74 results about "Root-mean-square speed" patented technology

The invention discloses a structural imaging method for processing reflected wave seismic data in an undulating surface area. The method comprises the steps of: carrying out spline interpolation on root-mean-square velocity on a discrete point for three times; correcting initial timing lines of all seismic data waiting for deviation to a stacked imaging reference surface of common midpoints; carrying out prestack time migration by different migration apertures, selecting the migration aperture with the optimal effect; calculating an imaging range of a seismic channel to be deviated in a deviation result space, calculating imaging of common imaging points at the position of each imaging point in the imaging space range, calculating ray travelling time, and carrying out integral summation, and finishing kirchhoff prestack time migration of each seismic data in an original data space. According to the method, the effect of topografic relief on the kirchhoff prestack time migration is overcome, and the adaptability of the kirchhoff prestack time migration imaging method on the terrain is expanded to all earth surfaces.

The invention provides a depth domain overall velocity model combination method and a device. The method comprises the following steps of collecting preliminary wave data in seismic data, obtaining a near earth surface velocity model through travel-time tomography inversion according to the collected preliminary wave data, conducting time domain velocity analysis on the seismic data to obtain a root-mean-square velocity model, converting the root-mean-square velocity model into a depth domain layer velocity model, obtaining a middle depth layer velocity model by adopting the depth domain layer velocity model as an initial model and optimizing the initial model, obtaining a depth domain overall velocity model by combining the near earth surface velocity model and the middle depth layer velocity model, conducting prestack depth migration on the depth domain overall velocity model. The depth domain overall velocity model combination method discloses a technology of combining the near earth surface velocity model and the middle depth layer velocity model, the depth domain overall velocity model of high precision is obtained, meanwhile, the requirements for calculating cost in industrial production are met.

The invention relates to a method for improving prestack migration imaging accuracy by mean square root speed in the fields of seismic data routine processing, depth migration processing and seismic explanation, dynamically correcting and stacking common midpoint gather data by a series of preset normal speeds in the time and space domains, respectively, converting the prestack common midpoint gather data into common midpoint stacked speed gather data, separating the common midpoint stacked speed gather data into common normal speed section data, and making filtration and 2D weighting processing on seismic amplitude values in the normal speed scanning gather at each common midpoint to obtain a vertical mean square root speed spectrum. It is suitable for any complex construction condition. The obtained results are reliable and the speed resolution reflected by the mean square root is higher.

The invention relates to a high-precision anisotropy speed analysis and a dynamic correction method, which comprise the following steps: preparation of seismic data: CMP seismic data gather is sorted; hyperbolic equation is adopted to perform the speed analysis without stretching influence on the small geophone offset reflected wave data; interactive interpretation is performed for velocity spectrum so as to obtain the hyperbolic velocity of the reflected wave; interval velocity is calculated with a non-delamination optimization method according to the two-way time and the hyperbolic velocity of the reflected wave; an exclusive interval velocity is calculated according to a least squares optimization principle; a vertical root mean square velocity is calculated; all geophone offset data is used for performing the anisotropy speed analysis without the stretching influence to obtain the anisotropy parameters; higher-precision root mean square and anisotropy parameters are calculated; anisotropy dynamic correction is performed; the calculation of the vertical root mean square velocity is automatically completed according to the calculated hyperbolic velocity and the offset range so as to perform the anisotropy velocity analysis and dynamic correction. The parameters obtained by calculating are free from being influenced by the dynamic correction stretching and have the advantages of high precision and high efficiency.

The invention relates to a two-dimensional two-step correction method of a stacking velocity and a root-mean-square velocity field, which comprises the steps of: firstly, acquiring the time difference delta T of each measuring line before correcting a T0 curve surface and a T0 in a closing way; correcting the stacking velocity with the delta T on reference plane, wherein when the delta T is larger than 0, a correction velocity uses a ground surface filling velocity, and when the delta T is less than 0, the correction velocity uses a velocity on a velocity spectrum; and aiming at the root-mean-square velocity closing error caused by apparent dip when the stacking velocity is converted into the root-mean-square velocity, firstly obtaining the time gradient of the stacking profile of a main measuring line and a communication measuring line, acquiring the apparent dip and the root-mean-square velocity of the directions of the different measuring lines, calculating the weighting coefficient at the point of intersection, interpolating and normalizing the weighting coefficient at the point of intersection, and stacking the root-mean-square velocity of the main measuring line and the communication line in a weighting way to obtain a final root-mean-square velocity field with the weighting coefficient of the directions of the different measuring lines. The method scientifically and effectively eliminates the closing error of the velocity of the intersected measuring lines, and improves the precision of the velocity field of a two-dimensional earthquake work area.

The invention relates to seismic data processing technology, and provides an accurate depth domain layer speed updating method. The accurate depth domain layer speed updating method comprises the steps as follows: converting a gather data depth domain layer speed field into a root-mean square speed field so as to obtain a speed value of the position of a common depth point; calculating the offset rest speed spectra of each root-mean square speed field and common reflection point gather; carrying out energy balance processing on the offset rest speed spectra; determining the rest speed value under the maximum energy in each depth position through existing vertical rest speed spectra; updating the root-mean square speed fields by utilizing the rest speed values, thus obtaining a new root-mean square speed field, and converting the root-mean square speed field into the depth domain layer speed field in the corresponding position; and carrying out prestack depth migration processing, so as to obtain an accurate depth domain structure seism imaging result. According to the accurate depth domain layer speed updating method provided by the invention, a depth distance curve under the same phase axis is parabola heightening order correction, therefore, a rest speed spectrum with higher resolution ratio can be obtained, and reliable basis is provided for the structuring of the accurate prestack depth migration.

The invention discloses a method for time migration of an inclined-shaft three-dimensional vertical seismic profile (VSP). The method includes: gridding an imaging area, and acquiring trajectories of an inclined shaft according to coordinates of demodulator points; extracting root-mean-square velocity from a root-mean-square velocity model obtained from ground data along the trajectories of the inclined shaft; moving the root-mean-square velocity to a time migration imaging datum plane of the VSP to acquire a root-mean-square velocity body; calculating aperture of time migration of VSP data by a formula that migration aperture equals to target layer depth is multiplied by the square of sine with the largest imaging angle and added with a half of the largest wellhead distance; acquiring total travel time of corresponding paths of seismic waves by the aid of a double-square-root equation; extending single-path VSP wave fields to the depth where a borehole geophone is located and completing pre-stack time migration of the VSP data. More reasonable structural imaging of the time migration of the three-dimensional VSP can be acquired through three-dimensional velocity space changing trend and distribution in the shaft trajectory direction and denoted by the inclined shaft, calculating efficiency is high, and simpleness in the process is achieved.

The invention relates to the technical field of earthquake velocity model building and discloses a method for building a three-dimensional high-precision velocity model. The method comprises following steps: geological information such as sonic logging data is acquired, interval velocity Vi is calculated on the basis of a time domain framework model through interpreting and analyzing the acquired information, and the interval velocity Vi is processed and constrained; the model is interpreted in combination with the time domain construction, statistics is performed to the interval velocity Vi according to the geological information, and the distribution rule of the interval velocity Vi is analyzed; two-dimensional horizons and the interval velocity Vi are filled in the three-dimensional framework; mean square root velocity and average velocity of a certain layer are calculated by use of the interval velocity Vi inserted into the model. The method and system make the process of converting an earthquake interpretation result from a time domain to a depth domain more efficient and accurate; timely maintenance and update can be realized when the geological information changes; the cost for enlarging the scope of the model is reduced.

The invention provides a well-constrained velocity spectrum pickup method for low-SNR (signal-to-noise ratio) seismic data, and belongs to the field of seismic data processing. The method comprises (1), well logging preprocessing: input interval transit time or acoustic velocity is corrected, and a corrected acoustic velocity is obtained; (2), acoustic logging data shallow layer compensation and downward extension processing are performed on the corrected acoustic velocity, and the acoustic velocity subjected to shallow layer compensation and downward extension is obtained; (3), time-depth conversion is performed on the acoustic velocity subjected to shallow layer compensation and downward continuation to obtain an interval velocity, and the interval velocity is subjected to root-mean-square velocity conversion to obtain a root-mean-square velocity; (4), projection of the root-mean-square velocity on the velocity spectrum is acquired. With adoption of the method, pickup randomness is reduced, and the velocity pickup accuracy is improved.

The invention provides a method for predicating a pre-stack fracture within common offset and common azimuth domains, and belongs to the technical field of oil exploration fracture prediction. The method comprises the following steps: collecting seismic data; performing independent pre-stack migration on all of the common offset and common azimuth domains obtained from the seismic data; carrying out horizon interpretation, wherein obtained CRP (Common Reflection Point) gathers are stacked to obtain a result data body, and the top and the bottom of a target zone are subjected to horizon interpretation; segmenting the CRP gathers, wherein a position partition scheme is determined according to a development direction of a main fracture in a work area, and the CRP gathers are segmented into n groups of sub-CRP gathers according to azimuth information in the CRP gathers; stacking sub-positions, wherein all of the CRP gathers are stacked to obtain n seismic traces, and the n stacked seismic traces are merged together to form a new CRP position gather; converting residual interval moveout to a root-mean-square velocity; converting the new root-mean-square velocity to an interval velocity; performing ellipse fitting to obtain velocities and directions of fast and slow waves; calculating the fracture density.

The present invention discloses a modeling method of a depth domain interval velocity initial model. The method comprises the steps of rejecting the inaccurate root-mean-square velocity in a time domain root-mean-square velocity model, and obtaining a corrected time domain root-mean-square velocity model; carrying out inversion on the corrected time domain root-mean-square velocity model, and obtaining a corresponding time domain interval velocity model; carrying out the prediction interpolation on the interval velocity corresponding to the inaccurate root-mean-square velocity in the time domain interval velocity model by taking the horizon time of the seismic horizons as a constraint condition, and obtaining a corrected time domain interval velocity model; converting the corrected time domain interval velocity model from a time domain to a depth domain, and obtaining the depth domain interval velocity initial model. The modeling method provided by the present invention can eliminate an error brought by the inaccurate root-mean-square velocity during a calculation process of time domain root-mean-square velocity-to-depth domain interval velocity conversion, thereby achieving the purpose of improving the prestack depth migration imaging quality by improving the precision of the depth domain interval velocity initial model. The modeling method of the present invention can be widely used for processing the oil-gas exploration actual seismic data information.

The invention discloses a speed model establishment method, comprising steps of obtaining a root-mean-square speed spectrum, picking up a first area root-mean-square speed from the root-mean-square speed spectrum, performing partitioning on a stratum of a work area according to the root-mean-square speed of the first area, obtaining the number of layers of the stratum and an initial depth and a gradient of each stratum, obtaining water speed of the work area, establishing a first speed model based on the water speed, performing pre-stack depth migration on the first speed model, obtaining a first interface of the work area, obtaining the second interface of the work area according to the first interface, with the second interface being an starting point, successively and downwardly calculate the layer speed of the first speed model based on the water speed of the work area, number of the layers of the stratum, initial depth of each stratum and the gradient, and embedding the first interface into the first speed model to obtain a second speed model. The speed model disclosed by the invention more accords with the geology rule, and improves the precision of the imaging depth.

The invention provides a VSP-CDP stacking method and a three-dimensional VSP coverage number calculation method. The method comprises the following steps: inputting rms velocity spectra of upstream waves and downstream waves; dividing imaging grids according to a three-dimensional rms velocity model, the grid spacing being the size of a three-dimensional surface seismic imaging grid, and sequentially finding corresponding receiving points according to the grids; laying a three-dimensional VSP observation system; applying binning iteration-based VSP-CDP stacking method to the calculation of coverage number of the observation system. The binning iteration-based VSP-CDP stacking method uses a lateral variation velocity field to replace a single well based velocity model, and a binning iterative method to replace a reflection point based analytical method. The VSP-CDP stacking method and the three-dimensional VSP coverage number calculation method provided by the invention have the advantages of further enhancing the accuracy of VSP stack imaging, ensuring that enough coverage number is obtained in a target area, and the time of acquisition design can be obviously reduced.

The invention provides a method for calculating the high-accuracy seismic wave velocity by utilizing the stacking velocity in a geophysical prospecting technology, proposes that a datum plane, inaccurate static correction, local change of formation lithology and thickness, an offset distance and the like in an area with earth's surface and underground geological conditions influence the stacking velocity, and establishes relation between the stacking velocity of complex areas and root-mean-square velocity. The method comprises the following steps of 1 calculating the stacking velocity of the datum plane under the near surface condition; 2 utilizing average of the stacking velocity or the stacking layer velocity in a limited surface element to eliminate the influence of the inaccurate static correction and formation anisotropism; 3 adopting layered velocity model time distance curve forward modeling to estimate an offset distance forming stacking velocity error. A depth error is within 10 meters through multiple-port VSP well logging inspection, a calculation result is reliable, and the accuracy is high.

The invention relates to a method and device for determining travel time of seabed seismic reflected wave and belongs to the field of seismic survey. The method comprises the steps of 1, acquiring seismic data of each seismic channel acquired; 2, determining sea water depth of each detection point based on the seismic data; 3, using a three-dimensional interpolation algorithm to establish a seabedmodel; 4, determining stack velocities or root-mean-square velocities, with the sea level as a base level, of multiple discrete points on the basis of seismic data historically acquired in sea leveltowing observation manner; 5, determining vrms of each sampling point on the basis of areal stack velocities or root-mean-square velocities, with the sea level as the base level, of the multiple discrete points as well as the seabed model; 6, for each sampling point, determining vrms' of the sampling point based on the vrms of the sampling point; 7, determining travel time t of the seabed seismicreflected wave of each sampling point from seismic data of each seismic channel, wherein an equation is shown in the description. By using the method and the device, it is possible to improve the accuracy of pre-stack time migration results.

The invention provides a time-domain seismic interval velocity inversion method, and belongs to the field of seismic exploration data processing. The time-domain seismic interval velocity inversion method includes acquiring initial instantaneous velocities by means of seismic logging; establishing relations among the instantaneous velocities and root-mean-square velocities; converting the initial instantaneous velocities into root-mean-square velocities; constraining actually picked root-mean-square velocities to create an objective function; solving the objective function to obtain variables required for updating a velocity model; acquiring a final interval velocity when a value of the objective function is smaller than a threshold value epsilon after repeated iteration. The time-domain seismic interval velocity inversion method has the advantages that the stable velocity can be acquired by the time-domain seismic interval velocity inversion method, the stable and smooth interval velocity model can be provided for migration, the velocity can be used for seismic migration imaging, and data support can be provided for oilfield development and petroleum drilling.

The invention relates to an optimizing design method of an observing system for geophysical exploration. The optimizing design method comprises the following steps of when the imaging travel of a target body is tracked by rays, converting a speed model to obtain a root mean square speed field, simulating shooting for a primarily proposed observing system, ensuring a full-coverage area to cover all target bodies, performing the integral pre-stack time migration on a shot-geophone pair in the root mean square speed field, obtaining the effective coverage spectrum of the target bodies, and selecting the proposed observing system with high coverage times, so as to complete the optimizing design of the observing system. The optimizing design method has the advantage that the illumination intensity of the observing system on underground complicated mediums is quickly and accurately calculated, so the qualities of different observing systems are evaluated, and the effect is good.

The present application provides a pre-stack time migration data processing method and device. The method includes: obtaining OVT-domain seismic data according to acquired wide-azimuth seismic data; performing static correction on the OVT-domain seismic data to obtain static correction processing data; performing speed analysis on the static correction processing data to obtain a root mean squarevelocity field; adding OVT information to the static correction processing data and regularizing the static correction processing data with the OVT information added so as to obtain OVT set seismic data; and performing pre-stack time migration processing according to the OVT set seismic data and the root mean square velocity field. The embodiments in the present application improve the processingefficiency of the pre-stack time migration, and save the time of pre-stack time migration data processing.

The invention relates to a geometric spreading compensation method based on a uniform horizontal layered medium model. The geometric spreading compensation method comprises the following steps: 1) reading root mean square speed information, two-way vertical traveltime information and shot and positioning point distribution information in a computer; 2) obtaining the uniform horizontal layered medium model comprising information about layer speed and layer thickness of each layer according to the root mean square speed information and the two-way vertical traveltime information; 3) performing ray tracing on the uniform horizontal layered medium model from a shot point to obtain ray position and traveltime information; 4) determining relative geometric spreading compensation values of reflecting layers according to a geometric spreading compensation formula; 5) obtaining a compensation value at detection points through linear interpolation, interpolating the relative geometric spreading compensation values to sampling points of corresponding seismic data volumes according to a seismic data format, and outputting data to be used for following data processing. The geometric spreading compensation method has the advantages that the accuracy of a geometric spreading compensation technology is improved, and can be widely applied to the geometric spreading compensation technology in the seismic data processing process.

The invention discloses a pre-stack time migration imaging method based on an equivalent offset distance. The method comprises the following steps: extracting each CSP gather and obtaining root-mean-square speed distribution, performing an equivalent offset distance migration on each CSP gather on the basis of a root-mean-square speed at a position of a corresponding target scattering point to obtain equivalent migration gathers of migration imaging results containing the target scattering points and nearby scattering points, extracting roads, which have the same horizontal plane projection coordinates as the target scattering points, from the equivalent migration gathers to form common equivalent point gathers, and horizontally stacking the common equivalent point gathers of the target scattering points to obtain image points, formed by near scattered wave energy and remote scattered wave energy, of all the scattering points. Scattered wave energy at positions of the common scattering point gathers and energy of remote scattering point gathers are used, so the final imaging effect noise is small, and imaging is relatively real.

The invention provides a method and a device for extracting a diffracted wave. The method comprises the steps of acquiring an instantaneous phase of a seismic wave; performing correction movable summit Radon transform on the instantaneous phase, and obtaining positioning information of a geological abnormal member; respectively extracting the left branch and the right branch of the diffracted waveaccording to the positioning information, and obtaining the diffracted wave. According to the method of the invention, the position of the geological abnormal member and the corresponding root mean square velocity can be obtained, thereby realizing more comprehensive diffracted wave information. The left branch and the right branch of the diffracted wave can be respectively extracted according tothe positioning information so that the original polarities of the extracted left branch and the extracted right branch of the diffracted wave are kept, namely the polarity reversal characteristic ofthe diffracted wave can be restored, thereby obtaining the high-fidelity diffracted wave, and determining the kind of the geological abnormal member according to the polarity reversal characteristicof the diffracted wave. The method and the device settle technical problems of no comprehensive diffracted wave information, severe distortion and incapability of determining the kind of the geological abnormal member.

The invention provides a Pre-stack time migration method based on a split-step Fourier algorithm. The method comprises the steps of inputting pre-processed seismic data; picking up the root mean square speed in an interactive mode; calculating the ray propagation time from an imaging point to a focus point; converting seismic data of a time-space domain into frequency-wave number; acquiring a continuation value of a background wave field; transforming the continued wave field into the frequency-space domain through Fourier transform, and performing a time shift operation through a split-step Fourier time shift operator of the time domain so as to realize continuation for a disturbance wave field; and performing phase shift on a frequency-space domain seismic wave field and carrying out integration on the effective frequency band by using a excitation time imaging condition so as to acquire a seismic imaging result of a shot record. The pre-stack time migration method based on the split-step Fourier algorithm can carry out migration by applying the root mean square speed, and improves the adaptive capacity for speed vertical and longitudinal variations and the amplitude preserving capacity for migration imaging of pre-stack time migration under the condition of not increasing the speed modeling difficulty.

The embodiments of the invention disclose a method and a device for determining a pre-stack time migration velocity field. The method comprises the following steps: acquiring seismic data, first arrival wave data and vertical seismic profile data of a target work area and near-surface acquisition information corresponding to an extremely shallow layer in the target work area, wherein the target work area includes the extremely shallow layer, a middle-shallow layer, and a middle-deep layer; determining the initial root-mean-squared velocity field on the extremely shallow layer according to the first arrival wave data or the near-surface acquisition information; determining the initial root-mean-squared velocity field on the middle-shallow layer according to the vertical seismic profile data; determining the initial root-mean-squared velocity field on the middle-deep layer based on the initial root-mean-squared velocity field on the middle-shallow layer; and acquiring well hierarchy data on a marker layer in the target work area, and determining the target root-mean-squared velocity field on the target work area according to the initial root-mean-squared velocity fields on the extremely shallow layer, on the middle-shallow layer and on the middle-deep layer and the well hierarchy data. The accuracy of the pre-stack time migration velocity field determined can be improved.

The invention discloses a vertical seismic profile imaging method based on equivalent offsets. The method includes the followings steps: extracting a VCSP trace gather of a vertical seismic profile and obtaining a root mean square velocity field, calculating a stacking trace of the VCSP trace gather according to the root mean square velocity field, conducting convolution on the stacking trace of the VCSP trace gather and a filter factor to obtain an offset imaging result of an equivalent offset in a place where the current VCSP trace gather is located, conducting transversal on all VCSP trace gathers on the vertical seismic profile, and combining all offset imaging results of equivalent offsets in places where the VCSP trace gathers are located into an imaging result of the whole seismic profile. Imaging can be achieved on the vertical seismic profile within a relatively large area, and accurate imaging effects can be obtained for regions with low signal to noise ratio and complex landforms.

The invention discloses an imaging processing method and device for an Ordovician fracture-cave system. The imaging processing method comprises the following steps of: acquiring, to be specific, acquiring a root-mean-square velocity function; converting, to be specific, converting the root-mean-square velocity function by utilizing a constraint velocity inversion method to acquire an interval velocity body; migrating, to be specific, performing prestack time migration to target seismic data to obtain migrated target seismic data; picking up, to be specific, performing automatic pickup residual velocity processing according to the migrated target seismic data to obtain a residual velocity; updating, to be specific, updating the interval velocity body according to the residual velocity body; repeatedly executing migrating, pickup processing and updating until the seismic data acquired in the migration processing step is in accordance with the requirement of geological laws so as to obtain a final interval velocity body; and performing prestack time migration processing to the whole seismic data according to the final interval velocity body. According to the imaging processing method and device for the Ordovician fracture-cave system, the imaging effect of prestack time migration can be improved, and the imaging is finer.

The invention provides a non-hyperbolic velocity scanning and dynamic correction method and a method of calculating stacking velocity errors caused by big offset distance in the geophysical prospecting technology. By adopting a time-difference analysis between a radial time curve of a seismic layer velocity model forward modeling and a stacking velocity speed Va time hyperbola, a new non-hyperbolic equation can be provided for the velocity scanning and the dynamic correction, and then the more accurate stacking velocity and dynamic correction time difference can be acquired. For a horizontally layered medium, the error can be caused by using the hyperbolic equation for the scanning of the stacking velocity and the root-mean-square velocity by adopting the time difference analysis between the radial time curve and the time hyperbola of the root-mean-square velocity, and then the method of estimating the stacking velocity error caused by the large offset distance can be provided. The method is used in a plurality of areas, and the good effect can be achieved.