Showing papers in "Oil Geophysical Prospecting in 2012"

High precision seismic time-frequency spectrum decomposition method and its application

Abstract: Because of Heisenberg's uncertainty principle,the linear algorithms of time-frequency spectral decomposition,for example wavelet transform and generalized S transform,cannot simultaneously have high resolution in time and frequency domains.Overcoming the window function limit,the matching pursuit can precisely characterize signal features in time and frequency domains.This paper firstly discusses the algorithm theory of matching pursuit to seismic signal,and then put forward the reasonable improvement to standard Morlet wavelet,which can perfect the time-frequency atomic database,thus enhancing the precision of seismic signal matching decomposition.Based on the time-bandwidth of Morlet wavelet,the paper finally uses window treatment technology to dynamically scan matching wavelet atoms at the same time in multi-windows,so that calculation efficiency can be appropriately increasing.The model test and actual data analysis show that matching pursuit of seismic signal based on improved Morlet wavelet is more precise and efficient,and has some antinoise ability,suitable for quantitative analysis of the spectrum variation of seismic data,which will be helpful to study oil gas reservoir distribution.

Seismic exploration for strati-lithologic reservoirs

Abstract: This paper discusses a few specific points on seismic exploration for strati-lithologic reservoirsFirstly we review the general idea of seismic technology for strati-lithologic reservoir identificationSecondly 8 issues of seismic data acquisition and 10 issues of seismic data processing are illuminated in order to obtain a good 3D data cubeThen a set of interpretation approaches for strati-lithologic reservoirs are demonstrated including seismic inversion,attribute analysis,petro-physics analysis,geologic model building,and seismic forward modelingFinally we conclude comprehensive geological researches on seismic dataThe author's observations are given and these could be meaningful for strati-lithologic reservoir identification

Carbonate reef-shoal reservoir identification in western Longgang,Sichuan Basin

Abstract: The discoveries of reef-shoal reservoirs in the regions of Puguang and Longgang in recent years have shown a promising exploration future in the Kaijiang-Liangping trough area.Using prestack migration seismic data combined with drilling and logging information,identifications of bioherm in the Changxing formation and oolitic reservoir of the Feixianguan formation in western Longgang region have been successfully achieved by a series of technologies such as horizon-flattening,volume-curvature,sequence stratigraphy,and prestack inversion.An assorted preliminary workflow for reef-shoal body identification is developed and may contribute an important reference for similar areas.

An improved method for P-P and P-SV wave time matching

Abstract: As the velocity ratio is changing with time,the time matching from P-SV to PP time domain will distort seismic wavelet which includes waveform stretch and phase delay.To solve this problem,we propose an improved method for P-P and P-SV wave time matching.This method,based on Fourier's time stretch theory,can correct simultaneously wavelet amplitude and phase resulted from the different stretch value with the seismic travel time.The modeling data results of a well log data indicate that the method can correct simultaneously wavelet amplitude and phase.And the method is still stable when the data is noised.

Integrated interpretation of 3D gravity,magnetic,electromagnetic and seismic data:a case study of conglomerate mass investigation in piedmont area of Kuche Depression

Abstract: In piedmont area of Kuche Depression,widely developed conglomerate masses seriously disturb seismic image and interpretation of deep structures.So integrated 3D gravity,magnetic and electromagnetic survey in the area was planned with the purpose of investigating conglomerate mass and its variation of lithology and lithofacies with the reference of logging data,seismic data and outcrops information.With improved approaches of data processing,3D EM data is integrated with seismic data on a united platform.This makes an integrated interpretation change from a simple qualitative comparison way to a more accurate study.A joint inversion on major sections gives the spatial distribution of conglomerate masses formed in different time.It provides bases for the investigation of subsalt structures,and velocity model building.

Seismic acquisition geometry building and optimization

Abstract: A method to optimize acquisition geometry design is introduced among a few proposed acquisition layouts.By parameters grouping and analyzing,different acquisition designs can be established.Quantitative evaluation criteria for parameter factors,such as uniformity,similarity,aspect ratio,acquisition costs and other factors,are proposed.With a comprehensive consideration of these factors,geometry design could be optimized.The method shows its feasibility in the field.In an experiment in the WN Block,Tarim Basin,the optimized acquisition geometry for 12L320S320T is considers as the best geometry design based on parameter argument after the acquisition.

GLCM parameters in fluvial texture analysis

Abstract: Channel texture is an acoustic expression of a fluvial facies via seismic amplitude fluctuations.The Gray Level Co-occurrence Matrix(GLCM) attribute has been proved to be a promising method for seismic texture analysis.As we try to extract seismic texture attributes,however,it is a big uncertainty how to select the optimal GLCM parameters which will impact the final estimated seismic texture results and also affect the computing time.In this paper,we study the relationship between GLCM parameters and final seismic texture results to simplify the computation of GLCM.We build an ideal synthetic channel reservoir model which is derived from a modern meandering river.Then we simulate a noise-free post-stack seismic data using 3D Gaussian beam approach.With the synthetic channel model data,we will show how to select the four key GLCM parameters including the gray levels,the size of moving window,and the distance and direction of gray pairs.Selecting various combinations of these four key parameters,we extract four GLCM secondary statistical measurements(Energy,Entropy,Contrast,and Homogeneity).Based on theoretical equations and horizontal slices of texture,we ultimately get a proper co-occurrence matrix parameter for fluvial reservoir from our synthetic channel model.For energy and entropy,the number of gray levels is lower.For contrast and homogeneity,the number of gray levels is higher.The size of moving window is smaller than the half of the size of geological target.The distance of gray pairs is usually 1.And we usually represent repetitive patterns of gray pairs at angles of 0°,45°,90° and 135° to the axes.At last,we apply our method on the field data from Bohai Bay,China.This real seismic example shows that GLCM is an effective method for accurate and reliable channel texture measurements.

P-wave attenuation by fracture parameter on physical models

Abstract: Three sets of physical models are built based on Hudson theory with different fracture density,aperture and length.Test amplitudes of P-wave on the models are recorded by the pulse transmission method.Experimental data are compared with theoretical data from Hudson theory and quality factor Q of models are obtained using classic spectral ratio method for determining attenuation.The study results show:①With the increase of fracture density,amplitude has a little decrease and azimuthal amplitude anisotropy.By the analysis of comparing results,it can be seen that Hudson theory's prediction is exact.②With the increase of fracture length,amplitude increases in the mass and the situation is similar in X and Z directions.But the prediction of Hudson theory is different with small decrease.③With the increase of fracture opevture,the variation of amplitude is much bigger than the prediction,which means that the theory underestimate the effect of fracture length.④The anisotropy of velocity and amplitude changes similarly with different fracture parameters.The influence of fracture aperture is most obvious and attenuation anisotropy is more sensitive to the change of fracture parameter than velocity anisotropy.

Gas-bearing reservoir prediction by elastic impedance inversion

Abstract: On basis of the principle of the prestack elastic impedance inversion,we present in this paper an idea to predict gas-bearing reservoir using the prestack elastic impedance inversion.Firstly we calculate elastic impedance curves of traces near wells.Secondly we transform prestack seismic data from offset domain to angle domain.Thirdly we estimate seismic wavelets corresponding to different angles.Then we perform inversion to obtain elastic impedance sections.Finally we extract various elastic parameters.Applications of this prestack elastic impedance inversion to seismic data from Block A,Erdos Basin obtain good results,and demonstrate its feasibility and effectivity of gas-bearing reservoir prediction.

3D electrical response characteristics modeling for surface-to-borehole vertical electromagnetic walkaway profile

Abstract: The surface-to-borehole electromagnetic technology is a method with great potential for detecting residual oil gas.Walkaway vertical electromagnetic profile of surface-to-borehole was put forward.In this paper some rules of dynamic reservoir process are drawn by modeling surface walkaway power supply and changing conductivity,size,depth and distance from receive well of model using 3D integral equation forward code.3D modeling comparison between homogeneous background and layered medium shows that it has wider detection range and more accurate,which can effectively monitor the dynamic oil gas process.The simulation study suggests practical application of walkaway vertical electromagnetic profile method for reservoir exploration as a new approach.

Mathematical classification of magnetotelluric inversion methods

Abstract: During the past five decades,significant progress has been made in magnetotelluric(MT) methodParticularly the inversion techniques have been transformed from 1D into 2D,or even 3DNowadays there are numerous MT inversion methods,most of which belong to linearized,iterated approaches that make use of the gradient of the objective function,and almost all of these methods adopt strategies based on the same theory to handle the general ill-posedness of the inverse problemThis paper briefly introduces the basic idea of MT inversion,which is known as regularization theoryIt then makes a mathematical classification of several main inversion methods according to the numerical optimization algorithms they employed so that the clear relationship among them can be acquiredIn addition,their main merits and drawbacks are compared with each otherFinally,trends for MT inversion are considered

Research and perspective on new geophysical technologies and methods in China

Abstract: Geophysical prospecting team of China National Petroleum Corporation(CNPC),has become one of the major geophysical service providers in the world as it stands first for land operation service in recent years.Nowadays,international geophysical service companies focus on their own special technologies to ensure their market share as international fierce competition is increasing.In order to improve the innovation ability and competitive power of CNPC geophysical business,researches on new technology and methods in six domains are deployed to concentrate on forelands,lithology,superimposed basins,deep targets,and unconventional hydrocarbon exploration.Its research and development ability will be improved and its key technologies for solving complex geological issues will be formed.Therefore higher innovation ability and higher success rate will be expected.With an improved core competence and a long term development potential,CNPC geophysical service will become a technological leader in the world geophysical industry.

Some static correction methods in coalbed methane seismic

Abstract: The static issue is one of the core techniques in coalbed methane(CBM) seismic data processing.According to the characteristics of coalbed methane seismic data in Qinshui Basin,we simply analyze in this paper the principles of different static methods.Through the analysis and application of actual data,we develop an effective processing sequence including refraction static correction,first break residual static correction and reflected residual static correction to solve the coalbed methane static problem in this area.The processing sequence of coalbed methane seismic data processing laid a good foundation for the geological structure characteristics research,coal reservoir fracture prediction and gas bearing layer detection.

Structure features and potential prospect of Wenan slope in Baxian Depression

Abstract: Wenan slope experienced twice reversals and three faultings,namely,NE faulting,NW faulting and NEE faultingThe characteristics between the North and the South were quite differentThe two netty faults in Suqiao area were in NE and NW directionsIn the central Shigezhuang area,NEE faults were developed en echelon distributionIn Changfeng town of the south part,NE faults were arranged in parallelControlled by faults in Wenan slope,three structure zones were developed:Suqiao-Xinanzhen fault structure zone,a nose structure zone in Shigezhuang,and a nose structure zone in Changfengzhen-YilunpuUsing merging 3D seismic data,we analyze in this paper the overall structures and obtain the following understanding:①Hydrocarbon source rocks in Baxian Depression was deep,thick,and large;②As exploration targets,there are multilayer in buried hills of the slope;③Tight sandstones in the slope may be deep low-abundance tight sandstone reservoirs;④Horizon-lithology reservoirs outside the slope may have geological conditions for large multi-layer hydrocarbon resources

Comparison of wave field characteristics among the fracture rock models

Abstract: This article focuses on comparing among the first-order accuracy Hudson model,the second-order accuracy Hudson model,the Schoenberg model,the Kachanov model and the Eshelby-Cheng modelThe paper summarizes the expressions of elasticity coefficient of the different modelsElastic wave equation numerical simulation is used to simulate propagation characteristics of waves in these fracture models respectively for dry fracture and water-filled fracture with different fracture density and fracture aspect ratioAnd wave field snapshots and the phenomenon of shear-wave splitting from the simulation are analyzedThe following observations are obtained from the study: The fracture density affects the anisotropy feature of the P-and S-waves and the fracture fillings influence the anisotropy of the medium;while the fracture aspect ratio and the fracture fillings impact on the propagation characteristics of shear wavesShear-wave splitting changes significantly with the increasing crack density,but the fracture aspect ratio and the fracture fillings have little effect on shear-wave splitting

Structure features and exploration potential of the Paleogene-Neogene depressions in Western Qaidam Basin

Abstract: By influence of tectonic activity of the Cenozoic Eastern Kunlun orogenic belt,the Western Qaidam Basin has deformed strongly.With regional structural feature,this part can be divided into compression-shear thrust belts in the piedmont of the Eastern Kunlun range,Mangya depression with the Yingxiong Mountains reverse structural belts in the shallow layers,and the Dafengshan Salient.The total hydrocarbon resources in the Paleogene-Neogene plateau saline lacustrine basin are about 25×108t in the Western Qaidam Basin,among which the area effective hydrocarbon source rock amounts to 53%.This region is a typical hydrocarbon-rich depression with abundant surplus resources and great exploration potential.According to the exploration concept of hydrocarbon-rich depression,combined with the analysis of exploration degree and exploration technology,we propose the inverse structural zones in Yingxiong Mountains,lithologic strata in southwest of Qaidam Basin,the paleo-uplift in the piedmont of Altun Mountains,and the Mangya Depression with the periphery dense oil areas as four exploration fields.