AVO Technology and its application in oildetection.docx

1、AVO Technology and its application in oil detection题 目: AVO Technology 指导老师: 邹 慧 芳 学生姓名： 张 鹏 所属院系： 地球科学学院 专 业： 矿物学、岩石学、矿床学 班 级： 矿物S131 完成日期： 2013年11月11日 AVO Technology Zhang Peng AbstractWith the development of oil and gas exploration and the deepening of the degree of seismic exploration, conventio

2、nal methods can not detect formation (lithology) oil and gas reservoir, then we use the AVO technique to detect oil and gas. AVO technology was used to identify the bright spots amplitude anomaly, as long as the development and application of computer technology in recent years, the AVO technology i

3、n the field of oil and gas exploration has more and more extensive application. This paper begins by searching large quantity of literatures,data and related books from AVO technology development, AVO principle, technical ideas, examples, advantages and disadvantages at the same time combined with t

4、he oilfield production example analysis the probability of use AVO technology to improve the production of oil and gas;Last come to a conclusion that in some areas when use conventional seismic techniques cannot detect oil effectively then can use AVO technology to detect oil and gas in order to inc

5、rease oil and gas production.keywords: AVO；AVO Technology；Poissons ratio；Forward；inversion； Oil and gas detection； Contents1 AVO Technology - 3 -2 Principles of AVO Technology - 3 -2.1 The physical basis of AVO Technology - 3 -2.1.1 wave equation - 3 -2.1.2 Zoeppritz equations - 4 -2.2 The geologica

6、l basis of AVO Technology - 6 -3 Application of AVO Technology - 8 -3.1 The true and false recognition highlights - 8 -3.2 Detection of oil gas water boundary - 9 -3.3 Lithologic interpretation - 9 -4 The example analysis - 10 -Case 1: - 10 -Case 2: - 12 -Case 3: - 13 -5 Advantages and limitations o

7、f AVO Technology - 14 -5.1 Advantages: - 15 -5.2 Limitations: - 15 -6 Influence factors analysis of AVO - 16 -7 conclusion - 16 -References - 16 -1 AVO TechnologyAVO is intended to amplitude variation with offset as shown in figure 1. Or amplitude versus offset. AVO technology is the use of CDP (com

8、mon depth point)gathers data, analysis of reflection wave amplitude versus offset (or incident angle) change rule,estimate Poisson ratio of the interface, further inferred lithology and hydrocarbons condition. Figure 1 relationship between amplitude and offset2 Principles of AVO TechnologyThe princi

9、ple of AVO technology contains two parts: the physical and geological foundation.2.1 The physical basis of AVO TechnologyThe core theory of AVO technology is the wave equation and its solutionZoeppritz equations. The physical basis of AVO technology is discussed the solution of wave equation (Zoeppr

10、itz equations), the specific application and the resulting conclusions in seismic exploration.2.1.1 wave equationThe wave equation is described as a partial differential equation which volume element of the elastic medium move from the equilibrium position. In the above formulais Laplace operator,It

11、 is expressed as:U, V, W, as a medium displacement in the X, Y, Z three direction of the component; as the physical density (describe the distribution of source)component, as medium density. and as the medium of Lame coefficient; as the volume strains.Zoeppritz equations is a solution of the wave eq

12、uation.2.1.2 Zoeppritz equations Assume that the boundary conditions for the wave equation: on the surface of 1.5 infinite elastic medium (such as surface), a harmonic wave to the interface of medium generates four waves, which reflected P-wave, S-wave reflection of P SV, P, SV transmission wave tra

13、nsmitted p-wave. figure 2 The reflection and transmission waveAccording to the boundary conditions and the solution of the wave equation ,bring the flection coefficient, the transmission coefficient and then can get the Zoeppritz equations.Which represents the P wave reflection coefficient, reflecti

14、on coefficient of SV wave, P wave and SV wave transmission coefficient and the transmission coefficient. represents interface on the density and velocity. as the incident angle, as the angle of reflection, and as the transmission angle.Bring the laboratory data into the Zoeppritz equations,Then get

15、the relationship between the incidence angle (or offset) and reflection coefficient ( amplitude of seismic wave) .figure 3 Relationship curves of reflection coefficient and angle of incidenceFigure 3 indicates that the relationship between the angle of incidence and the reflection coefficient: with

16、the incident angle (or offset) change, reflection coefficient (amplitude). 2.2 The geological basis of AVO TechnologyAfter solving the wave equation can obtain the relationship between seismic P-wave velocity and S-wave :In the formula, andas Lame coefficient; as medium density; E as the youngs modu

17、lus; as Poisson ratio.From the relation of P and S wave can leading-out the comparison expression of P-wave velocity and S-wave velocity ratio.The formula show that the ratio of P and S hear wave velocity is closely related to the Poissons ratio. Variation of Poissons ratio depends on the longitudin

18、al wave velocity, the magnitude of the change depends on the speed of the base value and speed variation amplitude.Laboratory according to the shear wave velocity ratio and Poissons ratio of different determination of the corresponding relations and their changes with the rock characteristics, test

19、results are shown in Figure 4. Figure 4 different lithologic rocks relations of Poisson ratio and aspect Bobbi As can be seen from Figure 4, gas bearing sand stone has the minimum Poissons ratio(0 0.16); andIncreases with the increase of porosity, and the weathering crust has the largest Poissons ra

20、tio.In addition, Dominic also gives a Poisson gas, oil, water sand ratio curve with the burial depth (Fig. 5)Figure 5 different sandstone Poissons ratio curve with the change of depthFigure 5 shows that gas bearing sand stone has the minimum Poissons ratio,It changes between 0.02 0.18,oil-bearing sa

21、ndstones ratio of Poisson is in between (0.24 0.4),and water sand has the maximum Poissons ratio ranging from 0.35 to 0.5.The following examples show that the relationship between the Poissons ratio and different rock properties, as shown in Figure 6: Fig. 6 Relationship between Poissons ratio and P

22、 wave interaction diagramPoissons ratio in Figure 6 clearly separated from the sandstone and shale and limestone;besides,the Poissons ratio of limestone and shale is higher than that of sandstone.To make a long story short, the Poissons ratio can distinguish lithology.Poissons ratio can predict the

23、characteristic layer and its oil and gas reservoir by using seismic data.3 Application of AVO Technology AVO technology has been applied to various areas with complex geological conditions, and have achieved good results, here are some examples to illustrate the application of AVO technology in hydr

24、ocarbon detection.Application of AVO technology in hydrocarbon detection mainly concentrated in:true and false recognition, several highlights detection of oil and gas water boundary, lithologic interpretation and so on.3.1 The true and false recognition highlightsBright spot may be a sign of oil an

25、d gas, but some of the highlights are not caused by the oil and gas accumulation; some non gas containing high or low velocity layer (such as limestone, igneous rock or coal) can also cause strong amplitude anomaly amplitude, but not with offset increases, so you can to distinguish the true from the

26、 false bright spots by AVO, as shown in figure 7.Fig.7 highlights of true and false identification In Figure 7, an increase in the amplitude of CDP gather two bright spot as the offset changes, but the increasing amplitude above the bright spot with offset and smaller, false bright spots; bright amp

27、litude versus offset below increases, is really bright spot.3.2 Detection of oil gas water boundaryDistribution of regional comprehensive study all logging, drilling data and oil gas water range statistics, Poissons ratio, reflection coefficient by means of different lithology and fluid bearing the

28、same lithology impedance boundary condition with the change of incident angle different to judge the oil gas water boundary.Figure 8 shows, gas in the Poissons ratio of the lower amplitude,oil-bearing sandstone, sandstone and water bearing sandstone top interface with offset (angle of incidence) cha

29、nges are not the same; gas bearing sandstone top interface of amplitude variation with offset maximum, the amplitude of oil-bearing sandstone, sandstone roof water interface changes with offset is minimal, so it can be used to judge the oil gas water boundary. Fig.8 relationship between sandstone re

30、servoir top interface amplitude and offset3.3 Lithologic interpretation Take advantage of The amplitude and angle of incidence curve of different lithology between impedance interface,we can inference and interpretation the lithology which the curve represented. (a) (b) Fig. 9 use the amplitude to i

31、nterpret lithologic Figure 9 (a) diagram is a graph seismic amplitude and offset, the amplitude of different offset corresponding to different values, using appropriate offset value curve, too (b) diagram. The different offset value into the Zoeppritz equations corresponding to the speed value. Acco

32、rding to the reflection layer S-wave and P-wave velocity can be calculated by using the Poissons ratio, Poissons ratio of the regional stratigraphic lithology explained.4 The example analysisCase 1:The south of Albertas Cretaceous sandstone Colony is a good reservoir, seismic data also showed the typical bright spot anomaly, FIG