The Analysis Of Azimuthal Anisotropy Of Multi Waves In HTI Media And Fracture Detection Methods

The fractured reservoirs which widely exist in kinds of oil and gas fields aroundthe world have the characters of common and complex. This takes some difficult toprecise delineation these reservoirs, so the research of the fractured reservoirs has aimportant practical significance.In the actual fractured reservoirs, because of the effect of pressure, thehigh-angle and near vertical cracks are easily saved. Usually we named this media asHTI media. The fractured reservoirs clearly have the characters of HTI azimuthalanisotropy which are the anisotropic changes of amplitude velocity and time of theseismic waves.So the first part of this paper mainly analysis the anisotropic forward in HTImedia. By establishing one layered and multi layered anisotropic models, the paperget the following conclusions:When the azimuth fixed, the amplitude and time of longitudinal wave andconverted wave changes, and the anisotropy is more obvious with the big incidenceangle; When the incidence angle fixed, the amplitude and time of longitudinal waveand converted wave changes periodically, and the period is;By contrasting the AVA of longitudinal wave and converted wave, the paperalso get the same conclusion which is based on AVO of converted wave indistinguishing the gas-saturated and brine-saturated sandstone, converted wave canget a better result than longitudinal wave;In multi HTI media, the anisotropy of upper layer can impact the lowerlayer(such as time anisotropy), so in the processing of seismic data, the anisotropiccorrection of upper layer of fractured reservoirs should considered.The latter part of this paper is theoretical based on the research of first part. In connection with the theoretical geological model, the paper uses the methods ofAVOA、VVAZ、IPVA of longitudinal wave to inverse the trend and growth of crack.By contrasting the results, the paper get the following conclusions:By the analysis of the inverse result, finding that the result will be more precisewith the increase of the lines number. So the AVOA method should use wide azimuthto improve the inverse effect;The ellipse get from VVAZ、IPVA can indicate the trend of crack(long axis)andthe crack growth(flat rate);By contrasting the AVOA method of longitudinal wave, using AVOA ofconverted wave has a operability in theory.