阅读说明：本技术 一种基于改进波形叠加函数的微地震事件偏移定位方法 (Microseism event migration positioning method based on improved waveform stacking function ) 是由 毛庆辉 王晨晨 唐永 王鹏 桂志先 于 2021-07-07 设计创作，主要内容包括：本发明属于石油地球物理勘探开发技术领域,提供了一种基于改进波形叠加函数的微地震事件偏移定位方法。该方法利用先将纵横波波形相似性函数与其波形振幅叠加函数进行乘积,然后再对其进行求和的思路,可提高波形叠加目标函数的收敛性,从而可提高微地震事件定位的精度。(The invention belongs to the technical field of geophysical exploration and development of petroleum and provides a microseism event migration positioning method based on an improved waveform stacking function. The method can improve the convergence of a waveform superposition target function by using the idea of multiplying the waveform similarity function of longitudinal waves and transverse waves with the waveform amplitude superposition function of the longitudinal waves and the transverse waves and then summing the products, thereby improving the precision of positioning the microseism event.)

1. A microseism event migration positioning method based on an improved waveform stacking function is characterized by comprising the following steps:

s1: inputting data, including:

s11: inputting any detector m in the microseism event, recording the rough estimation first arrival travel time of the longitudinal wave or the transverse waveWherein K may be a longitudinal wave P or a transverse wave S;

s12: inputting a corrected speed model and a longitudinal and transverse wave theory first arrival time table in a target area;

s13: inputting seismic data and carrying out polarity correction on the data in a scanning time window;

s2: constructing an objective function E based on improved waveform superposition according to the idea of multiplying a waveform similarity function of longitudinal waves and transverse waves with a waveform amplitude superposition function of the longitudinal waves and the transverse waves and then summing the products_ISWS；

S3: searching the imaging maximum value of the objective function through a grid searching technology;

s4: and outputting the corresponding seismic source position when the imaging value is maximum, namely the micro-seismic event position.

2. The method for migration positioning of micro-seismic events based on the improved waveform stacking function as claimed in claim 1, wherein in the above technical solution, in the step S12, the velocity model can be established by using the acoustic logging data and the geological stratification data to establish an initial velocity model, and then the velocity model is corrected by using the perforation data; the longitudinal and transverse wave theory first arrival time table in the target area can grid the target area, and then calculate the longitudinal and transverse wave theory first arrival time from each grid point to each detector through ray tracing.

3. The method as claimed in claim 1, wherein in step S13, the polarity correction is performed by a sign coefficientThe method is realized by judging the amplitude symbol in a scanning time window in the record of the detector, ensuring the consistency of the positive and negative signs and ensuring the homodromous superposition of the waveforms.

4. The method of claim 1, wherein in step S2, an objective function E based on modified waveform stacking is constructed_ISWSComprises the following steps:

in step S2 in the formula: i and j represent the detector number and discrete time number, respectively, n is the total number of detectors, u_iIs the amplitude value of the ith trace of the seismic data; l is_P(j)、L_S(j) Respectively is a longitudinal wave and transverse wave waveform amplitude superposition function at a time sequence j; s_P(j)、S_S(j) Respectively is a longitudinal wave waveform similarity superposition function and a transverse wave waveform similarity superposition function at the j position of the time sequence;is the original amplitude u of the longitudinal and transverse waves recorded by the ith detector_iThe corresponding polarity correction sign of (1);respectively assuming the longitudinal wave theoretical time and the transverse wave theoretical time from a seismic source point to the ith detector;the theoretical time of longitudinal or transverse waves from a seismic source point to the mth detector is assumed;the time differences correspond to the types of the longitudinal wave and the transverse wave combination time respectively.

5. The method for microseism event migration positioning based on the improved waveform stacking function of claim 4, wherein K and m in formulas (6) and (7) and the first arrival travel time roughly estimated in step S11The corresponding parameters are the same.

Technical Field

The invention belongs to the technical field of geophysical exploration and development of petroleum, and particularly relates to a microseism event migration positioning method based on an improved waveform stacking function.

Background

The hydraulic fracturing micro-seismic monitoring technology is widely applied to shale stratum fracturing development, the micro-seismic event positioning result can guide the evaluation of fracturing effect, the optimization of fracturing design scheme and the like, and a solid foundation is laid for shale gas yield increase.

Microseismic event positioning is divided into two main categories, the first category is a positioning method based on travel time category, and the second category is a positioning method based on waveform category. The theory of the former method is already mature, but the dependence on the first arrival precision and the accuracy of the velocity model is high, and the method is limited to be applied to the regions with low signal-to-noise ratio data and inaccurate velocity models to a certain extent. The latter is a new microseismic event positioning method which has the advantages that the method does not need first-arrival picking or does not depend on first-arrival precision, can adapt to low signal-to-noise ratio data, but the precision of the method is generally influenced by the precision of a waveform superposition function. Trojanowski et al (Trojanowski J, Eisner L. Complex of calibration-based positioning and detection methods for micro-electronics [ J ]. Geophanic profiling, 2017, 65 (1): 47-63.) and Kim et al (Kim J, Woo J U, Rhie J, Kang T S.2017.automatic calibration of first-motion polarity and its approximation to a micro-electronics analysis of micro-electronics [ J ]. Geosence Journal, 21 (5): 695-. After the original waveform is subjected to polarity correction, the convergence of the conventional waveform superposition target function method still needs to be further improved. Therefore, the development of a microseism event migration positioning method based on an improved waveform stacking function under waveform polarity correction is urgently needed.

Disclosure of Invention

The invention aims to overcome the defects of the background technology and provide a microseism event migration positioning method based on an improved waveform stacking function.

In order to achieve the above object, the present invention provides a microseism event migration positioning method based on improved waveform stacking function, which comprises the following steps for any microseism event (seismic source) positioning:

s1: inputting data, including:

s11: inputting any detector m in the microseism event and recording longitudinal waveOr rough estimation of first arrival travel time of transverse waveWherein K may be a longitudinal wave P or a transverse wave S;

s12: inputting a corrected speed model and a longitudinal and transverse wave theory first arrival time table in a target area;

s13: inputting seismic data and carrying out polarity correction on the data in a scanning time window;

s2: constructing an objective function E based on improved waveform superposition according to the idea of multiplying a waveform similarity function of longitudinal waves and transverse waves with a waveform amplitude superposition function of the longitudinal waves and the transverse waves and then summing the products_ISWSAs follows:

in step S2 in the formula: i and j represent the detector number and discrete time number, respectively, n is the total number of detectors, u_iIs the amplitude value of the ith trace of the seismic data; l is_P(j)、L_S(j) Respectively is a longitudinal wave and transverse wave waveform amplitude superposition function at a time sequence j; s_P(j)、S_S(j) Respectively is a longitudinal wave waveform similarity superposition function and a transverse wave waveform similarity superposition function at the j position of the time sequence; is the original amplitude u of the longitudinal and transverse waves recorded by the ith detector_iThe corresponding polarity correction sign of (1);respectively assuming the longitudinal wave theoretical time and the transverse wave theoretical time from a seismic source point to the ith detector;the theoretical time of longitudinal or transverse waves from a seismic source point to the mth detector is assumed; time differences corresponding to the longitudinal wave and transverse wave combination time types respectively;

s3: searching the imaging maximum value of the objective function through a grid searching technology;

s4: and outputting the corresponding seismic source position when the imaging value is maximum, namely the micro-seismic event position.

In the above-mentioned technical solution, in the step S11, the first arrival travel time is roughly estimated using the longitudinal or transverse waveThe unknown seismic source origin time in the conventional waveform superposition method is replaced, and a large amount of scanning calculation amount can be reduced.

In the above technical solution, in the step S12, the velocity model may establish an initial velocity model through the acoustic logging data and the geological stratification data, and then perform velocity model correction using the perforation data. The longitudinal and transverse wave theory first arrival time table in the target area can grid the target area, and then calculate the longitudinal and transverse wave theory first arrival time from each grid point to each detector through ray tracing.

In the above technical solution, in the step S13, the polarity correction may be performed by a sign coefficientThe method is realized by judging the amplitude symbol in a scanning time window in the record of the detector, ensuring the consistency of the positive and negative signs and ensuring the homodromous superposition of the waveforms.

In the above technical solution, in the step S2, K and m in the formulas (6) and (7) and the first arrival travel time in the step S11 are roughly estimatedThe corresponding parameters are the same.

Compared with the prior art, the invention has the following advantages:

the invention can improve the convergence of the waveform superposition target function by utilizing the idea of multiplying the waveform similarity function of the longitudinal wave and the transverse wave with the waveform amplitude superposition function of the longitudinal wave and the transverse wave and then summing the products, thereby improving the precision of the positioning of the microseism event.

Drawings

FIG. 1 is a schematic flow chart of the implementation of the present invention.

FIG. 2 is a two-dimensional micro seismic well observation system based on a homogeneous medium model in an embodiment of the invention.

FIG. 3 is a microseismic event theoretical model z-component record in an embodiment of the present invention.

Fig. 4a is a conventional waveform overlay objective function distribution plot.

FIG. 4b is a graph of the distribution of the objective function of the method of the present invention.

Detailed Description

The embodiments of the present invention will be described in further detail with reference to the drawings and examples, but they are not intended to limit the present invention and are merely examples. While the advantages of the invention will be apparent and readily appreciated by the description.

The microseism event migration positioning method based on the improved waveform stacking function, as shown in fig. 1, includes the following steps:

s1: inputting data, including:

s11: inputting any detector m in the microseism event, recording the rough estimation first arrival travel time of the longitudinal wave or the transverse waveWherein K may be a longitudinal wave P or a transverse wave S;

s12: inputting a corrected speed model and a longitudinal and transverse wave theory first arrival time table in a target area;

s13: inputting seismic data and carrying out polarity correction on the data in a scanning time window;

s2: constructing an objective function E based on improved waveform superposition according to the idea of multiplying a waveform similarity function of longitudinal waves and transverse waves with a waveform amplitude superposition function of the longitudinal waves and the transverse waves and then summing the products_ISWSAs follows:

in step S2 in the formula: i and j represent the detector number and discrete time number, respectively, n is the total number of detectors, u_iIs the amplitude value of the ith trace of the seismic data; l is_P(j)、L_S(j) Respectively is a longitudinal wave and transverse wave waveform amplitude superposition function at a time sequence j; s_P(j)、S_S(j) Respectively is a longitudinal wave waveform similarity superposition function and a transverse wave waveform similarity superposition function at the j position of the time sequence;is the original amplitude u of the longitudinal and transverse waves recorded by the ith detector_iThe corresponding polarity correction sign of (1);respectively assuming the longitudinal wave theoretical time and the transverse wave theoretical time from a seismic source point to the ith detector;the theoretical time of longitudinal or transverse waves from a seismic source point to the mth detector is assumed;time differences corresponding to the longitudinal wave and transverse wave combination time types respectively;

s3: searching the imaging maximum value of the objective function through a grid searching technology;

s4: and outputting the corresponding seismic source position when the imaging value is maximum, namely the micro-seismic event position.

In the above-mentioned technical solution, in the step S11, the first arrival travel time is roughly estimated using the longitudinal or transverse waveThe unknown seismic source origin time in the waveform superposition method is replaced, and a large amount of scanning calculation amount can be reduced.

In the above technical solution, in the step S12, the velocity model may establish an initial velocity model through the acoustic logging data and the geological stratification data, and then perform velocity model correction using the perforation data. The longitudinal and transverse wave theory first arrival time table in the target area can grid the target area, and then calculate the longitudinal and transverse wave theory first arrival time from each grid point to each detector through ray tracing.

In the above technical solution, in the step S13, the polarity correction may be performed by a sign coefficientThe method is realized by judging the amplitude symbol in a scanning time window in the record of the detector, ensuring the consistency of the positive and negative signs and ensuring the homodromous superposition of the waveforms.

In the above technical solution, in the step S2, K and m in the formulas (6) and (7) and the first arrival travel time in the step S11 are roughly estimatedThe corresponding parameters are the same.

Example (b): firstly, establishing a two-dimensional microseism well observation system based on a uniform medium model, wherein the longitudinal wave velocity Vp is 2000m/s, the transverse wave velocity Vs is 1200m/s, and the density is 2.0g/cm³. As shown in fig. 2, the depth z of 11-stage detectors in the monitoring well (vertical well) with the horizontal distance x of 200m is respectively located at 950-1050m (triangle in fig. 2), and the track pitch is 10 m. The true position of the target microseismic event (the five-pointed star in fig. 2) is set to (x, z) ═ (420, 1030) m. And then, performing two-dimensional elastic wave equation forward modeling by adopting 60Hz Rake wavelets, wherein the sampling interval is 0.5ms, and obtaining a theoretical model z-component seismic record of the target event (figure 3). Step 1 is applied to input the corresponding data, and for convenience of discussion herein, K is taken as the S wave.

In order to test the convergence of the waveform superposition target function of the method of the invention superior to that of the waveform superposition target function of the traditional method, the theoretical models are respectively used for carrying out comparative analysis on the convergence of the waveform superposition target function of the method of the invention and the traditional waveform superposition target function. And trial calculation is carried out on the waveform superposition target function by using a theoretical model, and respective target function distribution graphs can be obtained. In fig. 4a to 4B, the five-pointed star represents the true position of the micro-seismic event, the intersection point of two lines represents the offset positioning result of the micro-seismic event based on the respective waveform superposition objective function, the color scale area a represents the high-value area of the function, and the color scale area B represents the low-value area. Fig. 4a is a waveform-superimposed objective function profile and fig. 4b is an improved waveform-superimposed objective function profile proposed by the present invention. As can be seen from comparing fig. 4a with fig. 4b, fig. 4b is more convergent than the waveform superposition target function of fig. 4a, i.e. the improved waveform superposition target function proposed by the present invention is more convergent than the conventional waveform superposition target function.

In summary, the method of the invention improves the convergence of the waveform superposition target function by using the idea of multiplying the waveform similarity function of the longitudinal wave and the transverse wave with the waveform amplitude superposition function of the longitudinal wave and the transverse wave and then summing the products, thereby improving the precision of positioning the microseism event.

Details not described in this specification are within the skill of the art that are well known to those skilled in the art.