A method for monitoring and interpreting the wave propagation body of oil and gas fracturing based on the combination of seismic and electric methods

Abstract

The present invention discloses a method for monitoring and interpreting the fracture wave body based on the combination of seismic and electric methods, which includes arranging a plurality of first measuring points and a plurality of second measuring points on the fracture monitoring section; collecting microseismic signals of the plurality of first measuring points and electric field signals of the plurality of second measuring points; based on the processing of the microseismic signals and the electric field signals, determining the initial planar distribution contour, the initial upper undulating surface and the initial lower undulating surface of the fracturing fluid wave body; according to the initial planar distribution contour, the initial upper undulating surface and the initial lower undulating surface, determining the initial three-dimensional model of the fracturing fluid wave body; based on the processing of the initial three-dimensional model, determining the three-dimensional shape of the fracturing fluid wave body. The embodiments of the present invention effectively integrate the results of two methods, namely, the microseismic monitoring technology and the electromagnetic monitoring technology, to form a seismic-electric integrated fracturing monitoring and interpretation method, which solves the drawback that it is difficult to accurately monitor the effective transformation volume range of the fracturing operation by using any single method.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic fracturing monitoring of rock formations, and in particular to a method for monitoring and interpreting the wave propagation body of oil and gas fracturing based on the combination of seismic and electric methods. Background Art

[0002] In the oil field, during the process of hydraulic fracturing of rock formations, a large amount of fracturing fluid with high viscosity, containing proppants and having low resistance characteristics is injected into the formation through the wellbore by using a surface high-pressure pump, forcing the formation pressure to rise and the rock to fracture to generate fractures. During the fracture generation process, the fracturing fluid advances along the fractures, fills the fractures and supports the fractures so that they do not close. When the rock fractures, seismic wave signals will be generated, and the microseismic monitoring technology can be used to monitor the location and degree of the fracture event; after the crack space filled with low-resistance fracturing fluid is electrified, a current emission source can be formed, and the electromagnetic monitoring technology can be used to monitor the shape and size of the fracturing fluid wave propagation body.

[0003] The increase in pressure can cause some stress fractures at the far end. The seismic wave signals can reflect and locate the fracture event, but it is unknown whether the far-end fractures caused by this fracture event are connected to the main fracture space or filled with fracturing fluid. If they are not connected or filled with fracturing fluid, they are ineffective fractures, and the microseismic monitoring technology cannot judge this situation. The electromagnetic monitoring technology is based on the spatial distribution characteristics of the fracturing fluid wave propagation body, but it is difficult to determine the accurate position of the fracturing fluid wave propagation body from the ground electric field signal. If the positioning is inaccurate, it will affect the accuracy of the interpretation of the spatial distribution characteristics. Therefore, relying solely on the microseismic monitoring technology, it is impossible to judge the effective transformation volume range; and relying solely on the electromagnetic monitoring technology, the accuracy of the interpretation of the shape and size of the fracturing fluid wave propagation body is reduced, that is, it is difficult to accurately monitor the effective transformation volume range of the fracturing operation by using any single method. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for monitoring and interpreting the wave propagation body of oil and gas fracturing based on the combination of seismic and electric methods, which solves the problem of the limitations of using only the microseismic monitoring technology or the electromagnetic monitoring technology for monitoring and interpreting the wave propagation body of oil and gas fracturing.

[0005] The method for monitoring and interpreting the wave propagation body of oil and gas fracturing based on the combination of seismic and electric methods according to the embodiments of the present invention includes the following steps:

[0006] Arrange a plurality of first measuring points and a plurality of second measuring points on the fracturing monitoring section, where the first measuring points are used for microseismic monitoring and the second measuring points are used for electromagnetic monitoring;

[0007] Collect the microseismic signals of the plurality of first measuring points and the electric field signals of the plurality of second measuring points;

[0008] Based on the processing of the microseismic signal and the electric field signal, determine the initial planar distribution profile, the initial upper undulating surface, and the initial lower undulating surface of the fracturing fluid affected body;

[0009] According to the initial planar distribution profile, the initial upper undulating surface, and the initial lower undulating surface, determine the initial three-dimensional model of the fracturing fluid affected body;

[0010] Based on the processing of the initial three-dimensional model, determine the three-dimensional shape of the fracturing fluid affected body.

[0011] The method for monitoring and interpreting the oil and gas fracturing affected body based on the combination of seismic and electric methods according to the embodiments of the present invention has at least the following beneficial effects:

[0012] The embodiments of the present invention effectively integrate the achievements of two methods, namely, the microseismic monitoring technology and the electromagnetic monitoring technology, to form a seismic-electric integrated fracturing monitoring and interpretation method. The microseismic monitoring technology provides the position information of the emission source and the distribution of the fracture event points, and the electromagnetic monitoring technology provides the distribution of the surface abnormal potential. Taking the position information provided by the microseismic as the calculation premise, an initial three-dimensional model of the fracturing fluid affected body is established by comprehensively considering the distribution pattern of the microseismic event points and the distribution pattern of the electromagnetic abnormal potential, and inversion is carried out with the abnormal potential as the constraint to continuously adjust the three-dimensional model of the fracturing fluid affected body, so that the fitting error of the abnormal potential meets the agreed requirements. According to the finally obtained three-dimensional model, the shape and size of the fracturing fluid affected body can be accurately represented, and thus the effective transformation volume range of the fracturing operation can be determined.

[0013] According to some embodiments of the present invention, based on the processing of the microseismic signal and the electric field signal, determining the initial planar distribution profile of the fracturing fluid affected body includes the following steps:

[0014] Process the microseismic signal to obtain the distribution of microseismic fracture event points;

[0015] Process the electric field signal to obtain the relative abnormal potential planar distribution;

[0016] According to the distribution of the microseismic fracture event points, delineate the first planar distribution profile;

[0017] According to the relative abnormal potential planar distribution, delineate the second planar distribution profile;

[0018] According to the first planar distribution profile and the second planar distribution profile, determine the initial planar distribution profile.

[0019] According to some embodiments of the present invention, the processing of the electric field signal to obtain the relative abnormal potential planar distribution includes the following steps:

[0020] Perform mean processing on the electric field signals monitored before fracturing to obtain the background field potential signals;

[0021] Subtract the background field potential signals from the electric field signals monitored during fracturing to obtain the actual measured potential signals;

[0022] Calculate the relative abnormal potential signals based on the background field potential signals and the actual measured potential signals;

[0023] Process the relative abnormal potential signals based on the inverse distance weighted interpolation algorithm to obtain the planar distribution of the relative abnormal potential.

[0024] According to some embodiments of the present invention, the determining the initial planar distribution profile based on the first planar distribution profile and the second planar distribution profile includes the following steps:

[0025] Determine the center point, which is the midpoint of the line connecting two intersection points between the first planar distribution profile and the well trajectory;

[0026] Uniformly set a plurality of virtual rays at the center point so that each virtual ray intersects with the first planar distribution profile and the second planar distribution profile respectively, and correspondingly obtain a plurality of first intersection points and a plurality of second intersection points;

[0027] Determine a plurality of initial profile points, each initial profile point being the midpoint of the line connecting each first intersection point and the corresponding second intersection point;

[0028] Connect the plurality of initial profile points to determine the initial planar distribution profile.

[0029] According to some embodiments of the present invention, based on the processing of the microseismic signals and the electric field signals, determining the initial upper undulating surface and the initial lower undulating surface of the fracturing fluid affected body includes the following steps:

[0030] Outline the upper undulating surface and the lower undulating surface of the well trajectory horizontal plane according to the distribution of the microseismic rupture event points and the initial planar distribution profile;

[0031] Outline the relative abnormal undulating surface according to the planar distribution of the relative abnormal potential;

[0032] Determine the initial upper undulating surface and the initial lower undulating surface according to the upper undulating surface, the lower undulating surface and the relative abnormal undulating surface.

[0033] According to some embodiments of the present invention, outlining the upper undulating surface and the lower undulating surface of the well trajectory horizontal plane based on the distribution of the microseismic rupture event points and the initial plane distribution profile includes the following steps:

[0034] Taking the initial plane distribution profile as a boundary, dividing the range within the boundary into a plurality of regular grids;

[0035] According to the distribution of the microseismic rupture event points, determining the first three-dimensional position coordinates of each of the regular grids;

[0036] Using the plurality of first three-dimensional position coordinates to outline the upper undulating surface and the lower undulating surface.

[0037] According to some embodiments of the present invention, outlining the relative anomaly undulating surface based on the relative anomaly potential plane distribution includes the following steps:

[0038] According to the relative anomaly potential plane distribution, determining the second three-dimensional position coordinates of each of the regular grids;

[0039] Using the plurality of second three-dimensional position coordinates to outline the relative anomaly undulating surface.

[0040] According to some embodiments of the present invention, determining the initial upper undulating surface and the initial lower undulating surface based on the upper undulating surface, the lower undulating surface, and the relative anomaly undulating surface includes the following steps:

[0041] Respectively determining the maximum absolute values of the heights of the upper undulating surface, the lower undulating surface, and the relative anomaly undulating surface to correspondingly obtain a first height maximum value, a second height maximum value, and a third height maximum value;

[0042] According to the first height maximum value, the second height maximum value, and the third height maximum value, calculating an upper half amplification factor and a lower half amplification factor;

[0043] Processing the relative anomaly undulating surface using the upper half amplification factor and the lower half amplification factor to obtain upper half relative anomaly height node data and lower half relative anomaly height node data;

[0044] Performing a superposition averaging process on the upper half relative anomaly height node data and the upper half undulating surface to determine the initial upper undulating surface;

[0045] Perform superposition averaging on the relatively abnormal height node data of the lower half part and the undulating surface of the lower half part to determine the initial undulating surface of the lower half part.

[0046] According to some embodiments of the present invention, determining the initial three-dimensional model of the fracturing fluid swept body based on the initial plane distribution contour, the initial undulating surface of the upper half part, and the initial undulating surface of the lower half part includes the following steps:

[0047] Assign zero values to the height values at the boundaries of the initial undulating surface of the upper half part and the initial undulating surface of the lower half part respectively, so that the initial undulating surface of the upper half part and the initial undulating surface of the lower half part are respectively connected to the initial plane distribution contour;

[0048] Determine the initial three-dimensional model with the initial plane distribution contour, the initial undulating surface of the upper half part, and the initial undulating surface of the lower half part as the boundaries.

[0049] According to some embodiments of the present invention, determining the three-dimensional shape of the fracturing fluid swept body based on the processing of the initial three-dimensional model includes the following steps:

[0050] Establish a three-dimensional model coordinate system, and the origin of the three-dimensional model coordinate system is the center point;

[0051] Under the three-dimensional model coordinate system, divide the initial three-dimensional model into multiple sub-divided models according to a scale factor, and each sub-divided model is a different unit ellipsoid;

[0052] Select any one of the second measuring points as the first designated measuring point, and based on the potential expression at any point outside the conductive ellipsoid space, calculate the abnormal potential value of each sub-divided model at the designated measuring point and accumulate them to obtain the first measuring point calculated abnormal potential value;

[0053] Update the designated measuring point to the next second measuring point to calculate the next measuring point calculated abnormal potential value, continuously update the designated measuring point until the multiple measuring point calculated abnormal potential values corresponding to all the second measuring points are calculated, and then stop the update;

[0054] Compare the errors of the multiple measuring point calculated abnormal potential values to adjust the scale factor;

[0055] Determine the three-dimensional shape of the fracturing fluid swept body according to the finally adjusted scale factor.

[0056] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will be obvious from the specification or understood by implementing the present invention. Description of the Drawings

[0057] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, where:

[0058] Figure 1 is a flowchart of a method for monitoring and interpreting the wave propagation body of oil and gas fracturing based on the combination of seismic and electric signals according to an embodiment of the present invention;

[0059] Figure 2 is a schematic diagram of the layout of multiple first measurement points and multiple second measurement points according to an embodiment of the present invention; <*

[0060] Figure 3 is a schematic diagram of the distribution of microseismic rupture event points according to an embodiment of the present invention;

[0061] Figure 4 is a schematic diagram of the planar distribution of relative abnormal potential according to an embodiment of the present invention;

[0062] Figure 5 is a schematic diagram of the first planar distribution contour and the second planar distribution contour according to an embodiment of the present invention;

[0063] Figure 6 is a schematic diagram of the principle for determining the initial planar distribution contour based on the first planar distribution contour and the second planar distribution contour according to an embodiment of the present invention;

[0064] Figure 7 is a schematic diagram of the upper undulating surface, the lower undulating surface, the relative abnormal undulating surface, the upper relative abnormal height node data, the lower relative abnormal height node data, the initial upper undulating surface, and the initial lower undulating surface according to an embodiment of the present invention. Detailed Embodiments

[0065] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0066] In the description of the present invention, if the first, second, etc. are described, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0067] In the description of the present invention, it should be understood that with respect to the orientation description, such as the upper and lower directions, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0068] In the description of the present invention, it should be noted that unless otherwise clearly defined, terms such as "arrangement", "installation", and "connection" should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0069] To better illustrate the method for monitoring and interpreting the hydraulic fracturing wave propagation body based on the combination of seismic and electric methods in the embodiments of the present invention, it should be first noted that during the hydraulic fracturing process, the range of the fracturing fluid wave propagation body represents the effective transformation volume range of the fracturing operation. For the location and degree of the fracture events occurring in the rock formation during the fracturing process, microseismic monitoring technology can be used for monitoring; while for the fractures generated after fracturing, after they are filled with low-resistivity fracturing fluid and a current emission source is formed by power supply through the wellbore, electromagnetic monitoring technology can be used on the ground to monitor the change in their three-dimensional shape and size. Although these two methods can reflect the fracturing effect to a certain extent, they both have their own limitations, which are specifically reflected in:

[0070] The microseismic monitoring technology can locate the position of the fracture event based on the arrival time of the seismic waves caused by rock fractures. Since the entry and filling of the fracturing fluid do not cause seismic waves, it is impossible to determine whether the fractures caused by the fractures are filled with fracturing fluid. There may be a situation where fractures are caused by fractures but not filled with fracturing fluid. At this time, the position of the fracture event does not represent the position of the fracturing fluid wave propagation.

[0071] The electromagnetic monitoring technology regards the power supply of the low-resistivity fracturing fluid wave propagation body as a current emission source. The change in the shape and size of the emission source will cause a change in the surface potential. Electrodes are arranged on the ground to monitor the potential change. According to the potential change, the shape and size of the emission source and the shape and size of the fracturing fluid wave propagation body can be deduced. However, during the deduction process, relatively accurate emission source position information is required. If the position information is inaccurate, the calculation result will be deviated or even incorrect, and the electromagnetic method does not have the condition to obtain the position information of the divergent source.

[0072] Next, the technical solution of the present invention will be clearly and completely described with reference to the drawings. Obviously, the following described embodiments are part of the embodiments of the present invention, not all embodiments.

[0073] See Figure 1 As shown, it is a flowchart of a method for monitoring and interpreting a hydraulic fracturing wave propagation body based on the combination of seismic and electric methods provided by an embodiment of the present invention. The method includes the following steps:

[0074] A plurality of first measurement points and a plurality of second measurement points are arranged on the fracturing monitoring section. The first measurement points are used for microseismic monitoring, and the second measurement points are used for electromagnetic monitoring;

[0075] Collect microseismic signals of a plurality of first measurement points and electric field signals of a plurality of second measurement points;

[0076] Based on the processing of the microseismic signals and electric field signals, determine the initial planar distribution contour, the initial upper undulating surface, and the initial lower undulating surface of the fracturing fluid affected body;

[0077] According to the initial planar distribution contour, the initial upper undulating surface, and the initial lower undulating surface, determine the initial three-dimensional model of the fracturing fluid affected body;

[0078] Based on the processing of the initial three-dimensional model, determine the three-dimensional shape of the fracturing fluid affected body.

[0079] Specifically, as Figure 1 shown, first, two types of measurement points are arranged on the fracturing monitoring section to be used for microseismic monitoring and electromagnetic monitoring respectively. In some embodiments, referring to Figure 2 , the first measurement points are arranged in a "radial" shape, and the first measurement points specifically use microseismic geophones to collect microseismic signals; the second measurement points are arranged in a "grid" shape, and the second measurement points specifically use electromagnetic geophones to collect electric field signals through power supply in the metal wellbore. The microseismic geophones and electromagnetic geophones are arranged strictly in accordance with the specifications to ensure the signal-to-noise ratio of the microseismic signals and electric field signals.

[0080] Furthermore, by combining the microseismic method and the electromagnetic method, through comprehensive processing of the microseismic signals and electric field signals, the initial three-dimensional model of the fracturing fluid affected body can be determined, and then the initial three-dimensional model is continuously corrected and adjusted to finally determine the three-dimensional shape of the fracturing fluid affected body.

[0081] It can be understood that, referring to Figure 2 , the wellbore in the figure takes a horizontal well as an example, Figure 2 specifically, it is the top view projection of the horizontal plane. In some embodiments, the wellbore can be a vertical well. For a vertical well, the second measurement points need to be arranged in a "double-layer ring" shape.

[0082] It is understandable that the embodiments of the present invention effectively integrate the results of two methods, namely, microseismic monitoring technology and electromagnetic monitoring technology, to form a seismic-electric integrated fracturing monitoring and interpretation method. The microseismic monitoring technology provides the location information of the emission source and the distribution of fracture event points, and the electromagnetic monitoring technology provides the surface abnormal potential distribution. Based on the location information provided by the microseismic, an initial three-dimensional model of the fracturing fluid affected volume is established by comprehensively considering the distribution pattern of microseismic event points and the distribution pattern of electromagnetic abnormal potential. Then, inversion is carried out with the abnormal potential as a constraint, and the three-dimensional model of the fracturing fluid affected volume is continuously adjusted, so that the fitting error of the abnormal potential meets the agreed requirements. According to the finally obtained three-dimensional model, the shape and size of the fracturing fluid affected volume can be accurately represented, and thus the effective transformation volume range of the fracturing operation can be determined.

[0083] In some embodiments, referring to Figures 3 to 6 , based on the processing of microseismic signals and electric field signals, the initial planar distribution contour of the fracturing fluid affected volume is determined, including the following steps:

[0084] Process the microseismic signals to obtain the distribution of microseismic fracture event points;

[0085] Process the electric field signals to obtain the relative abnormal potential planar distribution;

[0086] According to the distribution of microseismic fracture event points, delineate the first planar distribution contour;

[0087] According to the relative abnormal potential planar distribution, delineate the second planar distribution contour;

[0088] According to the first planar distribution contour and the second planar distribution contour, determine the initial planar distribution contour.

[0089] Specifically, referring to Figure 3 , first, use the conventional microseismic processing means to process the microseismic signals. The conventional microseismic processing means include denoising the microseismic signals, identifying fracture events, establishing a velocity model, and performing source scanning and positioning processing, so as to obtain the distribution of microseismic fracture event points. It is understandable that the distribution of microseismic fracture event points is the distribution map composed of several microseismic fracture event points.

[0090] Furthermore, referring to Figure 4 , process the electric field signals, specifically: perform data preprocessing on the electric field signals to obtain the abnormal potential distribution U am , U am denoted as the actually measured potential signal; and further calculate the relative abnormal potential U per , and perform interpolation to form the relative abnormal potential planar distribution U ab .

[0091] Further, referring to Figure 5 , according to the distribution of microseismic rupture event points, the planar distribution contour C of microseismic event points is outlined in a man-machine interaction manner s , C s is the first planar distribution contour delineated; based on the relative abnormal absolute value of the abnormal potential distribution U am being equal to 5% as the boundary, the planar distribution contour C of the abnormal potential is delineated E , C E is the second planar distribution contour.

[0092] It should be noted that in some embodiments, in the X-Y axis plane (horizontal plane), the planar contour of microseismic events is outlined by man-machine interaction means. When outlining, it is inevitable to give play to the subjectivity of people, eliminate scattered event points in the distance, and connect the outermost event points in the densely distributed area one by one to obtain the first planar distribution contour C s , maintaining a certain smoothness when connecting, and ensuring that all uneliminated event points are within the contour line; the relative abnormal potential planar distribution U ab as a whole must show a decreasing trend from the center to the periphery. Taking the absolute value of the relative abnormal potential U per being equal to 5% as the boundary (if there is no value equal to 5%, the closest value shall prevail) to determine the second planar distribution contour C E .

[0093] Further, referring to Figure 6 , according to the above two planar distribution contours C s and C E , the initial planar distribution contour C0 of the fracturing fluid affected body is determined as C0=(C S + C E ) / 2. By integrating the planar distribution contour information obtained by the two methods, it is more accurate than using a single method.

[0094] In some embodiments, the electric field signal is processed to obtain the relative abnormal potential planar distribution, including the following steps:

[0095] Perform mean processing on the electric field signal monitored before fracturing to obtain the background field potential signal;

[0096] Subtract the background field potential signal from the electric field signal monitored during fracturing to obtain the actual measured potential signal;

[0097] Calculate the relative abnormal potential signal based on the background field potential signal and the actual measured potential signal;

[0098] Process the relative abnormal potential signal based on the inverse distance weighted interpolation algorithm to obtain the relative abnormal potential planar distribution.

[0099] Specifically, it can be understood that in some embodiments, electromagnetic monitoring must start half an hour before the fracturing begins, and the electric field signals monitored during this period before fracturing are averaged, and this average value is denoted as the background field potential signal U bg ; the electric field signals monitored during the period after the fracturing begins are denoted as U me ; subtracting U me from U bg gives the actual measured potential signal U am , that is, U am = U me - U bg .

[0100] Further, calculate the relative abnormal potential U per , and the relative abnormal potential is calculated by the following formula:

[0101] U per = ABS(U am / U bg ) × 100%,

[0102] where ABS represents the absolute value function. Using the inverse distance weighted interpolation algorithm, interpolate U per at a grid spacing of 2.5 meters to form the plane distribution of the relative abnormal potential U ab .

[0103] In some embodiments, referring to Figure 6 , according to the first plane distribution contour and the second plane distribution contour, determine the initial plane distribution contour, including the following steps:

[0104] Determine the center point, which is the midpoint of the line connecting the two intersections between the first plane distribution contour and the well trajectory;

[0105] Uniformly set a plurality of virtual rays at the center point, so that each virtual ray intersects with the first plane distribution contour and the second plane distribution contour respectively, and a plurality of first intersections and a plurality of second intersections are obtained accordingly;

[0106] Determine a plurality of initial contour points, and each initial contour point is the midpoint of the line connecting each first intersection and the corresponding second intersection;

[0107] Connect the plurality of initial contour points to determine the initial plane distribution contour.

[0108] Specifically, referring to Figure 6 , in some embodiments, in the X-Y axis plane, with the midpoint of the line connecting the two intersections of the first plane distribution contour C S and the well trajectory line as the center point O, perform 72 equal divisions at an interval of 5° at the center point O, and draw 72 virtual rays along the sides of the equal division angles, so that the 72 "virtual rays" respectively intersect with the contour Cs and C E intersect. Denote the intersection value of the virtual ray of the 0° angle and the contour C S as C S1 , and the intersection value of the virtual ray of the 0° angle and the contour C E as C E1 , and take the average value C 02 =(C S1 +C E1 ) / 2 as the new contour point value of the virtual ray of the 0° angle. By analogy, the new contour point values C 02 , C 03 , …, C 72 of the virtual rays in other different angular directions can be obtained in the same way. Connect C 01 , C 02 , C 03 , …, C 72 to obtain the initial planar distribution contour C0 of the fracturing fluid affected body, that is, generally expressed as C0=(C S +C E ) / 2.

[0109] It can be understood that in some embodiments, the angular interval can be appropriately reduced or increased according to actual needs. For example, it can be equally divided into 360 parts at 1° intervals to obtain 360 virtual rays; it can also be equally divided into 36 parts at 10° intervals to obtain 36 virtual rays.

[0110] In some embodiments, referring to Figure 7 , based on the processing of microseismic signals and electric field signals, the initial upper undulating surface and the initial lower undulating surface of the fracturing fluid affected body are determined, including the following steps:

[0111] According to the distribution of microseismic rupture event points and the initial planar distribution contour, outline the upper undulating surface and the lower undulating surface of the well trajectory horizontal plane;

[0112] According to the relative abnormal potential planar distribution, outline the relative abnormal undulating surface;

[0113] According to the upper undulating surface, the lower undulating surface and the relative abnormal undulating surface, determine the initial upper undulating surface and the initial lower undulating surface.

[0114] Specifically, it can be understood that determining the initial planar distribution contour C0 is to determine the affected range of the fracturing fluid affected body in the X-Y axis plane. Therefore, it is further necessary to determine the height contour of the fracturing fluid affected body on the Z axis based on the X-Y axis plane. Further referring to Figure 7 , it should be noted first that Figures 2 to 6 are all top-down schematic diagrams of the X-Y axis plane, while Figure 7Taking the X-Z axis as an example to show the longitudinal profile of the well trajectory and each undulating surface. First, based on the distribution of microseismic rupture event points and C0, determine the upper undulating surface S Su and the lower undulating surface S Sd ; then, based on U ab determine the relative abnormal undulating surface S E ; finally, based on S Su , S Sd , S E , the initial upper undulating surface S u and the initial lower undulating surface S d can be determined. S u and S d represent the height profile of the fracturing fluid swept body on the Z axis.

[0115] In some embodiments, referring to Figure 7 , based on the distribution of microseismic rupture event points and the initial plane distribution profile, outline the upper and lower undulating surfaces of the well trajectory horizontal plane, including the following steps:

[0116] Taking the initial plane distribution profile as the boundary, divide the range within the boundary into multiple regular grids;

[0117] Based on the distribution of microseismic rupture event points, determine the first three-dimensional position coordinates of each regular grid;

[0118] Use multiple first three-dimensional position coordinates to outline the upper and lower undulating surfaces.

[0119] Specifically, referring to Figure 7 , it can be understood that after removing the scattered event points in the distance, taking the initial plane distribution profile C0 as the boundary, the range within the boundary is meshed outward from the center point O at a preset interval to obtain multiple regular grids. In some embodiments, the regular grid can be a square with a preset side length of 5 meters.

[0120] Furthermore, take the maximum height among several microseismic rupture event points falling within the regular grid as the height value of the regular grid, and denote it as the first Z-axis position coordinate; take the center point of the regular grid as the plane position of the regular grid, and denote it as the first X-Y axis position coordinate. Therefore, the first three-dimensional position coordinate of each regular grid can be determined; at the same time, the regular grids without microseismic rupture event points do not need to be processed. Then, connect the multiple first three-dimensional position coordinates into a line along the well trajectory direction, and determine the height gap between the multiple first three-dimensional position coordinates through linear interpolation to make the connection smoother. Finally, the upper undulating surface S Su and the lower undulating surface S Sd are obtained.

[0121] It is understandable that when determining whether the microseismic rupture event point is within the regular grid, only the X-axis and Y-axis position coordinates of the microseismic rupture event point need to be considered whether they are within the regular grid, and the Z-axis position coordinate does not need to be considered; meanwhile, for the microseismic rupture event points located in the upper half of the well trajectory, the maximum height value is taken, and for the microseismic rupture event points located in the lower half of the well trajectory, the maximum value of the absolute value of the height is taken.

[0122] In some embodiments, referring to Figure 7 , according to the planar distribution of the relative abnormal potential, outlining the relatively abnormal undulating surface includes the following steps:

[0123] Determine the second three-dimensional position coordinates of each regular grid according to the planar distribution of the relative abnormal potential;

[0124] Use multiple second three-dimensional position coordinates to outline the relatively abnormal undulating surface.

[0125] Specifically, referring to Figure 7 , it is understandable that based on the above-mentioned well-divided regular grid, take the average value of several relative abnormal potential data points (including the points falling on the boundary of the regular grid) within each regular grid as the relative abnormal potential height value of this regular grid, and record it as the second Z-axis position coordinate; take the center point of the regular grid as the planar position corresponding to the relative abnormal potential height value, and record it as the second X-Y axis position coordinate. Therefore, the second three-dimensional position coordinates of each regular grid can be determined. Similarly, connect multiple second three-dimensional position coordinates to obtain the relatively abnormal undulating surface S E .

[0126] In some embodiments, referring to Figure 7 , according to the upper half undulating surface, the lower half undulating surface and the relatively abnormal undulating surface, determine the initial upper half undulating surface and the initial lower half undulating surface, including the following steps:

[0127] Respectively determine the maximum values of the absolute values of the heights of the upper half undulating surface, the lower half undulating surface and the relatively abnormal undulating surface to correspondingly obtain the first maximum height value, the second maximum height value and the third maximum height value;

[0128] Calculate the upper half amplification factor and the lower half amplification factor according to the first maximum height value, the second maximum height value and the third maximum height value;

[0129] Process the relatively abnormal undulating surface by using the upper half amplification factor and the lower half amplification factor to obtain the upper half relatively abnormal height node data and the lower half relatively abnormal height node data;

[0130] Perform superposition averaging on the upper half of the relative abnormal height node data and the upper half of the undulating surface to determine the initial upper half undulating surface;

[0131] Perform superposition averaging on the lower half of the relative abnormal height node data and the lower half of the undulating surface to determine the initial lower half undulating surface.

[0132] Specifically, referring to Figure 7 , it can be understood that the relative abnormal undulating surface S E reflects the longitudinal height undulation of the fracturing fluid affected body, but it is not equivalent to the longitudinal height and is not at the same level as the longitudinal height. Therefore, it is magnified based on the maximum absolute value of the height of each of the three undulating surfaces S Su , S Sd , S E to complete subsequent calculations.

[0133] Furthermore, denote the maximum absolute value of the height of each of the three undulating surfaces S Su , S sd , S E as the first height maximum value SU MAX , the second height maximum value SD MAX , and the third height maximum value SE MAX respectively; then calculate the upper half magnification factor K U = SU MAX / SE MAX , the lower half magnification factor K D = SD MAX / SE MAX ; then use the above magnification factors to magnify S E to reach the same order of magnitude as S Su , S Sd , so as to obtain the upper half relative abnormal height node data S eu = S E × K U and the lower half relative abnormal height node data S ed = S E × K D ; perform superposition averaging on S Su and S Eu to obtain the initial upper half undulating surface S u , perform superposition averaging on S Sd and S Ed to obtain the initial lower half undulating surface S d ;

[0134] It should be noted that the principle of superposition averaging is: if S Su and S Eu(S Sd and S Ed ) both have numerical values, then take the average of the two as the height value at this position; if only S Eu (S Ed ) has a numerical value, then take the value of S Eu (S Ed ) as the height value at this position.

[0135] In some embodiments, according to the initial plane distribution profile, the initial upper undulating surface, and the initial lower undulating surface, determine the initial three-dimensional model of the fracturing fluid swept body, including the following steps:

[0136] Assign zero values to the height values at the boundaries of the initial upper undulating surface and the initial lower undulating surface respectively, so that the initial upper undulating surface and the initial lower undulating surface are respectively connected to the initial plane distribution profile;

[0137] Determine the initial three-dimensional model with the initial plane distribution profile, the initial upper undulating surface, and the initial lower undulating surface as the boundaries.

[0138] Specifically, it can be understood that the actual fracturing fluid swept body should be gradually decreasing from the middle to the surrounding and tending to zero at the boundary, but the processed S u and S d may not be zero at the boundary, so further processing is required to make S u and S d zero at the boundary, while still maintaining the original spatial height undulation form. It should be noted that since the subsequent processing method only needs to maintain the initial model with spatial undulation form, the absolute size does not affect the result, so it can be processed in this way.

[0139] Furthermore, the specific processing method is as follows: Take the minimum values of S u and S d at the C0 nodes of the initial plane distribution profile as SU MIN and SD MIN respectively, and force the values of all nodes of S u and S d at C0 to be SU MIN and SD MIN respectively, and then subtract SU u and SD d from the values of all nodes of S MIN and S MIN respectively, so that the values at the contour boundaries of the initial upper undulating surface S u and the initial lower undulating surface S d are both zero; for S u and S dTaking the contour C0 interface as the integration surface and connecting them into a whole, the initial three-dimensional model V0 is obtained.

[0140] In some embodiments, based on the processing of the initial three-dimensional model, the three-dimensional shape of the fracturing fluid swept body is determined, including the following steps:

[0141] Establish a three-dimensional model coordinate system, and the origin of the three-dimensional model coordinate system is the center point;

[0142] Under the three-dimensional model coordinate system, the initial three-dimensional model is divided into multiple sub-division models according to a scale factor, and each sub-division model is a different unit ellipsoid;

[0143] Select any second measurement point as the first specified measurement point, and based on the potential expression at any point outside the conductive ellipsoid space, calculate the abnormal potential value of each sub-division model at the specified measurement point and accumulate them to obtain the first measurement point calculated abnormal potential value;

[0144] Update the specified measurement point to the next second measurement point to calculate the next measurement point calculated abnormal potential value, continuously update the specified measurement point until the multiple measurement point calculated abnormal potential values corresponding to all second measurement points are calculated, and then stop the update;

[0145] Compare the errors of the multiple measurement point calculated abnormal potential values to adjust the scale factor;

[0146] Determine the three-dimensional shape of the fracturing fluid swept body according to the finally adjusted scale factor.

[0147] Specifically, it can be understood that first, a three-dimensional model coordinate system is established for subsequent related calculations; then it should be noted that since the initial three-dimensional model V0 is an irregular three-dimensional body, it is almost impossible to calculate its electric potential distribution by analytical methods. At the same time, the initial three-dimensional model V0 only reflects the three-dimensional shape of the fracturing fluid swept body for the time being, and its specific size is unknown. Therefore, a scale factor needs to be introduced as a control variable to participate in subsequent calculations to determine the three-dimensional size of the swept body. Therefore, in some embodiments, according to the principle of electric potential superposition, the "sub-division and superposition" idea is adopted. First, the initial three-dimensional model V0 is scaled by a scale factor k to obtain the to-be-sub-divided model V1, and then the sub-division model V1 is divided into multiple unit ellipsoids with a length and width of 1 meter each but different heights, which can be specifically recorded as:

[0148]

[0149] Among them, represents different unit ellipsoids.

[0150] Further, according to the potential expression at any point outside the space of the conductive ellipsoid, calculate the abnormal potential value of each unit ellipsoid at the first second measurement point M, and according to the principle of superposition of electric potential, accumulate the abnormal potential values of all unit ellipsoids at the second measurement point M to obtain the calculated abnormal potential value at the first measurement point. The calculated abnormal potential value at the first measurement point represents the abnormal potential value U of V1 at the second measurement point M. m , which can be specifically recorded as:

[0151]

[0152] Among them, ξ0 is the ellipsoidal coordinate at the second measurement point M; I is the emission current; ρ is the resistivity of the underground medium, and a, b, and c are the length, width, and height of the unit ellipsoid respectively.

[0153] Further, by calculating in turn in the same way, the abnormal potential values of each unit ellipsoid at all the second measurement points can be obtained, that is, the calculated abnormal potential values at multiple measurement points, and can be specifically recorded as:

[0154] U total =(U1, U2, U3, …, U M , U M+1 , …, U N-1 , U N ),

[0155] Among them, each element in U total represents a calculated abnormal potential value at a measurement point.

[0156] Further, compare the errors of the calculated abnormal potential values at multiple measurement points. Specifically, compare U total with the above-mentioned actually measured potential signal U am , and the specific comparison method is:

[0157] If U total is much greater than U am , then adjust the above-mentioned proportional coefficient k in the decreasing direction;

[0158] If U total is much less than U am , then adjust the above-mentioned proportional coefficient k in the increasing direction;

[0159] If the error between U total and U am meets the preset requirements, then k is the proportional coefficient that meets the requirements; re-determine the to-be-meshed model V1 according to the determined proportional coefficient k after adjustment, and then finally determine the three-dimensional shape of the fracturing fluid swept body.

[0160] It should be noted that when performing the comparison between U total and U amWhen comparing the errors between them, in fact, the elements in U total are summed up to obtain U sum1 , and the elements in U am are summed up to obtain U sum2 . Then, by comparing U sum1 and U sum2 , the proportionality coefficient k is adjusted and determined accordingly.

[0161] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0162] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

[0163] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art in the technical field to which it pertains, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for monitoring and interpreting the wave propagation body of oil and gas fracturing based on the combination of seismic and electric methods, characterized in that, It includes the following steps: Arrange a plurality of first measuring points and a plurality of second measuring points on the fracturing monitoring section. The first measuring points are used for microseismic monitoring, and the second measuring points are used for electromagnetic monitoring; Collect microseismic signals of a plurality of the first measuring points and electric field signals of a plurality of the second measuring points; Based on the processing of the microseismic signals and the electric field signals, determine the initial planar distribution contour, the initial upper undulating surface and the initial lower undulating surface of the fracturing affected body; According to the initial planar distribution contour, the initial upper undulating surface and the initial lower undulating surface, determine the initial three-dimensional model of the fracturing affected body; Based on the processing of the initial three-dimensional model, determine the three-dimensional shape of the fracturing affected body; Based on the processing of the microseismic signals and the electric field signals, determining the initial planar distribution contour of the fracturing affected body includes the following steps: Process the microseismic signals to obtain the distribution of microseismic fracture event points; Process the electric field signals to obtain the relative abnormal potential planar distribution; According to the distribution of the microseismic fracture event points, delineate the first planar distribution contour; According to the relative abnormal potential planar distribution, delineate the second planar distribution contour; According to the first planar distribution contour and the second planar distribution contour, determine the initial planar distribution contour; Based on the processing of the microseismic signals and the electric field signals, determining the initial upper undulating surface and the initial lower undulating surface of the fracturing affected body includes the following steps: According to the distribution of the microseismic fracture event points and the initial planar distribution contour, sketch the upper undulating surface and the lower undulating surface; According to the relative abnormal potential planar distribution, sketch the relative abnormal undulating surface; According to the upper undulating surface, the lower undulating surface and the relative abnormal undulating surface, determine the initial upper undulating surface and the initial lower undulating surface; The step of determining the initial upper undulating surface and the initial lower undulating surface according to the upper undulating surface, the lower undulating surface and the relative abnormal undulating surface includes the following steps: Respectively determine the maximum absolute value of the height of the upper undulating surface, the lower undulating surface and the relative abnormal undulating surface to correspondingly obtain the first height maximum value, the second height maximum value and the third height maximum value; According to the first height maximum value, the second height maximum value and the third height maximum value, calculate the upper part amplification factor and the lower part amplification factor; Use the upper part amplification factor and the lower part amplification factor to process the relative abnormal undulating surface to obtain the upper part relative abnormal height node data and the lower part relative abnormal height node data; Perform superposition averaging processing on the upper part relative abnormal height node data and the upper undulating surface to determine the initial upper undulating surface; Perform superposition averaging processing on the relatively abnormal height node data of the lower half part and the undulating surface of the lower half part to determine the initial undulating surface of the lower half part.

2. The method for monitoring and interpreting the oil and gas fracturing wave propagation body based on the combination of seismic and electric waves according to claim 1, wherein The processing of the electric field signal to obtain the relatively abnormal potential plane distribution includes the following steps: Perform averaging processing on the electric field signal monitored before fracturing to obtain the background field potential signal; Subtract the electric field signal monitored during fracturing from the background field potential signal to obtain the actual measured potential signal; Calculate the relatively abnormal potential signal based on the background field potential signal and the actual measured potential signal; Process the relatively abnormal potential signal based on the inverse distance weighted interpolation algorithm to obtain the relatively abnormal potential plane distribution.

3. The method for monitoring and interpreting the hydraulic fracturing wave propagation body based on the combination of seismic and electric methods according to claim 2, characterized in that The determination of the initial plane distribution profile according to the first plane distribution profile and the second plane distribution profile includes the following steps: Determine the center point, which is the midpoint of the line connecting two intersection points between the first plane distribution profile and the well trajectory; Uniformly set a plurality of virtual rays at the center point so that each virtual ray intersects with the first plane distribution profile and the second plane distribution profile respectively, and correspondingly obtain a plurality of first intersection points and a plurality of second intersection points; Determine a plurality of initial profile points, and each initial profile point is the midpoint of the line connecting each first intersection point and the corresponding second intersection point; Connect the plurality of initial profile points to determine the initial plane distribution profile.

4. The method for monitoring and interpreting the oil and gas fracturing wave propagation body based on the combination of seismic and electric waves according to claim 1, characterized in that, The delineation of the undulating surface of the upper half part and the undulating surface of the lower half part according to the microseismic fracture event point distribution and the initial plane distribution profile includes the following steps: Take the initial plane distribution profile as the boundary and divide the range within the boundary into a plurality of regular grids; Determine the first three-dimensional position coordinates of each regular grid according to the microseismic fracture event point distribution; Use the plurality of first three-dimensional position coordinates to delineate the undulating surface of the upper half part and the undulating surface of the lower half part.

5. The method for monitoring and interpreting the hydraulic fracturing wavefront of oil and gas based on the combination of seismic and electric waves according to claim 4, characterized in that, The delineation of the relatively abnormal undulating surface according to the relatively abnormal potential plane distribution includes the following steps: Determine the second three-dimensional position coordinates of each regular grid according to the relatively abnormal potential plane distribution; Use the plurality of second three-dimensional position coordinates to delineate the relatively abnormal undulating surface.

6. The method for monitoring and interpreting the hydraulic fracturing wave propagation body based on the combination of seismic and electric waves according to claim 1, characterized in that The determination of the initial three-dimensional model of the fracture-affected body according to the initial plane distribution profile, the initial undulating surface of the upper half part, and the initial undulating surface of the lower half part includes the following steps: Perform a zero-value assignment process on the height values at the boundaries of the initial undulating surface of the upper half part and the initial undulating surface of the lower half part respectively, so that the initial undulating surface of the upper half part and the initial undulating surface of the lower half part are respectively connected to the initial plane distribution profile; Take the initial plane distribution profile, the initial undulating surface of the upper half part, and the initial undulating surface of the lower half part as the boundaries to determine the initial three-dimensional model.

7. The method for monitoring and interpreting the hydraulic fracturing wave propagation body based on the combination of seismic and electric methods according to claim 3, characterized in that, The determination of the three-dimensional shape of the fracture-affected body based on the processing of the initial three-dimensional model includes the following steps: Establish a three-dimensional model coordinate system, and the origin of the three-dimensional model coordinate system is the center point; Under the three-dimensional model coordinate system, the initial three-dimensional model is divided into a plurality of sub-divided models according to a scale factor, and each of the sub-divided models is a different unit ellipsoid; Select any one of the second measurement points as the first specified measurement point, and based on the potential expression at any point outside the conductive ellipsoid space, calculate the abnormal potential value of each of the sub-divided models at the specified measurement point and accumulate them to obtain the first measurement point calculated abnormal potential value; Update the specified measurement point to the next second measurement point to calculate the next measurement point calculated abnormal potential value, and continuously update the specified measurement point until the abnormal potential values calculated for all the second measurement points are obtained, and then stop the update; Compare the errors of the abnormal potential values calculated for multiple measurement points to adjust the scale factor; Determine the three-dimensional shape of the fracturing wave body according to the scale factor finally adjusted.

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