CN117452491A - Combined exploration method for identifying characteristics of gas reservoirs of coal series under complicated mountain land surface conditions - Google Patents
Combined exploration method for identifying characteristics of gas reservoirs of coal series under complicated mountain land surface conditions Download PDFInfo
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Abstract
The invention relates to the technical field of gas reservoir characteristic recognition, and discloses a combined exploration method for gas reservoir characteristic recognition under complex mountain land surface conditions, which comprises the following steps: analyzing the geological profile and geological conditions in the range of the work area, designing a seismic line according to the analysis result, and drawing a geological profile; according to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, designing an earthquake construction scheme; according to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, a preset processing method is adopted to process the seismic data; and performing seismic interpretation, inversion and gas reservoir characteristic identification. The combined exploration method for identifying the gas reservoir characteristics under the complex mountain land surface condition provided by the invention covers the key method technology of seismic exploration of seismic survey line design, seismic construction scheme design, seismic data processing, seismic interpretation and inversion and gas reservoir characteristic identification, and is used for identifying the gas reservoir characteristics under the complex mountain land surface condition.
Description
Technical Field
The invention relates to the technical field of gas reservoir characteristic recognition, in particular to a combined exploration method for gas reservoir characteristic recognition under complex mountain land surface conditions.
Background
The coal-based natural gas is natural gas generated by coal, carbonaceous shale and dark shale in the coal-based, and comprises continuous coalbed methane, shale gas, dense gas, trapped gas reservoirs and other resource types.
The coal-based gas reservoir is not equivalent to coal-bed gas, and compared with the exploitation of single gas reservoirs such as natural gas, shale gas and coal-bed gas in conventional sand bodies, the occurrence rules of reservoir gas content, physical properties, stacked gas-containing systems and the like in the coal-based gas reservoir are complex, so that the difficulties of layer selection, transformation technology, trial exploitation and the like are great, and the evaluation method for deeply researching the coal-based gas enrichment region is indistinct. In the face of a stacked coal-series gas reservoir of coal-bed gas, shale gas and dense gas with complex lithology combination relationship, how to search high-quality gas-containing combinations in coal-series stratum and predict potential blocks of coal-series gas becomes a difficulty. At present, the characteristic recognition technology of the gas reservoir of the coal system is in a starting stage, and a mature exploration method is not available. The seismic exploration can be applied to the identification of the characteristics of the target layer of the coal bed gas by means of construction fine interpretation, seismic attribute analysis, various inversion and the like; well logging provides a favorable support for coal bed gas seismic inversion interpretation, but a mature and effective technical method system for identifying the characteristics of the gas reservoir under the surface condition of the complex mountain land is not available.
Disclosure of Invention
The invention provides a combined exploration method for identifying the characteristics of a gas reservoir under the surface condition of a complex mountain land, which covers the key method technology of seismic exploration including seismic survey line design, seismic construction scheme design, seismic data processing, seismic interpretation and inversion and the identification of the characteristics of the gas reservoir and is used for identifying the characteristics of the gas reservoir under the surface condition of the complex mountain land.
The invention provides a combined exploration method for identifying characteristics of a gas reservoir under the condition of complex mountain land surfaces, which comprises the following steps:
analyzing the geological profile and geological conditions in the range of the work area, designing a seismic line according to the analysis result, and drawing a geological profile;
according to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, designing an earthquake construction scheme; the seismic construction scheme comprises observation system parameters, instrument factors, excitation factors and receiving factors;
according to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, a preset processing method is adopted to process the seismic data; the preset processing method comprises high-precision static correction, a multi-domain prestack denoising comprehensive noise technology, a relative amplitude maintaining processing technology, a resolution improving processing technology and a fine prestack time migration technology;
performing seismic interpretation, inversion and gas reservoir characteristic identification; including coal seam thickness prediction, density inversion, and gas-containing prediction.
Further, the steps of analyzing the geological profile and geological conditions in the range of the work area, designing a seismic line according to the analysis result, and drawing a geological profile comprise the following steps:
analyzing a geological profile in the range of a work area, wherein the analysis of the geological profile comprises stratum characteristic analysis and structural characteristic analysis, the stratum characteristic analysis comprises stratum distribution conditions, thickness and lithology characteristics from the earth surface to a target layer and deeper, and the structural characteristic analysis comprises anticline and fault;
analyzing earthquake geological conditions in a work area, wherein the geological conditions comprise surface earthquake geological conditions and deep earthquake geological conditions, the surface earthquake geological conditions comprise the topography, landform, surface lithology, stratum dip angle, weathering degree and water content of the work area, and the deep earthquake geological conditions comprise stratum lithology combination, sedimentation characteristics and structural development conditions;
designing a seismic line according to the analysis results of the geological profile and the geological conditions; wherein the seismic line compliance principle includes: the measuring line is perpendicular to the construction direction or the set angle is perpendicular to the construction direction; the survey lines avoid areas which cannot be traversed by the earthquake survey lines such as towns, rivers, lakes and the like; the survey lines are deployed relatively uniformly, and the seismic survey lines are drilled by known wells;
drawing a geological section according to the design condition of the seismic survey line and the geological data of the region so as to prepare for the interpretation of the comprehensive earthquake; wherein the geologic profile includes associated geologic elements from the earth's surface to the target layer and deeper, and the geologic profile length is no shorter than the designed seismic line length.
Further, the step of processing the seismic data by adopting a preset processing method according to the complex mountain land surface conditions and the underground geological conditions of the gas reservoir comprises the following steps:
the high-precision correction includes: performing chromatographic static correction through first arrival pickup, comparing and optimizing by combining Gao Chengjing correction, performing dominant frequency band reflected wave static correction speed analysis, and finally performing surface consistency residual static correction and global optimizing residual static correction;
the multi-domain prestack denoising technique comprises: static correction of a reference surface; manually removing bad cannons and bad tracks; single-frequency noise suppression; pressing the surface wave; linear noise suppression; abnormal amplitude suppression; deconvolution and residual static correction; stacking; denoising after stacking;
the relative amplitude maintenance processing technology comprises longitudinal compensation and transverse compensation, wherein the longitudinal compensation is stratum absorption compensation, and the transverse compensation is ground surface consistency compensation;
the resolution enhancement processing technology comprises surface consistency deconvolution and prediction deconvolution, wherein the surface consistency deconvolution is wavelet consistency, and the prediction deconvolution is compression wavelet;
the fine prestack time migration technique includes: relatively maintaining pre-stack processing data; PSTM parameter analysis; PSTM initial imaging and anti-NMO velocity analysis; the final curved ray PSTM is imaged.
Further, in the steps of performing seismic interpretation, inversion and gas reservoir feature identification, the predicting the thickness of the coal seam includes:
the single strong wave crest and the strong phase in the seismic waveform characteristics are used as a standard layer and a mark layer, and on the basis of the standard layer, the identification and division of other main geological layers are carried out by using the characteristics of the upper weak phase, the lower strong phase and the double strong phases of other wave groups; on the basis of accurately identifying the horizon, the thickness of the reservoir is predicted by utilizing the relation between the reflected wave kinematics and dynamics characteristic parameters and thickness statistics, and particularly, the coal seam is divided into the following steps by utilizing the relation between the thickness of the coal seam and the earthquake wavelength: a thin layer region, a thick layer transition region, and a thick layer region; and finally, extrapolating the coal thickness variation trend of the whole area by utilizing the seismic wave amplitude value at the drilling position and the coal seam thickness value.
Further, in the steps of performing seismic interpretation, inversion and gas reservoir feature identification, the density inversion and gas content prediction include:
after predicting the change trend of the coal thickness in the work area, establishing a unitary once simulation calculation formula by utilizing the correlation coefficient of the total gas content and the density obtained by logging data to obtain the gas content distribution around the wellhead; because the coal gas reservoir has the characteristic of relatively low longitudinal and transverse wave speed ratio, the pre-stack elastic parameter inversion can be utilized to predict the gas content of the whole work area.
Further, the elastic wave impedance inversion calculation formula is as follows:
k is defined as follows:
wherein EI represents elastic wave impedance, θ represents incident angle, ρ represents density, and V p And V s Representing longitudinal wave velocity and transverse wave velocity, respectively.
Further, the gas-bearing seismic inversion procedure for the gas reservoirs is as follows:
AVO analysis is carried out on the seismic trace set, and near angle theta is carried out 1 Superimposed, distant angle theta 2 Stacking;
near angle theta 1 Superimposed inversion to elastic impedance EI (θ) 1 ) Far angle theta 2 Superimposed inversion to elastic impedance EI (θ) 2 ) And taking EI as input while inverting V p 、V s And density;
by means of calibrated V p And V s Continuously iterating to invert the density until the inverted density value is basically consistent with the logging data, and stopping inversion; wherein, for V p And V s Constraint is performed by using known data;
and (5) carrying out gas content prediction of the whole work area by using the relation between density establishment and gas content.
Further, in the steps of performing seismic interpretation, inversion and gas reservoir feature recognition, the method further comprises predicting the gas-containing fullness degree by using a WVD time spectrum decomposition and RGB fusion technology based on a maximum entropy criterion, specifically comprising the following steps:
obtaining post-stack seismic data having high resolution characteristics according to the high-precision, high-resolution seismic processing steps described above;
according to the absorption and attenuation characteristics of the stratum, a Wigner-Ville distribution analysis method with high time-frequency focusing performance and time-frequency resolution capability and maximum entropy as a criterion is selected to analyze the post-stack seismic data channel by channel;
on the basis of obtaining time-frequency domain data of each channel of seismic data, selecting 3 different frequency band ranges according to spectrum analysis characteristics, performing spectrum decomposition processing on the obtained time-frequency joint domain result, converting an original data matrix into 3 data matrices with the same scale, wherein the 3 data matrices respectively correspond to low frequency, medium frequency and high frequency parts of the original data in a frequency domain;
after spectrum decomposition, the information reflected by the frequency components of different frequency bands is different, and 3 frequency domain components are displayed by fusion processing through an RGB fusion technology; the RGB fusion technology is to convert 3 kinds of data with the same scale into red, green and blue three primary color values respectively, and obtain normal color values through fusion display;
when the RGB fusion is completed, the larger the proportion of the white part in the image is, the more and the thicker the gas content of the part of coal bed gas is.
The beneficial effects of the invention are as follows:
aiming at the characteristic identification of the coal gas reservoir under the surface condition of the complex mountain land, the first step of seismic survey line design considers the surface condition of the complex mountain land and the underground geological condition of the coal bed gas reservoir, and the designed survey line can meet the exploration requirement; the design of the second step earthquake construction scheme is summarized through a large number of test works of real cases, and has good universality for similar target tasks; the third step of seismic data processing adopts a processing technical method aiming at complex mountain areas and gas reservoirs, so that the processing effect is good; the fourth step of seismic interpretation, inversion and gas reservoir characteristic identification adopts an improved seismic inversion method, so that inversion multi-solution property is reduced, and the thickness, density, gas content and the like of a coal bed are effectively predicted; and meanwhile, the WVD spectrum decomposition technology and the RGB fusion technology based on the maximum entropy criterion are utilized, so that the gas content of the gas reservoir of the coal system can be effectively predicted. In conclusion, the method can be effectively applied to the identification of the characteristics of the gas reservoirs under the surface condition of the complex mountain land, and has stronger guiding significance for the subsequent exploration and development of the gas reservoirs and the preferential selection of the favorable areas.
Drawings
FIG. 1 is a schematic flow chart of a combined exploration method for identifying characteristics of a gas reservoir of a coal system.
FIG. 2 is a schematic diagram of a construction plan observation system according to the present invention.
FIG. 3 is a schematic diagram of a high-precision static correction flow chart in the invention.
Fig. 4 is a schematic diagram of a multi-domain prestack integrated denoising process according to the present invention.
FIG. 5 is a schematic diagram of an amplitude compensation process according to the present invention.
FIG. 6 is a schematic diagram of a series deconvolution process in accordance with the present invention.
Fig. 7 is a schematic diagram of a pre-stack time migration flow in the present invention.
FIG. 8 is a schematic diagram showing a flow of predicting the gas content of a gas reservoir in the present invention.
FIG. 9 is a schematic diagram of a flow chart of predicting gas-containing property by using a WVD time spectrum decomposition fusion technology based on the maximum entropy criterion in the invention.
FIG. 10 is a graph comparing the discrimination capability of a single trace of measured seismic signals and the conventional GST and maximum entropy WVD according to the present invention.
FIG. 11 is a schematic diagram of a gas reservoir gas content inversion profile in accordance with the present invention.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in FIG. 1, the invention provides a combined exploration method for identifying characteristics of a gas reservoir under the condition of complex mountain land surfaces, which comprises the following steps:
the first step: the design of the seismic line, analyzing the geological profile and geological conditions in the range of the work area, designing the seismic line according to the analysis result, and drawing a geological profile;
(1) The geological profile in the range of the work area is analyzed, wherein the analysis of the geological profile comprises stratum characteristic analysis and structural characteristic analysis, the stratum characteristic analysis mainly comprises stratum distribution conditions, thickness, lithology characteristics and the like from the earth surface to a target layer and further, and the structural characteristic analysis mainly comprises anticline structure, fault and the like.
(2) Analyzing earthquake geological conditions in a work area, wherein the geological conditions comprise surface earthquake geological conditions and deep earthquake geological conditions, the surface earthquake geological conditions comprise work area topography, landform, surface lithology, stratum dip angle, weathering degree, water content and the like, and the deep earthquake geological conditions comprise stratum lithology combination, sedimentation characteristics, structural development conditions and the like;
(3) Designing a seismic line according to the analysis results of the geological profile and the geological conditions; wherein the seismic line compliance principle includes: (1) the measuring line is perpendicular to the construction direction or at a large angle; (2) the survey lines avoid areas which cannot be traversed by the earthquake survey lines such as towns, rivers, lakes and the like as far as possible; (3) the survey line deployment is relatively uniform and the seismic survey line passes through the known well.
(4) According to the design condition of the earthquake survey line, the geological profile of the region is drawn by combining the geological data of the region, so as to prepare for the interpretation of the comprehensive earthquake; wherein the geological profile includes the relevant geological elements (scale, profile trend, stratum, structure, special geologic volume, etc.) from the earth's surface to the target layer and deeper, and the geological profile length is not shorter than the designed seismic line length.
And a second step of: design of earthquake construction scheme
According to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, designing an earthquake construction scheme; the seismic construction scheme comprises observation system parameters, instrument factors, excitation factors and receiving factors; as shown in FIG. 2, a recommended solution is given, and the specific solution can be finely tuned according to the test results.
(1) Designing and observing system parameters
Observing the system type: 3 lines of 1 cannon and mid-point excitation; observation system: 4790-10-20-10-4790; number of received channels: 480×2=960 lanes; line distance: 20m; track distance: 20m; shot-distance: 80m; number of times of coverage: 120 times.
(2) Design instrument factors
Seismic instrument: 428XL digital seismograph; gain of the forward amplifier: g2 (12 db); sampling interval: 0.5ms; recording length: 5s; recording format: SEG-D.
(3) Design motivation factor
A seismic source: high-explosion-speed formed explosive column and instantaneous power generation detonator special for seismic exploration are detonated. The pore-forming method comprises the following steps: and (5) mechanically drilling holes. Well depth dose: in the exposed region of the sand shale, the well depth is 14m, and the dosage is 10kg; in the limestone exposure area, the well depth is 16m, and the dosage is 12kg.
(4) Design receiving factor
The model of the detector: 30DX-10Hz detector (dominant frequency 10 Hz). The combination form is as follows: 1 string of 10, stack, intra-group spacing 0m. The exposed receiving points of the individual hard rocks are earthed up for insertion, so that the coupling effect of the detectors is ensured.
And a third step of: seismic data processing
According to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, a preset processing method is adopted to process the seismic data; the preset processing method comprises high-precision static correction, a multi-domain prestack denoising comprehensive noise technology, a relative amplitude maintaining processing technology, a resolution improving processing technology and a fine prestack time migration technology.
(1) As shown in fig. 3, the high-precision correction is performed to eliminate the topographic relief effect, specifically including: performing chromatographic static correction through first arrival pickup, comparing and optimizing by combining Gao Chengjing correction, performing dominant frequency band reflected wave static correction speed analysis, and finally performing surface consistency residual static correction and global optimizing residual static correction;
(2) As shown in fig. 4, the multi-domain prestack denoising technology performs targeted suppression for different interference wave characteristics, improves the quality of seismic data, and specifically includes: static correction of a reference surface; manually removing bad cannons and bad tracks; single-frequency noise suppression; pressing the surface wave; linear noise suppression; abnormal amplitude suppression; deconvolution and residual static correction; stacking; and denoising after stacking.
(3) As shown in fig. 5, the relative amplitude preserving process technique restores the relative energy relationship of the reflective layer, specifically including longitudinal compensation, which is formation absorption compensation, and lateral compensation, which is surface consistency compensation.
(4) As shown in FIG. 6, the resolution enhancement processing technique is to compress the seismic wavelet by deconvolution, enhancing the longitudinal resolution, and specifically includes surface-consistent deconvolution, which is wavelet consistency, and predictive deconvolution, which is a compressed wavelet.
(5) As shown in fig. 7, the fine pre-stack time migration technique improves the imaging accuracy of the seismic section, and specifically includes: relatively maintaining pre-stack processing data; PSTM parameter analysis; PSTM initial imaging and anti-NMO velocity analysis; the final curved ray PSTM is imaged.
Fourth step: seismic interpretation, inversion and gas reservoir feature identification
Including coal seam thickness prediction, density inversion, and gas-containing prediction.
(1) Coal seam thickness prediction
The single strong wave crest and the strong phase in the seismic waveform characteristics are used as a standard layer and a mark layer, and on the basis of the standard layer, the identification and division of other main geological layers are carried out by using the characteristics of the upper weak phase, the lower strong phase and the double strong phases of other wave groups; on the basis of accurately identifying the horizon, the thickness of the reservoir is predicted by utilizing the statistical relation between certain characteristic parameters of reflected wave kinematics and dynamics and thickness, and particularly, the coal seam is divided into the following steps by utilizing the relation between the thickness of the coal seam and the earthquake wavelength: a thin layer region, a thick layer transition region, and a thick layer region; and finally, extrapolating the coal thickness variation trend of the whole area by utilizing the seismic wave amplitude value at the drilling position and the coal seam thickness value.
(2) Density inversion and gas-containing prediction
Referring to fig. 11, after predicting the trend of coal thickness variation in the work area, a unitary once simulation calculation formula is established by using the correlation coefficient of total gas content and density obtained by logging data to obtain the gas content distribution around the wellhead; because the coal gas reservoir has the characteristic of relatively low longitudinal and transverse wave speed ratio, the pre-stack elastic parameter inversion can be utilized to predict the gas content of the whole work area.
The elastic wave impedance inversion calculation formula is as follows:
k is defined as follows:
wherein EI represents elastic wave impedance, θ represents incident angle, ρ represents density, and V p And V s Representing longitudinal wave velocity and transverse wave velocity, respectively. First, the Elastic Impedance (EI) is inverted, as input, while V is inverted p 、V s And density, then using the calibrated V p And V s The inversion is performed by iteration until the density value of the inversion is basically consistent with the logging data, which is beneficial in that V can be used p And V s The inversion result is constrained to be a function of the inversion result,to reduce inversion polyneuryales and improve inversion stability; after the density is inverted, the air content of the whole work area is predicted by means of a density-air content calculation formula, and the flow is shown in figure 8.
Referring to fig. 8, the gas reservoir gas-containing seismic inversion procedure is as follows:
s1, AVO analysis is carried out on the seismic trace set, and a near angle theta is carried out 1 Superimposed, distant angle theta 2 Stacking;
s2, near angle θ 1 Superimposed inversion to elastic impedance EI (θ) 1 ) Far angle theta 2 Superimposed inversion to elastic impedance EI (θ) 2 ) And taking EI as input while inverting V p 、V s And density;
s3, utilizing the calibrated V p And V s Continuously iterating to invert the density until the inverted density value is basically consistent with the logging data, and stopping inversion; wherein, for V p And V s Constraint is performed by using known data;
s4, establishing a relation between the density and the gas content, and predicting the gas content of the whole work area.
(3) WVD time spectrum decomposition and RGB fusion technology based on maximum entropy criterion for predicting gas-containing fullness degree
The seismic waves are absorbed and attenuated during passage through the formation, and the absorption and attenuation effects are more pronounced during passage through the hydrocarbon-bearing formation, resulting in a reduction in energy and frequency. Therefore, the time-frequency analysis technology can be utilized to analyze the time and frequency domains of the seismic channels, and the absorption and attenuation characteristics of the seismic waves are researched from the perspective of the frequency domain or the time-frequency combined domain, so that the gas-containing fullness degree of the coal bed can be qualitatively analyzed.
As shown in fig. 9, the flow specifically includes:
s1, obtaining post-stack seismic data with high resolution characteristics according to the high-precision and high-resolution seismic processing steps;
s2, selecting a Wigner-Ville (WVD) distribution analysis method with high time-frequency focusing performance and time-frequency resolution capability according to the absorption attenuation characteristics of the stratum, and analyzing the post-stack seismic data channel by taking maximum entropy as a criterion; the resolving power of the time-frequency analysis method is shown in fig. 10, and it can be seen that, aiming at the actually measured single-channel seismic signal with complex waveform characteristics, the traditional time-frequency analysis technology is as follows: the Generalized S Transform (GST) has a certain analysis effect on the S transform, but the resolution is poor. The maximum entropy WVD is obviously advantageous in that it has high focusing performance, better time resolution and frequency resolution. The time-frequency analysis method with good resolution capability is the basis for the subsequent extraction of high-resolution attributes. Thus, the technique is selected to analyze the seismic traces (seismic signals or seismic waveforms).
S3, on the basis of obtaining time-frequency domain data of each seismic data, selecting 3 different frequency band ranges of low, medium and high according to spectrum analysis characteristics (fast Fourier transform characteristics of the whole seismic data), performing spectrum decomposition processing on the obtained time-frequency joint domain result, converting an original data matrix into 3 data matrices with the same scale, wherein the 3 data matrices respectively correspond to low frequency, medium frequency and high frequency parts of the original data in a frequency domain. At present, the spectrum decomposition of most software is fixed bandwidth, generally 3 different components of 0-40Hz, 20-60Hz and 40-80Hz, and is determined according to normalized amplitude after FFT conversion, and according to actual frequency distribution, the preferred frequency band range is more important, which directly influences the accuracy of the subsequent RGB fusion, and the spectrum decomposition is more reasonable by selecting 5-30Hz, 24-45Hz and 35-70 Hz.
S4, after spectrum decomposition, the information reflected by the frequency components of different frequency bands is different, and in order to highlight the commonality and weaken the difference, the fusion processing display is carried out on 3 frequency domain components by using an RGB fusion technology so as to highlight the commonality and weaken the difference. The RGB fusion technology is to convert 3 kinds of data in the same scale into red, green and blue three primary color values, and to obtain normal color value through fusion display.
S5, the RGB technology is effective in representing the thickness of the coal bed gas, because the energy of the high-frequency part of the seismic waves is absorbed and attenuated when passing through the coal bed gas, and the energy attenuation of the low-frequency part is not obvious. When the RGB fusion is completed, the larger the proportion of the white part in the image is, the more and the thicker the gas content of the part of coal bed gas is.
Aiming at the characteristic identification of the coal gas reservoir under the surface condition of the complex mountain land, the first step of seismic survey line design considers the surface condition of the complex mountain land and the underground geological condition of the coal bed gas reservoir, and the designed survey line can meet the exploration requirement; the design of the second step earthquake construction scheme is summarized through a large number of test works of real cases, and has good universality for similar target tasks; the third step of seismic data processing adopts a processing technical method aiming at complex mountain areas and gas reservoirs, so that the processing effect is good; the fourth step of seismic interpretation, inversion and gas reservoir characteristic identification adopts an improved seismic inversion method, so that inversion multi-solution property is reduced, and the thickness, density, gas content and the like of a coal bed are effectively predicted; and meanwhile, the WVD spectrum decomposition technology and the RGB fusion technology based on the maximum entropy criterion are utilized, so that the gas content of the gas reservoir of the coal system can be effectively predicted. In conclusion, the method can be effectively applied to the identification of the characteristics of the gas reservoirs under the surface condition of the complex mountain land, and has stronger guiding significance for the subsequent exploration and development of the gas reservoirs and the preferential selection of the favorable areas.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, apparatus, article, or method that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, apparatus, article, or method. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, apparatus, article or method that comprises the element.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes using the descriptions and drawings of the present invention or directly or indirectly applied to other related technical fields are included in the scope of the invention.
Claims (8)
1. A combined exploration method for identifying characteristics of a gas reservoir of a coal system under complex mountain land surface conditions, comprising:
analyzing the geological profile and geological conditions in the range of the work area, designing a seismic line according to the analysis result, and drawing a geological profile;
according to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, designing an earthquake construction scheme; the seismic construction scheme comprises observation system parameters, instrument factors, excitation factors and receiving factors;
according to the surface conditions of the complex mountain land and the underground geological conditions of the gas reservoir, a preset processing method is adopted to process the seismic data; the preset processing method comprises high-precision static correction, a multi-domain prestack denoising comprehensive noise technology, a relative amplitude maintaining processing technology, a resolution improving processing technology and a fine prestack time migration technology;
performing seismic interpretation, inversion and gas reservoir characteristic identification; including coal seam thickness prediction, density inversion, and gas-containing prediction.
2. The combined exploration method for identifying characteristics of a gas reservoir under the surface condition of a complex mountain area according to claim 1, wherein the steps of analyzing the geological profile and geological conditions in the range of the work area, designing a seismic line according to the analysis result, and drawing a geological profile comprise the following steps:
analyzing a geological profile in the range of a work area, wherein the analysis of the geological profile comprises stratum characteristic analysis and structural characteristic analysis, the stratum characteristic analysis comprises stratum distribution conditions, thickness and lithology characteristics from the earth surface to a target layer and deeper, and the structural characteristic analysis comprises anticline and fault;
analyzing earthquake geological conditions in a work area, wherein the geological conditions comprise surface earthquake geological conditions and deep earthquake geological conditions, the surface earthquake geological conditions comprise the topography, landform, surface lithology, stratum dip angle, weathering degree and water content of the work area, and the deep earthquake geological conditions comprise stratum lithology combination, sedimentation characteristics and structural development conditions;
designing a seismic line according to the analysis results of the geological profile and the geological conditions; wherein the seismic line compliance principle includes: the measuring line is perpendicular to the construction direction or the set angle is perpendicular to the construction direction; the survey lines avoid areas which cannot be traversed by the earthquake survey lines such as towns, rivers, lakes and the like; the survey lines are deployed relatively uniformly, and the seismic survey lines are drilled by known wells;
drawing a geological section according to the design condition of the seismic survey line and the geological data of the region so as to prepare for the interpretation of the comprehensive earthquake; wherein the geologic profile includes associated geologic elements from the earth's surface to the target layer and deeper, and the geologic profile length is no shorter than the designed seismic line length.
3. The combined exploration method for identifying characteristics of a gas reservoir under complex mountain surface conditions according to claim 1, wherein the step of processing seismic data by a preset processing method according to complex mountain surface conditions and underground geological conditions of the gas reservoir comprises the following steps:
the high-precision correction includes: performing chromatographic static correction through first arrival pickup, comparing and optimizing by combining Gao Chengjing correction, performing dominant frequency band reflected wave static correction speed analysis, and finally performing surface consistency residual static correction and global optimizing residual static correction;
the multi-domain prestack denoising technique comprises: static correction of a reference surface; manually removing bad cannons and bad tracks; single-frequency noise suppression; pressing the surface wave; linear noise suppression; abnormal amplitude suppression; deconvolution and residual static correction; stacking; denoising after stacking;
the relative amplitude maintenance processing technology comprises longitudinal compensation and transverse compensation, wherein the longitudinal compensation is stratum absorption compensation, and the transverse compensation is ground surface consistency compensation;
the resolution enhancement processing technology comprises surface consistency deconvolution and prediction deconvolution, wherein the surface consistency deconvolution is wavelet consistency, and the prediction deconvolution is compression wavelet;
the fine prestack time migration technique includes: relatively maintaining pre-stack processing data; PSTM parameter analysis; PSTM initial imaging and anti-NMO velocity analysis; the final curved ray PSTM is imaged.
4. The combined exploration method for identifying gas reservoir characteristics under complex mountain surface conditions of claim 1, wherein in said steps of performing seismic interpretation, inversion and gas reservoir characteristic identification, the coal seam thickness prediction comprises:
the single strong wave crest and the strong phase in the seismic waveform characteristics are used as a standard layer and a mark layer, and on the basis of the standard layer, the identification and division of other main geological layers are carried out by using the characteristics of the upper weak phase, the lower strong phase and the double strong phases of other wave groups; on the basis of accurately identifying the horizon, the thickness of the reservoir is predicted by utilizing the relation between the reflected wave kinematics and dynamics characteristic parameters and thickness statistics, and particularly, the coal seam is divided into the following steps by utilizing the relation between the thickness of the coal seam and the earthquake wavelength: a thin layer region, a thick layer transition region, and a thick layer region; and finally, extrapolating the coal thickness variation trend of the whole area by utilizing the seismic wave amplitude value at the drilling position and the coal seam thickness value.
5. The combined exploration method for gas reservoir feature identification under complex mountain surface conditions of claim 1, wherein in said steps of performing seismic interpretation, inversion and gas reservoir feature identification, density inversion and gas-containing prediction comprise:
after predicting the change trend of the coal thickness in the work area, establishing a unitary once simulation calculation formula by utilizing the correlation coefficient of the total gas content and the density obtained by logging data to obtain the gas content distribution around the wellhead; because the coal gas reservoir has the characteristic of relatively low longitudinal and transverse wave speed ratio, the pre-stack elastic parameter inversion can be utilized to predict the gas content of the whole work area.
6. The combined exploration method for identifying characteristics of a gas reservoir under complex mountain surface conditions according to claim 5, wherein an elastic wave impedance inversion calculation formula is as follows:
k is defined as follows:
wherein EI represents elastic wave impedance, θ represents incident angle, ρ represents density, and V p And V s Representing longitudinal wave velocity and transverse wave velocity, respectively.
7. The combined exploration method for identifying characteristics of a gas reservoir under complex mountain surface conditions as claimed in claim 6, wherein the gas reservoir gas-containing seismic inversion process is as follows:
AVO analysis is carried out on the seismic trace set, and near angle theta is carried out 1 Superimposed, distant angle theta 2 Stacking;
near angle theta 1 Superimposed inversion to elastic impedance EI (θ) 1 ) Far angle theta 2 Superimposed inversion to elastic impedance EI (θ) 2 ) And taking EI as input while inverting V p 、V s And density;
by means of calibrated V p And V s Continuously iterating to invert the density until the inverted density value is basically consistent with the logging data, and stopping inversion; wherein, for V p And V s Constraint is performed by using known data;
and (5) carrying out gas content prediction of the whole work area by using the relation between density establishment and gas content.
8. The combined exploration method for identifying gas reservoir characteristics under complex mountain land surface conditions according to claim 3, wherein in the steps of performing seismic interpretation, inversion and gas reservoir characteristic identification, the method further comprises predicting the gas-containing fullness degree by using WVD time spectrum decomposition and RGB fusion technology based on maximum entropy criteria, specifically comprises the following steps:
obtaining post-stack seismic data having high resolution characteristics according to the high-precision, high-resolution seismic processing steps described above;
according to the absorption and attenuation characteristics of the stratum, a Wigner-Ville distribution analysis method with high time-frequency focusing performance and time-frequency resolution capability and maximum entropy as a criterion is selected to analyze the post-stack seismic data channel by channel;
on the basis of obtaining time-frequency domain data of each channel of seismic data, selecting 3 different frequency band ranges according to spectrum analysis characteristics, performing spectrum decomposition processing on the obtained time-frequency joint domain result, converting an original data matrix into 3 data matrices with the same scale, wherein the 3 data matrices respectively correspond to low frequency, medium frequency and high frequency parts of the original data in a frequency domain;
after spectrum decomposition, the information reflected by the frequency components of different frequency bands is different, and 3 frequency domain components are displayed by fusion processing through an RGB fusion technology; the RGB fusion technology is to convert 3 kinds of data with the same scale into red, green and blue three primary color values respectively, and obtain normal color values through fusion display;
when the RGB fusion is completed, the larger the proportion of the white part in the image is, the more and the thicker the gas content of the part of coal bed gas is.
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