231 results about "Prestack" patented technology

A method of prestack reverse-time migration of seismic data that yields significant gains in computer storage and memory bandwidth efficiency is disclosed. The values only of the source wave incident on the boundaries of a simulation domain are saved, rather than all of the values of the wavefield throughout the entire simulation domain. This data allows an accurate and robust approximation of the forward propagated source wave for all finite-difference approximation orders of the acoustic wave equation. The method reduces the amount of data storage required by an order of magnitude and overcomes the present challenge of requiring special large memory hardware while allowing for the implementation of 3D prestack reverse-time migration on off-the-shelf platforms.

System and method for analyzing seismic data from a formation. Stacked seismic data are provided, including a plurality of stack traces, e.g., by collecting seismic data from source and receiver locations and stacking the collected seismic data to produce the stacked seismic data. 3-dimensional (3-D) prestack traces are generated from the plurality of stack traces, e.g., by performing inverse moveout of stack traces, e.g., in a specified neighborhood, at common-depth-points, e.g., by inverse normal moveout, ray tracing, spike synthesis, etc. The inverse moveout corrected traces are convolved to compute predicted multiples which are useable in analyzing the formation. The multiples may be adaptively subtracted from the stacked seismic data, or optionally, from prestack data, to generate processed seismic data useable in analyzing the formation, e.g., for petroleum production potential. Dip moveout (DMO) corrected seismic data may be used, where DMO velocities are adjusted by dividing by cosine of the dip angle.

The invention provides a method for carrying out shale gas reservoir evaluation and finding a dessert area for shale gas exploration and development comprehensively through comprehensive application of rock physics, log data and omnibearing or wide-azimuth three-dimensional seismic data. The method is characterized by analyzing the characteristics of the dessert area in a shale reservoir by applying comprehensive geophysical exploration technologies of laboratory rock geophysical measurement, log data comprehensive analysis, rock physical modeling, vertical seismic section data, omnibearing or wide-azimuth three-dimensional seismic data high precision surface layer comprehensive modeling static correction processing, prestack de-noising processing, amplitude relative fidelity processing, resolution enhancement processing which is carried out by utilizing well constraint and well seismic data to drive ground seismic data, fine excision, iteration velocity analysis, interval velocity field analysis, prestack depth migration processing, high resolution processing, azimuth classification processing, high-precision anisotropy processing, prestack and post-stack data inversion processing, and neural network analysis and the like, and thus gas bearing characteristic prospect of the shale gas reservoir is evaluated accurately and the dessert area for shale gas exploration and development is delineated.

The invention provides a gas pool prediction method and system of a carbonate reservoir based on pore structure characteristics. The method comprises the following steps: collecting a rock sample of a target reservoir section of the carbonate reservoir; authenticating geological thin sheets of the rock sample so as to obtain rock basic parameters comprising the rock constituents, the pore shape, the surface porosity and the sedimentary phase belt; carrying out pore permeation measurement on the rock sample so as to obtain pore permeation basic parameters comprising the porosity, the permeation rate and the density; constructing a rock bare-bone model according to the rock basic parameters, the pore permeation basic parameters and a differential equivalent medium model; carrying out fluid replacement on the rock bare-bone model so as to generate a rock physical plate; acquiring prestack seismic inversion data of the carbonate reservoir; intersecting the prestack seismic inversion data and the rock physical plate, thereby obtaining the prediction results of the porosity and the gas saturation of the carbonate reservoir. The accurate quantitative gas pool prediction is realized.

The invention relates to a direct prestack time migration method for the seismic data acquired under the undulant ground surface. The method is applied to reflection seismic data processing during earthquake exploration and is a prestack migration imaging method aiming at the seismic data acquired under the undulant ground surface. The method can be directly applied to the seismic data which is acquired under the undulant ground surface and is acquired at shot points and demodulation points of different heights. Accordingly, the method can avoid errors caused by field static correction processing as well as correct the speed of a speed reducing belt in a migration process. The method can self-adaptively determine time-varying migration aperture and can correctly compensate geometric spreading effect of seismic waves during an imaging process so as to obtain an amplitude-preserved common reflection point gather. The core of the method is to use a one-way wave theory and a stable phase point principle to analyze so that the travel time and the amplitude of the seismic waves, which depend on the speed and thickness of the speed reducing belt, the heights of the shot points and the demodulation points, and stacking speed based on a floating datum plane, are obtained. The method has important application value for the explorations of oil, gas and mineral resources in areas with complex ground surfaces.

A prestack migration method allowing imaging of an underground zone, for a given velocity model of arbitrary complexity. By means of conventional wave propagation and retropropagation modelling tools, the method allows to obtain elementary migrated images associated with the values assumed by a parameter and the sum of the images obtained for the different values of the parameter (post-migration stacking), in the depth domain as well as in the time domain. This migration is obtained at an attractive price (calculation cost) because it is independent of the volume of the results calculated and of the number of seismic traces recorded. Only the volume of the zone in which the waves are propagated, the complexity of the events to be imaged and the desired accuracy have an effect on the calculation cost. Volume images are thus obtained by taking account of all the seismic traces. It is thus possible to implement a plane wave migration procedure in cases where acquisition does not allow synthesis of the subsurface response to a plane wave excitation, a response required from the outset in conventional plane wave migration algorithms. The method can be applied for imaging of geologic interfaces or heterogeneities of a part of an underground zone.

A method of constructing a 3D geologically plausible velocity model for efficient and accurate prestack imaging wherein embodiments of the invention provide: (1) a method of calibrating velocity functions, appropriately and effectively taking into account well (hard) and seismic (soft) data as well as geological features, and trend fitting (“iDEPTHing”) RMS velocities before curved-ray prestack time migration; (2) a method of calibrating and trend fitting (“iDEPTHing”) interval velocities before prestack depth migration, appropriately and effectively taking into account well (hard) and seismic (soft) data as well as geological features; and (3) a method of constructing a geologically plausible velocity model using the previous steps of velocity calibration and trend fitting RMS and interval velocities, for efficient sequential use in prestack time migration followed by prestack depth migration. Advantages of the embodiments include providing a quick turnaround of prestack time and depth migration to interpreters and cutting back resource-intensive interpretation efforts for 3D seismic data The invention has significant implications for improving aspects of oil and gas exploration and production technologies, including pore pressure prediction, prospect evaluation and seismic attribute analysis.

Methods, apparatus and products for processing 4D+ prestack seismic data having the form of 3D prestack gathers, single fold 3D volumes, and a mapping table to link the gathers and the volumes coherently.

The invention relates to a multi-wave AVO reservoir elastic parameter inversion method based on the precise Zoeppritz equation. The method includes: a. defining amplitude scaling factors; b. counting the prior information of model parameters and calculating the covariance matrix of the relevance of the three parameters; c. building an initial elastic parameter model of the time domain; d. forward modeling the multi-wave seismic pre-stack gather based on the elastic parameter mode and the precise Zoeppritz equation and calculating the inversion residual error between the PP wave and the PS wave according to the forward modeling records and the actual records; e. building and solving the inversion objective function and obtaining the solution expression of the disturbance quantity of the model parameters; f. calculating the disturbance quantity of the model parameters according to the inversion residual error and the solution expression of the disturbance quantity; g. repeating and iterating the steps of d, e and f and obtaining an optimal model parameter. The multi-wave AVO reservoir elastic parameter inversion method based on the precise Zoeppritz equation effectively improves the calculating precision and the stability of the existing pre-stack AVO inversion method, and meets the requirement of the inversion identification of oil and gas reservoir of the seismic prestack, especially the requirement of the characterization of the shale gas reservoir.

The invention relates to a diffracted wave separation processing method based on reflection wave layer leveling extraction and elimination. The diffracted wave separation processing method comprises the following steps that (1) the processing is carried out; (2) the CDP (common depth point) gather record in the preprocessing is subjected to dynamic correction and static correction processing, and the shot gather record is generated according to trace header information; (3) the target level picking is carried out according to superposition data, the level leveling time quantum is extracted, and the level leveling time information is reflected onto each trace record in the prestack shot gather record according to the relationship of each trace record in the CDP and shot gather record; (4) the reflection wave layer leveling processing of the prestack shot record is carried out according to the level leveling time quantum; (5) the reflection wave layer leveling shot gather is recorded, reflection waves are extracted and are subtracted from original records, and the diffracted wave shot record is obtained; (6) the diffracted wave shot record is subjected to reverse leveling processing; (7) the shot gather record is withdrawn to the CDP gather record, and the superposition processing is carried out; and (8) the velocity field obtained through velocity analysis is subjected to migration processing, and diffracted wave migration imaging result data is obtained.

An apparatus and a method for migration of three components, 3-Dimensions seismic (3-C, 3-D) data acquired by down-hole receivers and surface seismic sources. This method utilizes full 3 components reflection wave field. It uses a dynamic, vector energy mapping method to image a reflection position and maps each time sample only to its reflected image point. Therefore, this method reduces unwanted data smearing and false mirror images. This method overcomes the weakness of using only a single component trace or pre-rotated three-component traces in the 1-C or 3-C 3-D VSP migration and produces better 3-D image.

The invention discloses a horizontal drilling real-time seismogeology comprehensive guiding method. The method comprises the following steps that (1) three-dimensional prestack time deepened seismic data are explained in a known oil and gas field work zone, and an initial guiding model of a well to be drilled is obtained; (2) lithological, electrical and seismic reflection characteristics of marker beds, a target oil and gas layer and adjacent stratums in the oil and gas field work zone are determined; (3) before a forward drilled well enters the target, the velocity field is updated in real time, and an improved guiding model of the forward drilled well is obtained; (4) when the forward drilled well encounters one marker bed and is about to enter the tarter, the altitude depth of a target-entering point of the forward drilled well is predicted, and trajectory optimization before target entering is conducted; (5) after the forward drilled well enters the target, the velocity field is updated again, and thus the newest guiding model is obtained; and (6) under the guidance of the newest guiding model, a horizontal section guiding is conducted by combining with practical drilling analysis. According to the seismogeology comprehensive guiding method capable of correcting the guiding model in real time, the effects that the horizontal well enters the target layer accurately and efficiently penetrates through the target layer can be guaranteed.

The invention provides method and system for inverting elastic parameters of multi-wave AVO reservoir based on the reflectivity method. The method comprises the steps of acquiring a seismic prestack gather, log data and an actual seismic gather of an angle area beside the well; determining seismic wavelet and amplitude extension factors according to the eismic prestack gather, the log data and the actual seismic gather of the angle area beside the well; acquiring statistical model parameters of the log data; determining model parameter prior distribution functions meeting the working area according to the statistical model parameters; acquiring seismotectonics interpreting data; building an initial elastic parameter model of a depth area according to the seismotectonics interpreting data and the log data; determining inversion residuals of PP wave and PS wave according to the initial elastic parameter model; creating the inversion target function under the maximum posterior probability significance; determining an optimal elastic parameter model according to the inversion target function and the inversion residuals of PP wave and PS wave. According to the scheme, the method meets the requirements on inversing to recognize the characterization of a seismic prestack oil and gas reservoir, in particular a shale gas reservoir.

Three data subsets are obtained in three selected azimuthal directions from seismic data in heterogeneous, anisotropic media. Azimuthal velocities are determined for each of the data subsets. A linear system of equations in the three selected azimuthal directions and the three determined azimuthal velocities is solved for three independent parameters. An azimuthal time migration velocity function is constructed from the three solved independent parameters. A time migration traveltime function is constructed from the constructed azimuthal time migration velocity function.

The invention relates to the prestack depth migration technique during the data processing of petroleum seismic prospecting, including the following concrete steps: establishing depth rate pattern of prestack seismic data; well designing observation grids, and solving wave equation in sphere coordinate system to simulate the communication process of seismic waves; changing and converting the calculated seismic wave field of a frequency domain into a time domain, and fitting the Green function energy spectrum of the seismic wave field in the time domain to detect the arriving time and the vibration amplitude when the maximum energy arrives; transferring the travel time and the vibration amplitude field calculated in the sphere coordinate system to a rectangular coordinate system; accomplishing the maximum energy integral prestack depth migration according to the well calculated travel time and the vibration amplitude; analyzing the operation of speed to the imaging gather of the prestack depth migration to modify the depth rate pattern; and modifying the depth rate pattern by iteration, and outputting the ultimate result until the migration result meets the precision requirement. The invention provides the self-adapting variation difference grid calculation technique so as to achieve the purpose that the difference grids are automatically and gradually thinned along with radius increase, thereby guaranteeing the finite difference calculation precision.

The invention provides a Gauss beam prestack depth migration method and device. The Gauss beam prestack depth migration method includes the steps that (1), collected seismic wave data are processed to generate time domain shot gather seismic record data and determine a speed interface; (2), a depth domain speed structural model and a speed grid model are built; (3), ray tracing is carried out on the time domain shot gather seismic record data according to the depth domain speed structural model, the speed grid model and the speed interface, and a shot point Gauss beam and a receiver point Gauss beam are generated; (4), the total complex value travel time is determined according to the shot point Gauss beam and the receiver point Gauss beam; (5), saddle points of the total complex value travel time are scanned, and the maximum energy Gauss beam is determined; (6), accumulated imaging is carried out according to the determined Gauss beam with the maximum energy contribution to generate a migration result. The ray tracing in the migration method is carried out by means of the speed grid model and the speed structural model at the same time, so that the accuracy of the ray tracing is improved, and the imaging quality is improved.

The invention relates to pre-fold depth excursion technology in the data processing of the oil and earthquake exploration. It includes: setting up the depth speed module for the pro-fold earthquake data; designing the observation grating to solve the wave equation which modulates the propagating process of the earthquake wave in the ball coordinate system; the earthquake wave field switch with computed the frequency field is changed to the time field, then to fit the earthquake wave field Green function energy spectrum and get the reaching time and the swing of the max energy; transforming the travel time and the swing field computed in the ball coordinate system to the orthogonal coordinate system; according to the travel time and the swing to get the max energy integral pro-fold depth excursion; analyzing the speed of the image path collection to modify the depth speed module; by iteration to modify the module until the excursion result fit for the precision. The invention provides the self adaptive switch difference grating computing technology to make the difference grating change thin along with the radius, so the limit difference computing precision can be assured.

The invention provides a depth domain layer speed correcting method suitable for an undulating surface, belonging to the field of the seismic data processing of the physical prospection in the petroleum geochemistry. The method comprises the following steps of: firstly, segmenting an offset distance, grouping input trace gathers according to the offset distances, carrying out the undulating surface prestack depth migration, and generating a common imaging point trace gather; carrying out undulating surface residual speed analysis, computing a high-order residual curvature spectrum, picking up a depth-residual curvature pair according to the local maximum value of the high-order residual curvature spectrum, and obtaining speed model correction quantity; carrying out spatial interpolation and smoothness on the speed model correction quantity, and adding the speed model correction quantity with an initial speed model to obtain an updated undulating surface depth domain layer speed model; and replacing the initial speed model with the updated undulating surface depth domain layer speed model, and carrying out the analysis of undulating surface prestack depth migration and the undulating surface residual speed once again, so that the precision of the speed model can be continuously improved.

The invention discloses a 2.5-times three-dimensional seismic exploration method of a complex geological target applied to the petroleum geology exploration. The 2.5-times three-dimensional seismic exploration method comprises the following steps of: calculating coverage times needed by the 2.5-times three-dimension according to the relationship of signal-to-noise ratios and coverage times of stack section data and original single-shot data; treating and analyzing limited shot-geophone distance with utilization of two-dimensional test wire data with long shot-geophone distances and high coverage, and preferably choosing proper maximum shot-geophone distance; determining key parameters of an observation system according to the analytic conclusions; establishing an uniform coordinate grids by adopting an uniform origin of coordinates, and realizing fusion of time-domain three-dimensional seismic data; and realizing high-precision imaging of the complex target by establishment of a regular and high-precise velocity field of the three-dimensional seismic data and migration treatment of three-dimensional prestack time. The 2.5-times three-dimensional seismic exploration method of the complex geological target has the following effects: through the fusion of the three-dimensional seismic data, the coverage times is increased and the signal-to-noise ratio of the data is improved; the imaging precision of the data is improved by utilizing the prestack time migration technology, and the fine description of the complex geological target is realized.

A prestack time migration method for compensating absorptive attenuation is applied to the processing of reflex seismic data in seismic prospecting. According to the method, attenuation of amplitude of high frequency seism, caused by earth medium viscosity and thin layer scattering, is compensated in the migration process, the attenuated high frequency component is restored, so that the image resolution ratio of intermediate and deep constructions reaches up to the degree approximately to the shallow construction, and the stability is guaranteed and the noise amplification is avoided. No hypothesis is made on lamination or uniformity of a Q-value space distribution, and by introducing an equivalent Q-value describing absorptive attenuation of the seismic amplitude, the compensation of absorptive attenuation and prestack time migration are effectively combined together. The method can determine the equivalent Q-value on the basis of reflex seismic data collected on the ground, so that the difficulty in determining the Q-value by the existing various absorptive attenuation compensation methods is avoided. The method can better indicate rupture and stratum deposition patterns of the intermediate and deep constructions and is of great application value for the exploration of oil gas and mineral resources.