基于地震波阻抗随机反演的岩性模型建立  

Lithology Model Establishment Based on Seismic Wave Impedance Random Inversion

作　　者：陈旭 印森林[2] 程士桐 刘娟霞 李重逢 雷章树 CHEN Xu;YIN Sen-lin;CHENG Shi-tong;LIU Juan-xia;LI Chong-feng;LEI Zhang-shu(School of Earth Sciences,Yangtze University,Wuhan 430000,China;School of Logging Engineering,Yangtze University,Jingzhou 434000,China;China France Bohai Geoservices Co.,Ltd.,Tianjin 300450,China)

机构地区：[1]长江大学地球科学学院,武汉430000 [2]长江大学录井技术与工程学院,荆州434000 [3]中法渤海地质服务有限公司,天津300450

出　　处：《科学技术与工程》2024年第25期10667-10676,共10页Science Technology and Engineering

基　　金：长江大学地质资源与地质工程一流学科开放基金(2019KFJJ0818022)。

摘　　要：位于WT凹陷的三角洲外前缘储层的砂体尺度较小、非均质性较强,这导致了该类储层面临着岩性预测刻画困难的问题。根据岩心分析与测井资料表明,研究区目的层广泛发育泥质砂岩储层,但泥质砂岩与细砂岩、泥岩的纵波阻抗差异较小,无法有效利用纵波阻抗对细砂岩、泥质砂岩、泥岩3种岩性进行有效识别,且研究区井网稀疏,无法有效提取变差函数,影响后续叠后地震随机反演的效果进而影响储层岩性的预测。针对上述复杂问题,通过采用小波重构与信息统计加权方法对纵波阻抗曲线进行重构,通过地震属性对砂地比的敏感性分析,应用地震均方根(root-mean-square,RMS)属性对砂体进行刻画,并从中提取变差函数。利用重构曲线并结合变差函数进行了叠后地震随机反演,结果表明:利用信息统计加权重构的纵波阻抗的对岩性有较好的识别效果;通过叠后地震随机反演并结合贝叶斯算法建立的岩性模型与验证井岩性高度匹配;通过岩性模型所制作的砂地比平面分布符合地质认识。可见利用上述方法所建立的纵波阻抗随机反演模型可靠性较高,对砂体平面展布的预测与水平井轨迹设计具有重要勘探指导意义。The sand bodies of the delta front reservoirs in the WT Sag have small scales and strong heterogeneity,which leads to the difficulty of lithology prediction and characterization for this type of reservoirs.According to core analysis and logging data,muddy sandstone reservoirs are widely developed in the target layer of the study area,but the difference in compressional wave impedance between muddy sandstone,fine sandstone,and mudstone is small,and it is not possible to effectively use compressional wave impedance to identify the three lithologies.Moreover,the well network in the study area is sparse,and it is not possible to effectively extract the variogram,which affects the effect of post-stack seismic stochastic inversion and further affects the prediction of reservoir lithology.To solve these complex problems,the compressional wave impedance curve was reconstructed by using wavelet reconstruction and information statistics weighting methods.Sensitivity analysis of seismic attributes to sand to ground ratio was conducted,and root mean square(RMS)attributes were applied to characterize the sand body and extract a variation function from it.Random inversion of post stack seismic data was performed using reconstructed curves combined with variation functions.The results show that the compressional wave impedance reconstructed by information statistics weighting has a good identification effect on lithology.The lithology model established by post-stack seismic stochastic inversion and Bayesian algorithm matches well with the validation well lithology.The planar distribution of sand ratio made by the lithology model is consistent with geological understanding.It can be seen that the compressional wave impedance stochastic inversion model established by using the above methods has high reliability,and has important exploration guidance significance for predicting the planar distribution of sand bodies and designing horizontal well trajectories.

关 键 词：珠江口盆地 泥质砂岩 小波重构 叠后随机反演 岩性预测 

分 类 号：P631[天文地球—地质矿产勘探]