叠后地震反演技术预测河道砂体

PREDICTION OF THE CHANNEL SANDBODY BY POST-STACK SEISMIC INVERTING TECHNIQUE

大庆油田A区葡萄花油层井网密度大,砂体厚度薄,平面上零散分布,且波阻抗曲线对砂体响应不明显,仅依靠井点信息或单纯地震信息进行河道砂体预测难度较大。以葡Ⅰ1~3单元为例,通过储层岩石物理分析,选择密度曲线和原始波阻抗曲线构建拟波阻抗曲线;建立三维拟声波阻抗地质模型框架,应用快速趋势约束脉冲算法获得约束稀疏脉冲反演波阻抗体;利用井旁合成记录内插、外推反复估算模型得到地震特征反演的拟波阻抗体;将约束稀疏脉冲反演的波阻抗体和地震特征反演的拟波阻抗体融合得到联合反演的波阻抗体。该方法描述河道砂体,纵向上分辨率高,横向延伸自然,准确地确定河道宽度、描述河道砂体边界、判别河道砂体组合及连通关系,精细地描述了各类河道砂体特征,提高了油田开发储层描述的精度,为油田精细高效开发提供了技术基础。

In Area A of Daqing Oilfield,Putaohua reservoirs are characterized by lager well spacing density,thinner sandbody thickness,scattered planar sandbody distribution and fuzzy wave impedance curve response to the sandbody. It is very difficult to predict the channel sandbody based on the well-point information or simple seismic information. Taking UnitⅠ1-3 of Putaohua reservoirs as an example,through the petrophysical analysis,the density and the original impedance were selected to establish the quasi-wave impedance curve; the geologic model framework of the 3 D quasi-acoustic impedance was established,the wave impedance body by the constrained surging inversion（ CSSI） was obtained by the fast trend constrained pulse algorithm; the quasi-wave impedance body of the seismic characteristic inversion was obtained by the interpolation and extrapolation repeated estimated models with the help of the near-well composite traces; the joint-inverted impedance body was achieved by the integration of the impedance body inverted by the CSSI and the quasi-wave impedance body by the seismic characteristic inversion.The method was applied to characterize the channel sandbody,the described vertical resolution was pretty higherand the horizontal extension was quite natural,the width of the channel was correctly determined,the boundary of the channel sandbody was described,the combination and connectivity among the channel sandbody were identified,the sandbody characteristics of each channel were finely characterized,thus the precision of describing the oilfield developed reservoirs was enhanced,the technical basis was laid for fine high-efficiency oilfield development.