocity in the known acoustic logging velocity model, and supposing that the microseism event occurs in the K-th layer in the velocity model, V_PK、V_SKThe longitudinal wave velocity and the transverse wave velocity in the K-th layer are respectively.

5. The method of claim 1, wherein the target equation OPJ is:

OPJ＝OPJ_S+0.1·OPJ_P+0.01·OPJ_PS

wherein, T_well,P、T_well,SRespectively the longitudinal and transverse wave travel time of the micro earthquake in the well with known pickup,

6. The positioning method according to claim 5, wherein the step S3 includes the steps of:

s31, picking up the longitudinal and transverse wave travel time T of the perforation in the well_well,shoot,P、T_well,shoot,SAnd substituting the known perforation space position and the known acoustic logging longitudinal and transverse wave velocity into the target equation OPJ to obtain a perforation target equation OPJ_shoot：

OPJ_shoot＝OPJ_shoot,S+0.1·OPJ_shoot,P+0.01·OPJ_shoot,PS

Wherein, OPJ_shoot，SFor perforation anisotropy shear wave time-of-flight positioning equation, OPJ_shoot，PFor perforation anisotropy longitudinal wave travel time localization equation, OPJ_shoot，PSIs emitted toHole anisotropy vertical and horizontal wave time difference positioning equation, T_well,shoot,P、T_well,shoot,SLongitudinal and transverse wave travel time of the perforation in the well which is known to be picked up;

s32, inverting the perforation anisotropy, and solving the anisotropy parameters epsilon and delta of the exit hole by using the following partial derivative equation:

7. the method of claim 6, wherein inverted perforation anisotropy parameter Δ ═ { ε, δ } satisfies the following condition: the perforation anisotropy parameter Δ ═ { ε, δ } enables the perforation target equation OPJ_shootThe value of (c) is minimized.

8. The positioning method according to claim 5, wherein the step S4 includes the steps of:

s41, taking inverted perforation anisotropy parameter delta ═ { epsilon, delta } as the initial anisotropy parameter of the microseism event;

s42, picking up the longitudinal and transverse wave travel time T of the microseism event in the well_well,event,P、T_well,event,SSubstituting the initial anisotropy parameters of the micro-seismic event, the known longitudinal and transverse wave velocities of the acoustic logging into the target equation OPJ to obtain a micro-seismic event target equation OPJ_event，

OPJ_event＝OPJ_event,S+0.1·OPJ_event,P+0.01·OPJ_event,PS

Wherein, OPJ_event,SPositioning equation for microseism event anisotropy transverse wave travel time, OPJ_event,PPositioning equation for microseism event anisotropy longitudinal wave travel time, OPJ_event,PSPositioning equation for microseism event anisotropy vertical and horizontal wave time difference, T_well,event,P、T_well,event,SThe longitudinal and transverse wave travel time of the micro seismic event in the well which is known to be picked up;

s43, taking the initial anisotropic parameter of the micro seismic event as the parameter center, taking the initial positioning result of the micro seismic event as the space position center, and utilizing the target equation OPJ of the micro seismic event in the disturbance range_eventFor radial coordinates L describing the spatial location of the microseismic event_eventDepth coordinate Z_eventAnd inverting the anisotropy parameters epsilon and delta of the microseism event, and solving a final positioning result of the microseism event by using the following partial derivative equation:

9. the method according to claim 8, wherein the solving of the partial derivative equation in step S4 by using a least squares method or a grid search method specifically includes the following steps:

within the disturbance range, inverting the radial coordinate and the depth coordinate of the space position of the microseism event corresponding to the possible value of the anisotropic parameter of each microseism event according to the possible value of the anisotropic parameter of each microseism event, inverting the longitudinal and transverse wave travel time of the corresponding microseism event in the well according to the radial coordinate and the depth coordinate, and calculating the error between the inverted longitudinal and transverse wave travel time of the microseism event in the well and the picked longitudinal and transverse wave travel time of the microseism event in the well;

and searching the minimum value of all possible errors, wherein the radial coordinate, the depth coordinate and the anisotropic parameter corresponding to the minimum value are the final positioning result of the micro-seismic event and the corresponding corrected anisotropic parameter of the micro-seismic event.

10. The positioning method according to claim 9, wherein the final positioning result of the micro-seismic event obtained in the step S4 satisfies the following condition: and (4) according to the micro-seismic event final positioning result obtained in the step (S4), the error between the longitudinal and transverse wave travel time of the micro-seismic event in the well and the picked longitudinal and transverse wave travel time of the micro-seismic event in the well is minimum.

Technical Field

The invention belongs to the technical field of microseism monitoring signal processing, and particularly relates to an anisotropic vector wave field well-ground combined positioning method.

Background

The microseism fracturing monitoring technology is one of key technologies in unconventional compact sandstone gas and shale gas reservoir oil and gas field development, and can obtain fracture attributes (main stress trend, fracture width, density and the like) according to inversion-positioned seismic source information for evaluating the fracturing effect, analyzing the fracture induction rule, optimizing well placement and the like. Therefore, in micro-seismic signal processing, the ultimate goal is source localization, also known as the most core technique of micro-seismic signal processing.

Microseismic monitoring is mainly divided into surface microseismic and borehole microseismic. The ground microseism is characterized in that a conventional ground detector is adopted to collect microseism signals, and the collection mode of the microseism signals is similar to that of a well seismic VSP. The ground micro-seismic detectors are large in number and distributed in various arrangements, and can fully acquire micro-seismic signals, but the ground micro-seismic positioning has the characteristics of stability, low precision and the like due to the fact that the distance between the underground seismic source and the detectors is long and the received micro-seismic signals are weak. The underground microseism is characterized in that an underground three-component detector is placed in an observation well section to receive microseism full wavefield signals, and compared with ground microseism monitoring, the underground microseism monitoring system has the advantages that the signal-to-noise ratio of data received in a well is high, and the number and types of microseism events are rich. However, different from the network monitoring of hundreds of detectors on the ground, the number of the micro-seismic detectors in the well is limited (generally 12-32-stage three-component borehole detectors), the micro-seismic detectors in the well are placed in a vertical well section, and the distance between the detectors is generally 10 meters, so that the monitoring range is small, and therefore the micro-seismic positioning method in the well is prone to generating unstable and low-precision micro-seismic positioning results. In order to solve this problem, a new positioning method with higher positioning accuracy needs to be developed.

At present, the method for positioning the micro earthquake in the well mainly has two ideas: firstly, forward modeling is carried out when events of P waves and S waves travel, a network search method, a simulated annealing method, a geiger method and the like are represented by algorithms, the method has the advantages of easy realization, and the defects that the events of the P waves and the S waves are difficult to accurately pick up when traveling due to weak first arrival phase signals, and positioning results are influenced; and secondly, based on the convolution of the wave equation, the representative algorithm comprises an interference method, a reverse time migration method and a passive source imaging method, the method has the advantages that the first arrival of an event does not need to be picked up, and the defects of high requirements on a data signal-to-noise ratio and a speed model, more detectors and high calculation cost are caused. And thirdly, the calculation difference is between anisotropy and isotropy travel time, and in an anisotropic medium, the calculation error is larger when the isotropy travel time is used, and the corresponding positioning error is also larger.

Aiming at the problems that in the fracturing microseism development of unconventional tight sandstone gas and shale gas reservoir reservoirs, the stratum has heterogeneity and belongs to anisotropic media, the travel time and the propagation path of longitudinal and transverse waves of the microseism are different from isotropy, and both the radial direction and the depth direction of a microseism event and high-precision positioning cannot be guaranteed at the same time no matter the microseism in a well or the ground microseism.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for jointly positioning the micro-earthquake in the longitudinal and transverse wave wells based on the anisotropic medium vector wave field and the ground micro-earthquake, and the influence of the stratum anisotropy on the travel time of the longitudinal and transverse waves is considered, so that the instability and inaccuracy of positioning of the micro-earthquake event are eliminated or reduced, and the requirements of unconventional micro-earthquake monitoring of coal bed gas, shale gas and the like are met. The method mainly comprises the following steps:

s1, collecting underground micro seismic signals by using a ground vector detector, carrying out primary positioning on the micro seismic events based on the instantaneous amplitude of longitudinal and transverse waves of the micro seismic signals, and estimating the initial positioning result RT of the micro seismic events_event＝{L_event,Z_eventIn which L is_event、Z_eventRespectively describing radial coordinates and depth coordinates of the space position of the microseism event;

s2 equation OPJ for the location of longitudinal wave travel time of anisotropic microseismic_PAnisotropic microseism transverse wave time-of-flight positioning equation OPJ_SAnd the anisotropic microseism longitudinal and transverse wave travel time difference positioning equation OPJ_PSPerforming linear combination to establish a target equation OPJ;

s3, picking up perforation longitudinal and transverse wave travel time in a well, carrying out positioning analysis on the perforation by using the target equation OPJ in combination with the known perforation space position and the known acoustic wave logging longitudinal and transverse wave speed, and inverting an anisotropy parameter delta of the perforation as { epsilon, delta }, wherein epsilon and delta are two parameters for describing perforation anisotropy;

and S4, taking inverted perforation anisotropy parameter delta ({ epsilon, delta } as a microseism event initial anisotropy parameter, taking the microseism event initial anisotropy parameter as parameter constraint, taking a microseism event initial positioning result as space constraint, and performing further chromatography positioning processing on the microseism event by using the target equation OPJ in a disturbance range to obtain a microseism event final positioning result with higher positioning precision.

According to an embodiment of the present invention, the above step S1 includes the steps of:

s11, collecting underground micro seismic signals by using a ground vector detector, picking up the instantaneous amplitude of longitudinal and transverse waves of a micro seismic, and establishing a micro seismic amplitude cross-correlation function f (n) of the 1 st detector on the ground and other detectors on the ground;

s12, performing curve fitting on the cross-correlation function f (n), searching the serial numbers N, N +1 of two adjacent detectors when the cross-correlation function f (n) crosses zero, and estimating the initial positioning result RT of the microseism event according to the known radial coordinates and the longitudinal and transverse wave travel time of the two detectors by combining the sound wave speed_event＝{L_event,Z_event}。

According to an embodiment of the present invention, the above step S11 includes the steps of:

acquiring underground micro-seismic signals by using a ground vector detector, picking up micro-seismic longitudinal and transverse wave instantaneous amplitudes from a micro-seismic signal vector wave field by taking the maximum value of the absolute value of the longitudinal and transverse wave amplitudes as the center and adding a time window with the same width, and performing cross-correlation on the micro-seismic instantaneous amplitudes of the ground 1 st detector and other ground detectors to establish a cross-correlation function f (n):

wherein M is the width of the time window, n is the serial number of the ground detector, A_1,P(i)、A_1,S(i) Respectively is the instantaneous amplitude value of the longitudinal and transverse waves of the 1 st ground detector in the time window, A_n,P(i)、A_n,S(i) Respectively being a time windowAnd (4) the instantaneous amplitude value of the longitudinal wave and the transverse wave of the inner nth ground detector.

According to an embodiment of the present invention, the above step S12 includes the steps of:

performing curve fitting on the cross-correlation function f (n), searching the serial numbers of adjacent detectors at the zero-crossing point, assuming that the serial numbers are N, N +1, and picking up the longitudinal and transverse wave travel time t of the ground microseismic detector N, N +1_N,P、t_N,S、t_N+1,P、t_N+1,SEstimating the initial positioning result RT of the microseism event according to the following formula according to a known acoustic logging speed model_event＝{L_event,Z_event}：

L_event＝(L_N,receiver+L_N+1,receiver)/2

Wherein L is_N,receiver、L_N+1,receiverRespectively are the radial coordinates of the Nth and the (N + 1) th ground detectors,

Z_event＝(Z_P,event+Z_S,event)/2

wherein Z is_P,evevt、Z_S,evevtVertical self-excited self-receiving depth H of longitudinal and transverse wave ground detector of microseism event_model,j、V_Pj、V_SjRespectively the j-th layer thickness, the longitudinal wave velocity and the transverse wave velocity in the known acoustic logging velocity model, and supposing that the microseism event occurs in the K-th layer in the velocity model, V_PK、V_SKThe longitudinal wave velocity and the transverse wave velocity in the K-th layer are respectively.

According to an embodiment of the present invention, the above target equation OPJ is:

OPJ＝OPJ_S+0.1·OPJ_P+0.01·OPJ_PS

wherein, T_well,P、T_well,SRespectively the longitudinal and transverse wave travel time of the micro earthquake in the well with known pickup,

respectively the longitudinal and transverse wave travel time of the micro earthquake in the well to be inverted.

According to an embodiment of the present invention, the above step S3 includes the steps of:

s31, picking up the longitudinal and transverse wave travel time T of the perforation in the well_well,shoot,P、T_well,shoot,SAnd substituting the known perforation space position and the known acoustic logging longitudinal and transverse wave velocity into the target equation OPJ to obtain a perforation target equation OPJ_shoot：

OPJ_shoot＝OPJ_shoot,S+0.1·OPJ_shoot,P+0.01·OPJ_shoot,PS

Wherein, OPJ_shoot，SFor perforation anisotropy shear wave time-of-flight positioning equation, OPJ_shoot，PFor perforation anisotropy longitudinal wave travel time localization equation, OPJ_shoot，PSFor the perforating anisotropy vertical and horizontal wave time difference positioning equation, T_well,shoot,P、T_well,shoot,SIn wells known to pick upLongitudinal and transverse wave travel time of perforation;

the longitudinal and transverse wave travel time of the perforation in the well needing inversion is obtained;

s32, inverting the perforation anisotropy, and solving the anisotropy parameters epsilon and delta of the exit hole by using the following partial derivative equation:

according to the embodiment of the invention, inverted perforation anisotropy parameter delta ═ epsilon, delta satisfies the following condition: the perforation anisotropy parameter Δ ═ { ε, δ } enables the perforation target equation OPJ_shootThe value of (c) is minimized.

According to an embodiment of the present invention, the above step S4 includes the steps of:

s41, taking inverted perforation anisotropy parameter delta ═ { epsilon, delta } as the initial anisotropy parameter of the microseism event;

s42, picking up the longitudinal and transverse wave travel time T of the microseism event in the well_well,event,P、T_well,event,SSubstituting the initial anisotropy parameters of the micro-seismic event, the known longitudinal and transverse wave velocities of the acoustic logging into the target equation OPJ to obtain a micro-seismic event target equation OPJ_event，

OPJ_event＝OPJ_event,S+0.1·OPJ_event,P+0.01·OPJ_event,PS

Wherein, OPJ_event,SAnisotropy for microseismic eventsTransverse wave time-of-flight positioning equation OPJ_event,PPositioning equation for microseism event anisotropy longitudinal wave travel time, OPJ_event,PSPositioning equation for microseism event anisotropy vertical and horizontal wave time difference, T_well,event,P、T_well,event,SThe longitudinal and transverse wave travel time of the micro seismic event in the well which is known to be picked up;

the longitudinal and transverse wave travel time of the microseism event in the well needing inversion is obtained;

s43, taking the initial anisotropic parameter of the micro seismic event as the parameter center, taking the initial positioning result of the micro seismic event as the space position center, and utilizing the target equation OPJ of the micro seismic event in the disturbance range_eventFor radial coordinates L describing the spatial location of the microseismic event_eventDepth coordinate Z_eventAnd inverting the anisotropy parameters epsilon and delta of the microseism event, and solving a final positioning result of the microseism event by using the following partial derivative equation:

according to the embodiment of the present invention, solving the partial derivative equation in step S4 by using the least square method or the grid search method specifically includes the following steps:

within the disturbance range, inverting the radial coordinate and the depth coordinate of the space position of the microseism event corresponding to the possible value of the anisotropic parameter of each microseism event according to the possible value of the anisotropic parameter of each microseism event, inverting the longitudinal and transverse wave travel time of the corresponding microseism event in the well according to the radial coordinate and the depth coordinate, and calculating the error between the inverted longitudinal and transverse wave travel time of the microseism event in the well and the picked longitudinal and transverse wave travel time of the microseism event in the well;

and searching the minimum value of all possible errors, wherein the radial coordinate, the depth coordinate and the anisotropic parameter corresponding to the minimum value are the final positioning result of the micro-seismic event and the corresponding corrected anisotropic parameter of the micro-seismic event.

According to the embodiment of the invention, the final positioning result of the micro-seismic event obtained in the step S4 meets the following conditions: and (4) according to the micro-seismic event final positioning result obtained in the step (S4), the error between the longitudinal and transverse wave travel time of the micro-seismic event in the well and the picked longitudinal and transverse wave travel time of the micro-seismic event in the well is minimum.

Compared with the prior art, the invention has the following advantages or beneficial effects:

the invention provides an anisotropic vector wave field well-ground combined positioning method, which is a microseism processing method with higher microseism positioning precision and better effect. Firstly, compared with isotropy, the positioning method provided by the invention considers the formation anisotropy, and the inverted longitudinal and transverse wave travel time is closer to the actual observed value. Secondly, the positioning method provided by the invention considers the existence of anisotropy of an unconventional (such as shale gas) reservoir, inverts the travel time of longitudinal and transverse waves at high precision, establishes a more practical well-ground combined positioning target equation (hereinafter referred to as a target equation) by linearly combining the travel time of P waves, the travel time of S waves and the travel time of PS waves, quickly obtains the initial positioning result of the microseism event by combining a ground microseism vector wave field and analyzing the amplitude correlation of the vertical and horizontal wave vector wave fields of the ground microseism, carries out microseism perforation positioning analysis in an anisotropic well by using the target equation to obtain the initial anisotropy parameter value of the microseism event, and finally obtains the positioning result of the microseism event with higher positioning precision by using the target equation and the vertical and horizontal wave chromatography positioning analysis of the microseism event in the anisotropic well.

Compared with the current common longitudinal and transverse wave combination, the invention adopts the combined monitoring of the ground micro-earthquake and the micro-earthquake in the well, so long as the abundant micro-earthquake signals can be obtained, the abundant fracture attributes (main stress trend, fracture width, density and the like) can be obtained through the accurate positioning technology, and the method can be used for evaluating the fracturing effect, analyzing the fracture induction rule, optimizing well arrangement and the like. The positioning method provided by the invention is simple and feasible, has controllable errors, and can provide reliable technical support for positioning processing of the micro earthquake in the well.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the technology or prior art of the present application and are incorporated in and constitute a part of this specification. The drawings expressing the embodiments of the present application are used for explaining the technical solutions of the present application, and should not be construed as limiting the technical solutions of the present application.

Fig. 1 is a schematic diagram of a positioning method according to an embodiment of the present invention;

FIG. 2 is a side view of a combined surface and borehole microseismic observation system according to a second embodiment of the present invention: detector position, event position;

FIG. 3a is a schematic representation of the radial component of the vector wavefield of microseismic signals monitored by a geophone according to a second embodiment of the present invention;

FIG. 3b is a schematic diagram of the vertical component of the vector wavefield of the microseismic signals monitored by the geophone in accordance with the second embodiment of the present invention;

FIG. 4 is a graph of longitudinal and transverse wave travel times of microseismic signals monitored by a borehole geophone in accordance with a second embodiment of the present invention;

FIG. 5 is a statistical plot based on the geophone microseismic amplitude cross correlation function f (n) of FIG. 3;

FIG. 6 is a schematic diagram of the comparison of the ground microseismic fast location result and the event real position according to the second embodiment of the present invention;

FIG. 7 is a schematic diagram of the comparison of the well-to-ground co-location result and the actual location of the event according to the second embodiment of the present invention.

Detailed Description

The following detailed description of the embodiments of the present invention will be provided with reference to the accompanying drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the corresponding technical effects can be fully understood and implemented. The embodiments and the features of the embodiments can be combined without conflict, and the technical solutions formed are all within the scope of the present invention.