CN114896673A - Hot dry rock reservoir hydraulic fracturing reconstruction volume prediction method - Google Patents
Hot dry rock reservoir hydraulic fracturing reconstruction volume prediction method Download PDFInfo
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Abstract
The invention discloses a method for predicting the hydraulic fracturing modification volume of a dry hot rock reservoir, which comprises the following steps: s1, before fracturing monitoring of the dry heat rock reservoir, carrying out a controllable source three-dimensional electromagnetic method acquisition parameter test and optimization design; s2, obtaining three-dimensional controllable source electromagnetic data before the dry hot rock reservoir is modified, and obtaining the three-dimensional controllable source electromagnetic data after the dry hot rock reservoir is modified; and S3, constructing a new inversion target function based on regularization inversion and conjugate gradient inversion technologies, optimizing the target function by using a conjugate gradient method, and performing three-dimensional inversion on three-dimensional controllable source electromagnetic data before and after the dry hot rock reservoir is modified by combining the advantages of regularization inversion and conjugate gradient inversion to obtain a fracturing area depth and resistivity data volume in the dry hot rock reservoir monitoring area before and after fracturing. The method is close to the real volume of the fracturing modification of the dry hot rock reservoir, and the controllable source electromagnetic technology improves the accuracy of the yield prediction after the fracturing modification of the dry hot rock reservoir.
Description
Technical Field
The invention relates to the technical field of geophysical exploration, in particular to a method for predicting the hydraulic fracturing modification volume of a dry hot rock reservoir.
Background
The hot dry rock is a clean new energy source, has large occurrence potential, and needs to perform hydraulic fracturing modification on a reservoir stratum in the exploration and development process to achieve the purpose of increasing yield, and the modification volume of the reservoir stratum is a main factor for evaluating the fracturing effect and predicting the yield.
At present, the size of the modified reservoir volume and the evaluation of the fracturing effect are mainly judged by generating a microseismic volume (SRV) through a positioned microseismic event point. But microseismic monitoring also has the following defects: microseism monitoring is easily influenced by fracturing operation, surrounding noise and background seismic events, high-quality data are difficult to acquire, and microseism event detection and positioning are greatly influenced; the occurrence of a microseismic event does not necessarily indicate the creation of a fracture, nor does it mean that the proppant or fluid reaches a reservoir modification volume that is only effective where the proppant or fluid reaches. Therefore, the microseismic volume (SRV) generated at the microseismic event point is larger than the fracture fluid swept volume, so that the productivity predicted based on the microseismic and the actual productivity coincidence rate of the fracturing well have a large difference.
The hydraulic fracturing operation can cause the cracks of the dry hot rock reservoir to be filled with the fracturing fluid with low resistivity, so that the electrical structure of the high-resistance dry hot rock reservoir is changed, and a geophysical basis is provided for electrical monitoring. However, the conventional electrical method has great difficulty in monitoring, which is mainly shown in the following steps: the problems of strong interference of man-made noise such as fracturing operation and industrial electricity in a fracturing monitoring area, poor interference resistance and weak reservoir transformation resolution capability in magnetotelluric depth measurement are solved; the potential method can research the orientation of the hydraulic fracturing fracture, but cannot determine the spatial distribution characteristics of the fracture; the general active source electromagnetic method has shallow detection depth and cannot detect reservoir bodies buried deeply. The conventional electromagnetic method data acquisition and processing technology cannot completely meet the fracturing monitoring requirement, and a monitoring method and an inversion processing technology which are high in anti-interference capability, high in resolution and large in detection depth are required.
Disclosure of Invention
The invention aims to provide a method for predicting the hydraulic fracturing modification volume of a hot dry rock reservoir, which aims to solve the technical problems that high-quality data are difficult to acquire and the predicted productivity and the actual productivity coincidence rate of a fracturing well have large difference in the prior art.
In order to solve the technical problems, the invention specifically provides the following technical scheme:
a method for predicting the hydraulic fracturing modification volume of a hot dry rock reservoir comprises the following steps:
s1, before fracturing monitoring of the hot dry rock reservoir, performing a controllable source three-dimensional electromagnetic method acquisition parameter test and optimization design to improve observation precision and data acquisition quality;
s2, arranging three-dimensional controllable source electromagnetic measuring points above fracturing perforations in a dry hot rock reservoir monitoring area, using artificial source excitation, carrying out data acquisition at the three-dimensional controllable source electromagnetic measuring points before fracturing to obtain three-dimensional controllable source electromagnetic data before dry hot rock reservoir modification, carrying out data acquisition at the three-dimensional controllable source electromagnetic measuring points after fracturing to obtain the three-dimensional controllable source electromagnetic data after dry hot rock reservoir modification, keeping excitation and receiving conditions before and after fracturing consistent, and keeping the position of a transmitting source unchanged to reduce errors caused by excitation and receiving condition changes to improve transverse detection precision;
s3, constructing a new inversion target function based on regularization inversion and conjugate gradient inversion technologies, optimizing the target function by using a conjugate gradient method, and performing three-dimensional inversion on three-dimensional controllable source electromagnetic data before and after the dry hot rock reservoir is modified by combining the advantages of regularization inversion and conjugate gradient inversion to obtain a fracturing area depth and resistivity data volume in a dry hot rock reservoir monitoring area before and after fracturing;
s4, processing the obtained fracturing zone depth and resistivity data body, calculating relative resistivity abnormity, and obtaining a data body with the abnormal relative resistivity so as to clearly reflect the transformation range of the dry-hot rock reservoir;
and step S5, performing coordinate conversion on the abnormal data volume of the relative resistivity to obtain a scattered data volume under a rectangular coordinate system in a three-dimensional space, performing interpolation processing on the scattered data volume by adopting an inverse distance weighting method or a Criging method, performing three-dimensional space imaging, and calculating the abnormal volume of the relative resistivity based on the three-dimensional space imaging to be used as the fracturing reconstruction volume of the dry heat rock reservoir, wherein the abnormal volume of the relative resistivity is reflected as a quantitative index of the arrival range of fracturing liquid.
As a preferred scheme of the present invention, the developing a controllable source three-dimensional electromagnetic method acquisition parameter test and optimization includes:
according to the actual noise condition of the dry hot rock reservoir monitoring area, establishing a geoelectric model by using monitoring well logging data of the dry hot rock reservoir monitoring area, developing forward simulation to determine the optimal excitation period of target layer detection, and increasing the excitation frequency for the dry hot rock reservoir so as to improve the longitudinal resolution of the dry hot rock reservoir;
on the basis of simulation demonstration, a receiving and transmitting distance test, an excitation period test and an electric dipole distance test are developed by combining the geoelectrical condition and the noise level of a work area to optimize acquisition parameters;
the interference source investigation test is carried out in the dry hot rock reservoir monitoring area to obtain the interference source type of the dry hot rock reservoir monitoring area, the distance and the degree of the interference source influencing the data quality are determined through the field test in the dry hot rock reservoir monitoring area, the point selection of the three-dimensional controllable source electromagnetic measuring point is guided according to the distance and the degree of the interference source influencing the data quality, and the emission current is determined, so that the data acquisition quality and the observation precision are guaranteed.
As a preferred embodiment of the present invention, the maintaining of consistent excitation and reception conditions before and after fracturing and unchanged emission source position comprises: the grounding resistance change states of the transmitting end and the receiving end of the artificial source are regularly checked, and the grounding conditions before and after fracturing are kept unchanged by taking measures of regularly watering saline to reduce the grounding resistance and timely replacing a damaged electrode, so that the consistency of the excitation conditions before and after fracturing and the receiving conditions, the position of the transmitting source is kept unchanged, and errors caused by the change of the excitation conditions and the receiving conditions are reduced.
As a preferred scheme of the invention, the artificial source adopts high-power excitation to enhance the anti-interference capability, improve the signal-to-noise ratio of data acquisition and increase the monitoring depth to the hot dry rock reservoir.
As a preferred scheme of the invention, after the three-dimensional controllable source electromagnetic data is acquired each time, signal-to-noise ratio analysis is performed to realize quality evaluation on the three-dimensional controllable source electromagnetic data to acquire and screen the three-dimensional controllable source electromagnetic data, a relatively stable long-period signal is selected from the three-dimensional controllable source electromagnetic data, noise and signals are separated according to a positive half shaft and a negative half shaft overlapping technology which is not over zero baud, the signal-to-noise ratios of all three-dimensional controllable source electromagnetic measuring points are calculated, and the three-dimensional controllable source electromagnetic data is evaluated based on the signal-to-noise ratios;
the signal-to-noise ratio calculation formula is as follows:
in the formula (I), the compound is shown in the specification,SNRfor the purpose of the signal-to-noise ratio,Tin order to be the length of the period,Nthe number of total sample points in a half period,A z (T,t i )is composed oft i Acquired at all timesThe intensity of the signal is measured and compared to the signal,iare the metering constants.
As a preferable aspect of the present invention, the evaluating three-dimensional controllable source electromagnetic data based on the signal-to-noise ratio includes:
if the signal-to-noise ratio is within a confidence interval of the technical specification requirement, the three-dimensional controllable source electromagnetic data meet the technical specification requirement;
and if the signal-to-noise ratio is outside the confidence interval required by the technical specification, the three-dimensional controllable source electromagnetic data does not meet the requirement of the technical specification.
As a preferred aspect of the present invention, the method for constructing the new inversion objective function includes:
the method comprises the steps of constructing a regularized inversion target function, carrying out minimization solving on the regular inversion target function by using a conjugate gradient method to obtain a new inversion target function, improving the inversion precision by fusing the advantages of regularized inversion and conjugate gradient inversion, and obtaining a three-dimensional inversion profile of the hot dry rock reservoir which reveals the change characteristics before and after reservoir transformation.
As a preferable aspect of the present invention, the calculation formula of the relative resistivity anomaly is:
in the formula (I), the compound is shown in the specification,
in order for the relative resistivity to be abnormal,
for the resistivity of the hot dry rock reservoir after fracturing,
is the resistivity of the hot dry rock reservoir before fracturing.
As a preferable scheme of the invention, the three-dimensional controllable source electromagnetic method is used for carrying out area observation and improving the transverse observation precision.
As a preferable aspect of the present invention, the method for calculating the relative resistivity anomaly volume includes: and (3) the abnormal volume of the relative resistivity is equivalent to a cuboid, and the abnormal volume of the relative resistivity is approximately calculated according to the volume size calculation mode of the cuboid.
Compared with the prior art, the invention has the following beneficial effects:
the controllable source electromagnetic method is sensitive to underground resistivity change, adopts artificial source power supply, has strong anti-jamming capability, acquires surface electromagnetic field data before and after fracturing by using the controllable source electromagnetic method, performs inversion processing to obtain depth and resistivity data volumes before and after fracturing of a reservoir, calculates the abnormal volume of relative resistivity, obtains the fracturing modification volume of the dry and hot rock reservoir, directly reflects the distribution and migration trend of fracturing fluid by the abnormal volume of relative resistivity, is closer to the real volume of fracturing modification of the dry and hot rock reservoir, and improves the precision of yield prediction after fracturing modification of the dry and hot rock reservoir by using the controllable source electromagnetic technology.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
FIG. 1 is a flow chart for predicting a formation volume of a hot dry rock reservoir by using a controllable source electromagnetic technique;
FIG. 2 is a schematic diagram of ground layout of an XB01 well dry heat rock vertical well fracturing three-dimensional controllable source observation system;
FIG. 3 is a diagram of an XB01 well background field three-dimensional resistivity inversion slice, and the longitudinal resistivity change characteristics on the inversion slice are basically consistent with an XB01 well logging curve;
FIG. 4 is a three-dimensional resistivity inversion slice after reservoir reconstruction of an XB01 well;
FIG. 5 is a three-dimensional relative resistivity anomaly slice of an XB 01-passing well;
FIG. 6 is a three-dimensional relative resistivity anomaly volume map in a rectangular spatial coordinate system;
FIG. 7 is a top-view comparison of three-dimensional relative resistivity anomaly versus post-location microseismic event range.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 to 7, the invention provides a method for predicting the hydraulic fracturing modification volume of a dry heat rock reservoir, which comprises the following steps:
s1, before fracturing monitoring of the hot dry rock reservoir, performing a controllable source three-dimensional electromagnetic method acquisition parameter test and optimization design to improve observation precision and data acquisition quality;
according to the actual noise condition of the dry hot rock reservoir monitoring area, establishing a geoelectric model by using monitoring well logging data of the dry hot rock reservoir monitoring area, developing forward simulation to determine the optimal excitation period of target layer detection, and increasing the excitation frequency for the dry hot rock reservoir so as to improve the longitudinal resolution of the dry hot rock reservoir;
on the basis of simulation demonstration, a receiving and transmitting distance test, an excitation period test and an electric dipole distance test are carried out by combining the geoelectricity condition and the noise level of a work area to optimize the acquisition parameters;
the interference source investigation test is carried out in the dry hot rock reservoir monitoring area to obtain the interference source type of the dry hot rock reservoir monitoring area, the distance and the degree of the interference source influencing the data quality are determined through the field test in the dry hot rock reservoir monitoring area, the point selection of the three-dimensional controllable source electromagnetic measuring point is guided according to the distance and the degree of the interference source influencing the data quality, and the emission current is determined, so that the data acquisition quality and the observation precision are guaranteed.
The grounding resistance change states of the transmitting end and the receiving end of the artificial source are regularly checked, and the grounding conditions before and after fracturing are kept unchanged by taking measures of regularly watering saline to reduce the grounding resistance and timely replacing a damaged electrode, so that the consistency of the excitation conditions before and after fracturing and the receiving conditions, the position of the transmitting source is kept unchanged, and errors caused by the change of the excitation conditions and the receiving conditions are reduced.
The artificial source is excited by high power so as to enhance the anti-interference capability, improve the signal-to-noise ratio of data acquisition and increase the monitoring depth to a hot dry rock reservoir.
S2, arranging three-dimensional controllable source electromagnetic measuring points above fracturing perforations in a dry hot rock reservoir monitoring area, using artificial source excitation, carrying out data acquisition at the three-dimensional controllable source electromagnetic measuring points before fracturing to obtain three-dimensional controllable source electromagnetic data before dry hot rock reservoir modification, carrying out data acquisition at the three-dimensional controllable source electromagnetic measuring points after fracturing to obtain the three-dimensional controllable source electromagnetic data after dry hot rock reservoir modification, keeping excitation and receiving conditions before and after fracturing consistent, and keeping the position of a transmitting source unchanged to reduce errors caused by excitation and receiving condition changes to improve transverse detection precision.
The method comprises the steps that signal-to-noise ratio analysis is carried out on three-dimensional controllable source electromagnetic data after the three-dimensional controllable source electromagnetic data are collected each time, so that quality evaluation on the three-dimensional controllable source electromagnetic data is achieved to collect and screen the three-dimensional controllable source electromagnetic data, relatively stable long-period signals are selected from the three-dimensional controllable source electromagnetic data, noise and signals are separated according to a positive half shaft and negative half shaft superposition technology which is not over zero, the signal-to-noise ratios of all three-dimensional controllable source electromagnetic measuring points are calculated, and the three-dimensional controllable source electromagnetic data are evaluated on the basis of the signal-to-noise ratios;
the signal-to-noise ratio calculation formula is as follows:
in the formula (I), the compound is shown in the specification,SNRfor the purpose of the signal-to-noise ratio,Tin order to be the length of the period,Nthe number of total sample points in a half period,A z (T,t i )is composed oft i The strength of the signal acquired at a time,iare the metering constants.
The evaluating three-dimensional controllable source electromagnetic data based on the signal-to-noise ratio comprises:
if the signal-to-noise ratio is within a confidence interval of the technical specification requirement, the three-dimensional controllable source electromagnetic data meet the technical specification requirement;
and if the signal-to-noise ratio is outside the confidence interval required by the technical specification, the three-dimensional controllable source electromagnetic data does not meet the requirement of the technical specification.
And S3, constructing a new inversion target function based on regularization inversion and conjugate gradient inversion technologies, optimizing the target function by using a conjugate gradient method, and performing three-dimensional inversion on three-dimensional controllable source electromagnetic data before and after the dry hot rock reservoir is modified by combining the advantages of regularization inversion and conjugate gradient inversion to obtain a fracturing area depth and resistivity data volume in the dry hot rock reservoir monitoring area before and after fracturing. The three-dimensional inversion technology improves the inversion accuracy of the hot dry rock reservoir, the three-dimensional inversion profile reveals the change of the reservoir before and after modification, and the longitudinal coincidence with an electric logging curve is good.
And S4, in order to highlight the change of the dry and hot rock reservoir before and after modification, processing the obtained fracturing zone depth and resistivity data body, calculating the relative resistivity anomaly, and obtaining the data body with the relative resistivity anomaly so as to clearly reflect the modification range of the dry and hot rock reservoir.
The calculation formula of the relative resistivity anomaly is as follows:
in the formula (I), the compound is shown in the specification,
in order for the relative resistivity to be abnormal,
for the resistivity of the hot dry rock reservoir after fracturing,
is the resistivity of the hot dry rock reservoir before fracturing.
And performing coordinate conversion on the abnormal data volume of the relative resistivity to obtain a scattered data volume under a rectangular coordinate system in a three-dimensional space, performing interpolation processing on the scattered data volume by adopting an inverse distance weighting method or a kriging method, performing three-dimensional space imaging, and calculating the abnormal volume of the relative resistivity based on the three-dimensional space imaging to be used as the fracturing reconstruction volume of the hot dry rock reservoir, wherein the abnormal volume of the relative resistivity is reflected as a quantitative index of the arrival range of fracturing liquid. The relative resistivity anomaly reflects the liquid reach and can be used to represent the dry heat rock reservoir stimulated volume.
The method for calculating the relative resistivity abnormal volume comprises the following steps: and (4) enabling the abnormal volume of the relative resistivity to be equivalent to a cuboid, and approximately calculating the abnormal volume of the relative resistivity according to the volume calculation mode of the cuboid.
In the embodiment, the dry hot rock XB01 well in the northwest region is taken as an example, the well depth of the well is 4000m, the vertical well is fractured, the fracture section is-3500 to-3900 m, the thickness is 400m, the well is granite in the impression period, and the average resistivity is 5000 omega.m. Figure 1 shows a flow chart for carrying out the invention.
According to the present invention, step S1 is executed: before fracturing monitoring of the hot dry rock reservoir, a controllable source three-dimensional electromagnetic method acquisition parameter test and optimization design are carried out for improving observation precision and data acquisition quality.
According to the actual noise condition of the monitoring area, a geoelectric model is established by utilizing the dry hot rock XB01 well logging data, forward modeling is carried out, the optimal excitation period for target layer detection is determined to be 0.4s-2.5s, the excitation frequency is increased for the target layer, and the longitudinal resolution of a target body is improved.
On the basis of simulation demonstration, a receiving and transmitting distance test, an excitation period test and an electric dipole distance test are carried out by combining the geoelectrical condition and the noise level of a monitoring area, and the acquisition parameters are further optimized.
And further carrying out an interference source investigation test, determining that the types of the interference sources in the monitoring area are mainly high-voltage transmission lines near the monitoring area, field fracturing operation, field industrial power utilization and the like, determining that monitoring points are arranged at positions which are 500 meters away from the high-voltage transmission lines through the field test, selecting positions with relatively less interference to arrange measuring points in the fracturing field, and increasing the emission current to 100A so as to suppress the field interference and ensure the data acquisition quality.
According to the present invention, step S2 is executed: three-dimensional controllable source electromagnetic measuring points are distributed by taking a dry hot rock XB01 well as the center, the measuring net is 50m multiplied by 50m, the observation area is 1000m multiplied by 600m =0.6km 2 And collecting the electric field component Ex. The transmitter power is 200kw, the exciting current is 100A, the exciting waveform is a square wave which is not over zero, the exciting period is 0.1-25 s, the AB distance is 5.6km, and the transmitting resistance is 6 omega; the transmitting-receiving distance is 6km, the electric dipole distance is 100m, and the grounding resistance is less than 500 omega. The controllable source electromagnetic observation system is shown in figure 2.
The background field data before the hot dry rock reservoir is transformed is collected, the signal-to-noise ratio of all the measuring point data is calculated by using a relative resistivity anomaly calculation formula, the maximum signal-to-noise ratio is 70.0dB, the minimum signal-to-noise ratio is 35.0dB, and the technical specification requirements are met.
After fracturing of the dry hot rock XB01 well, three-dimensional controllable source electromagnetic data after reservoir transformation is collected, signal-to-noise ratios of data of all measuring points are calculated by using a relative resistivity anomaly calculation formula, the signal-to-noise ratio is maximum 80.0 dB and minimum 40.0dB, and technical specification requirements are met.
According to the present invention, step S3 is executed: based on regularization inversion and conjugate gradient inversion technologies, a new inversion target function is constructed, a conjugate gradient method is used for optimizing the target function, the advantages of regularization inversion and conjugate gradient inversion are combined, three-dimensional inversion is carried out on three-dimensional controllable source electromagnetic data before and after dry hot rock reservoir transformation, and fracture zone depth and resistivity data volumes in the dry hot rock reservoir before and after fracturing are obtained. And performing three-dimensional inversion on the ambient field data and the three-dimensional controllable source electromagnetic data after reservoir transformation to obtain a fracturing area depth and resistivity data volume before and after fracturing. Fig. 3 is a three-dimensional resistivity inversion section of a background field of a well passing XB01, fig. 4 is a three-dimensional resistivity inversion section of a reservoir after reservoir reconstruction of a well passing XB01, the three-dimensional resistivity inversion section reveals changes before and after reservoir reconstruction, and the longitudinal coincidence with an electric logging curve is good.
According to the present invention, step S4 is executed: in order to highlight the change of the dry-hot rock reservoir before and after the transformation, the obtained depth and resistivity data bodies before and after the fracturing are processed, the relative resistivity abnormity is calculated, the data body with the relative resistivity abnormity is obtained, the transformation range of the reservoir is highlighted, and the transformation range of the reservoir is clearly reflected. Fig. 5 is a relative resistivity abnormal profile of the XB01 well, which highlights the scope of reservoir transformation, so that the scope of reservoir transformation is clearly reflected.
According to the present invention, step S5 is executed: and performing coordinate conversion on the relative resistivity abnormal data body to obtain a scatter data body under a three-dimensional rectangular coordinate system, performing interpolation processing on the scatter data body under the three-dimensional rectangular coordinate system by using Matlab Software or Golden Software Voxler professional Software by adopting an inverse distance weighting method or a Crigy method, and performing three-dimensional space imaging. FIG. 6 is a three-dimensional relative resistivity abnormal volume map under a rectangular spatial coordinate system, wherein the relative resistivity abnormal volume is equivalent to a cuboid, and the volume is calculated according to the cuboid to be 2174 × 10 4 m 3 (length 630m, width 230m, height 150 m).
The implementation of the embodiment shows that the controllable source electromagnetic method is sensitive to the change of the underground resistivity and can reflect the change of the resistivity before and after the hydraulic fracturing reconstruction of the dry heat rock reservoir, as shown in fig. 3, 4 and 5, and the abnormal range of the relative resistivity is obviously smaller than the range of the microseism event after positioning, as shown in fig. 7. Compared with the prior art, the relative resistivity abnormal volume directly reflects the distribution and migration trend of the fracturing fluid and is closer to the real volume of the fracturing modification of the hot dry rock reservoir, and the controllable source electromagnetic technology improves the precision of the production prediction after the fracturing modification of the hot dry rock reservoir
The controllable source electromagnetic method is sensitive to underground resistivity change, adopts artificial source power supply, has strong anti-jamming capability, acquires surface electromagnetic field data before and after fracturing by using the controllable source electromagnetic method, performs inversion processing to obtain depth and resistivity data volumes before and after fracturing of a reservoir, calculates the abnormal volume of relative resistivity, obtains the fracturing modification volume of the dry and hot rock reservoir, directly reflects the distribution and migration trend of fracturing fluid by the abnormal volume of relative resistivity, is closer to the real volume of fracturing modification of the dry and hot rock reservoir, and improves the precision of yield prediction after fracturing modification of the dry and hot rock reservoir by using the controllable source electromagnetic technology.
The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present application and such modifications and equivalents should also be considered to be within the scope of the present application.
Claims (10)
1. A method for predicting the hydraulic fracturing modification volume of a hot dry rock reservoir is characterized by comprising the following steps:
s1, before fracturing monitoring of the hot dry rock reservoir, performing a controllable source three-dimensional electromagnetic method acquisition parameter test and optimization design to improve observation precision and data acquisition quality;
s2, arranging three-dimensional controllable source electromagnetic measuring points above fracturing perforations in a dry hot rock reservoir monitoring area, using artificial source excitation, carrying out data acquisition at the three-dimensional controllable source electromagnetic measuring points before fracturing to obtain three-dimensional controllable source electromagnetic data before dry hot rock reservoir modification, carrying out data acquisition at the three-dimensional controllable source electromagnetic measuring points after fracturing to obtain the three-dimensional controllable source electromagnetic data after dry hot rock reservoir modification, keeping excitation and receiving conditions before and after fracturing consistent, and keeping the position of a transmitting source unchanged to reduce errors caused by excitation and receiving condition changes to improve transverse detection precision;
s3, constructing a new inversion target function based on regularization inversion and conjugate gradient inversion technologies, optimizing the target function by using a conjugate gradient method, and performing three-dimensional inversion on three-dimensional controllable source electromagnetic data before and after the dry hot rock reservoir is modified by combining the advantages of regularization inversion and conjugate gradient inversion to obtain a fracturing area depth and resistivity data volume in a dry hot rock reservoir monitoring area before and after fracturing;
s4, processing the obtained fracturing zone depth and resistivity data body, calculating relative resistivity abnormity, and obtaining a data body with the abnormal relative resistivity so as to clearly reflect the transformation range of the dry-hot rock reservoir;
and step S5, performing coordinate conversion on the abnormal data volume of the relative resistivity to obtain a scattered data volume under a rectangular coordinate system in a three-dimensional space, performing interpolation processing on the scattered data volume by adopting an inverse distance weighting method or a Criging method, performing three-dimensional space imaging, and calculating the abnormal volume of the relative resistivity based on the three-dimensional space imaging to be used as the fracturing reconstruction volume of the dry heat rock reservoir, wherein the abnormal volume of the relative resistivity is reflected as a quantitative index of the arrival range of fracturing liquid.
2. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 1, wherein the method comprises the following steps: the developing of the controllable source three-dimensional electromagnetic method acquisition parameter test and optimization comprises the following steps:
according to the actual noise condition of the dry hot rock reservoir monitoring area, establishing a geoelectric model by using monitoring well logging data of the dry hot rock reservoir monitoring area, developing forward simulation to determine the optimal excitation period of target layer detection, and increasing the excitation frequency for the dry hot rock reservoir so as to improve the longitudinal resolution of the dry hot rock reservoir;
on the basis of simulation demonstration, a receiving and transmitting distance test, an excitation period test and an electric dipole distance test are carried out by combining the geoelectricity condition and the noise level of a work area to optimize the acquisition parameters;
the interference source investigation test is carried out in the dry hot rock reservoir monitoring area to obtain the interference source type of the dry hot rock reservoir monitoring area, the distance and the degree of the interference source influencing the data quality are determined through the field test in the dry hot rock reservoir monitoring area, the point selection of the three-dimensional controllable source electromagnetic measuring point is guided according to the distance and the degree of the interference source influencing the data quality, and the emission current is determined, so that the data acquisition quality and the observation precision are guaranteed.
3. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 2, wherein the method comprises the following steps: the method for keeping the excitation and receiving conditions consistent before and after fracturing and the position of the emission source unchanged comprises the following steps: the grounding resistance change states of the transmitting end and the receiving end of the artificial source are regularly checked, and the grounding conditions before and after fracturing are kept unchanged by taking measures of regularly watering saline to reduce the grounding resistance and timely replacing a damaged electrode, so that the consistency of the excitation conditions before and after fracturing and the receiving conditions, the position of the transmitting source is kept unchanged, and errors caused by the change of the excitation conditions and the receiving conditions are reduced.
4. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 3, wherein the method comprises the following steps: the artificial source is excited by high power so as to enhance the anti-interference capability, improve the signal-to-noise ratio of data acquisition and increase the monitoring depth to a hot dry rock reservoir.
5. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 4, wherein the method comprises the following steps: the method comprises the steps that signal-to-noise ratio analysis is carried out on three-dimensional controllable source electromagnetic data after the three-dimensional controllable source electromagnetic data are collected each time, so that quality evaluation on the three-dimensional controllable source electromagnetic data is achieved to collect and screen the three-dimensional controllable source electromagnetic data, relatively stable long-period signals are selected from the three-dimensional controllable source electromagnetic data, noise and signals are separated according to a positive half shaft and negative half shaft superposition technology which is not over zero, the signal-to-noise ratios of all three-dimensional controllable source electromagnetic measuring points are calculated, and the three-dimensional controllable source electromagnetic data are evaluated on the basis of the signal-to-noise ratios;
the signal-to-noise ratio calculation formula is as follows:
in the formula (I), the compound is shown in the specification,SNRfor the purpose of the signal-to-noise ratio,Tin order to be the length of the period,Nthe number of total sample points in a half period,A z (T,t i )is composed oft i The strength of the signal acquired at a time,iare the metering constants.
6. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 5, wherein the method comprises the following steps: the evaluating three-dimensional controllable source electromagnetic data based on the signal-to-noise ratio comprises:
if the signal-to-noise ratio is within a confidence interval of the technical specification requirement, the three-dimensional controllable source electromagnetic data meet the technical specification requirement;
and if the signal-to-noise ratio is outside the confidence interval required by the technical specification, the three-dimensional controllable source electromagnetic data does not meet the requirement of the technical specification.
7. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 6, wherein the method comprises the following steps: the new construction method of the inversion target function comprises the following steps:
the method comprises the steps of constructing a regularized inversion target function, carrying out minimization solving on the regular inversion target function by using a conjugate gradient method to obtain a new inversion target function, improving the inversion precision by fusing the advantages of regularized inversion and conjugate gradient inversion, and obtaining a three-dimensional inversion profile of the hot dry rock reservoir which reveals the change characteristics before and after reservoir transformation.
8. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 7, wherein the method comprises the following steps:
the calculation formula of the relative resistivity anomaly is as follows:
in the formula (I), the compound is shown in the specification,
in order for the relative resistivity to be abnormal,
for the resistivity of the hot dry rock reservoir after fracturing,
is the resistivity of the hot dry rock reservoir before fracturing.
9. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 8, wherein the method comprises the following steps: the three-dimensional controllable source electromagnetic method is used for carrying out area observation and improving the transverse observation precision.
10. The method for predicting the hydraulic fracturing modification volume of the thermite reservoir according to claim 9, wherein the method comprises the following steps: the method for calculating the relative resistivity abnormal volume comprises the following steps: and (3) the abnormal volume of the relative resistivity is equivalent to a cuboid, and the abnormal volume of the relative resistivity is approximately calculated according to the volume size calculation mode of the cuboid.
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