Three-dimensional Research Of Azimuthal Anisotropy And Fracture Detection Methods

Fractured reservoir is one of the important oil and gas reservoirs, and bythe vertical alignment of the anisotropy caused by cracks in the media - HTImedia is an important study to the fractured reservoirs. Vertical cracks caused the anisotropy, making the dynamics and kinematics fractured media have different characteristics. The author predictive crack direction and intensity accordingto the differences.In this thesis, the author start with the AVO forward analysis, and to study of the azimuthally anisotropy in cracked media which cause the amplitude differences, velocity difference and shear wave splitting, that lead to basis of thefracture detection method, thus some clues have been summarized: (1) For theHTI media, the reflected P-wave and S-wave amplitude, P-wave travel time and P-wave velocity with the observed direction of the changes are similar to an ellipse; (2) From the ellipse majior and minor axis can determine fracture orientation and intensity properties; (3) using of amplitude detection is more sensitivity to detect crack than using speed property; (4) the azimuthally travel-time"ellipse" feature can correct the azimuth of cracks caused by the media residual moveout NMO; (5) The sensitivity of C-wave to the crack is more than thereflected P-wave, and sensitivity of the C-wave to the oil and gas in crack isalso higher. The results of these studies for the fracture prediction method provide a good theoretical basis.According to the research and implementation of HTI media fracture prediction method - (1) According to the azimuthally changes of the amplitude achieved RVA method to predict crack realization: Ruger (1998) proposed the weakanisotropic medium wave approximate formula derived for the reflection coefficient inversion fracture parameters. (2) According to the azimuthally speed variation achieved VVA method to predict fracture: The fractured formation of P-wave velocity with azimuth change the formula as the inversion of the basis, the use of wave direction "ellipse" predict crack growth direction and strength; (3)According to shear wave splitting achieved rotation analysis method of C-wave to predict fractures: using Monophyletic, two components sections in the C-waveform data coordinate rotation, to keep consistency of the collection coordinatesand natural coordinates achieving purpose that to separate the fast and slow C-wave and prediction crack attributes. And the author also gets in the realization of theoretical models to prove the accuracy and adaptability of the method validation.