利用AVO理论识别MTD与BSR的技术方法

Method of identifying MTD and BSR through AVO theory

似海底反射层(BSR)是识别天然气水合物最为有效的标志,是由于天然气水合物地层与下伏游离气地层存在波阻抗差异形成的,与地质产状无关.而块体搬运沉积体系(MTDs)是一种常见的陆坡沉积作用,与地质产状有关.MTD在地震剖面上形成的地震反射特征和水合物形成的地震反射特征(BSR)存在极大的相似性:负极性、强反射、其上方存在空白带等特征.一般来说可以通过地质解释、测井识别等方法对MTD与BSR进行区分.本文尝试利用AVO技术对MTD与BSR进行识别.首先对存在MTD与BSR的CDP道集进行单点AVO特征分析,然后根据AVO分析结果对AVO属性进行交汇分析,从而区分MTD和BSR.在实际地震资料中得到了很好的效果,发现MTD属于第四类AVO特征,BSR属于第三类AVO特征,从而验证了该方法的可行性.

Bottom Simulating Reflectors（BSR） is the most effective identification of gas hydrate,which is due to the difference of the wave impedance between the gas hydrate formation and the underlying free gas formation,and it is not related to the geological occurrence. And the Mass Transport Deposits（MTDs） is a common slope sedimentation,which is related to the geological occurrence.The seismic reflection characteristics of MTDs and gas hydrate（BSR） exists great similarities： negative polarity,strong reflection,blanking zone on the MTD or BSR. In general,we can identify MTD and BSR by the methods of geological and logging data. This paper attempts to identify MTD and BSR through AVO theory.Firstly,the single point AVO feature analysis was performed on the CDP gathers set with MTD and BSR,and the AVO properties were analyzed according to the AVO intersection analysis results to distinguish MTD and BSR. Using this approach,it is found that MTD belongs to the fourth AVO feature,and BSR belongs to the third AVO feature,which proves the feasibility of this method.