Geophysical method and system for monitoring oil and gas fracturing
Through the integrated seismic and electrical monitoring method, combined with the acquisition of micro-seismic and electromagnetic signals and the calculation of inversion algorithms, the accuracy and efficiency of oil and gas fracturing monitoring are achieved, and the problem of low monitoring resolution and accuracy in the prior art is solved.
Patent Information
- Application Number
- CN202510048813.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-13
- Publication Date
- 2025-03-28
AI Technical Summary
The prior art has problems in oil and gas fracturing monitoring with low resolution ability, large electromagnetic interference, and difficult to improve data quality. The micro-seismic monitoring data points are divergent, resulting in large fracture parameters, and the resolution and accuracy decrease after increasing depth, and poor timeliness.
The integrated seismic and electrical monitoring method is adopted. By collecting electromagnetic signals as baseline data before the fracturing operation begins, micro-seismic and electromagnetic measurement lines are arranged on the fracturing monitoring section, micro-seismic and electromagnetic signals are collected, and the conductivity changes in the fracture area are calculated using the inversion algorithm. Combined with the distribution of micro-seismic rupture event points, the results are fused to achieve oil and gas fracturing monitoring.
It improves the accuracy of oil and gas fracturing monitoring, ensures efficient and safe operation of the equipment, solves the problem that it is difficult to accurately monitor fracturing operations by a single method, and achieves higher monitoring resolution and accuracy.
Smart Images
Figure CN119717057A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of oil and gas fracturing, and in particular to a geophysical method and system for monitoring oil and gas fracturing. Background Art
[0002] Fracturing refers to the process of using a high-pressure ground 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, and the rock to break and produce cracks. During the process of crack formation, the fracturing fluid advances along the crack, which can make the crack continue to extend forward on the one hand, and fill the crack and support the crack so that it does not close on the other hand, 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. After the implementation of fracturing transformation measures in oil and gas wells, effective monitoring methods are needed to determine the effect of fracturing operations. In the existing technology, conventional electromagnetic detection methods have problems such as low resolution, large electromagnetic interference, and difficulty in improving data quality. The microseismic monitoring data points diverge, and the fracture parameters calculated thereby are larger than the actual values. With the increase of depth, the resolution and accuracy decrease, the timeliness is poor, and the accuracy of identifying fracturing fluids and fracturing cracks is limited. It can be seen that it is difficult to accurately monitor fracturing operations using any single method. Summary of the invention
[0003] The purpose of the present invention is to provide a geophysical method and system for oil and gas fracturing monitoring to solve the problems raised in the background technology and realize accurate monitoring of oil and gas fracturing operations.
[0004] To achieve the above object, the present invention provides the following solutions: On the one hand, a geophysical method for oil and gas fracturing monitoring is provided, and the specific steps include the following:
[0005] Before the fracturing operation begins, electromagnetic signals are collected to obtain electromagnetic characteristic data of the original underground formation as baseline data;
[0006] Laying a first survey line and a second survey line on the fracturing monitoring section, wherein the first survey line is used for microseismic monitoring, and the second survey line is used for electromagnetic monitoring;
[0007] Acquiring microseismic signals of the first survey line and electromagnetic signals of the second survey line;
[0008] Comparing the electromagnetic signal with the baseline data, calculating the change in conductivity of the fracture area using an inversion algorithm, and then estimating the geometric parameters of the fracture to obtain a first monitoring result;
[0009] Processing the microseismic signal to determine the distribution of microseismic rupture event points and obtain a second monitoring result;
[0010] The first monitoring result and the second monitoring result are integrated to obtain an oil and gas fracturing monitoring result.
[0011] Preferably, the specific steps of calculating the change in conductivity of the fracture area using the inversion algorithm are:
[0012] Based on regularized inversion and conjugate gradient inversion techniques, a new inversion objective function is constructed;
[0013] The conjugate gradient method is used to optimize the inversion objective function and perform three-dimensional inversion on the electromagnetic data.
[0014] Preferably, the arrangement of the first survey line includes ground arrangement and in-well arrangement; wherein, the ground arrangement is arranged in a manner of uniformly distributing detectors in a geometric shape on the ground around the fracturing well; the in-well arrangement is arranged in an observation well adjacent to the fracturing well, lowering the detector into the well through a cable, and arranging a detector every 10-20 meters according to the depth range to be monitored, such as from 50 meters above the target layer to 100 meters below the target layer.
[0015] Preferably, the second survey line and the microseismic geophones are arranged in layers and staggered, and an electromagnetic receiving antenna is set between every two microseismic geophones, evenly distributed from the top to the bottom of the target depth range, for simultaneously acquiring electromagnetic signals at different depths.
[0016] Preferably, the specific steps of fusing the first monitoring result with the second monitoring result to obtain the oil and gas fracturing monitoring result are:
[0017] Converting the first monitoring result and the second monitoring result into individual matching degrees according to a matching degree matrix; the individual matching degrees represent the degree of trust in the monitoring results given by each monitoring method;
[0018] According to the individual matching degree of the transformation, a confidence rule base is pre-established to determine the confidence of multiple fracturing monitoring results; the confidence rule base is pre-established according to multiple monitoring fusion samples, and the confidence represents the degree of trust in each monitoring method;
[0019] The first monitoring result and the second monitoring result are integrated according to the confidence level to determine the final oil and gas fracturing monitoring result.
[0020] Preferably, the method further includes preprocessing the acquired microseismic signal and the electromagnetic signal, performing denoising on the microseismic signal, removing background noise and interference signals by filtering technology; and removing electromagnetic interference by wavelet transform on the electromagnetic signal.
[0021] On the other hand, a geophysical system for oil and gas fracturing monitoring is provided, comprising a baseline data acquisition module, a survey line arrangement module, a signal acquisition module, a first monitoring module, a second monitoring module, and a fusion module; wherein:
[0022] The baseline data acquisition module is used to collect electromagnetic signals before the fracturing operation begins, and obtain electromagnetic characteristic data of the original underground formation as baseline data;
[0023] The survey line arrangement module is used to arrange a first survey line and a second survey line on the fracturing monitoring section, wherein the first survey line is used for microseismic monitoring and the second survey line is used for electromagnetic monitoring;
[0024] The signal acquisition module is used to collect the microseismic signal of the first survey line and the electromagnetic signal of the second survey line;
[0025] The first monitoring module is used to compare the electromagnetic signal with the baseline data, calculate the change of conductivity in the fracture area by using an inversion algorithm, and then estimate the geometric parameters of the fracture to obtain a first monitoring result;
[0026] The second monitoring module is used to process the microseismic signal, determine the distribution of microseismic rupture event points, and obtain a second monitoring result;
[0027] The fusion module is used to fuse the first monitoring result with the second monitoring result to obtain an oil and gas fracturing monitoring result.
[0028] According to the specific embodiment provided by the present invention, the present invention discloses a geophysical method and system for oil and gas fracturing monitoring, which has the following technical effects:
[0029] 1. Effectively integrate the results of microseismic monitoring technology and electromagnetic monitoring technology to form a seismic-electric integrated fracturing monitoring and interpretation method, which solves the problem of limitations in oil and gas fracturing monitoring and interpretation using only microseismic monitoring technology or electromagnetic monitoring technology;
[0030] 2. Improve the accuracy of oil and gas fracturing monitoring and ensure the efficient and safe operation of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.
[0032] Figure 1 is a flow chart of the method of the present invention;
[0033] Figure 2 It is a system structure diagram of the present invention. DETAILED DESCRIPTION
[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0035] The object of the present invention is to provide a geophysical method for monitoring oil and gas fracturing, such as Figure 1 As shown, the specific steps include the following:
[0036] S1. Before the fracturing operation begins, collect electromagnetic signals to obtain electromagnetic characteristic data of the original underground formation as baseline data;
[0037] S2. Laying out a first survey line and a second survey line on the fracturing monitoring section, wherein the first survey line is used for microseismic monitoring and the second survey line is used for electromagnetic monitoring;
[0038] S3, collecting microseismic signals of the first survey line and electromagnetic signals of the second survey line;
[0039] S4, comparing the electromagnetic signal with the baseline data, using an inversion algorithm to calculate the change in conductivity in the fracture area, and then estimating the geometric parameters of the fracture to obtain a first monitoring result;
[0040] S5, processing the microseismic signal, determining the distribution of microseismic rupture event points, and obtaining a second monitoring result;
[0041] S6. The first monitoring result is integrated with the second monitoring result to obtain an oil and gas fracturing monitoring result.
[0042] Furthermore, before the fracturing operation begins, electromagnetic signals are collected to obtain electromagnetic characteristic data of the original underground strata as baseline data. This set of data is very important for the subsequent analysis of strata changes during the fracturing process. During the collection process, information such as the collection time, transmission parameters (such as frequency, current intensity, etc.) and receiving parameters (such as gain, etc.) should be recorded.
[0043] Furthermore, in step S2, the microseismic monitoring principle and the first survey line arrangement are as follows:
[0044] During the oil and gas fracturing process, rock fractures will generate tiny seismic waves. These microseismic waves will propagate to the surrounding medium, and these seismic wave signals will be received by detectors (first survey line) arranged on the ground or in the well. According to the arrival time, amplitude, frequency and other characteristics of the microseismic waves, the location, time and intensity of the rock fracture can be determined. For example, the time difference between the microseismic waves received by the detectors at different locations can be used to invert the location of the earthquake source (i.e., the rock fracture point) through triangulation, thereby determining the generation and expansion direction of the crack.
[0045] The arrangement of the first survey line includes ground arrangement and well arrangement; on the ground, the first survey line is usually arranged in a certain geometric shape around the fracturing well, such as a circle, rectangle or fan. This arrangement can ensure that microseismic wave signals are received from multiple directions, improving the accuracy of source location. For example, for a larger-scale fracturing operation, a circular survey line with a radius of several hundred meters or even thousands of meters may be arranged, and the detectors are evenly distributed on the circumference at a certain distance (such as 10-50 meters). When arranged in the well, the detectors of the first survey line can be placed in adjacent observation wells, and arranged in layers in the vertical direction according to the depth range to be monitored. Generally, a detector is set every 10-20 meters to accurately obtain microseismic information generated by rock fractures at different depths.
[0046] The electromagnetic monitoring principle and the layout of the second measuring line are as follows:
[0047] Electromagnetic monitoring is based on the principles of electromagnetic induction and electromagnetic wave propagation. During the fracturing process, due to the injection of fracturing fluid and the formation of rock cracks, the electrical properties of the underground medium (conductivity, dielectric constant, etc.) change, resulting in changes in the electromagnetic field. These changes are detected by electromagnetic receiving devices (second survey lines) arranged on the ground or in the well to infer the situation in the fracturing area. For example, when the fracturing fluid is filled into the rock cracks, the conductivity of the area increases, which will cause changes in the intensity, phase and other characteristics of the secondary magnetic field. By analyzing these changes, information such as the location, direction and fluid distribution of the cracks can be determined.
[0048] The second survey line layout:
[0049] On the surface, the second survey line can also be arranged in a variety of geometric shapes, but its layout may be different from the first survey line to obtain electromagnetic signal information at different angles and depths. For example, a cross-line survey line layout or additional survey lines can be added to the first survey line to ensure that the fracturing area and its possible impact range can be fully covered.
[0050] When arranged in the well, the electromagnetic receiving antenna (part of the second survey line) can be arranged in layers and staggered with the microseismic geophone (part of the first survey line) in the same observation well, so that microseismic and electromagnetic signals can be obtained at the same location at the same time, which is convenient for comparative analysis of the relationship between the two and improves the accuracy and reliability of monitoring the fracturing process. In this embodiment, the second survey line and the microseismic geophone are arranged in layers and staggered, and an electromagnetic receiving antenna is set between every two microseismic geophones, evenly distributed from the top to the bottom of the target depth range, for simultaneously obtaining electromagnetic signals at different depths.
[0051] Before fracturing, the microseismic monitoring system of the first survey line is turned on to record background noise data for a period of time (such as 1-2 hours) as a reference for subsequent data processing. During the fracturing process, microseismic signals are continuously collected, and the time, amplitude, frequency and other parameters of the signal received by each detector are recorded. Since the frequency of microseismic waves generated by rock fracture is generally between several hundred hertz and several thousand hertz, the sampling frequency of the acquisition system must be high enough, for example, set to about 10kHz, to ensure that the microseismic signals can be fully recorded. Similarly, before fracturing, the electromagnetic monitoring system of the second survey line is used to collect the original electromagnetic data of the underground, including parameters such as electric field strength, magnetic field strength, and phase. During the fracturing process, electromagnetic data is collected regularly (such as every 1-5 minutes). The frequency range of the acquisition is determined according to the electromagnetic monitoring method. For example, when low-frequency electromagnetic monitoring is used, the frequency range can be 1-10kHz, which is used to monitor deep stratum changes; the frequency range of high-frequency electromagnetic monitoring can be 100kHz-1 MHz, which is used to obtain shallow fracture information.
[0052] Furthermore, step S3 also includes preprocessing the acquired microseismic signal and the electromagnetic signal, performing denoising on the microseismic signal, removing background noise and interference signals by filtering technology; and removing electromagnetic interference by wavelet transform on the electromagnetic signal.
[0053] Furthermore, in step S4, the specific steps of calculating the conductivity change of the fracture area using the inversion algorithm are:
[0054] S41. Based on regularized inversion and conjugate gradient inversion techniques, a new inversion objective function is constructed;
[0055] S42, and using the conjugate gradient method to optimize the inversion objective function, and perform three-dimensional inversion on the electromagnetic data.
[0056] Furthermore, in step S6, the first monitoring result and the second monitoring result are merged to obtain the oil and gas fracturing monitoring result. The specific steps are:
[0057] S61, converting the first monitoring result and the second monitoring result into individual matching degrees according to the matching degree matrix; the individual matching degrees represent the degree of trust in the monitoring results given by each monitoring method;
[0058] S62, according to the converted individual matching degree, a pre-established confidence rule base is used to determine the confidence of multiple fracturing monitoring results; the confidence rule base is pre-established according to multiple monitoring fusion samples, and the confidence represents the degree of trust in each monitoring method;
[0059] S63: The first monitoring result and the second monitoring result are integrated according to the confidence level to determine the final oil and gas fracturing monitoring result.
[0060] In another aspect, a geophysical system for oil and gas fracturing monitoring is provided, such as Figure 2 As shown, it includes a baseline data acquisition module, a survey line layout module, a signal acquisition module, a first monitoring module, a second monitoring module, and a fusion module; wherein,
[0061] The baseline data acquisition module is used to collect electromagnetic signals before the fracturing operation begins, and obtain electromagnetic characteristic data of the original underground formation as baseline data;
[0062] A survey line arrangement module, used to arrange a first survey line and a second survey line on the fracturing monitoring section, the first survey line is used for microseismic monitoring, and the second survey line is used for electromagnetic monitoring;
[0063] A signal acquisition module, used for collecting microseismic signals of the first survey line and electromagnetic signals of the second survey line;
[0064] The first monitoring module is used to compare the electromagnetic signal with the baseline data, calculate the change of the conductivity of the fracture area by using the inversion algorithm, and then estimate the geometric parameters of the fracture to obtain the first monitoring result;
[0065] The second monitoring module is used to process the microseismic signal, determine the distribution of microseismic rupture event points, and obtain a second monitoring result;
[0066] The fusion module is used to fuse the first monitoring result with the second monitoring result to obtain the oil and gas fracturing monitoring result.
[0067] Real-time monitoring technology for fracturing plays a vital role in oil and gas production. First, through real-time monitoring, potential safety hazards can be discovered and resolved in a timely manner, reducing the probability of accidents. Second, this technology can optimize the fracturing operation process, improve production efficiency, and reduce production costs. Finally, real-time monitoring of fracturing can also help protect the environment and reduce environmental pollution caused by improper operation.
[0068] Real-time monitoring technology for fracturing is an important innovation in the field of oil and gas production. It not only improves production efficiency and safety, but also provides strong support for the sustainable development of the industry.
[0069] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of the present invention. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.
Claims
1. A geophysical method for oil and gas fracturing monitoring, characterized in that: The specific steps include the following: Before the fracturing operation begins, electromagnetic signals are collected to obtain electromagnetic characteristic data of the original underground formation as baseline data; Laying a first survey line and a second survey line on the fracturing monitoring section, wherein the first survey line is used for microseismic monitoring and the second survey line is used for electromagnetic monitoring; collecting microseismic signals of the first survey line and electromagnetic signals of the second survey line; Comparing the electromagnetic signal with the baseline data, calculating the change in conductivity of the fracture area using an inversion algorithm, and then estimating the geometric parameters of the fracture to obtain a first monitoring result; Processing the microseismic signal to determine the distribution of microseismic rupture event points and obtain a second monitoring result; The first monitoring result and the second monitoring result are integrated to obtain an oil and gas fracturing monitoring result.
2. A geophysical method for oil and gas fracturing monitoring according to claim 1, characterized in that: The specific steps for calculating the conductivity change in the fracture area using the inversion algorithm are as follows: Based on regularized inversion and conjugate gradient inversion techniques, a new inversion objective function is constructed; The conjugate gradient method is used to optimize the inversion objective function and perform three-dimensional inversion on the electromagnetic data.
3. A geophysical method for oil and gas fracturing monitoring according to claim 1, characterized in that: The arrangement of the first survey line includes ground arrangement and in-well arrangement; wherein, the ground arrangement is as follows: geophones are evenly distributed in a geometric shape on the ground around the fracturing well; and the in-well arrangement is as follows: geophones are arranged in an observation well adjacent to the fracturing well, and geophones are lowered into the well via cables. According to the depth range to be monitored, for example, from 50 meters above the target layer to 100 meters below the target layer, a geophone is arranged every 10-20 meters.
4. A geophysical method for oil and gas fracturing monitoring according to claim 1, characterized in that: The second survey line and the microseismic geophones are arranged in layers and staggered, and an electromagnetic receiving antenna is set between every two microseismic geophones, evenly distributed from the top to the bottom of the target depth range, for simultaneously acquiring electromagnetic signals at different depths.
5. The geophysical method for oil and gas fracturing monitoring according to claim 1, characterized in that: The specific steps of fusing the first monitoring result and the second monitoring result to obtain the oil and gas fracturing monitoring result are: Converting the first monitoring result and the second monitoring result into individual matching degrees according to a matching degree matrix; the individual matching degrees represent the degree of trust in the monitoring results given by each monitoring method; Based on the converted individual matching degrees, the pre-established confidence rule base is used to determine the confidence levels of various fracturing monitoring results; The confidence rule base is pre-established based on multiple monitoring fusion samples, and the confidence level represents the degree of trust in each monitoring method; The first monitoring result and the second monitoring result are integrated according to the confidence level to determine the final oil and gas fracturing monitoring result.
6. A geophysical method for oil and gas fracturing monitoring according to claim 1, characterized in that: It also includes preprocessing the acquired microseismic signals and electromagnetic signals, performing denoising on the microseismic signals, removing background noise and interference signals through filtering technology; and removing electromagnetic interference from the electromagnetic signals by using wavelet transform.
7. A geophysical system for oil and gas fracturing monitoring, characterized in that: It includes a baseline data acquisition module, a survey line layout module, a signal acquisition module, a first monitoring module, a second monitoring module, and a fusion module; wherein, The baseline data acquisition module is used to collect electromagnetic signals before the fracturing operation begins, and obtain electromagnetic characteristic data of the original underground formation as baseline data; The survey line arrangement module is used to arrange a first survey line and a second survey line on the fracturing monitoring section, wherein the first survey line is used for microseismic monitoring and the second survey line is used for electromagnetic monitoring; The signal acquisition module is configured to acquire the microseismic signal of the first survey line and the electromagnetic signal of the second survey line; The first monitoring module is configured to compare the electromagnetic signal with the baseline data, calculate the change in conductivity of the fracture area using an inversion algorithm, and then estimate the geometric parameters of the fracture to obtain a first monitoring result; The second monitoring module is configured to process the microseismic signal, determine the distribution of microseismic rupture event points, and obtain a second monitoring result; The fusion module is used to fuse the first monitoring result and the second monitoring result to obtain an oil and gas fracturing monitoring result.