基于高低频速度闭合技术的地层压力预测

摘要

Because the seismic interval velocity is low-frequency,merely reflecting the variation trend of velocity on a macro-scale,absence of velocity changes in vertical.It leads to low resolution of predicting the formation pore pressure of the longitudinal and don't favor to reflect the vertical distribution the formation pore pressure.Therefore,in this paper we proposed a technique of merging high frequency velocity with the low frequency velocity to improve the vertical resolution of seismic interval velocity bodies and pressure prediction data.Its workflow includes:using post-stack impedance to invert a high frequency velocity body with rich details,standardizing this inverted velocity body from seismic interval velocity body,getting a closed velocity body by merging the high frequency velocity with the low frequency velocity,finally the closed velocity body is used to calculate the formation pore pressure from the pressure predicting model.Application results of actual data show that,this method can seamlessly integrate the impedance inversion velocity and seismic interval velocity,processed velocity block not only keeps the low frequency trend of seismic interval velocity,but also has the high frequency characteristic of impedance inversion velocity.It significantly improves the vertical resolution of pressure prediction data the predicted accuracy is consistent with poststack impedance accuracy,and effectively guides the drilling construction.%常规地震处理后的地震层速度是主频较低的速度,只能反映速度宏观变化趋势,在纵向上不能体现速度的细节变化,导致预测的地层孔隙压力纵向分辨率较低,不利于反映地层孔隙压力的纵向分布情况.为此,提出了高低频速度闭合技术,以提高地震层速度体和压力预测数据的纵向分辨率.利用叠后阻抗得到具有丰富细节的主频较高的速度体,然后用地震层速度体对叠后阻抗反演速度体进行标准化处理,得到高低频闭合速度体,最终利用Fillippone压力预测模型计算地层孔隙压力.实际资料应用结果表明,该方法能够将阻抗反演速度与地震层速度进行无缝对接,处理后的层速度体既保持了地震层速度的低频变化趋势,又具备阻抗反演速度的高频变化特征,提高了压力预测数据的纵向分辨率,预测精度与叠后阻抗精度保持一致,能有效指导钻井施工.