基于KT模型流体替换的岩石物理参数反演方法

岩石物理模型中包含了很多不同的岩石物理参数，一般可以通过测井资料或者实验室资料获得，但是诸如矿物基质弹性模量以及孔隙几何形状这些参数，不能从实测数据中直接获取，必须通过反演得到，因此，研究获取这些岩石物理参数的反演方法十分必要。对于砂岩油气储层，利用3种孔隙纵横比模拟岩石的孔隙结构，引用Biot系数公式确定矿物基质弹性模量的变化范围，并结合模拟退火优化算法提出了一种基于KT模型流体替换的岩石物理参数反演方法。该方法的最大优势是能够在只知道常规测井数据的情况下，直接反演出岩石的矿物基质弹性模量和孔隙纵横比谱。针对实验室测试的42块细砂岩样品，利用该方法精确地获取了所有样品的矿物基质体积模量、剪切模量以及孔隙纵横比谱。分析反演获取的多种岩石物理参数表明：孔隙纵横比谱对岩石的弹性性质影响最大；孔隙纵横比谱可用来描述储层岩石的孔隙结构；利用3种孔隙纵横比的KT模型进行流体替换模拟的适用性很好；裂缝孔隙的体积分数对岩石弹性模量的敏感性最高。研究结果可为叠前地震属性反演和叠后储层定量预测提供参考。

Inversion of rock physics parameters based on KT model fluid substitution

There are many rock physics parameters in rock physics model,some parameters are directly obtained from log data or lab data,and the others are indirectly obtained by inversion,such as mineral matrix elastic modulus and pore geometry. It's important to investigate estimation methods for these rock physics parameters. For the sandstone reservoir,three different pore aspect ratios were used to describe the pore structure of sandstone,Biot's coefficient was used to determine the variation range of mineral matrix elastic modulus,and combined with simulated annealing simulated annealing algorithm,an inversion method for estimating rock physics parameters based on KT model fluid substitution was proposed. The mineral matrix bulk and shear modulus of 42 sandstone samples were inversed,and their pore aspect ratio spectrum were inversed simultaneously. The results show that:pore aspect spectrum has a great effect on rock elastic properties;pore aspect spectrum can be used to depict pore structure and diagenesis;using KT model with three pore aspect ratios to carry out fluid substitution simulation has a good adaptability;percentages of crack pores have a high sensitivity to rock elastic modulus.