储层流体识别是油气勘探领域的重要研究方向.页岩储层具有较强的垂直横向各向同性(Transverse Isotropy with a Vertical Axis of Symmetry,VTI)介质特征,在流体因子估测中带来不容忽视的影响.为此,根据Rüger纵波反射系数方程,提出了一种基于VTI介质弹性阻抗的流体因子、杨氏模量及各向异性参数反演方法.首先,推导以Russell流体因子、杨氏模量和等效各向异性参数表示的反射系数近似公式和弹性阻抗方程;然后,通过弹性阻抗反演估计流体因子、杨氏模量和各向异性参数,并比较了各向异性参数对反演结果的影响.模型测试和实际工区数据应用结果表明,该方法可以合理、准确地预测流体因子、杨氏模量和各向异性参数,为页岩储层流体识别、脆性参数和各向异性发育程度预测提供了一种新的方法.
Direct inversion method for fluid factors and anisotropy parameters in VTI media
Reservoir fluid identification is an important research direction in the field of oil and gas exploration.Shale reservoirs have strong transverse isotropy with a vertical axis of symmetry(VTI),undeniably impacting fluid factor estimation.Based on the Rüger longitudinal wave reflection coefficient equation,this paper pro-poses an inversion method for fluid factor,Young's modulus,and anisotropy parameters based on the elastic impedance of VTI media.Firstly,a reflection coefficient approximate formula and an elastic impedance equa-tion represented by Russell fluid factor,Young's modulus,and equivalent anisotropic parameters are derived.Then,the fluid factor,Young's modulus,and anisotropic parameters are estimated through elastic impedance inversion,and the influence of anisotropic parameters on the inversion results is compared.Model testing and practical application of work area data show that this method can reasonably and accurately predict fluid factors,Young's modulus,and anisotropic parameters,providing a new method for identifying shale reservoir fluids,predicting brittle parameters,and predicting the anisotropic development degree.
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