A fracturing monitoring system and method based on electromagnetic array

Abstract

The present invention relates to the field of fracturing monitoring technology, and in particular to a fracturing monitoring system and method based on an electromagnetic array, wherein the system comprises: a fracturing control module for controlling the injection volume and injection pressure of fracturing fluid; a data acquisition module, comprising an electromagnetic sensor array and a microseismic sensor array; a data analysis module for performing data analysis based on electromagnetic signals detected by the electromagnetic sensor array and microseismic signals detected by the microseismic sensor array to obtain the fracturing range of the current fracturing area, and determining the crack morphology and crack growth within the fracturing range based on changes in the electromagnetic signal and the injection volume of the fracturing fluid; and a control adjustment module for making adjustments based on the crack morphology and crack growth. The present invention can improve the accuracy of monitoring the fracturing effect by combining microseismic monitoring and electromagnetic array monitoring, and can change the fracturing method based on the real-time monitoring effect to improve the final fracturing effect.

Description

Technical Field

[0001] The present invention relates to the field of fracturing monitoring technology, and in particular to a fracturing monitoring system and method based on an electromagnetic array Background Art

[0002] In the oil field, fracturing refers to the process of using a surface high-pressure pump to squeeze a large amount of fracturing fluid with high viscosity, proppant and low resistance into the formation through the wellbore during oil or gas production, forcing the formation pressure to increase, causing the rock to break and produce cracks. During the process of crack formation, the fracturing fluid advances along the cracks, which can, on the one hand, make the cracks continue to extend forward, and on the other hand, fill the cracks and support them so that they do not close, leaving one or more cracks of different shapes in the oil layer, so that a new fluid channel is established between the oil layer and the wellbore. After fracturing, the output of oil and gas wells generally increases significantly.

[0003] The monitoring methods used in the conventional scheme include downhole microseismic method and ground electromagnetic method. The downhole microseismic method is based on the principle that fluid injection can induce microseismic events. It uses the response characteristics of the returned wave field to the fractures of the gas reservoir to perform wave field response analysis, which can monitor the location and extent of the fracture event; and when the fracture space filled with low-resistance fracturing fluid is energized, a current emission source can be formed. The electromagnetic monitoring technology can monitor the shape and size of the body affected by the fracturing fluid. The increase in pressure can produce some stress fractures at the far end. The seismic wave signal can respond to and locate the fracture event, but it is unknown whether the far-end fracture caused by the fracture event is connected to the main fracture space or whether there is fracturing fluid injection. If it is not connected or filled with fracturing fluid, it is an invalid fracture, and the microseismic monitoring technology cannot judge this situation. In addition, due to the continuous attenuation of the signal when the seismic wave propagates in the formation, the high noise of the wellbore environment, the pump pressure and pump speed, etc., it is not very effective and intuitive to describe the growth process, geometry and spatial distribution of the fractures in the reservoir transformed by fracturing fluid. The ground electromagnetic method is sensitive to the parameters of the oil and gas reservoir such as porosity, permeability and saturation, and has the advantages of high efficiency, low cost and strong adaptability to complex surfaces. The electromagnetic monitoring technology is based on the spatial distribution characteristics of the fracturing fluid affected body, but it is difficult to determine the exact position of the fracturing fluid affected body by the ground electric field signal. If the positioning is inaccurate, it will affect the accuracy of the interpretation of the spatial distribution characteristics. Therefore, it is impossible to determine the effective transformation volume range by relying solely on microseismic monitoring technology; and the interpretation accuracy of the shape and size of the fracturing fluid affected body by relying solely on electromagnetic monitoring technology is reduced, that is, it is difficult to accurately monitor the effective transformation volume range of the fracturing operation using any single method.

[0004] Chinese patent publication number CN108983298A discloses a four-dimensional real-time electromagnetic monitoring method and system for oil and gas fracturing, the method comprising: during the construction process of each fracturing section, electromagnetic wave excitation signals of different frequencies are emitted along the direction of the fracturing pilot well to obtain the electric field signals before fracturing and the electric field signals during fracturing at several monitoring points within the monitoring range of the fracturing pilot well; based on the electric field signals before fracturing and the electric field signals during fracturing, the residual electric field of each monitoring point is obtained, and the electric field residual degree is obtained according to the residual electric field; based on the electric field residual degree of each monitoring point, the spatial distribution range and fracturing effect of the fracturing cracks are obtained, and the distribution range of the horizontal and vertical distribution cracks of the fracturing section is monitored by emitting electromagnetic wave excitation signals and receiving the feedback electric field signals at the same time, and the variation characteristics of the electric field signals in space and time are used to monitor the distribution range of the horizontal and vertical distribution cracks of the fracturing section; the variation curve characteristics of the electric field signal over time are obtained by continuous observation to analyze the crack characteristics and judge whether the cracks are main large cracks or uniform crack networks.

[0005] It can be seen that the above invention has the following problems: it is difficult to determine the exact position of the fracturing section based only on the electric field signal. If the positioning is inaccurate, it will affect the accuracy of the interpretation of the spatial distribution characteristics. Summary of the invention

[0006] To this end, the present invention provides a fracturing monitoring system and method based on an electromagnetic array, which is used to overcome the problems in the prior art of low accuracy in monitoring the fracturing effect based only on electric field signals and inability to change the fracturing mode according to real-time monitoring results.

[0007] To achieve the above objectives, on the one hand, the present invention provides a fracturing monitoring system based on an electromagnetic array, comprising:

[0008] A fracturing control module, used to control the injection volume and injection pressure of the fracturing fluid;

[0009] A data acquisition module, comprising an electromagnetic sensor array disposed in a monitoring area for continuously monitoring electromagnetic signals of a current fracturing area, and a microseismic sensor array disposed in the monitoring area and not in a position of the electromagnetic sensor array for continuously monitoring microseismic signals of the current fracturing area;

[0010] a data analysis module, which is connected to the fracturing control module and the data acquisition module respectively, and is used to perform data analysis based on the electromagnetic signal detected by the electromagnetic sensor array and the microseismic signal detected by the microseismic sensor array to obtain the fracturing range of the current fracturing area, and determine the fracture morphology and fracture growth within the fracturing range based on the change of the electromagnetic signal and the injection amount of the fracturing fluid;

[0011] A control adjustment module, which is connected to the data analysis module and the fracturing control module respectively, and is used to make adjustments according to the fracture morphology and fracture growth conditions;

[0012] wherein, judging whether the crack morphology and crack growth conditions meet the expected standards;

[0013] If not, determining a fracturing adjustment method according to the crack morphology and crack growth conditions, including a first adjustment method, a second adjustment method, and a third adjustment method;

[0014] In the first adjustment mode, the current fracturing area is abandoned and the injection of fracturing fluid is stopped;

[0015] In the second adjustment mode, the injection of the fracturing fluid is suspended, and the suspension time is a first preset time;

[0016] In the third adjustment mode, the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change of the electromagnetic signal;

[0017] If it is in compliance, the fracturing conditions in the future target time period are predicted according to the fracture morphology and fracture growth conditions, and the injection amount and injection pressure of the fracturing fluid are adjusted according to the prediction results.

[0018] Furthermore, the data analysis module determines the abnormal electromagnetic plane distribution according to the continuously monitored electromagnetic signals, determines the microseismic abnormal point distribution according to the continuously monitored microseismic signals, and determines the fracturing range of the current fracturing area according to the abnormal electromagnetic plane distribution and the microseismic abnormal point distribution.

[0019] Furthermore, the data analysis module determines the fracture morphology within the fracturing range according to the change between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment.

[0020] Furthermore, the data analysis module determines the growth of cracks within the fracturing range according to the changes in the continuously detected electromagnetic signals and the comparison between the injection volume of the fracturing fluid and the initial injection volume of the fracturing fluid.

[0021] Furthermore, the expected standard in the control and adjustment module is that the crack morphology is a first preset crack morphology and the crack growth condition is a first preset growth condition.

[0022] Furthermore, the control and adjustment module determines the fracturing adjustment method according to the crack morphology and crack growth conditions.

[0023] in,

[0024] If the crack shape is the second preset crack shape, determining the fracturing adjustment mode to be the first adjustment mode;

[0025] If the crack morphology is the first preset crack morphology and the crack growth condition is the second preset growth condition, determining the fracturing adjustment mode to be the second adjustment mode;

[0026] If the crack morphology is the first preset crack morphology and the crack growth condition is the third preset growth condition, the fracturing adjustment method is determined to be the third adjustment method.

[0027] Furthermore, in the third adjustment mode, the control adjustment module determines the adjustment amount of the injection pressure of the fracturing fluid according to the change amount of the electromagnetic signal amplitude between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment.

[0028] Furthermore, the electromagnetic sensors in the electromagnetic sensor array in the data acquisition module are evenly distributed in a grid shape within the monitoring area with the horizontal well as the axis; and the microseismic sensors in the microseismic sensor array are radially distributed at equal distances outward from the center of the monitoring area.

[0029] Furthermore, the first preset crack morphology is a uniform network of cracks, and the second preset crack morphology is mainly large cracks; the first preset growth condition is that the crack growth rate is greater than the first preset growth rate and less than the second preset growth rate, the second preset growth condition is that the crack growth rate is not less than the second preset growth rate, and the third preset growth condition is that the crack growth rate is not greater than the first preset growth rate; wherein the first preset growth rate is less than the second preset growth rate.

[0030] On the other hand, the present invention also provides a fracturing monitoring method, comprising:

[0031] Step S1, obtaining the initial injection volume and initial injection pressure of the fracturing fluid;

[0032] Step S2, obtaining a number of electromagnetic signals and a number of microseismic signals in a critical time period of the current fracturing area;

[0033] Step S3, determining the fracturing range of the current fracturing area according to the plurality of electromagnetic signals and the plurality of microseismic signals, and determining the fracture morphology and fracture growth within the fracturing range according to the change of the electromagnetic signals and the initial injection volume of the fracturing fluid;

[0034] Step S4, adjusting according to the crack morphology and crack growth;

[0035] wherein, judging whether the crack morphology and crack growth conditions meet the expected standards;

[0036] If not, determining a fracturing adjustment method according to the crack morphology and crack growth conditions, including a first adjustment method, a second adjustment method, and a third adjustment method;

[0037] In the first adjustment mode, the current fracturing area is abandoned and the injection of fracturing fluid is stopped;

[0038] In the second adjustment mode, the injection of the fracturing fluid is suspended, and the suspension time is a first preset time;

[0039] In the third adjustment mode, the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change of the electromagnetic signal;

[0040] If it is in compliance, the fracturing conditions in the future target time period are predicted according to the fracture morphology and fracture growth conditions, and the injection amount and injection pressure of the fracturing fluid are adjusted according to the prediction results.

[0041] Compared with the prior art, the beneficial effect of the present invention is that the present invention controls the injection amount and injection pressure of the fracturing fluid by setting a fracturing control module, and can adjust in real time according to the monitoring situation. By setting a data acquisition module, the electromagnetic signal and microseismic signal of the current fracturing area are continuously monitored according to the electromagnetic sensor array and microseismic sensor array set in the monitoring area, which can provide a data basis for the subsequent determination of the fracturing range of the current fracturing area. The accuracy of fracturing monitoring can be improved by combining the electromagnetic sensor array and the microseismic sensor array to monitor the fracturing area. By setting a data analysis module, the electromagnetic signal and microseismic signal collected by the data acquisition module are analyzed to obtain the fracturing range of the current fracturing area. After fracturing, the injection of fracturing fluid will change the electromagnetic signal of the fracturing area. Therefore, according to the change of the electromagnetic signal and the injection amount of the fracturing fluid, the crack morphology and crack growth within the fracturing range can be determined. By controlling the adjustment module to determine the fracturing adjustment method and the injection amount and injection pressure of the fracturing fluid according to the crack morphology and crack growth, the fracturing quality of the subsequent stage can be effectively improved.

[0042] Furthermore, the data analysis module of the present invention can determine the fracturing range of the current fracturing area by monitoring the microseismic signals generated by formation rupture during the fracturing process through the microseismic sensor array and the electromagnetic signal changes caused by the fracturing fluid seeping into the cracks through the electromagnetic sensor array. By combining the two methods to make judgments, the accuracy of the determined fracturing range can be improved.

[0043] Furthermore, since there is a difference between the electromagnetic signals detected by the fracturing fluid infiltrating the cracks after fracturing and those monitored by the formation before fracturing, the data analysis module can determine the crack morphology within the fracturing range based on the changes in the electromagnetic signals detected before fracturing and the electromagnetic signals detected at the current moment, thereby improving the accuracy and efficiency of determining the crack morphology.

[0044] Furthermore, the data analysis module of the present invention determines the crack growth within the fracturing range by continuously detecting changes in electromagnetic signals, combining the injection volume of the fracturing fluid with the initial injection volume of the fracturing fluid, thereby improving the accuracy of determining the crack growth within the fracturing range.

[0045] Furthermore, the control adjustment module of the present invention determines the fracturing adjustment mode according to the crack morphology and crack growth conditions, which can improve the subsequent fracturing effect, reduce resource waste, and improve production quality.

[0046] Furthermore, since different crack morphologies will affect the amount of fracturing fluid infiltration, thereby affecting the amplitude change of the electromagnetic signal, the adjustment amount of the fracturing fluid injection pressure can be determined based on the change in the electromagnetic signal amplitude between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment, which can improve the subsequent fracturing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural block diagram of the electromagnetic array-based fracturing monitoring system of the present invention;

[0048] Figure 2 It is a flow chart of the electromagnetic array-based fracturing monitoring system of the present invention;

[0049] Figure 3 It is a logic judgment diagram of the fracturing adjustment method according to an embodiment of the present invention;

[0050] Figure 4 is a flow chart of the fracturing monitoring method of the present invention;

[0051] Figure 5 The figure is a schematic diagram of the deployment of the electromagnetic sensor array and the microseismic sensor array in the monitoring area according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0053] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0054] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0055] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] See also Figure 1 and Figure 2 As shown, Figure 1 It is a structural block diagram of the electromagnetic array-based fracturing monitoring system of the present invention; Figure 2 It is a flow chart of the electromagnetic array-based fracturing monitoring system of the present invention;

[0057] The present invention provides a fracturing monitoring system based on an electromagnetic array, comprising:

[0058] A fracturing control module, used to control the injection volume and injection pressure of the fracturing fluid;

[0059] During implementation, fracturing fluid is injected into the wellbore at an initial injection volume and initial injection pressure. Generally, based on historical fracturing conditions, statistical analysis can be performed on the characteristics of each formation, crack characteristics after fracturing, and oil and gas production to determine the initial injection volume and initial injection pressure of the fracturing fluid corresponding to the current fracturing area.

[0060] A data acquisition module, comprising an electromagnetic sensor array disposed in a monitoring area for continuously monitoring electromagnetic signals of a current fracturing area, and a microseismic sensor array disposed in the monitoring area and not in a position of the electromagnetic sensor array for continuously monitoring microseismic signals of the current fracturing area;

[0061] It should be noted that the location and extent of the rupture events in the formation during the fracturing process can be determined by monitoring the characteristics of the seismic waves caused by the rupture through the microseismic sensor array, but the entry of fracturing fluid into the cracks does not cause seismic waves; after fracturing, the fracturing fluid is filled into the cracks and powered through the wellbore to form a transmitting source. Changes in the fracturing fluid will cause the shape and size of the transmitting source to change, thereby causing changes in the electromagnetic signal. Therefore, the changes in the electromagnetic signal monitored by the electromagnetic sensor array can determine the crack morphology and crack growth at the fracturing fluid filling position.

[0062] See also Figure 5 , which is a schematic diagram of the layout of the electromagnetic sensor array and the microseismic sensor array in the monitoring area according to an embodiment of the present invention;

[0063] Specifically, the electromagnetic sensors in the electromagnetic sensor array in the data acquisition module are evenly distributed in a grid shape within the monitoring area with the horizontal well as the axis; the microseismic sensors in the microseismic sensor array are radially distributed at equal distances outward from the center of the monitoring area.

[0064] In implementation, the layout spacing distances of the electromagnetic sensors and the microseismic sensors may be determined according to the specific scope of the current fracturing area and the performance characteristics of the electromagnetic sensors and the microseismic sensors.

[0065] a data analysis module, which is connected to the fracturing control module and the data acquisition module respectively, and is used to perform data analysis based on the electromagnetic signal detected by the electromagnetic sensor array and the microseismic signal detected by the microseismic sensor array to obtain the fracturing range of the current fracturing area, and determine the crack morphology within the fracturing range according to the change of the electromagnetic signal, and determine the crack growth within the fracturing range according to the change of the electromagnetic signal and the injection amount of the fracturing fluid;

[0066] Specifically, the data analysis module determines the abnormal electromagnetic plane distribution according to the continuously monitored electromagnetic signals, determines the microseismic abnormal point distribution according to the continuously monitored microseismic signals, and determines the fracturing range of the current fracturing area according to the abnormal electromagnetic plane distribution and the microseismic abnormal point distribution.

[0067] In the implementation, the microseismic signal is preprocessed to obtain the distribution of microseismic abnormal points; the data preprocessing includes conventional technical means such as denoising, rupture event identification, velocity model establishment, and source scanning and positioning processing, which will not be described here. The electromagnetic signal monitored before fracturing is processed by averaging to obtain the initial electromagnetic signal; the electromagnetic signal monitored during fracturing is subtracted from the initial electromagnetic signal to obtain the fracturing electromagnetic signal; the relative abnormal electromagnetic signal XD=abs(YD / CD)×100% is determined based on the initial electromagnetic signal CD and the fracturing electromagnetic signal YD; abs() is a preset absolute value determination function; the relative abnormal electromagnetic signal is processed based on the inverse distance weighted interpolation algorithm to obtain the abnormal electromagnetic plane distribution.

[0068] Specifically, "crack growth" in the field of oil fracturing is explained as "the generation and distribution of artificial cracks."

[0069] The data analysis module of the present invention can determine the fracturing range of the current fracturing area by monitoring the microseismic signals generated by formation rupture during the fracturing process through the microseismic sensor array and the electromagnetic signal changes caused by the fracturing fluid seeping into the cracks monitored by the electromagnetic sensor array. By combining the two methods, the accuracy of the determined fracturing range can be improved.

[0070] Specifically, the data analysis module determines the fracture morphology within the fracturing range according to the change between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment.

[0071] In implementation, the distribution of the fracturing fluid at the current moment is determined by the change between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment monitored by each electromagnetic sensor in the electromagnetic sensor array, thereby determining the fracture morphology within the fracturing range at the current moment.

[0072] Since there is a difference between the electromagnetic signals detected by the fracturing fluid infiltrating the cracks after fracturing and those monitored in the formation before fracturing, the data analysis module can determine the crack morphology within the fracturing range based on the changes in the electromagnetic signals detected before fracturing and the electromagnetic signals detected at the current moment, thereby improving the accuracy and efficiency of determining the crack morphology.

[0073] Specifically, the data analysis module determines the growth of cracks within the fracturing range according to the changes in the continuously detected electromagnetic signals and the comparison between the injection volume of the fracturing fluid and the initial injection volume of the fracturing fluid.

[0074] In practice, as the fracturing process continues to change, the cracks will continue to change. As the fracturing fluid is injected, the fracturing fluid will continue to fill the cracks, causing the electromagnetic signals detected by each electromagnetic sensor to change continuously. The crack growth is preliminarily judged based on the changes in the electromagnetic signals continuously detected by each electromagnetic sensor. If the injection volume of the fracturing fluid is less than the initial injection volume of the fracturing fluid, it means that the crack growth rate is relatively slow, otherwise, it means that the crack growth rate is relatively fast.

[0075] The data analysis module of the present invention determines the crack growth within the fracturing range by continuously detecting changes in electromagnetic signals, combining the injection volume of the fracturing fluid with the initial injection volume of the fracturing fluid, thereby improving the accuracy of determining the crack growth within the fracturing range.

[0076] See also Figure 3 As shown, it is a logic judgment diagram of the fracturing adjustment method according to an embodiment of the present invention;

[0077] A control adjustment module, which is connected to the data analysis module and the fracturing control module respectively, and is used to make adjustments according to the fracture morphology and fracture growth conditions;

[0078] wherein, judging whether the crack morphology and crack growth conditions meet the expected standards;

[0079] If not, determining a fracturing adjustment method according to the crack morphology and crack growth conditions, including a first adjustment method, a second adjustment method, and a third adjustment method;

[0080] In the first adjustment mode, the current fracturing area is abandoned and the injection of fracturing fluid is stopped;

[0081] In the second adjustment mode, the injection of the fracturing fluid is suspended, and the suspension time is a first preset time;

[0082] In the third adjustment mode, the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change of the electromagnetic signal;

[0083] If it is in compliance, the fracturing conditions in the future target time period are predicted according to the fracture morphology and fracture growth conditions, and the injection amount and injection pressure of the fracturing fluid are adjusted according to the prediction results.

[0084] In implementation, the length of the target time period can be determined by the actual implementation personnel according to the actual situation. If the fracture morphology and fracture growth in the future target time period in the prediction results meet the expected standards, the production capacity can be predicted, and the injection volume and injection pressure of the fracturing fluid can be adjusted according to the actual production requirements and the production capacity prediction results. If the predicted production capacity is less than the actual production requirements, the injection volume and injection pressure of the fracturing fluid can be increased within the adjustment threshold range to increase the scope and diffusivity of the fractures, thereby increasing production capacity and improving production quality.

[0085] The control adjustment module of the present invention determines the fracturing adjustment mode according to the crack morphology and crack growth conditions, which can improve the subsequent fracturing effect, reduce resource waste, and improve production quality.

[0086] Specifically, the expected standard in the control adjustment module is that the crack morphology is a first preset crack morphology and the crack growth condition is a first preset growth condition.

[0087] Specifically, the control and adjustment module determines the fracturing adjustment method according to the crack morphology and crack growth conditions.

[0088] in,

[0089] If the crack shape is the second preset crack shape, determining the fracturing adjustment mode to be the first adjustment mode;

[0090] If the crack morphology is the first preset crack morphology and the crack growth condition is the second preset growth condition, determining the fracturing adjustment mode to be the second adjustment mode;

[0091] If the crack morphology is the first preset crack morphology and the crack growth condition is the third preset growth condition, the fracturing adjustment method is determined to be the third adjustment method.

[0092] Specifically, in the third adjustment mode, the control adjustment module determines the adjustment amount of the injection pressure of the fracturing fluid according to the change amount of the electromagnetic signal amplitude between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment.

[0093] In implementation, the adjustment amount of the injection pressure of the fracturing fluid is P=P0 / (abs(U-U0) / U0)-P0, where P0 is the initial injection pressure of the fracturing fluid, U is the electromagnetic signal amplitude detected at the current moment, and U0 is the electromagnetic signal amplitude detected before fracturing.

[0094] Since different crack morphologies will affect the amount of fracturing fluid infiltration, thereby affecting the amplitude change of the electromagnetic signal, the adjustment amount of the fracturing fluid injection pressure can be determined based on the change in the electromagnetic signal amplitude between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment, which can improve the subsequent fracturing effect.

[0095] Specifically, the first preset crack morphology is a uniform network of cracks, and the second preset crack morphology is mainly large cracks; the first preset growth condition is that the crack growth rate is greater than the first preset growth rate and less than the second preset growth rate, the second preset growth condition is that the crack growth rate is not less than the second preset growth rate, and the third preset growth condition is that the crack growth rate is not greater than the first preset growth rate; wherein the first preset growth rate is less than the second preset growth rate.

[0096] In implementation, the first adjustment method corresponds to a crack morphology that is mainly large cracks, the main large cracks have a small range, the crack diffusivity is relatively low, the fracturing effect is relatively poor, and it is not conducive to production. Therefore, under the first adjustment method, the current fracturing area should be abandoned and the injection of fracturing fluid should be stopped to avoid waste of resources. The second adjustment method corresponds to a crack morphology that is uniform mesh and the crack growth condition is that the crack growth rate is not less than the second preset growth rate. The crack growth rate is relatively fast. The range of uniform mesh is large, the crack diffusivity is relatively high, and the fracturing effect is relatively good. It is an ideal crack morphology, but the crack growth rate is relatively fast. The injection of fracturing fluid may cause abnormal rupture of the surrounding formations. If there are rock blocks falling into the fracturing fluid, it will not only affect the subsequent electromagnetic signal monitoring, but also be not conducive to production. Therefore, the injection of fracturing fluid is suspended, and the suspension time is the first preset time. The third adjustment method corresponds to a crack morphology that is uniform mesh and the crack growth condition is that the crack growth rate is not greater than the first preset growth rate. The crack growth rate is relatively slow. The injection pressure of the fracturing fluid can be adjusted to increase the range and diffusivity of the crack.

[0097] It should be noted that the actual implementers can set the first preset growth rate and the second preset growth rate based on the expert system according to the actual situation, or determine them by statistical analysis based on the crack growth rate of the fracturing process in historical data.

[0098] The present invention controls the injection amount and injection pressure of the fracturing fluid by setting a fracturing control module, and can adjust in real time according to the monitoring situation. By setting a data acquisition module, the electromagnetic signal and microseismic signal of the current fracturing area are continuously monitored according to the electromagnetic sensor array and microseismic sensor array set in the monitoring area, which can provide a data basis for the subsequent determination of the fracturing range of the current fracturing area. The accuracy of fracturing monitoring can be improved by combining the electromagnetic sensor array and the microseismic sensor array to monitor the fracturing area. By setting a data analysis module, the electromagnetic signal and microseismic signal collected by the data acquisition module are analyzed to obtain the fracturing range of the current fracturing area. The injection of fracturing fluid after fracturing will change the electromagnetic signal of the fracturing area, so the crack morphology and crack growth within the fracturing range can be determined according to the change of the electromagnetic signal and the injection amount of the fracturing fluid. By controlling the adjustment module to determine the fracturing adjustment method and the injection amount and injection pressure of the fracturing fluid according to the crack morphology and crack growth, the fracturing quality of the subsequent stage can be effectively improved.

[0099] See also Figure 4 As shown, it is a flow chart of the fracturing monitoring method of the present invention;

[0100] The present invention also provides a fracturing monitoring method, comprising:

[0101] Step S1, obtaining the initial injection volume and initial injection pressure of the fracturing fluid;

[0102] Step S2, obtaining a number of electromagnetic signals and a number of microseismic signals in a critical time period of the current fracturing area;

[0103] Step S3, determining the fracturing range of the current fracturing area according to the plurality of electromagnetic signals and the plurality of microseismic signals, and determining the fracture morphology and fracture growth within the fracturing range according to the change of the electromagnetic signals and the initial injection volume of the fracturing fluid;

[0104] Step S4, adjusting according to the crack morphology and crack growth;

[0105] wherein, judging whether the crack morphology and crack growth conditions meet the expected standards;

[0106] If not, determining a fracturing adjustment method according to the crack morphology and crack growth conditions, including a first adjustment method, a second adjustment method, and a third adjustment method;

[0107] In the first adjustment mode, the current fracturing area is abandoned and the injection of fracturing fluid is stopped;

[0108] In the second adjustment mode, the injection of the fracturing fluid is suspended, and the suspension time is a first preset time;

[0109] In the third adjustment mode, the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change of the electromagnetic signal;

[0110] If it is in compliance, the fracturing conditions in the future target time period are predicted according to the fracture morphology and fracture growth conditions, and the injection amount and injection pressure of the fracturing fluid are adjusted according to the prediction results.

[0111] Specifically, the fracturing monitoring method provided by the present invention can be applied to the above-mentioned electromagnetic array-based fracturing monitoring system to achieve the same technical effect, which will not be described in detail here.

[0112] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A fracturing monitoring system based on an electromagnetic array, characterized in that: include: A fracturing control module, used to control the injection volume and injection pressure of the fracturing fluid; A data acquisition module, comprising an electromagnetic sensor array disposed in a monitoring area for continuously monitoring electromagnetic signals of a current fracturing area, and a microseismic sensor array disposed in the monitoring area and not in a position of the electromagnetic sensor array for continuously monitoring microseismic signals of the current fracturing area; a data analysis module, which is connected to the fracturing control module and the data acquisition module respectively, and is used to perform data analysis based on the electromagnetic signal detected by the electromagnetic sensor array and the microseismic signal detected by the microseismic sensor array to obtain the fracturing range of the current fracturing area, and determine the crack morphology within the fracturing range based on the change of the electromagnetic signal, and determine the crack growth within the fracturing range based on the change of the electromagnetic signal and the injection amount of the fracturing fluid, wherein the crack growth is preliminarily judged based on the change of the electromagnetic signal continuously detected by each electromagnetic sensor, if the injection amount of the fracturing fluid is less than the initial injection amount of the fracturing fluid, the crack growth condition is that the crack growth rate is slow, and if the injection amount of the fracturing fluid is greater than or equal to the initial injection amount of the fracturing fluid, the crack growth condition is that the crack growth rate is fast; A control adjustment module, which is connected to the data analysis module and the fracturing control module respectively, and is used to adjust the injection amount and / or injection pressure of the fracturing fluid according to the fracture morphology and fracture growth conditions; wherein, judging whether the crack morphology and crack growth conditions meet the expected standards; If not, determining a fracturing adjustment method according to the crack morphology and crack growth conditions, including a first adjustment method, a second adjustment method, and a third adjustment method; In the first adjustment mode, the current fracturing area is abandoned and the injection of fracturing fluid is stopped; In the second adjustment mode, the injection of the fracturing fluid is suspended, and the suspension time is a first preset time; In the third adjustment mode, the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change of the electromagnetic signal, wherein the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change amount of the electromagnetic signal amplitude between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment; If it is in compliance, the fracturing conditions in the future target time period are predicted according to the fracture morphology and fracture growth conditions, and the injection amount and injection pressure of the fracturing fluid are adjusted according to the prediction results; in, If the crack shape is the second preset crack shape, determining the fracturing adjustment method to be the first adjustment method; If the crack morphology is the first preset crack morphology and the crack growth condition is the second preset growth condition, determining the fracturing adjustment mode to be the second adjustment mode; If the crack morphology is the first preset crack morphology and the crack growth condition is the third preset growth condition, determining the fracturing adjustment mode to be the third adjustment mode; The first preset crack morphology is a uniform mesh crack, the second preset crack morphology is a main large crack; the first preset growth condition is that the crack growth rate is greater than the first preset growth rate and less than the second preset growth rate, the second preset growth condition is that the crack growth rate is not less than the second preset growth rate, and the third preset growth condition is that the crack growth rate is not greater than the first preset growth rate; wherein the first preset growth rate is less than the second preset growth rate; The expected standard is that the crack morphology is a first preset crack morphology and the crack growth condition is a first preset growth condition.

2. The electromagnetic array-based fracturing monitoring system according to claim 1, characterized in that: The data analysis module determines the abnormal electromagnetic plane distribution according to the continuously monitored electromagnetic signals, determines the microseismic abnormal point distribution according to the continuously monitored microseismic signals, and determines the fracturing range of the current fracturing area according to the abnormal electromagnetic plane distribution and the microseismic abnormal point distribution.

3. The electromagnetic array-based fracturing monitoring system according to claim 2, characterized in that: The data analysis module determines the fracture morphology within the fracturing range according to the change between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment.

4. The electromagnetic array-based fracturing monitoring system according to claim 3, characterized in that: The data analysis module determines the growth of cracks within the fracturing range according to the changes in the continuously detected electromagnetic signals and the comparison between the injection volume of the fracturing fluid and the initial injection volume of the fracturing fluid.

5. The electromagnetic array-based fracturing monitoring system according to claim 1, characterized in that: The electromagnetic sensors in the electromagnetic sensor array in the data acquisition module are evenly distributed in a grid shape within the monitoring area with the horizontal well as the axis; the microseismic sensors in the microseismic sensor array are radially distributed at equal distances outward from the center of the monitoring area.

6. A fracturing monitoring method applied to the electromagnetic array-based fracturing monitoring system according to any one of claims 1 to 5, characterized in that: include: Step S1, obtaining the initial injection volume and initial injection pressure of the fracturing fluid; Step S2, obtaining a number of electromagnetic signals and a number of microseismic signals in a critical time period of the current fracturing area; Step S3, determining the fracturing range of the current fracturing area according to the plurality of electromagnetic signals and the plurality of microseismic signals, determining the crack morphology within the fracturing range according to the change of the electromagnetic signals, and determining the crack growth within the fracturing range according to the change of the electromagnetic signals and the injection amount of the fracturing fluid, wherein the crack growth is preliminarily judged according to the change of the electromagnetic signals continuously detected by each electromagnetic sensor, if the injection amount of the fracturing fluid is less than the initial injection amount of the fracturing fluid, the crack growth condition is that the crack growth rate is slow, and if the injection amount of the fracturing fluid is greater than or equal to the initial injection amount of the fracturing fluid, the crack growth condition is that the crack growth rate is fast; Step S4, adjusting the injection amount and / or injection pressure of the fracturing fluid according to the fracture morphology and fracture growth; wherein, judging whether the crack morphology and crack growth conditions meet the expected standards; If not, determining a fracturing adjustment method according to the crack morphology and crack growth conditions, including a first adjustment method, a second adjustment method, and a third adjustment method; In the first adjustment mode, the current fracturing area is abandoned and the injection of fracturing fluid is stopped; In the second adjustment mode, the injection of the fracturing fluid is suspended, and the suspension time is a first preset time; In the third adjustment mode, the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change of the electromagnetic signal, wherein the adjustment amount of the injection pressure of the fracturing fluid is determined according to the change amount of the electromagnetic signal amplitude between the electromagnetic signal detected before fracturing and the electromagnetic signal detected at the current moment; If it is in compliance, the fracturing conditions in the future target time period are predicted according to the fracture morphology and fracture growth conditions, and the injection amount and injection pressure of the fracturing fluid are adjusted according to the prediction results; in, If the crack shape is the second preset crack shape, determining the fracturing adjustment method to be the first adjustment method; If the crack morphology is the first preset crack morphology and the crack growth condition is the second preset growth condition, determining the fracturing adjustment mode to be the second adjustment mode; If the crack morphology is the first preset crack morphology and the crack growth condition is the third preset growth condition, determining the fracturing adjustment mode to be the third adjustment mode; The first preset crack morphology is a uniform mesh crack, the second preset crack morphology is a main large crack; the first preset growth condition is that the crack growth rate is greater than the first preset growth rate and less than the second preset growth rate, the second preset growth condition is that the crack growth rate is not less than the second preset growth rate, and the third preset growth condition is that the crack growth rate is not greater than the first preset growth rate; wherein the first preset growth rate is less than the second preset growth rate; The expected standard is that the crack morphology is a first preset crack morphology and the crack growth condition is a first preset growth condition.

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