北大港浅层含气砂岩AVO异常响应特征与应用

Characteristics of AVO Abnormal Responses from Shallow Gas-bearing Sandstone in Beidagang and Application

北大港油田浅层气第三系明化镇组,埋深600～1200m层段以上的气层。岩石物性研究发现,当砂岩中含气时,P波速度明显降低,并且含气时泊松比也明显低于含水时泊松比,从而构成利用AVO方法进行气藏检测的理论基础。根据对北大港189井区的三维剖面进行AVO处理,从已知井出发,在原始测井曲线的基础上建立AVO正演模型;通过对邻井剖面AVO属性参数的分析,利用泊松比参数来判断地层是否含气,好的含气砂岩所表现的是负异常的泊松比叠合在AVO截距的波谷上展示含气砂岩的AVO异常响应特征,根据这些异常特征,在平面上对含气性进行了预测。

The shallow gas in Beidagang oilfield refers to the gas reservoirs buried within depth of 600~1200m in Minghuazhen Formation of Neogene.The study of Petrophysical property finds that P-wave velocity decreases significantly when sandstone contains gas bearing,and Poisson＇s ratio of gas bearing was significantly lower than Poisson＇s ratio of water bearing.Thus it forms a method for gas detection on the basis of AVO theory.Applying AVO processing to the 3d profile of Gang 189 well area in Beidagang,from the known well,AVO forward modeling is established based on the original logging curves.Through the analysis of AVO property parameters of the adjacent Wells＇ profile,Poisson＇s ratio parameters are used to judge whether there is gas-bearing strata.Good performance of gas-bearing sandstone is that the Poisson＇s ratio of negative anomaly overlaps on trough of AVO intercepting the AVO and it shows abnormal response characteristics of gas-bearing sandstone.According to these anomalous characteristics,the gas-bearing characteristic is predicted in this aspect.