Method and system for determining ground microseism observation system

Abstract

The invention provides a method and system for determining a ground microseism observation system, and belongs to the field of seismic exploration. According to the method, the layout range, the channel spacing and the channel number of the ground microseism observation system are obtained through the microseism signal energy level and the effective receiving minimum energy level of the detector. According to the method, through analysis and statistics of the energy level of the microseismic signal and determination of the effective receiving minimum energy level of the detector, through simulation demonstration, the arrangement range of the ground microseismic monitoring and observation system can be effectively determined, the ground detector is arranged in a favorable receiving range, and therefore the construction cost is reduced. After the arrangement range of the observation system is determined, the channel spacing of the ground micro-seismic monitoring and observation system can be determined through the wavelength of the micro-seismic signal. According to the invention, a ground microseism monitoring effect can be simulated, a ground microseism monitoring and observation system is reasonably optimized, and the positioning precision of a microseism event is considered.

Description

Technical Field

[0001] The present invention belongs to the field of seismic exploration, and in particular relates to a method and a system for determining a ground microseismic observation system, which are mainly used for ground microseismic monitoring. Background Art

[0002] With the gradual development and increasing 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. The monitoring results also provide a very important guarantee for improving shale gas exploration technology and increasing the recovery rate of unconventional oil and gas.

[0003] There are two main ways of microseismic monitoring: in-well monitoring and ground monitoring. In-well microseismic monitoring requires selecting a well near the fracturing well as a monitoring well and lowering the detector into the monitoring well. At the same time, in-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 scenarios are very limited. Relatively speaking, the construction conditions for ground microseismic monitoring are lower and can better meet actual production needs. However, the microseismic signal generated by the fracture of formation rocks during fracturing is weak in energy and is easily interfered by formation attenuation and environmental noise, so that effective signals cannot be identified during data processing. Therefore, the determination of the ground microseismic observation system is directly related to the effect of ground microseismic monitoring.

[0004] The conventional method of determining the ground microseismic observation system is mainly to establish a geological model, use the depth of the target layer, the observation angle, and the ray simulation of the propagation mode of the microseismic signal to determine the layout range of the ground microseismic observation system, and ignore the problem of energy attenuation of the microseismic signal energy during the propagation process. As a result, the layout range of the ground microseismic monitoring observation system is often too large, and it is basically difficult to receive effective microseismic signals at the far end of the survey line, resulting in poor acquisition effect and high construction cost.

[0005] At present, the ground microseismic monitoring and observation system is mainly designed as an overall system through ray tracing simulation, which is not very targeted and it is difficult to obtain high-quality data collection results. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art, to provide a method and system for determining a ground microseismic observation system, to improve the ground microseismic monitoring and collection effect, and to save construction costs.

[0007] The present invention is achieved through the following technical solutions:

[0008] The first aspect of the present invention provides a method for determining a ground microseismic observation system, wherein the method obtains the deployment range, track spacing and number of tracks of the ground microseismic observation system through the microseismic signal energy level and the minimum energy level effectively received by the detector.

[0009] A further improvement of the present invention is:

[0010] The method comprises:

[0011] (1) Establish a geological model;

[0012] (2) Obtaining the energy level of microseismic signals;

[0013] (3) Determine the minimum energy level for effective reception of the detector through experiments;

[0014] (4) Determine the deployment range of ground geophones;

[0015] (5) Determine the track spacing and number of tracks;

[0016] (6) Output microseismic detection observation system.

[0017] A further improvement of the present invention is:

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

[0019] Collect seismic data, logging data and surface conditions in the work area and establish a geological model.

[0020] A further improvement of the present invention is:

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

[0022] By analyzing the previous fracturing monitoring well data or microseismic monitoring data with the same reservoir lithology in the work area, the microseismic signal energy level is statistically determined.

[0023] A further improvement of the present invention is:

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

[0025] (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 effective reception of the detector;

[0026] (42) The deployment radius is used to determine the deployment range of the ground microseismic monitoring observation system.

[0027] A further improvement of the present invention is:

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

[0029] 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 in the ground microseismic monitoring observation system.

[0030] A further improvement of the present invention is:

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

[0032] The four vertices of the lateral space where the fracture network is developed are selected as the four boundary source points;

[0033] Draw circles with the four boundary epicenter points as the center and the layout radius as the radius to obtain four circles;

[0034] The union area of ​​the four circles is used as the deployment range of the ground microseismic monitoring observation system.

[0035] A further improvement of the present invention is:

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

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

[0038]

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

[0040] (52) Selecting the track spacing in the range of 0-P;

[0041] (53) Divide the length of the survey line by the track spacing and add 1 to obtain the number of tracks for each survey line; add the number of tracks for each survey line to obtain the total number of tracks for microseismic monitoring.

[0042] A second aspect of the present invention provides a system for determining a ground microseismic observation system, the system comprising:

[0043] Modeling unit: used to build geological models;

[0044] Microseismic signal energy level acquisition unit: used to acquire the microseismic signal energy level;

[0045] Detector energy level acquisition unit: used to determine the minimum energy level of the detector for effective reception through experiments;

[0046] Parameter determination unit: connected to the modeling unit, the microseismic signal energy level acquisition unit, and the detector energy level acquisition unit, respectively, to determine the layout range, track spacing, and number of tracks of the ground detectors;

[0047] Output unit: connected with the parameter determination unit, used to output the microseismic detection observation system.

[0048] According to a third aspect of the present invention, a computer-readable storage medium is provided, wherein 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 of a method for determining a ground microseismic observation system of the present invention.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The present invention can effectively determine the deployment range of the ground microseismic monitoring and observation system by analyzing and statistically analyzing the energy levels of microseismic signals and determining the minimum energy level for effective reception of the detector through simulation demonstration, and deploy the ground detectors within a favorable reception range, thereby reducing construction costs.

[0051] (2) After the deployment range of the observation system is determined, the track spacing of the ground microseismic monitoring observation system can be determined by the wavelength of the microseismic signal. The present invention can simulate the ground microseismic monitoring effect, reasonably optimize the ground microseismic monitoring observation system, and take into account the positioning accuracy of microseismic events. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The figure is a flowchart of the steps of the method of the present invention.

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

[0054] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0055] At present, in the demonstration of the observation system of ground microseismic monitoring, the propagation mode of seismic waves is mainly used, combined with the geological conditions to carry out simulation and deduction to determine the layout range and track spacing of ground microseismic monitoring. The influence of earthquake energy level on the reception effect of ground microseismic monitoring is often ignored, resulting in a large ground microseismic layout range, but the inability to effectively receive effective microseismic signals, and high construction costs.

[0056] Microseismic monitoring technology monitors the rock fracture signals generated during fracturing to interpret the parameters, distribution characteristics and expansion laws of the fracture network, which has important guiding significance for the efficient development of oil and gas fields.

[0057] Preliminary research on the acquisition effect of ground microseismic monitoring in different work areas and different target layers shows that the event positioning accuracy of ground microseismic monitoring is directly related to the deployment range of the ground microseismic monitoring observation system and the number of geophones. When the target layer is shallow, the deployment range of the ground geophones is required to be relatively small, and the more geophones there are, the higher the positioning accuracy of the microseismic events; when the target layer is deep, the deployment range of the geophones is required to be wider, but when the microseismic event positioning accuracy reaches a certain level, increasing the number of geophones does not significantly improve the event positioning accuracy. Therefore, how to scientifically and effectively determine the ground microseismic monitoring observation system and select a reasonable receiving range and number of geophones will directly affect the monitoring effect and construction cost of ground microseisms.

[0058] like Figure 1 As shown, the present invention provides a method for determining a ground microseismic observation system, wherein the method obtains the deployment range, track spacing and number of tracks of the ground microseismic observation system through the microseismic signal energy level and the minimum energy level effectively received by the detector.

[0059] The method comprises:

[0060] (1) Establish a geological model;

[0061] (2) Obtaining the energy level of microseismic signals;

[0062] (3) Determine the minimum energy level for effective reception of the detector through experiments;

[0063] (4) Determine the deployment range of ground geophones;

[0064] (5) Determine the track spacing and number of tracks;

[0065] (6) Output microseismic detection observation system.

[0066] The embodiments of the method of the present invention are as follows:

[0067] Embodiment 1:

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

[0069] Collect seismic data, logging data and surface conditions in the work area, and use existing methods to establish a geological model; the geological model includes multiple parameters such as formation depth and formation velocity.

[0070] Embodiment 2:

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

[0072] By analyzing the previous fracturing monitoring well data or microseismic monitoring data with the same reservoir lithology in the work area, the microseismic signal energy level is statistically determined;

[0073] Microseismic events are generated by rock fractures, which release energy. The amount of energy released is called energy level. During the fracturing process, many microseismic events will occur, and their energy levels are also large and small. In order to better design the observation system, a statistical analysis of the energy level is performed based on the existing data, and the average value is taken as the microseismic signal energy level. For example, the microseismic signal energy level f in a certain work area is A. The data here refers to the production data that has been monitored by fracturing in the same work area, or microseismic data with the same reservoir lithology, and data from physical experimental simulations.

[0074] Embodiment 3:

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

[0076] The receiving ability of the detector is verified by using knocking experiments with different forces. For example, when the knocking experiment is performed with a force of 100N, the detector can receive effective signals, while when a force of 10N is used, the signal will be submerged in the background noise. By continuously changing the force, it is possible to determine the minimum force required for the detector to receive the signal. The energy level of this signal is the energy level at which the ground detector receives effective signals, that is, the minimum energy level for the detector to effectively receive. For example, the minimum energy level for the detector to effectively receive is determined to be B through experiments.

[0077] Embodiment 4:

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

[0079] (41) The deployment radius of the ground microseismic monitoring observation system is determined based on the geological model, microseismic signal energy level and the minimum energy level of the effective receiver:

[0080] When the energy level of the microseismic signal and the minimum energy level for effective reception by the detector are known, the propagation distance of the microseismic signal is inversely calculated using the parameters in the geological model. The propagation distance is the distance from the earthquake source to a point on the surface. The horizontal distance is then calculated using trigonometric formulas. The horizontal distance is the distance from the projection point of the earthquake source on the surface to the surface detector. The horizontal distance is the deployment radius of the ground microseismic monitoring observation system.

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

[0082] The functional expression of the basic earthquake motion attenuation relationship is as follows:

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

[0084] The above expressions are quoted expressions, which represent the relationship of interaction.

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

[0086] In the present invention, the distance effect function and the site effect function are mainly considered. Seismic waves attenuate with distance during propagation. There are two mechanisms for the influence of distance on the attenuation function, one is geometric attenuation or geometric diffusion, and the other is inelastic attenuation. Therefore, the function expression is:

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

[0088] Among them, f 21 (R) is the geometric attenuation function, f 22 (R) is the inelastic attenuation. Its 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 in the energy per unit area caused by the continuous expansion of the wavefront, which causes the amplitude to decay with increasing distance, which is called geometric attenuation or geometric diffusion. If the seismic wave is a spherical wave, the body wave decays with the negative square of the distance from the earthquake source. The attenuation of the amplitude is proportional to the negative power of the distance. It is difficult to distinguish different types of seismic waves in empirical analysis, so the function form representing the geometric attenuation of the medium 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 empirical attenuation relationship, the site function can be expressed as:

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

[0094] C7 is a constant.

[0095] Where S is the site factor. Different integer values ​​can be selected for simple classification methods. For those using average wave velocity or equivalent dominant period as site parameters, continuous values ​​can be selected, such as bedrock S=0, hard soil S=1, and soft soil S=2.

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

[0097] (42) The deployment radius is used to determine the deployment range of the ground microseismic monitoring observation system:

[0098] The receiving range is formed by drawing a circle with the microseismic signal source point as the center and the layout radius as the radius. Without considering other factors such as background noise, it is believed that the ground detector can fully receive the microseismic signal within this receiving range.

[0099] However, the microseismic signals generated during fracturing change continuously with the fracturing section, fracturing scale and time, rather than a fixed position. Therefore, the source point has spatial attributes and is distributed in a formation space near the fracturing section of the fracturing well. Therefore, when defining the microseismic receiving range, it is necessary to consider the spatial attributes of the source point signal for comprehensive definition.

[0100] Therefore, the present invention selects four vertices of the geometric space (i.e., the lateral space where the fracture network develops) near the fracturing section well trajectory (the geometric space has 8 vertices, but the height of the artificial fracture is usually not too large, so usually only 4 vertices of the horizontal plane are considered) as four boundary source points, and draws circles with the four boundary source points as the center and the layout radius as the radius to obtain 4 circles. The union area of ​​the 4 circles is determined as the layout range of the detector (the union refers to the collection of M3, M4, M5, and M6), that is, the layout range of the ground microseismic monitoring observation system, such as Figure 2 shown.

[0101] Figure 2 In the figure, M1 is the trajectory of the fracturing well (looking down); M2 is the lateral space where the fracturing network is developed (obtained using the general technology in this field, which will not be repeated here). With the four vertices of M2 as the center and the layout radius as the radius, four circles are drawn: M3, M4, M5, and M6. The union of the four circles, M7, is the layout range of the ground microseismic monitoring observation system. M7 is the concentrated area covered by the microseismic signal energy, and the ground geophone can take into account the microseismic event signals of all fracturing sections.

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

[0103] In the present invention, the four vertices of the geometric space near the fracturing section well trajectory are selected as the four boundary source points, and the layout radius is the radius to draw a circle. The union area of ​​all circles is the layout range of the detector, and the intersection area of ​​all circles is the area that is most conducive to all survey lines within the layout range to receive microseismic signals, that is, the encryption section range. After determining the encryption section range, whether to encrypt or not needs to be determined based on the number of coverage times or the actual specific needs of production. Judging whether to encrypt and how to encrypt is a prior art and is not within the protection scope of the present invention.

[0104] Embodiment 5:

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

[0106] After obtaining the deployment range of the ground microseismic monitoring observation system, it is necessary to determine the track spacing and number of tracks (i.e., the number of geophones) of the ground survey lines.

[0107] (51) Using formula (6), we can obtain the imaging aperture P:

[0108]

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

[0110] (52) P is taken as the maximum value of the track spacing. As long as the track spacing is less than P, the smaller the track spacing, the more tracks there are. According to the actual situation, the requirements for the number of coverage times, and the structure of the instrument (such as the maximum distance between two detectors, etc.), the track spacing can be selected within the range of 0-P. For example, if the obtained P is 40, the track spacing can be selected between 0 and 40, such as 20 or 30.

[0111] (53) Divide the line length by the trace spacing and add 1 to get the number of traces for each line; add the number of traces for each line to get the total number of traces for microseismic monitoring:

[0112] After the deployment range and track spacing are determined, the number of tracks for each survey line is the length of the survey line (starting from the center of the fracturing section and ending at the edge of the deployment range, the length of the connecting line is the length of the survey line) divided by the track spacing plus one, that is, n=r / a+1, where r is the length of the survey line, a is the track spacing, and n is the number of tracks; the total number of tracks for microseismic monitoring is the sum of the number of tracks for each survey line, that is, N=n1+n2+...+n n, where N is the total number of channels, n1, n2...n n is the number of channels for each survey line.

[0113] Through the above four steps, the layout range, track spacing, and number of tracks in the ground observation system are determined. These three parameters determine the microseismic monitoring observation system.

[0114] Embodiment 6:

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

[0116] Output the layout range, track spacing, and number of tracks.

[0117] After the microseismic monitoring observation system is determined, a forward simulation analysis can be carried out, that is, ray tracing and illumination are performed through the geological model to simulate and analyze the effect of the microseismic monitoring observation system to determine whether the observation system is reasonable.

[0118] The present invention 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 comprises:

[0121] Modeling unit: used to build geological models;

[0122] Microseismic signal energy level acquisition unit: used to acquire the microseismic signal energy level;

[0123] Detector energy level acquisition unit: used to determine the minimum energy level of the detector for effective reception through experiments;

[0124] Parameter determination unit: connected to the modeling unit, the microseismic signal energy level acquisition unit, and the detector energy level acquisition unit, respectively, to determine the layout range, track spacing, and number of tracks of the ground detectors;

[0125] Output unit: connected with the parameter determination unit, used to output the microseismic detection observation system.

[0126] The present invention also provides a computer-readable storage medium, which stores at least one computer-executable program. When the at least one program is executed by the computer, the computer executes the steps of a method for determining a ground microseismic observation system of the present invention.

[0127] The present invention can effectively simulate and demonstrate the attenuation of microseismic signal energy during the propagation process, reasonably optimize the effective deployment range, thereby achieving good acquisition and reception effects and reducing construction costs. The present invention is mainly used in the field of oil and gas development, and provides applications for the implementation of microseismic monitoring in unconventional oil and gas exploration and development. The present invention combines relevant information such as the geological characteristics of the fracturing area, the energy intensity of the microseismic signal, and its attenuation function to demonstrate and analyze the ground microseismic monitoring and observation system, which can effectively improve the ground microseismic acquisition effect and save economic costs.

[0128] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the principles disclosed in the present invention, and it is not limited to the technical solution described in the above specific embodiments of the present invention. Therefore, the above description is only preferred and does not have a restrictive meaning.

Claims

1. A method for determining a ground microseismic observation system, characterized in that: The method obtains the layout range, track spacing and track number of the ground microseismic observation system through the microseismic signal energy level and the minimum energy level of the effective reception of the detector.

2. The method for determining a ground microseismic observation system according to claim 1, characterized in that: The method comprises: (1) Establish a geological model; (2) Obtaining the energy level of microseismic signals; (3) Determine the minimum energy level for effective reception of the detector through experiments; (4) Determine the deployment range of ground geophones; (5) Determine the track spacing and number of tracks; (6) Output microseismic detection observation system.

3. The method for determining a ground microseismic observation system according to claim 2, characterized in that: The operation of step (1) includes: Collect seismic data, logging data and surface conditions in the work area and establish a geological model.

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

5. The method for determining a ground microseismic observation system according to claim 2, characterized in that: 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 effective reception of the detector; (42) The deployment radius is used to determine the deployment range of the ground microseismic monitoring observation system.

6. The method for determining a ground microseismic observation system according to claim 5, characterized in that: 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 in the ground microseismic monitoring observation system.

7. The method for determining a ground microseismic observation system according to claim 5, characterized in that: The operation of step (42) includes: The four vertices of the lateral space where the fracture network is developed are selected as the four boundary source points; Draw circles with the four boundary epicenter 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 deployment range of the ground microseismic monitoring observation system.

8. The method for determining a ground microseismic observation system according to claim 2, characterized in that: The operation of step (5) includes: (51) The imaging aperture P is obtained using the following formula: In the formula, P represents the imaging aperture, d represents the focal depth, and λmin represents the shortest wavelength of the microseismic signal; (52) Selecting the track spacing in the range of 0-P; (53) Divide the length of the survey line by the track spacing and add 1 to obtain the number of tracks for each survey line; add the number of tracks for each survey line to obtain the total number of tracks for microseismic monitoring.

9. A system for determining a ground microseismic observation system, 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, the microseismic signal energy level acquisition unit, and the detector energy level acquisition unit, respectively, to determine the layout range, track spacing, and number of tracks of the ground detectors; Output unit: connected with the parameter determination unit, used to output the microseismic detection observation system.

10. 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 as described in any one of claims 1-8.

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