基于综合信息的三维层速度场建立及其在涪陵页岩气田应用研究

Three-dimensional interval velocity building based on comprehensive data analysis and its application in Fuling shale gas field exploration

分析现有层速度求取方法发现,常规方法构建的层速度场无法满足页岩气勘探中水平井钻探对构造层位的精度要求,为此,提出了一种基于叠加速度、测井数据、构造解释数据、地震数据等多源信息和不同层速度计算方法(Dix公式方法、模型层析方法和波阻抗反演方法等)的综合信息三维层速度建场方法。首先,根据测井数据的起始深度将地层分为上、下段地层,对上段地层采用3种常规的基于叠加速度和构造解释数据的层速度计算方法计算层速度,对下段地层采用基于三维叠后地震数据、测井数据和层位数据的波阻抗反演方法计算层速度;然后,进行上、下段地层的层速度组合和优选分析,充分利用波阻抗反演得到的高分辨率层速度的优点,优选出研究区的最佳组合层速度。涪陵页岩气田实例计算结果表明,基于该层速度场得到的深度构造图与钻井实测的页岩地层深度误差小,可以有效应用于后续的勘探开发工作,表明所提出的综合信息三维层速度建场方法具有重要的实际应用价值。

The velocity field produced by conventional methods does not meet the accuracy requirement for the detection of structure and formations in horizontal well drilling in shale gas exploration.In this paper,we present a 3D interval velocity field building method based on comprehensive analysis of the following data:stacking velocity,logging data,structural interpretation results and seismic data.We adopted several techniques for estimating the interval velocity for the proposed method,namely,the Dix formula,the constrained Dix formula,model tomography,and wave impedance inversion.First,we divided the formation into upper and lower strata according to the initial depth of logging data.Then,for the upper strata,we use the first three conventional techniques mentioned above to estimate its interval velocity based on stacking velocity and structural interpretation results.We use the wave impedance inversion for the lower strata to obtain its interval velocity based on 3D post stack seismic data,logging data,and structural interpretation results.Finally,we combine the upper velocities estimated via the three techniques and the inverted lower velocity.We then select the best combined interval velocity in the study area.This method takes advantage of the high resolution wave impedance inversion.The test results of seismic data in the Fuling shale gas field showed the decrease in depth error between the depth structure map from the velocity field obtained using the proposed method and the shale formation depth measured by drilling,which indicates that this method is practical for the exploration and development in the Fuling shale gas field.