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English Abstrcts of Papers

 

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Geophysical Exploration for Oil-Gas and Coal Fieid

(Conveners: LING Yun  WEI Xiucheng  NIU Binhua )

 

1£®The Field Preprocessing,Display and Analysis of Seismic Ghosting Information

WANG Guangzhi,YANG Ruchao

(Exploration & Development Science Institution, ZPEB, Pu Yang 457001)

     The ghosting is the first-hand information for studying wavelet forming mechanism and selecting source depth in geophysical prospecting. The data acquisition method of ghosting records is double well up-hole shooting in field practice. By displaying and analyzing these records, we can selecting the depth of ghosting reflection interface, analyses the frequency spectrum characteristic and frequency components of these records shot nearly interface, determine the optimum shooting depth. Then, We can obtain the seismic records with good frequency response, the high perk frequency and the wide bandwidth and without the high frequency notch in production.

 

Key Words: Ghosting Information, Display, Analysis, Field Preprocessing

 

 

2£®An Approach to Compute the Length of Seismic Wavelet

Zhang Guang-zhi     Yin Xing-yao  et. al.

£¨Department of Resource, University of Petroleum£©

 

At present there are many methods to extract seismic wavelet, but they all suppose the length of the seismic wavelet is given. In some sense, there is no good method to determine the length of the seismic wavelet now. We suppose that  the several seismic traces have the same the seismic wavelet, the number of the smaller eigenvalues of the matrix which is constructed from the seismic traces is equal to the length of the seismic wavelet. The method , which works well if the signal- noise-ratio is high, is illustrated by means of two  synthetic examples and a real example.

 

3. A New Method for 3-D Refraction Statics

Jianzhong ZHANG      Xixiang ZHOU

(Department of Information Engineering and Geophysics, Chengdu University of Technology, Chengdu 610059, Sichuan, China)

Feng XU

£¨Exploration Department of Tarim Oil Field, Korla 841000, Xinjiang, China£©

     A new method for 3-D refraction statics in CMP gathers is presented, which can determine both long and short wavelength refraction statics at same time. The long wavelength delay times and refraction velocity are obtained in the light of the linear equation of first-break traveltime in a CMP gather. After the long wavelength delay times being removed from original pick times the residual refraction traveltimes with short wavelength disturbances is obtained, which, then, is decomposed into shot and receiver short wavelength statics. The real example shows that the simple and convenient method has a fast convergence and a high precision.

 

4. ANALYSIS OF STATISTIC ATTRIBUTES IN FIELD SEISMIC ENVIRONMENT NOISE

Cao siyuan  Cai zhiguang

University of Petroleum (Bei Jing)

 A successful seismic exploration demands a good quality of field seismic data acquisition. The strength of environment noise is a major factor for deciding whether raw seismic records are in good quality or not. In this paper, the environment noise data recorded in the down well and on the surface was respectively evaluated by computing the five trace statistic attributes of average trace energy , dominant frequency based on a count of zero crossing within a signal window, frequency deviation based on statistical scatter of frequency estimates, estimated trace energy decay rate in db and the ratio of maximum magnitude sample to trace signal amplitude. All traces used above were from a spread 120 trace data set and the analysis was done separately for each trace with no attempt to capture the spatial trace-to-trace or record-to-record relation. The result gave a lot helpful conclusions about the environment noise which can be used to improve the quality of field seismic data acquisition.

 

5. ANALYSIS OF STATISTIC ATTRIBUTES IN SEISMIC SIGNAL OBSERVED UNDER DIFFERENT CONDITION

Cao siyuan  Cai zhiguang

University of Petroleum (Bei Jing)

Abstract: A good quality of field seismic data acquisition based on a strict quality control of seismic field acquisition. The field exploration condition is a major factor for deciding whether raw seismic records are in good quality or not. To different condition, suitable acquisition methods should be adopted. In this paper, the seismic signal data observed in the well and on the surface was respectively evaluated by computing the five trace statistic attributes of average trace energy, dominant frequency based on a count of zero crossing within a signal window, frequency deviation based on statistical scatter of frequency estimates, estimated trace energy decay rate in db and the ratio of maximum magnitude sample to trace signal amplitude. All traces used above were from a spread 120 trace data set and the analysis was done separately for each trace with no attempt to capture the spatial trace-to-trace or record-to-record relation. The result gave a lot helpful conclusions about the field seismic exploration, which can be used to improve the quality of field seismic data acquisition.

 

 

 6£®Improving Signal-to-Noise Ratio of Seismic Data by Wavelet Inversion Approach

Zhang Fanchang,  et al

£¨Department of Resource, University of Petroleum, Dongying, Shandong, 257061£©

 

It is very important to attenuate noise in seismic data processing. Making use of the localization characteristic of wavelet transform in time and frequency domain and the advantages of inversion method, a new noise attenuation method in wavelet domain is put forward. In this way, different processing methods can be used in different frequency bands. It is proved to be an excellent method for noise attenuation by its application in many theoretical and real data. It can obtain more continuous events and retain more subsurface information.

 

7. The Necessity and Realization of 2D Large-offset Ray Forward Modeling

Zhou Yatong                       Wu Jianjun

(Xi¡¯an Jiaotong University  710049)    (Zhangye teacher-training school 734000)

Huang Deji

(Chengdu University of Technology  610059)

 

 The prospecting experience of line TD98-607 shows that the profile¡¯s quality can be improved when large-offset setup is adopted in field data gathering. Based on 2D large-offset ray forward modeling we can analyse the causation that profile¡¯s quality has been improved. Accordingly the large-offset forward modeling also provide theoretical basis for setup¡¯s disposition and seismic data processing. But 2D large-offset ray forward modeling can¡¯t be completed by conventional ray forward modeling module because seismic wave¡¯s propagation laws have been changed when the offset increasing gradually. A new module based on Gauss beam theory that can complete the task of large-offset forward modeling has been given in this paper.

Keywords:   Large-offset 2D ray forward modeling    Seismic data processing

            Gauss beam theory    Ray forward modeling

 

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8. The Application of Wavelet Neural Network Edge Detection To Seismic Data Processing 

GAO Meijuan  TIAN Jingwen  YU Jie

In Seismic exploration, Seismic section which are gotten by various processing and are used to seismic interpretation are actually regarded as some images. In this way, we can learn the problem from the image processing point, the characteristics of image have edges and region, so a seismic event can be thought of as edges on the seismic image. Artificial nerve network is a  new technology not long ago, it can make edge detection of two-dimension image, from this, We apply the artificial nerve network edge detection algorithm to seismic section processing, in order to enhance the quality of seismic section, furthermore enhance the signal/noise ratio and resolution of seismic data, We use this algorithm to process the real seismic section, the effect of this method is good, so this method is feasible and valid.

 

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9. A Study of Virtual Reality technique and its Application in Seismic Exploration

GAO Meijuan  TIAN Jingwen

 

Virtual reality technique is a new man _machine interface , it provides a real 3D man _machine interface ,virtual reality technique as a new means of man _machine exchange and a new way of solve problem of reality world, bring a very extensive shock, so far ,it has important function in aviation ,machinery design, science calculate which include geophysics ,and so on.  The paper mainly discusses virtual reality technique and its application in seismic exploration.

 

10. Use The Multi-frequeucy Technique to Detect Water-bearing Structruein the Roof and Floor of Coal Seam

 

Written by Wang Xinwen, Zhang Zhongli, Wang Yi,

China Coal Research Institute, Xian Branch

    By extensively analysis of the principle of electro-magnitic sounding method, and combined with the work-site application of coal mine electro-magnitic sounding transmission detect method, the paper described that to solve the depth of water bearing structure in the roof and floor of coal seam wich around working face, selecting a proper frequency to do electro-magnitic sounding transmission detect is a high efficiency working way. The paper gives out a typical exsample to prove ahove theory is correct.

 

11. A New type geophysical instrument specially use for detect water bearing structure in roof and floor of coal seam DTS¨DI explosion-proof low frequency electro-magnitic sounding transmission instrument

Written by Zhang Zhongli, Wang Xinwen, Wang Yi,

China Coal Research Institute, Xian Branch

 

 Abstract:    The paper principlly described the research purpose, designed method and structure of the DTS-I instrument.It selected a method of sound signal trasmiting and iso- frequency signal receiving. By this way, it can increase the feature both of anti-noice and high sensive. The detecting procision can be come up to m-uv. The instrument suitable be used to detect water bearing, rock pillar and small faults of the geological structure in roof and floor of coal seam which around working face, and also can be used to detect with similar case of geological structure problem in surface engineering projects.

  

12. A Theoretical Study of Differentially nomalized Electrical Prospecting Method

Liu Song  Xue Jian  Lu Yongkang

(China University of Geosciences, Wuhan, 430074)

 

    Theoretical curves in frequency domain of Differentilly-nomalized Electrical Prospecting Method (DNM) for homogeneous, 2-layer and 3-layer earth models are calculated and studied. It is shown that DNM is neither an IP method nor an electromagnetic sounding. It is also shown that DNM is an electrical prospecting method which is lased on the differences in conductivity and chargeability between the geological target and its country rock and which delineates oil and gas deposits according to the behavior of measured  P  curves sensitive to the ratio of IP response to EM response. Since the physical bases for DNM to delineate oil and gas deposits are the differences in IP and EM responses between oil and gas layer and/or the electrochemical chimney over them and their country rock, DNM resembles CR method, hence its effectiveness in oil and gas exploration should be similar to CR method. DNM is more efficient and economic than CR method, thesefore, it is a better electrical prospecting method in oil and gas exploration.ª¤

 

 

 

13£®Study on self-potential detection principle of oil/gas reservoir

 

Wang Jun-heng

 

Geology and geophysics Research Institute of China Academy of Science  Beijing  100029

 

Self-potential is one of important criteria in geophysical exploration. The important content of self-potential study is the mechanism of natural polarization. This paper introduces theories of oxidation-reduction potential and non-polarized cracking of long chain hydrocarbons. Mechanisms for ion polarization of oil/gas-aqueous solution and that of rock-oil/gas are suggested. Conditions responsible for polarized potential production are diffusion-migration of oil and gas, downward descending of aqueous solution, as well as the change of reduction potential gradient in former; and diffusion-migration of oil and gas in the later. A conceptual model polarization is established. The presence of polarized potential is a general property of the existence of oil/gas reservoir. The whole oil/gas reservoir together with its diffusion-flowing belt can be taken as the source of the potential field, and the polarized potential can be described by a model of polarized dipole. An analytical expression of potential field is derived based on a viewpoint of polarized dipole and electrical current. Calculations by using in-house model, field model experiment, and various models prove the correctness of this theory. On the basis of laboratory experiment, self-potential technique is applied effectively to locate highly effective block and extension of oil/gas field. With the criteria of an oil/gas reservoir in Northeastern China such as size, wide, boarder gradient of its surface self-potential etc. and combined with other factors, the development results of 65 development wells are predicted with success ratio reaching 85%.

 

14.The Characteristics and Application of Distributed Intelligent

Multi-electrodes Resistivity Imaging System

DONG Haobin WANG Chuanlei

£¨China University of Geosciences 430074)

  Resistivity imaging is a survey technique recently developed for the investigation of areas of complex geology where the use of resistivity sounding and other techniques is unsuitable. The traditional instrument consists of multicore cable. This type is complex, no flexibility. The new distributed resistivity meter use smart electrode and switch A, B, M,N automatically. This technique is first invitation in China that belongs to China University of Geosciences ( Wuhan ). The distributed intelligent resistivity imaging system made of CUG applied in cave detecting, hidden danger inspecting in dam and others geological and engineering prospecting.

 

 

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24-bit ADC Technology and its Application in Geophysics

DONG Haobin

China University of Geosciences(430074)

 

Abstract: This paper discussed the 24-bit ADC technology and its application in geophysics. 24-bit ADC used the ¦¤¡ª¦² modulator and decimator/digital filter. A high performance ADC is realized by using this technology. That is high dynamic range, high resolution, high stability and low cost. In geophysical prospecting, for example seismic prospecting, the dynamic range of reflection or refraction signal is more than 120dB. In old seismic instrument, the IFP and low bit ADC was used. But instrument¡¯s circuits was complexion and its cost was so expensive. Now 24-bit ADC is widely used in petroleum seismic prospecting, MT sounding and sea floor MT. It will be effect the geophysical instruments extremely.

 

 

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              Instantaneous Effects of Elastic Waves on Conductivity of Porous Media

                                LiLi  TaoGuo  Dai shikun

                            University of Petroleum, Beijing,102200

 

Abstract

The propagation of elastic waves through the media always leads to the dynamic deformation of the media. This has important effects on the physical properties and pore structures of the two-phase materials. In this paper, we have concentrated our discussion on the instantaneous effects of dynamic deformations on conductivity of the media and their relations with pore structures. This kind of dynamic deformations changes the local electric potential, and hence the conductivity of the fluids in the pores. Furthermore, the dynamic deformation due to elastic vibrations can get the closing or opening of porous paths and result in considerable changes of effective specific areas of pores. Since the specific area of pores and the conductivity of the pore fluids are two key factors controlling the conductivity of a medium, their changes due to the deformation of the media are responsible for the changes of the bulk conductivity of the two-phase medium.

 

17. INVESTIGATION INTO THE MECHANISM OF CONDUCTIVE OIL-GAS BED IN LIAOHE OILFIELD AND APPLICATION IN HAINA 3 BLOCK

ZHAO Ji-wen¹ , LI Rui² , LI Neng-gen¹

(1.   Liaohe oilfield well logging Company,Liaoning  124011,China;

2.Chengdu Institute of Technology,Chengdu  610059,China)

 

Abstract: A logging interpretation model of conductive oil-gas bed has been built by means of investigation into the mechanism and the forming cause of representative conductive oil-gas bed and application in Hainan conformation that is  important exploration area in liaohe oilfield .The various kinds of reservoir parameters about this reservoir has been computed precisely and quantitatively .The exploration efficiency has been improved observably. Aiming at various causes of conductive oil-gas bed formation ,we make a study about the cause of conductive oil-gas bed formation ,kinds identification , electric mechanism with the synthetic use of Hainan structure information of   lithology analysis ,core data depth comeback and basing on well logging data beforehand procession. A set of interpretive and processing program that is very good for conductive oil-gas bed identification has been built by means of the restrict  inversion optimum method ,the fuzzy cluster analysis ,the stepwise discrimination analysis ,the neural networks and well logging theories.

Keywords: Liaohe oilfield  Conductive oil-gas bed  Conductive mechanism

          Nural network  Fuzzy cluster analysis   Stepwis discrimination analysis

 

 

18. Method and Effect about to MT High¡ªresolution

SU Hongyao

(Construct Engineering Quality Surveillant Station of Huadu City)

He Zhanxiang

(Fifth Column Rock Oil Geophysical Prospecting Bureau)

 

[Abstract]       It¡¯s  a  troublesome  question  to  correct  static  displacement. Someone  has  always  tried  to  exhibit the  achivements  of  MT  through advanced  graph  showing  in  recent  years. In  this  paper,  a simple  and  direct  method  is  provided  by  image  on  the interface technique for exhibiting  the  achivements  of  MT. The method opens out infinitely the resolution of MT curve , makes little anomaly can show clearly.  secondly, after differential  coefficient  processing, we  can  get  frequency  field  tectonics  graph  removed  adequately  static  displacement, and get  references  and  datums  during  we  correct  static  displacement. This  method  is  good  for tapping  the  resolving  power  of  MT,  and  for  seeing  and  correcting  the  static  displacement.

[keywords]satic dsplacement image on the interface technique resolution

 

 

19. To develop technique of vector wave field

separation for 3C reflection
      Yao Chen
Institute of Geology CSB, China, 100029
    Abstract:

With increasing of three-component reflection records, we have to deal with three dimensional vector wave-fields as result of P-wave, converted shear-wave splitting and their interference. A wave vector has polarization as first characteristic then its arrival time, amplitude waveform and others as vector parameters. Vector wave field separation (VWFS) is to separate each vector from 3C wave-field. In order to develop new technique VWFS, we adopt rotated Cartesian coordinates in case of three vectors are nearly orthogonal. Further we set up covariant affine coordinates to process 3C data, as the interfered vectors have non-orthogonal polarization. The spatial polarization of each vector can be determined by its linear property appeared on 3C records. Many data processing methods already used for shear-wave splitting from direct shear-waves from VSP or earthquake are inconvenient to 3C reflection data. The principal of perfect vector wave field separation is that reflection processing is independent of any priori knowledge about medium and wave characteristic, so corresponding technique could be developed along its self-governed approach. There is a fundamental difference between VWFS and other filter either by velocity difference or by frequency difference of waves on single component. VWFS could provide us more parameters on records that contain a lot of information for structure-fracture composite imaging.
    NSFC NO. 49874012 supports this work.

 

20.   Study Seismic Dynamic Supervision in Oil Field Exploitation
  Yao Chen  and  Chongtao Hao
  Institute of Geology CSB, China, 100029

Abstract

    Detecting cracks (fracture, crack and pore) and supervising its temporal change have great importance in oil field exploitation since cracks control liquid flow direction. By explaining shear-wave splitting from local earthquakes before and after large evens, the temporal changes of crack density and aspect ratio have been supervised. Such data processing and interpretation technique could be transformed to VSP and cross-hole for crack detecting, but such approach only provides information restricted near wells. In order to get exact information about cracks and to detect its temporal change from three-component reflection as repeated survey, new data processing and explanation technique is required based on theoretical development of seismic reflection. We have calculated synthetic seismograms for varied crack parameters and got following conclusions.
    1. The method of converted wave on 3C reflection due to explosion source could be developed in stead of shear-wave source exploration.
    2. Since converted waves have energy depending on interface properties of media, the exploration design should be carried out in combination with numerical modeling.
    3. The technique of vector wave field separation can be applied in stead of stacking.
    4. It is needed to increase the comprehensive interpretation ability especially for PTL+EDA medium in east part of China. In such medium, it is much more difficult to get information about cracks than that only cracks occur.
   NSFC NO. 49874012 supports this work.

 

21. The high-order difference scheme and its numerical dispersion relation of 3-D acoustic wave equation

He Bingshou£¬ Wei Xiuchen£¬ Liu Yang

 

(Department of Geoscience, University of Petroleum, Beijing  102200 )

ABSTRACT £ºBy using high-accurate finite-difference to approximate the derivative of 3-D acoustic wave equation, a forward modeling technique applicable for anisotropic media called high-order difference scheme of 3-D seismic simulation is established. A numerical dispersion relationship is proposed in the paper, which is mainly influenced by both the finite difference accuracy and the grid size in which the latter factor has more influence on it. In same conditions, the numerical dispersion will worsen when the grid became bigger or difference accuracy became lower. It is indicated that the grid space has a function of low-pass filter, so the main frequency component of the hypocenter should be far away from to the cut frequency to insure the result¡¯s accuracy. On the basis of all these analyses, the technique is used to achieve prestack and poststack numerical simulation of geologic models. The results indicated that the scheme can improve the simulation accuracy and the numerical dispersion analysis can suppress the numerical dispersion greatly.

 

22. Characteristics of P-wave stacking profile from reflection

in PTL and EDA
  Chongtao Hao  and  Yao Chen
  Institute of Geology CSB, China, 100029
 

Abstract:     For layered media with top layer as crack-induced anisotropy and PTL, we have calculated CSP gather from curved wave front of energy reflection by anisotropic reflectivity technique and have constructed stacking profiles based on reduced isotropic P-wave velocity (reduced velocity briefly). Both for cracks filled with gas and water respectively, the reduced velocity can be obtained for different survey line azimuths and high quality stacking can be realized. It is noticed that the reduced isotropic velocity is varied with azimuth for cracks. In case of PTL with anisotropy degree of 22and 36respectively, although P-wave has strong velocity anisotropy as phase propagation, the perfect stacking profiles can also be obtained based on reduced isotropic velocity. Except a few largest offsets, NMO and stacking for stronger PTL anisotropy could be carried out with equivalence of isotropic reflection. As time-depth conversion, the depth errors of reflection interface due to reduced velocity occur, which have variation with azimuth for crack layer reflection. Compared with true reflector depth 2000m in our model, the depth errors of interface are changed from tens of meters to hundreds of meters for weak and strong velocity anisotropy. It is interested that the interface depth from stacking is shallower for crack layer while deeper for PTL.
    NSFC NO. 49874012 supports this work.

23. The Propagation Characteristic of Seismic Wave in Transverse Isotropic Medium

Yuan Shujin  Dong Minyu  Wei Xiucheng  Liu Gouming

(University of  Petroleum (Beijing)  102200)

 

The energy of seismic wave propagates with the direction of raying. In isotropic medium, the phase angle (or phase velocity) of the seismic wave is the same as that of the group angle (or group velocity). In anisotropic media, The propagation characteristic of seismic wave varies with the propagation direction , It usually presents that the phase angle (or phase velocity) of the seismic wave differs from that of the group angle (or group velocity).

Based on Thomsen¡¯s parameters, the feature of P-wave and SV-wave and influence of Thomsen¡¯s parameters is studied in this paper using theory models to study the feature of  propagating, to study the Thomsen¡¯s parameters affecting the phase velocity of the P-wave  in vertical transvers isotropic. It is very importance for elastic parameters inversion, velocity inversion, normal moveout correction, dip moveout removal and migration in time-domain.

 

24. Reflection Traveltimes Analysis for Transverse Isotropic Medium

Yuan Shujin  Dong Minyu  Wei Xiucheng  Qu Xiangming

(University of  Petroleum (Beijing)£¬102200)

 

Conventional seismic exploration is based on the assumption of isotropy, reflection moveout curves are conventionally approximated by the hyperbolic equation. The hyperbolic moveout equation is strictly valid only for a homogeneous isotropic (or elliptically anisotropic) plane layer.  The presence of anisotropy causes two principal distortions of reflection moveouts.  First, the short spread moveout velocity in the presence of anisotropy is not equal to the rms vertical velocity, even for horizontal layers. Second, anisotropy leads to nonhyperbolic moveout, event in a homogeneous layer.

We present the calculating methods of the P-wave and SV-wave reflection trveltimes for three sorts spread-length in transverse isotropic medium. The travetime curves obtained by numerical calculation show the effectiveness of the methods and characteristic of reflection traveltime curves. It is very useful in the elastic parameter inversion , migration and precise interpretation.

25. Fracture detection using azimuthal variation of P-wave velocity

Fan Guozhang

Petroleum University  Beijing  102249

 

Abstract  According to geological condition and lack of S-wave data in China, it is important to improve the method to detect fracture using P-wave data. Under a series of hypotheses, the stiffness tensor of the material with complex fracture is derived: C = C⁰ + C¡¯¹ + C¡¯² + C¡¯³ +¡¤¡¤¡¤where C⁰ is the stiffness tensor for the isotropic matrix, C¡¯ⁱ is the term of different fracture sets which can be perpendiculor or inclined to the formation and received by the Bond transformation of a simple fracture sets. Then, the azimuthal variation of P-wave velocity can be calculated by a necessary condition of Christoffel equation. Thus, a relation is established between the fracture and P-wave data. In practical case, it is needed to select suitable fracture model by geological and logging data to detect fracture by P-wave velocity.

 

26. The Research of 3-D Coherence Cube Acquisition Method and its Application

Wang Yonggang  Zhang Junhua et.al.

(University of Petroleum  Dongying  257061)

 

The 3-D coherence cube technique is very useful and important in the seismic interpretation. It can not only relax interpreter but also reduce 3-D interpretation period.  The technology is effective for solving geologic problems such as faults, special lithologic body and so on. The algorithm can be used to realize the conversion from 3-D amplitude data to semblance or coherence attribute data by calculating coherency between seismic traces. However, when using the traditional method£¬the running time is always very long , can not satisfy the practical need. In the paper, We put forward the recursive method of calculating seismic attribute by signal energy analysis. The calculating speed is 45 times faster than before. It is successfully used in the TJH area, the processing results are satisfied.

Keywords:  coherence cube, fault, recursive method, detection

 

 

27. Multi-component AVO study and lithology analysis

Zhang Guangjuan  Hu Tianyue

Department of Geophysics, Peking University, Beijing 100871, China

   The anisotropy of medium is one of the significant factors which disturb amplitude variation with offset (AVO). The equations of Banny (1994) and Banik (1987) for the reflection and the conversion coefficients for small angle P wave incidence are simplified and get the approximate expressions for weak elastic transverse isotropic medium. When the incident angle is less than 30 degrees, the approximate expressions are very accurate and the anisotropy effects for the AVO of P-P and P-SV waves are dominated by the difference of Thomsen¡¯s anisotropic parameter between two layers. Both AVO curves of using the above approximate expressions and the full expressions of the reflection and the conversion coefficients are calculated to confirm the accuracy of the above approximate expressions. The AVO study of P-P and P-SV waves would be useful in identifying the low impedance gas sand.

 

28. Stacking profile of P-wave energy reflection from TI anisotropy and its implication

Yao Chen

(Institute of Geology CSB, 100029)

Abstract

There may have a significant difference between energy reflection and phase propagation reflection for seismic wave propagating though anisotropic layer, particularly through strong anisotropic layer. The energy reflection usually appears normal time-distance relationship due to group velocity vector deviated from phase velocity vector especially in direction. This means that an equivalent isotropic reduced velocity could be obtained for stacking data of reflection. And such idea has been demonstrated from stacking synthetic CSP profiles calculated by reflectivity technique for horizontal layer of crack induced anisotropy and Periodic Thinner Layer respectively. This could clear a series of puzzles in seismic exploration in recent 10 years. 1. Stacking for reflection could be carried out based on reduced isotropic velocity even in stronger anisotropic area. 2. Reflection times on stacking profiles for across survey lines in various azimuths are different as reflection time unclosing. 3. More than 10% error about reflector depth could occur on stacking profiles. The reflection time unclosing on stacking profiles for across lines could be remarkable signature for existence of azimuthal anisotropy that could be used for P-wave crack detecting and monitoring temporal changes of medium for oil and gas production.

This work is supported by of NSFC No. 49874012.