Three-dimensional Analysis Of Azimuthal Anisotropy And Fracture Detection

Fractured reservoir is one of the most important hydrocarbon reservoirs.In the fractured reservoir anisotropy often obvious impact, mainly for the azimuth difference in the amplitude, speed, phase and reflection waveform.This article attempts to predict the parameters of fracture by azimuth difference of the amplitude and velocity.The study from the forward modeling, analyzing the EDA medium wave amplitude, travel time and velocity of the azimuth anisotropy, provide a basis for predicting fracture.Through the experiment on the following understanding:(1) for weak anisotropic fractured medium, the amplitude and the travel time and the velocity of reflected wave change with the observation position can be approximated as an ellipse. (2)The indicated direction of the amplitude short axis needs to decide according to the specific elastic parameters of medium, in the actual data can be assisted by other attributes or logging,geological data to be judged.(3)The minor axis of azimuth ellipse of travel time indicates crack growth direction,the long axis directed to the crack laws and the flat rate showed the relative fracture density.(4)The long axis of the azimuth ellipse of velocity indicates the direction of crack growth.(5)The azimuth anisotropy of the velocity is weaker than the amplitude.These experimental results for the crack provide a strong basis for forecasting.In order to quantify the inversion of crack, the first under the Ruger P-wave reflection coefficient given by the formulas for the inversion of the inversion formula of fracture parameters, carried out by numerical simulation of fracture parameters of the inversion calculation.Analysis for anti-noise property of inversion crack by azimuth amplitude.Interval velocity of crack and the angle between offset and fracture strike compose the formular, that is V = A + B cos2? ,the approximation for the ellipse,the long axis of the ellipse indicates the direction of crack growth,the flat rate of the ellipse indicates the development of cracks in strength.Based on this relationship ,using three-dimensional multi-directional interval velocity,direction and inversion calculation of crack development strength,and through numerical simulation and actual data for the crack growth direction and strength of the inversion.The azimuth remaining time will exist in CMP gathers because of crack and impact the stack along offset or azimuth. The travel times of different lines in a fixed offset have the elliptic distribution.Each survey line direction can move school to t0 through removing the azimuth time difference .The theoretical model dealing with the feasibility of this method is proved.