基于叠前弹性信息直接提取的高灵敏烃类检测方法

Methods of high sensitive hydrocarbon detecting based on pre-elastic informationextracted directly

中深部低孔渗储层横向非均质强、岩石物理特性叠置严重、地震资料品质差,给定量地震油藏描述带来巨大挑战.本文提出一种基于叠前弹性参数反演的高灵敏流体因子烃类检测方法.首先推导了盖斯曼流体项的包含围岩刚性参数、孔隙度和流体体积模量的近似解析表达式.其次引入与流体性质变化无关,仅由岩石骨架控制的剪切模量,削弱孔隙度等因素的畸变影响,构建了新烃检因子.并推导了包含该烃检因子的AVO近似式和弹性阻抗方程.最后利用弹性阻抗反演技术直接提取敏感流体信息,实现储集体烃类检测.研究区实例应用验证了方法的有效性和适用性,为复杂构造-岩性油气藏勘探开发提供重要技术支撑.

The reservoirs in mid-depth formation usually confront the problems of strong transverse heterogeneity, seriously superposed rock-physical feature, poor quality of seismic data and so on. It brings a big challenge to quantitative seismic reservoir description. In this article, we propose a new method of hydrocarbon detection with highly sensitive Direct Hydrocarbon Indicator(DHI) based on pre-stack elastic parameters inversion. Firstly, the approximate expression of Gassmann fluid/porosity is derived which can clearly show the comprehensive influence of the stiffness of the material surrounding the pore, porosity and fluid bulk modulus. And then, a new DHI that the distorted influence of porosity minimized is constructed with introducing shear modulus which independent of fluid, but mainly controlled by rock solid matrix and porosity. Furthermore, a new AVO approximation equation and elastic impedance equation has been proposed respectively. Finally, the sensitive information of fluid extracted directly using elastic impedance inversion. Thus, the results of oil-gas reservoir hydrocarbon detection is acquired by this method. The validity and accuracy of scheme is verified in practical applications. It can distinguish the property of fluid accurately and reliably, and provide critical support for exploration and development of complex structure-lithology reservoirs.