速度建模技术在吉林探区复杂构造成像处理中的应用

针对吉林探区伊通盆地西北缘地震资料的复杂构造成像,叠前深度偏移是目前比较有效的成像技术,而复杂构造准确成像面临的核心问题不是偏移算法,而是速度模型的准确性问题。速度模型的准确与否直接关系到偏移成像的效果。结合伊通盆地复杂构造成像的实践经验,提出了速度建模思路和关键技术。经过叠前时间偏移、时间域层位解释这两步工作,建立了均方根速度场和时间域的构造模型;在时间域速度体上抽取和计算层速度,经过平滑、编辑、速度约束等一系列处理后进行时深转换,形成深度域初始深度-层速度模型。通过采用沿层剩余速度拾取与叠前深度偏移迭代来对初始模型进行更新,形成了精度更高的叠前深度偏移的深度-速度模型。通过采用井资料约束、地质构造模式约束、地震成像约束等手段对速度模型进行了有效质量控制。与叠前时间偏移剖面对比,叠前深度偏移剖面波组特征更清楚,层间内幕更清晰,西北缘成像精度更高。

Application of Velocity Model Building on Complex Structural Imaging in Jilin Exploration Area

Pre-stack depth migration is an effective imaging technique now for the complex structural imag- ing of seismic data at northwest edge of Yitong basin in Jilin exploration area.The key of the complex structural imaging is the accuracy of the velocity model not the migration algorithm.Resuh of the migration imaging depends on the accuracy of the velocity model.According to the practical experience of the com- plex structural imaging in Yitong basin, clue and critical technique of the velocity model building are pro- posed.After pre-stack time migration and interval interpretation of time-domain,structural models of root- mean-square velocity field and time-domain are built.Time-depth conversion may be done after a series of treatments of smoothing,editing and restricting for the interval velocity collected and calculated from time-domain velocity body.And the model between initial depth of depth domain and interval velocity is formed.The initial model may be updated through bedded residual velocity pickoff and pre-stack depth mi- gration iteration,and the depth-velocity model on the pre-stack depth migration with higher accuracy is built.Quality of the velocity model may be controlled effectively through the restriction on well data,geo- logic structure mode and seismic imaging.Compared with the pre-stack time migration section,the pre- stack depth migration section has clearer train feature of waves and intrabed and higher accuracy on the northwest edge imaging.