A method and system for determining a ground microseismic observation system

Abstract

The application provides a method and system for determining a ground microseismic observation system, and belongs to the field of seismic exploration. The method obtains the layout range, trace interval and trace number of the ground microseismic observation system through the microseismic signal energy level and the minimum energy level of effective receiving of a geophone. Through the analysis and statistics of the microseismic signal energy level and the determination of the minimum energy level of effective receiving of the geophone, the layout range of the ground microseismic monitoring observation system can be effectively determined through simulation demonstration, the ground geophone is arranged in the favorable receiving range, and thus the construction cost is reduced. After the layout range of the observation system is determined, the trace interval of the ground microseismic monitoring observation system can be determined through the wavelength of the microseismic signal. Through the application, the ground microseismic monitoring effect can be simulated, the ground microseismic monitoring observation system can be reasonably optimized, and the microseismic event positioning accuracy is considered.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of seismic exploration, and particularly relates to a method and system for determining a ground microseismic observation system, which is mainly used for ground microseismic monitoring. BACKGROUND

[0002] With the gradual development and importance of unconventional oil and gas (shale gas, etc.) exploitation, microseismic monitoring technology has become an important basis for judging the formation and development of fracturing cracks, and the monitoring results provide a very important guarantee for improving shale gas exploration technology and improving unconventional oil and gas recovery.

[0003] There are mainly two ways of microseismic monitoring: well monitoring and ground monitoring. Well microseismic monitoring needs to select a well near the fracturing well as a monitoring well, and lower the detector into the monitoring well, at the same time, well microseismic monitoring is limited by the performance of the detector itself (detector temperature and pressure resistance parameters), observation angle and spatial distance, and the application scene is very limited. Relatively speaking, the ground microseismic monitoring has lower construction condition requirements and can better meet the actual production needs. However, the microseismic signal energy generated by the rock rupture in the fracturing is weak and is easily disturbed by the stratum attenuation and environmental noise, so that in the data processing, the effective signal cannot be identified, and thus the determination of the ground microseismic observation system is directly related to the effect of the ground microseismic monitoring.

[0004] The conventional method for determining the ground microseismic observation system mainly establishes a geological model, uses the depth of the target layer, the observation angle and the ray simulation of the microseismic signal propagation mode to determine the layout range of the ground microseismic observation system, and ignores the energy attenuation problem of the microseismic signal energy in the propagation process, so that the layout range of the ground microseismic monitoring observation system is often too large, and the far end of the measuring line is basically difficult to receive effective microseismic signals, thereby resulting in poor acquisition effect and large construction cost.

[0005] At present, the ground microseismic monitoring observation system is mainly designed as a whole through ray tracing simulation, and the pertinence is not strong, and it is difficult to obtain high-quality acquisition effect. SUMMARY

[0006] The present application aims to solve the problems existing in the prior art, and provides a method and system for determining a ground microseismic observation system, which improves the ground microseismic monitoring acquisition effect and saves the construction cost.

[0007] The present application is realized by the following technical solutions:

[0008] The first aspect of the present application provides a method for determining a ground microseismic observation system, which obtains a layout range, a trace interval and a trace number of the ground microseismic observation system through a microseismic signal energy level and a minimum energy level of effective receiving of a geophone.

[0009] The further improvement of the present application is that:

[0010] The method comprises:

[0011] (1) establishing a geological model;

[0012] (2) obtaining a microseismic signal energy level;

[0013] (3) determining a minimum energy level of effective receiving of a geophone through an experiment;

[0014] (4) determining a layout range of a ground geophone;

[0015] (5) determining a trace interval and a trace number;

[0016] (6) outputting a microseismic detection observation system.

[0017] The further improvement of the present application is that:

[0018] The operation of step (1) comprises:

[0019] Collecting seismic data, well logging data and surface conditions of a work area, and establishing a geological model.

[0020] The further improvement of the present application is that:

[0021] The operation of step (2) comprises:

[0022] Through analysis of previous fracturing monitoring well data or microseismic monitoring data with the same reservoir lithology of the work area, a microseismic signal energy level is determined.

[0023] The further improvement of the present application is that:

[0024] The operation of step (4) comprises:

[0025] (41) determining a layout radius of a ground microseismic monitoring observation system according to a microseismic signal energy level and a minimum energy level of effective receiving of a geophone;

[0026] (42) determining a layout range of the ground microseismic monitoring observation system by using the layout radius.

[0027] The further improvement of the present application is that:

[0028] The operation of step (41) comprises:

[0029] Firstly, the propagation distance of the microseismic signal is calculated, and the horizontal distance, i.e. the layout radius of the ground microseismic monitoring observation system, is calculated according to the propagation distance.

[0030] The further improvement of the present application is that:

[0031] The operation of step (42) comprises:

[0032] Four top corners of the transverse space where the fracture network develops are selected as the four boundary source points;

[0033] Circles are drawn with the four boundary source points as the centers and the layout radius as the radii, respectively, to obtain four circles.

[0034] The union region of the four circles is taken as the layout range of the ground microseismic monitoring observation system.

[0035] The further improvement of the present application is that:

[0036] The operation of step (5) comprises:

[0037] (51) The imaging aperture P is obtained by using the following formula:

[0038]

[0039] In the formula, P represents the imaging aperture, d represents the source depth, and λmin represents the shortest wavelength of the microseismic signal.

[0040] (52) The trace interval is selected in the range of 0-P.

[0041] (53) The number of traces of each line is obtained by dividing the length of the line by the trace interval and adding one, and the total number of traces of the microseismic monitoring is obtained by adding the number of traces of each line.

[0042] In the second aspect of the present application, a system for determining a ground microseismic observation system is provided, and the system comprises:

[0043] A modeling unit is configured to establish a geological model.

[0044] A microseismic signal energy level acquisition unit is configured to acquire a microseismic signal energy level.

[0045] A geophone energy level acquisition unit is configured to determine a minimum effective receiving energy level of a geophone through experiments.

[0046] A parameter determination unit is connected with the modeling unit, the microseismic signal energy level acquisition unit and the geophone energy level acquisition unit, respectively, and is configured to determine a ground geophone layout range, a trace interval and a number of traces.

[0047] An output unit is connected with the parameter determination unit and is configured to output a microseismic monitoring observation system.

[0048] In a third aspect, the present application provides a computer readable storage medium, which stores at least one program executable by a computer, and the at least one program, when executed by the computer, causes the computer to perform the steps of the method for determining a ground microseismic observation system of the present application.

[0049] Compared with the prior art, the present application has the following advantages:

[0050] (1) The present application can effectively determine the layout range of the ground microseismic monitoring observation system by analyzing and statistically processing the energy level of the microseismic signal and determining the minimum energy level of the effective receiver of the geophone, and through simulation demonstration, the ground geophone is laid in the favorable receiving range, thereby reducing the construction cost.

[0051] (2) After the layout range of the observation system is determined, the trace interval of the ground microseismic monitoring observation system can be determined by the wavelength of the microseismic signal. Through the present application, the ground microseismic monitoring effect can be simulated, and the ground microseismic monitoring observation system can be reasonably optimized, and the microseismic event positioning accuracy is considered. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The figure is a step block diagram of the method of the present application.

[0053] Figure 2 The figure is a schematic diagram of the layout range of the observation system. DETAILED DESCRIPTION

[0054] The present application will be further described in detail below in combination with the drawings:

[0055] At present, in the observation system demonstration of the ground microseismic monitoring, the propagation mode of the seismic wave is mainly used, and the simulation deduction is carried out in combination with the geological conditions to determine the layout range and the trace interval of the ground microseismic monitoring, and the influence of the seismic energy level on the receiving effect of the ground microseismic monitoring is often ignored, thereby resulting in that the layout range of the ground microseismic is large, but the effective microseismic signal cannot be effectively received, and the construction cost is high.

[0056] The microseismic monitoring technology is to monitor the rock rupture signal generated in the fracturing, to explain the fracturing fracture network parameters, the distribution characteristics and the expansion law, and to have important guiding significance for the efficient development of the oil and gas field.

[0057] The preliminary study on the collection effect of the ground microseismic monitoring in different work areas and different target layers shows that the event positioning accuracy of the ground microseismic monitoring has a direct relationship with the range and the number of the ground microseismic monitoring observation system, when the target layer is shallow, the range of the ground receiver is required to be relatively small, and the more the number of the receiver is, the higher the positioning accuracy of the microseismic event is; when the target layer is deep, the range of the receiver is required to be wide, but when the positioning accuracy of the microseismic event reaches a certain degree, the increase of the number of the receiver is not obvious to the improvement of the positioning accuracy of the event, then how to scientifically and effectively determine the ground microseismic monitoring observation system and select the reasonable receiving range and the number of the receiver will directly affect the monitoring effect of the ground microseismic and the construction cost.

[0058] As shown in Figure 1 The present application provides a method for determining a ground microseismic observation system, the method obtains the layout range, the trace interval and the trace number of the ground microseismic observation system through the microseismic signal energy level and the minimum energy level of the effective receiver of the receiver.

[0059] The method comprises:

[0060] (1) establishing a geological model;

[0061] (2) obtaining a microseismic signal energy level;

[0062] (3) determining the minimum energy level of the effective receiver of the receiver through experiments;

[0063] (4) determining the layout range of the ground receiver;

[0064] (5) determining the trace interval and the trace number;

[0065] (6) outputting a microseismic detection observation system.

[0066] The implementation of the method of the present application is as follows:

[0067] Example 1:

[0068] The operation of step (1) comprises:

[0069] Collecting seismic data, well logging data and surface conditions of the work area, and establishing a geological model by using existing methods; the geological model includes various parameters such as formation depth and formation velocity.

[0070] Example 2:

[0071] The operation of step (2) comprises:

[0072] Through the analysis of the previous fracturing monitoring well data or the microseismic monitoring data with the same reservoir lithology in the work area, the microseismic signal energy level is determined by statistics;

[0073] Microseismic events are caused by rock rupture, and the rock rupture will release energy, and the size of the released energy is called energy level. In the process of fracturing, many microseismic events will be generated, and the energy levels of the microseismic events are also large or small. In order to better design the observation system, according to the existing data, the energy level is statistically analyzed, and the average value is taken as the energy level of the microseismic signal, such as the energy level f of the microseismic signal in a certain work area is A. Here, the data refers to the production data of the same work area which has been monitored by fracturing, or the microseismic data with the same reservoir rock properties and the data of physical experiment simulation.

[0074] Embodiment 3:

[0075] The operation of step (3) includes:

[0076] The receiving ability of the geophone is verified by using different force knocking experiments. For example, when the knocking experiment is performed by using 100N force, the geophone can receive effective signals, and when the force of 10N is used, the signals are submerged in the background noise. By continuously changing the size of the force, it can be determined that when the geophone can receive signals by using the minimum force for knocking, the energy level of the signals is the energy level of the effective signals received by the ground geophone, that is, the minimum energy level of the effective reception of the geophone. For example, it is determined by the experiment that the minimum energy level of the effective reception of the geophone is B.

[0077] Embodiment 4:

[0078] The operation of step (4) includes:

[0079] (41) determining the layout radius of the ground microseismic monitoring observation system according to the geological model, the energy level of the microseismic signal and the minimum energy level of the effective reception of the geophone:

[0080] When the energy level of the microseismic signal and the minimum energy level of the effective reception of the geophone are known, the propagation distance of the microseismic signal is calculated by using the parameters in the geological model, and the propagation distance is the distance from the source point to a point on the surface. Then the horizontal distance is calculated by the triangular formula, and the horizontal distance is the distance from the projection point of the source point on the surface to the geophone on the surface, and the horizontal distance is the layout radius in the ground microseismic monitoring observation system.

[0081] When the energy level of the microseismic signal and the minimum energy level of the effective reception of the geophone are known, the operation of calculating the propagation distance of the microseismic signal by using the parameters in the geological model includes:

[0082] The function relationship expression of the basic ground motion attenuation relationship is as follows:

[0083] y = f1(M).f2(R).f3(S) (1)

[0084] The above expression is a cited expression, which is expressed as an interaction relationship.

[0085] where y is an arbitrary ground motion parameter, f1(M) is a source influence function, f2(R) is a distance influence function, f3(S) is a site influence function, M is the magnitude, R is the distance from the source to the site, and S is the site parameter.

[0086] In the present application, the distance influence function and the site influence function are mainly considered. The seismic wave attenuates with distance in the propagation process, and the influence of distance on the attenuation function has two mechanisms, one is geometric attenuation or geometric diffusion, and the other is inelastic attenuation, so the function expression is:

[0087] f2(R) = f 21 (R)f 22 (R)(2)

[0088] where f 21 (R) is a geometric attenuation function, and f 22 (R) is an inelastic attenuation. The function expression is as follows:

[0089] f 21 (R) = (R + R0) -c3 (3)

[0090] f 22 (R) = exp(-c6R) (4)

[0091] f 21 (R) is the decrease of wave energy per unit area caused by the continuous expansion of the wave front, so that the amplitude attenuates with the increase of distance, which is called geometric attenuation or geometric diffusion. If the seismic wave is a spherical wave, the body wave attenuates with the square of the distance from the source to the site. The attenuation of amplitude is proportional to the negative power of distance. In empirical analysis, it is difficult to distinguish different types of seismic waves, so the function form of medium geometric attenuation is f 21 (R) = (R + R0) -c3 , where R and R0 are the propagation distances of different types of seismic waves, and c3 is a constant.

[0092] According to the site function in the empirical attenuation relationship, it can be expressed as:

[0093] f3(S) = exp(c7S) (5)

[0094] C7 is a constant.

[0095] where S is the site factor, different integer values can be selected for a simple classification method, and continuous values can be selected for using average wave velocity or equivalent predominant period as the site parameter, such as bedrock S = 0, hard soil S = 1, and soft soil S = 2.

[0096] The above formulas (1) to (5) are existing formulas, and the propagation distance of the microseismic signal can be obtained by the above formulas, and the specific solving method is an existing algorithm, which will not be described here.

[0097] (42) Determine the layout range of the ground microseismic monitoring observation system by using the layout radius:

[0098] A circle is drawn with the microseismic signal source point as the center and the layout radius as the radius, and the circle formed is the receiving range. Without considering background noise and other factors, it is considered that the ground geophone can completely receive the microseismic signal in the receiving range.

[0099] However, the microseismic signal generated in the fracturing is constantly changing with the fracturing section, fracturing scale and time, and is not a fixed position, so the source point has a spatial attribute, and it is distributed in a stratum space near the fracturing section of the fracturing well, so when the microseismic receiving range is circled, the spatial attribute of the source point signal needs to be considered for comprehensive circling.

[0100] Therefore, the present application selects the four top corners of the geometric space (i.e. the transverse space of the fracture network development) near the fracturing section well trajectory (the geometric space has 8 top points, but usually the fracture height of the artificial fracture is not too large, so usually only the 4 top points of the horizontal plane are considered) as the four boundary source points, and draws a circle with the four boundary source points as the center and the layout radius as the radius, to obtain 4 circles, and the union area of the 4 circles is determined as the layout range of the geophone (the union refers to the union of M3, M4, M5 and M6), that is, the layout range of the ground microseismic monitoring observation system, as shown in Figure 2 .

[0101] Figure 2 In the middle, M1 is the fracturing well trajectory (from the top); M2 is the transverse space of the fracture network development (obtained by using the general technology in the art, which will not be described here.), and 4 circles M3, M4, M5 and M6 are drawn with the four top corners of M2 as the center and the layout radius as the radius, and the union M7 of the 4 circles is the layout range of the ground microseismic monitoring observation system. M7 is the concentration area of the microseismic signal energy, and the ground geophone can consider the microseismic event signal of all fracturing sections.

[0102] In actual construction, in order to enhance the collection effect of weak signals, improve the signal-to-noise ratio, and thus obtain higher quality collection data, it is necessary to encrypt the measuring line.

[0103] In the present application, four top corners of the geometric space near the well trajectory of the fracturing section are selected as four boundary seismic source points, a circle with a radius of r is drawn, the union area of all circles is the layout range of the detector, and the intersection area of all circles is the area most beneficial to receiving microseismic signals of all survey lines in the layout range, i.e. the range of the densification section. After the range of the densification section is determined, whether to perform densification needs to be determined according to the specific needs of the number of coverages or production practice. The judgment of whether to perform densification and how to perform densification are prior art and are not within the protection scope of the present application.

[0104] Embodiment 5:

[0105] The operation of step (5) includes:

[0106] After the layout range of the ground microseismic monitoring observation system is obtained, the trace interval and the number of traces (i.e. the number of detectors) of the ground survey line need to be determined.

[0107] (51) Obtain the imaging aperture P by using formula (6):

[0108]

[0109] In the formula, P represents the imaging aperture, d represents the depth of the seismic source, and λmin represents the shortest wavelength of the microseismic signal. In the fracturing, the seismic source is usually concentrated near the fracturing well section and is distributed in a certain geometric space, so the depth of the fracturing well section can be taken as the value of the depth of the seismic source d. The wave field of the seismic wave has a certain range of values, so λmin in the formula is also a certain value, so the imaging aperture P can be calculated. min

[0110] (52) Take P as the maximum value of the trace interval, as long as the trace interval is less than P. The smaller the trace interval, the more the number of traces. According to the actual situation, the requirement of the number of coverages and the structure of the instrument equipment (such as the farthest distance between two detectors), the trace interval can be selected within the range of 0-P. For example, if P obtained is 40, the trace interval can be selected between 0 and 40, for example, 20 or 30 is selected as the trace interval.

[0111] (53) Divide the length of the survey line by the trace interval and add one to obtain the number of traces of each survey line; and add the number of traces of each survey line to obtain the total number of traces of the microseismic monitoring:

[0112] After the layout range and the trace interval are determined, the number of traces of each survey line is the length of the survey line (the length of the line connected with the center point of the fracturing section as the starting point and the edge of the layout range as the ending point is the length of the survey line) divided by the trace interval and added by one, i.e. n=r / a+1, wherein r is the length of the survey line, a is the trace interval, and n is the number of traces; and the total number of traces of the microseismic monitoring is the sum of the number of traces of each survey line, i.e. N=n1+n2+...+n n ​Wherein, N is the total number of channels, n1, n2...n are the number of channels of each line. n The number of channels of each line.

[0113] Through the above four steps, the layout range, channel spacing and channel number in the ground observation system are determined, and the microseismic monitoring observation system is determined through the three parameters.

[0114] Embodiment 6:

[0115] The operation of step (6) includes:

[0116] The layout range, channel spacing and channel number are output.

[0117] After the microseismic monitoring observation system is determined, forward modeling analysis and demonstration can be carried out, that is, ray tracing and illumination are carried out through the geological model, the effect of the microseismic monitoring observation system is simulated and analyzed, and whether the observation system is reasonable is judged.

[0118] The application also provides a system for determining a ground microseismic observation system, and an embodiment of the system is as follows:

[0119] Embodiment 7:

[0120] The system includes:

[0121] The modeling unit is used for establishing a geological model.

[0122] The microseismic signal energy level acquisition unit is used for acquiring a microseismic signal energy level.

[0123] The geophone energy level acquisition unit is used for determining a minimum effective receiving energy level of a geophone through experiments.

[0124] The parameter determination unit is connected with the modeling unit, the microseismic signal energy level acquisition unit and the geophone energy level acquisition unit respectively, and is used for determining a ground geophone layout range, channel spacing and channel number.

[0125] The output unit is connected with the parameter determination unit, and is used for outputting a microseismic monitoring observation system.

[0126] The application also provides a computer readable storage medium, which stores at least one computer executable program, and the at least one program makes the computer execute the steps in the method for determining a ground microseismic observation system when the computer executes the at least one program.

[0127] The application can effectively simulate the attenuation of microseismic signal energy in the propagation process, reasonably optimize the effective layout range, so as to achieve good acquisition and receiving effect and reduce the construction cost. The application is mainly applied to the field of oil and gas development, and provides application for implementing microseismic monitoring in unconventional oil and gas exploration and development. The application comprehensively considers the geological characteristics of the fracturing work area, the microseismic signal energy intensity and the related information such as the attenuation function to demonstrate and analyze the ground microseismic monitoring observation system, so that the ground microseismic acquisition effect can be effectively improved and the economic cost can be saved.

[0128] The technical solution described above is only one embodiment of the application, and for those skilled in the art, on the basis of the disclosed principles, various types of improvements or modifications can be easily made, and the technical solution described in the above specific embodiments is not limited to the application, therefore, the above description is only preferred, and is not limited in nature.

Claims

1. A method for determining a ground microseismic observation system, characterized by: The method obtains the layout range, trace spacing and number of traces of the ground microseismic observation system through the microseismic signal energy level and the minimum energy level of the effective reception of the detector; The method comprises: (1) Establish a geological model; (2) Obtaining the energy level of microseismic signals; (3) Determine the minimum energy level of the detector for effective reception through experiments; (4) Determine the layout range of ground detectors; (5) Determine the track spacing and number of tracks; (6) Output microseismic detection and observation system; The operation of step (1) includes: Collect seismic data, well logging data and surface conditions in the work area and establish a geological model; The operation of step (4) includes: (41) Determine the deployment radius of the ground microseismic monitoring observation system based on the microseismic signal energy level and the minimum energy level of the detector for effective reception; (42) Determine the deployment range of the ground microseismic monitoring observation system using the deployment radius; The operation of step (41) includes: First, the propagation distance of the microseismic signal is calculated, and the horizontal distance is calculated based on the propagation distance. The horizontal distance is the deployment radius of the ground microseismic monitoring observation system.

2. The method for determining a ground microseismic observation system according to claim 1, characterized in that: The operation of step (2) includes: By analyzing the data of previous fracturing monitoring wells in the work area or the microseismic monitoring data with the same reservoir lithology, the energy level of the microseismic signal is statistically determined.

3. The method for determining a ground microseismic observation system according to claim 1, characterized in that: The operation of step (42) includes: The four vertex corners of the lateral space where the fracture network is developed are selected as the four boundary earthquake source points; Draw circles with the four boundary earthquake source points as the center and the layout radius as the radius to obtain four circles; The union area of ​​the four circles is used as the layout range of the ground microseismic monitoring observation system.

4. The method for determining a ground microseismic observation system according to claim 1, characterized in that: The operation of step (5) includes: (51) The imaging aperture P is obtained using the following formula: Where P represents the imaging aperture, d represents the focal depth, and λmin represents the shortest wavelength of the microseismic signal; (52) Select the track spacing within the range of 0-P; (53) Divide the line length by the track spacing and add one to obtain the number of tracks for each line; add the track numbers of each line to obtain the total number of tracks for microseismic monitoring.

5. A system for determining a ground microseismic observation system, for implementing the method according to any one of claims 1 to 4, characterized in that: The system comprises: Modeling unit: used to build geological models; Microseismic signal energy level acquisition unit: used to acquire the microseismic signal energy level; Detector energy level acquisition unit: used to determine the minimum energy level of the detector for effective reception through experiments; Parameter determination unit: connected to the modeling unit, microseismic signal energy level acquisition unit, and detector energy level acquisition unit respectively, used to determine the layout range, trace spacing, and number of ground detectors; Output unit: connected to the parameter determination unit, used to output the microseismic detection observation system.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores at least one computer-executable program, and when the at least one program is executed by the computer, the computer executes the steps in the method for determining a ground microseismic observation system according to any one of claims 1 to 4.

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