Landmark Graphics Corporation

China Petroleum Chemical Corporation

Fan Xia

Shengwen Jin

Yiqing Ren

Yequan Chen

Shiyong Xu

Richard Ottolini

A method and system for generating and displaying a low frequency model for a seismic survey region are provided. The method and system may include defining a seismic survey geometry of the seismic survey region; processing seismic data to generate a stacked seismic data and well log data to obtain elastic attributes; importing stacked seismic data and processed well log data into the defined seismic survey geometry; generating envelope data using the stacked seismic data; generating a low frequency trace for each well; calculating a least-squares optimized coefficient model at each well location based upon the generated envelope data and the low frequency trace for each well; interpolating the coefficient model to the seismic survey geometry using a covariance technique and the imported stacked seismic data; and generating a three-dimensional low frequency model by inversion using the envelope data and the interpolated coefficient model for display.

Method and apparatus for building envelope guided low frequency model for seismic exploration of subsurface formations

A computing program product and method for interpolating wavelets coefficients and estimating spatial varying wavelets using the covariance interpolation method in the data space over a survey region having multiple well locations, are disclosed. The method and computing program product, embodied in a non-transitory computer readable device, that stores instructions for performing by a device are based on interpolating coefficient models in the data space domain using covariance analysis methods to overcome inaccuracy and instability issues commonly observed during wavelet estimation and interpolation.

Computing program product and method that interpolates wavelets coefficients and estimates spatial varying wavelets using the covariance interpolation method in the data space over a survey region having multiple well locations

A computer-implemented method, and system implementing the method, are disclosed for computing a final model of elastic properties, using nonlinear direct prestack seismic inversion for Poisson impedance. User inputs and earth-model data is obtained over points of incidence of a survey region, at various angles of incidence. Various models are then computed that serve for lithology identification and fluid discrimination and take part in preliminary seismic exploration and reservoir characterization. Therefore, further refinement of these models is required due to changes in burial depths, compaction and overburden pressure, as they provide limitations for reservoirs on porous media. The further refinement using nonlinear direct prestack seismic model is performed on a system computer, which produces a final model of elastic properties. This model can then be applied for lithology prediction and fluid detection to identify potential targets of oil and gas exploration and estimating spots in unconventional shale gas applications.

Computer-implemented method and system employing nonlinear direct prestack seismic inversion for poisson impedance

A method and a system for implementing the method are disclosed wherein the pre-stack seismic input data, an initial anellipticity anisotropy parameter, and a baseline normal moveout velocity from a non-flat surface, are sometimes mild or foothill topography as well as the shot and receiver lines might not necessarily be straight, and often curve to avoid obstacles on the land surface. In particular, the method and system disclosed, allows for updating the anisotropy parameters iteratively and when the stopping criteria is satisfied, the final estimated parameter can be directly used for time migration. This method and system are mainly used for time migration with the purpose of obtaining the high fidelity (accurate amplitude, i.e. not only travel-time correct but also amplitude correct) image gathers which are used for reservoir characterization and interpretation.

Method and system that uses an anisotropy parameter to generate high-resolution time-migrated image gathers for reservoir characterization, and interpretation

Methods and systems are presented in this disclosure for semblance-based anisotropy parameter estimation using isotropic depth-migrated common image gathers. Far-offset image gathers can be generated from seismic data associated with a subterranean formation migrated based on an isotropic depth migration that uses an isotropic velocity model. Based on the far-offset image gathers, a plurality of semblance values can be calculated as a function of an anisotropy parameter of the subterranean formation for the different depths and the surface locations. Effective values of the anisotropy parameter of the subterranean formation can be then chosen that result in maxima of the plurality of semblance values for the different depths and the surface locations. Anisotropy model of the subterranean formation can be obtained based on the effective values of the anisotropy parameter.

Semblance-based anisotropy parameter estimation using isotropic depth-migrated common image gathers

An apparatus and a method for estimating interval anellipticity parameter by inversing effective anellipticity parameter in the depth domain using a least-squares method. One embodiment of interval anellipticity parameter estimator includes: 1) an interface configured to receive seismic data and borehole information; 2) a depth convertor configured to obtain a function of depth of effective anisotropy parameter based on said borehole information; 3) an inverse transformer configured to set up said function of depth of effective anisotropy parameter as a least-squares fitting problem based on said P-wave data; and 4) an iterative solver configured to use iterative methods to solve said least-squares fitting problem and to obtain an anisotropy model containing interval anellipticity parameter.

Estimating interval anisotropy parameter for pre-stack depth migration using a least-squares method

An example method for tomographic migration velocity analysis may include collecting seismographic traces from a subterranean formation and using an initial velocity model to generate common image gathers and a depth image volume based, at least in part, on the seismographic traces. A structure tensor may be computed with the depth image volume for automated structural dip and azimuth estimation. A semblance may be generated using said plurality of common image gathers and said structure tensor. Image depth residuals may be automatically picked from said semblance. A ray tracing computation may be performed on said initial velocity models using said structure tensor. An updated velocity model may be generated with a tomographic inversion computation, wherein said tomographic inversion computation uses said plurality of image depth residuals and said ray tracing computation.

Structure tensor constrained tomographic velocity analysis

Seismic imaging systems and methods that employ sensitivity kernel-based migration velocity analysis in 3D anisotropic media may demonstrate increased stability and accuracy. Survey data analysts employing the disclosed systems and methods are expected to provide better images of the subsurface and be better able to identify reservoirs and deposits for commercial exploitation. Certain embodiments migrate seismic survey data with an anisotropic velocity model to obtain common angle image gathers. These gathers are processed to obtain depth residuals along one or more horizons. Angle-domain sensitivity kernels are used to convert the depth residuals into velocity errors, which are then used to refine the velocity model. A user is then able to view a representation of the subsurface structure determined in part from the refined velocity model. Multiple iterations may be needed for the velocity model to converge. The velocity model may be a layered to have constant velocity values between formation boundaries.

Sensitivity kernal-based migration velocity analysis in 3D anisotropic media

In at least some embodiments, the system obtains shot gathers for a survey region and migrates the shot gather data with an initial velocity model to obtain angle-domain common image gathers. The system processes the common image gathers to determine depth residuals and corresponding angle-dependent time deviations throughout a seismic survey region. The system solves a set of tomographic equations which employ ray theory to establish a relationship between a travel time deviation and the depth residual of a reflector in the depth-offset ray parameter (z,p) domain. The resulting updates are applied to the velocity model and can be used to re-migrate the shot gather data. The system generates a representation of the survey region that can be displayed to a user.

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Houston, TX, United States of America

Fan Xia