JI-FI反演技术在薄砂岩储层预测中的应用——以XH地区K_(1)bs^(3)上部储层为例

Application of JI-FI inversion technology to prediction of thin sandstone reservoir:A case study of K_(1)bs^(3)upper thin sandstone reservoir in XH area

XH地区K_(1)bs^(3)上部发育的三角洲前缘薄砂岩储层是构造—岩性油气藏勘探的重要领域。近年来在该区应用常规波阻抗、叠前确定性反演都无法准确预测目的层薄砂岩储层的分布。应用JI-FI(阻抗与相联合反演技术),利用叠前地震道集数据,在不同岩相/流体相的纵波、横波速度和密度深度趋势约束下,将同时反演与贝叶斯分类相结合,采用最大期望算法,对阻抗和相进行迭代,实现了目标区岩相/流体相及岩石物理性质(纵波阻抗、横波阻抗、密度及纵横波速度比等)的定量预测。该方法克服了常规叠前反演依赖井建立低频模型,特别是在井少、薄互层地质条件下,井间波阻抗内插存在不确定性问题。储层预测结果与井吻合度高,为该区岩性勘探及井位部署提供了依据。

The thin sandstone reservoir in the delta front developed in the upper part of the K_(1)bs^(3)formation is an important area for the exploration of structural-lithological oil and gas reservoirs in the XH area.In recent years,Application of P-impedance and pre-stack deterministic inversion could not accurately predict the distribution of thin sandstone reservoirs in the target layer.In this paper,joint impedance and facies inversion(JI-FI)impedance and facies joint inversion technology is used.This technique uses pre-stack seismic gather data,and combines simultaneous inversion and Bayesian classification under the constraints of the P-wave,S-wave velocity and density depth trend of each lithofacies or fluid facies,the maximum expectation algorithm is used to iterate the impedance and facies,and the quantitative prediction of lithofacies/fluid facies and petrophysical properties(such as P-wave,shear wave impedance,density,V_(p)/V_(s),etc.)in the target area is achieved.This method overcomes the uncertainty of inter-well P-impedance interpolation when conventional pre-stack inversion relies on wells to establish low-frequency models,especially under geological conditions with few wells and thin interbeds.The reservoir prediction results are in good agreement with the well,which provides a basis for lithological exploration and well location deployment in this area.