深部储层流体因子直接反演方法

Direct inversion for fluid factor of deep reservoirs

深层油气藏勘探是目前油气勘探的热点之一,但是由于缺乏高质量的大角度地震道集数据,基于叠前地震反演的储层流体识别难以有效实施。为此,从Zoeppritz方程的近似方程出发,结合弹性参数间的岩石物理关系,推导了包含Gassmann流体项和剪切模量项的两项地震反射系数近似方程。利用模型试验证明了该方程的精度与三项方程相当,可以用于叠前地震反演。在贝叶斯反演理论框架下,基于该近似方程建立了不需要大角度地震数据的概率化叠前地震反演方法,用于直接反演Gassmann流体项,并进行储层流体识别。模型试算结果表明,该方法具有较高的准确度和稳定性;实际资料应用结果表明,该方法具有一定的实用性。

Exploration of deep reservoirs has been one focus of oil and gas exploration However, it is difficult to discriminate reservoir fluids in deep reservoirs based on prestack seismic inversions,because of the lack of high-quality large offset prestack gathers. In this study,based on an approximation of the Zoeppritz equations and rock physics theory, we derive a two-term reflection coefficient approximation equation containing the Gassmann fluid and shear modulus terms. A model test shows that this approximation equation has comparative accuracy with the three-term equation, indicating that it can be used for the prestack inversion Based on Bayesian inversion theory, we establish a probabilistic prestack seismic inversion method with no need for large offset prestack gathers, to invert the Gassmann fluid term directly for reservoir fluid discrimination A synthetic test proves its accuracy and ro-bustness and a real data test demonstrates its applicability and validity.