59 results about "Normal moveout" patented technology

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.

A method for estimating seismic velocities in vertically transversely isotropic media includes generating an initial estimate of vertical interval velocity and interval normal moveout velocity with respect to depth from seismic data. An initial estimate is generated of a first anisotropy parameter with respect to depth. The first anisotropy parameter is related to the interval normal moveout velocity and the interval vertical velocity. An initial estimate is generated with respect to depth of a second anisotropy parameter. The second anisotropy parameter is related to the first anisotropy parameter and an interval anelliptic parameter. A first tomographic inversion is performed with respect to the interval normal moveout velocity and the second anisotropy parameter at a constant value of the first anisotropy parameter until travel time differentials reach minimum values. Layer depths are adjusted with the initial estimate of vertical interval velocity. Using values of the second anisotropy parameter determined in the first tomographic inversion, a second tomographic inversion is performed of interval normal moveout velocity and the first anisotropy parameter with respect to depth. The adjusted layer depths, interval normal moveout velocities and interval vertical velocities are again adjusted and interval anelliptic parameters are calculated from the second tomographic inversion.

The invention discloses a method for determining a fluid by utilizing seismic fluid impedance. The method comprises the following steps: exciting and recording a seismic wave to obtain an angle gather; eliminating signal frequency distortion caused by a normal moveout correction stretching effect; extracting longitudinal wave reflectivity attributes and weighted transverse wave reflectivity attributes from the compensated angle gather; computing improved fluid factors; obtaining logging data to obtain a fluid impedance curve; performing iterative inversion to obtain a section of the fluid impedance; qualitatively analyzing fluid anomalies in pores by the fluid factors, and describing spatial distribution of the fluid by the fluid impedance. The method helps accurately extract the fluid factors and directly identify components of the fluid in the pores without an assumption of a velocity ratio of the longitudinal wave to the transverse wave as well as the relation between density and the longitudinal wave velocity, which reduces ambiguity of gas layer identification, realizes direct conversion from the fluid factors to the fluid impedance and improves the precision of gas reservoir identification.

The present invention provides a method and apparatus for arriving at true relative amplitude destretched seismic traces from stretched seismic traces. The method compensates for offset varying reflection interference effects due to normal moveout. Stretch factors β and also input spectra are determined for NMOR stretched seismic traces. Estimates are then made of stretched wavelet spectra from the input spectra. A destretched wavelet spectra is then obtained. Shaping correction factors are determined by taking the ratio of the destretched wavelet spectra to the stretched wavelet spectra and are applied to the input spectra of the stretched traces to arrive at a destretched trace spectra. True relative amplitude scaling factors are computed by taking the ratio of a true relative amplitude property of the destretched wavelet spectra to a corresponding true relative amplitude property of the stretched wavelet spectra. Finally, the true relative amplitude scaling factors are applied to the destretched trace spectra to arrive at true relative amplitude destretched seismic traces.

Methods of processing seismic data to remove unwanted noise from meaningful reflection signals are provided for. The methods comprise the steps of assembling seismic data into common geometry gathers in an offset-time domain without correcting the data for normal moveout. The amplitude data are then transformed from the offset-time domain to the time-slowness domain using a Radon transformation. A corrective filter is then applied to enhance the primary reflection signal content of the data and to eliminate unwanted noise events. The corrective filter has a pass region with a lower pass limit and a higher pass limit. The higher pass limit is set within 15% above the slowness of the primary reflection signals and, preferably, it is more closely set to the slowness of the primary reflection signals. The lower pass limit is also preferably set within 15% below the slowness of the primary reflection signals. The tau-P filter preferably is defined by reference to the velocity function of the primary reflection signals, and preferably is expressed as:

where r₁ and r₂ are percentages expressed as decimals. After filtering, the enhanced signal content is inverse transformed from the time-slowness domain back to the offset-time domain using an inverse Radon transformation.

A walkaway VSP survey is carried out using a receiver array. First arrivals to a plurality of receivers are picked and used to estimate a normal-moveout (NMO) velocity. Using the NMO velocity and vertical velocities estimated from the VSP data, two anisotropy parameters are estimated for each of the layers. The anisotropy parameters may then be used to process surface seismic data to give a stacked image in true depth and for the interpretation purposes. For multi-azimuthal walkaway or 3D VSP data, we determine two VTI parameters ε and δ for multi-azimuth vertical planes. Then we determine five anisotropic interval parameters that describe P-wave kinematics for orthorhombic layers. These orthorhombic parameters may then be used to process surface seismic data to give a stacked image in true depth and for the interpretation purposes.

Object images captured by a wide-angle camera are distorted due to the optical effects of the wide-angle lens. The disclosed innovations allow an automatic analysis on the corrected image distinguishing normal movement from an unusual event movement. The analysis is based on Markov Modeling on moving object trajectories and motion angles.

A method for de-ghosting marine seismic trace data is described. A reference seismic trace and a candidate seismic trace are selected from acquired seismic data. The acquired seismic data is gathered using a configuration wherein either a first streamer and a second streamer are disposed at different depths relative to one another and are laterally offset relative to one another, or using a configuration wherein a first source and a second source are disposed at different depths relative to one another and are laterally offset from one another. The reference seismic trace and the candidate seismic trace are processed, e.g., to perform normal moveout correction and/or vertical datum shifting, and the processed reference seismic trace is de-ghosted using the processed, candidate seismic trace.

The invention relates to a technique for processing petroleum geophysical prospecting seismic data, which is a method for improving the velocity spectrum resolution by using phase information. The method comprises the following steps of: stimulating and recording seismic waves to obtain a common midpoint gather; performing a first-order derivative operation along a time direction, and performing Hilbert transform to obtain a complex seismic trace; superimposing P(t) traces to obtain the optimal velocity of normal moveout correction (NMO); calculating a velocity spectrum by using a conventional velocity analysis method; and performing side lobe suppression on the selected common midpoint (CMP) for velocity analysis and each time sample vector in SPS to finally obtain the velocity spectrum. By the method, influences on the velocity analysis due to amplitude changes can be avoided, the distribution of noises is converted into the distribution with gauss distribution characteristics, so that influences on the velocity analysis due to abnormal noises can be effectively inhibited, and the resolution of the velocity spectrum and the accuracy of the velocity analysis are improved.

Method for processing seismic data to correct for errors caused by variation in water conditions. In one implementation, the method may include (a) applying a dip correction to a plurality of observed water bottom reflection times using a model water velocity and an estimate of geologic dip; (b) applying a normal moveout (NMO) correction to the dip corrected observed water bottom reflection times using the model water velocity; (c) applying a common mid point (“CMP”) bin centering correction to the NMO corrected, dip corrected observed water bottom reflection times using the model water velocity and the estimate of geologic dip; (d) solving for Δs_i, which is an estimate of the difference in slowness between the observed water bottom reflection times and the water bottom reflection times that would have been observed had the water velocity been the same as the model water velocity; (e) solving for an estimate of observed water velocity based on s_obs,i=s_m+Δs_i, where s_obs,i is an estimate of observed slowness and s_m is defined as the model slowness; (f) layer replacing the observed water bottom reflection times using the estimate of the observed water velocity and the model water velocity; and (g) repeating steps (a) to (f) using the layer replaced observed water bottom reflection times until the changes in the estimate of observed water velocity approach zero.

The invention provides a three-dimensional high-precision bin fractionation processing and evaluation technology for seismic data, and the method comprises the following steps: analyzing original data, and carrying out trace header modification, grid definition and linear normal moveout correction on data acquired by an observation system, thus acquiring a prestack multi-domain composite denoised image; based on the relationship between bin fractionation and the signal-to-noise ratio as well as the relationship between bin fractionation and the multiplicity during forward modeling, comprehensively compensating for the vibration amplitude, thus acquiring a tomographic inversion refracted wave static correction image; analyzing the quantitative relationship between bin fractionation and the longitudinal resolution and lateral resolution, carrying out prestack shot-domain optimized deconvolution, and carrying out azimuth restrained bin fractionation and speed optimized analysis, thus acquiring a progressive frequency-divided residual correction image; and carrying out multiple three-dimensional prestack migrations, and establishing a three-dimensional prestack migration speed model, thus acquiring a prestack migration image. Thus, the method provided by the invention provides a reliable guarantee for improving the exploration development precision and upgrading a seismic exploration technology.

Method for processing seismic data. In one implementation, the method includes converting a common midpoint (CMP) gather of seismograms into one or more interferogram common midpoint (ICMP) gathers, generating a semblance spectrum for each ICMP gather, stacking the semblance spectrum from each ICMP gather to generate a combined semblance spectrum and deriving a normal moveout (NMO) velocity profile from the combined semblance spectrum.

The invention provides a normal moveout stretch cutting method for processing geophysical exploitation seismic data. According to the method, a stacking velocity field is utilized, average speed is calculated, or interval velocity is calculated after smoothing the average speed. Further, by using the velocity and shot-geophone distance information, approximate calculation of an incident angle is performed according to the theory of ray (straight ray or curved ray) propagated by seismic wave, and a 1D or 3D space varying incident angle threshold value reference is used as a standard of measurement to determine the cut of each seismic channel. Thus, more accurate automatic cutting of the normal moveout stretch is realized, the interference caused by net normal moveout stretch can be cut, effective wave amplitude can also be protected to the greatest extent, and finally, the resolution and the signal-noise ratio of a stacked section are improved.

The invention provides a method for matching longitudinal wave and converted wave data through dynamic time adjustment. The method includes the steps that acquired seismic waves are processed through normal moveout correction and the like to generate a longitudinal wave gather with amplitude changing along with offset and a converted wave gather with amplitude changing along with offset; inversion of changes of amplitude along with offset is performed on the longitudinal wave gather and the converted wave gather respectively, and an attribute set of changes of amplitude along with offset of longitudinal waves and an attribute set of changes of amplitude along with offset of converted waves are obtained; the attribute set of changes of amplitude along with offset of longitudinal waves and the attribute set of changes of amplitude along with offset of converted waves are calculated based on dynamic time adjustment, and the time shift quantity sequence between the longitudinal waves and the converted waves is obtained; time shift is performed on the converted wave gather according to the time shift quantity sequence, and a converted wave data set is obtained after the converted wave gather is matched in the time domain of longitudinal waves. Through the method, the time shift quantity of each sampling point can be obtained so that the method is adaptive to intense changes of the time shift quantities and free of influences of relevant time windows and thresholds, and a good result can also be obtained on the basis of data with a low signal-to-noise ratio and resolution ratio.

The invention discloses a recurve bow response on-line detection system. Resistance strain testing, vibration testing and a control virtual-type signal analyzing soft and hardware technology are adopted; the static and dynamic strain and acceleration response of selected testing points on a recurve bow and mechanical dynamic parameters of the recurve bow are detected in real time on line, and objective experiment data are provided for the training of sportsmen and the development of a novel recurve bow. The particular implementation is that a small-type three-shaft resistance strain rosettes and a micro-piezoelectric-type acceleration transducer are bonded on the selected testing points of the recurve bow; response signals are transmitted to a strain meter and a vibration testing meter by leads; and after being converted and amplified, the response signals are transmitted to a control virtual-type signal analyzing meter for real-time analyzing treatment, thus the corresponding data curve diagrams and animation display and the like are obtained. The detection system can not influence the using performance of the recurve bow and the normal motion of users, not only can be used for the training of contestants, but also can be used for the detection analysis of stress and response of the recurve bow and prevents from adopting and installing each type of shock absorbers blindly, and is an effective means for archery coaches, sportsmen and the recurve bow researchers.

The invention relates to a seismic scattering P-P wave imaging method which comprises the following steps: step 1: reading the seismic data into a two-dimensional array F, simultaneously loading observation system parameters into an original seismic data header, and calculating positions and coordinates of scattering points according to an observation system and acquisition parameters; step 2: according to the time-distance hyperbolic equation of scattering waves, under the condition of fixing t0i on a shot set, determining the scattering hyperbolic trace through the imaging speed, and then, calculating the seismic scattering P-P wave normal moveout; step 3: subtracting the seismic scattering P-P wave normal moveout from the seismic wave traveltime; step 4: calculating the weighted sum of the scattering amplitude of the hyperbolic trace from which the seismic scattering P-P wave normal moveout is subtracted on each shot-geophone distance, thereby realizing the seismic scattering P-P wave imaging; and step 5: outputting the imaging data in the seismic format. The invention has the characteristics of improving the stacking times of the horizontal stacking imaging technique and effectively improving the signal-to-noise ratio and the imaging precision.

Improved methods of processing seismic data which comprise amplitude data assembled in the offset-time domain in which primary reflection signals and noise overlap are provided for. The methods include the step of enhancing the separation between primary reflection signals and coherent noise by transforming the assembled data from the offset-time domain to the time-slowness domain. More specifically, the assembled amplitude data are transformed from the offset-time domain to the time-slowness domain using a Radon transformation according to an index j of the slowness set and a sampling variable Δp; wherein $j=\frac{p_{\max }-p_{\min }+1\mu \sec \text{/}m}{\Delta p},$

Δp is from about 0.5 to about 4.0 μsec/m, p_max is a predetermined maximum slowness, and p_min is a predetermined minimum slowness. Alternately, an offset weighting factor xⁿ is applied to the assembled amplitude data, wherein 0<n<1, and the amplitude data are transformed with a Radon transformation. The assembled amplitude data also may be transformed with a Radon transformation applied within defined slowness limits p_min and p_max, where p_min is a predetermined minimum slowness and p_max is a predetermined maximum slowness, with a hyperbolic Radon transformation, or, as applied to data which have been uncorrected for normal moveout, with a hyperbolic or parabolic Radon transformation. Thus, the primary reflection signals and coherent noise transform into different regions of the time-slowness domain to enhance the separation therebetween.