估算饱和岩石裂隙结构参数的模型研究  

A Model for Estimating Fracture Structure Parameters of Saturated Rocks

作　　者：吴春芳 Wu Chunfang(Shanghai Technical Institule of Electronics&Information,Shanghai 201411)

机构地区：[1]上海电子信息职业技术学院,上海201411

出　　处：《中外能源》2023年第9期49-55,共7页Sino-Global Energy

基　　金：国家自然科学基金面上项目“基于微观孔隙结构特征构建致密砂岩衰减岩石物理模型”(编号:41974123)。

摘　　要：从弹性波速对压力依赖性的关系可以反演岩石裂隙参数分布。然而在超声波频率段,Gassmann方程不能有效解释压力梯度的非驰豫现象。为了从饱和岩石波速得到裂隙结构参数,构建双孔(裂隙与孔隙)结构岩石骨架模型,获取裂隙结构参数与有效压力的关系。利用Gurevich关系式解释高频条件下压力梯度的非驰豫现象,形成岩石骨架在高频饱和状态下的弹性特征。结合岩石骨架模型,通过饱和岩石弹性波速度对裂隙结构参数进行估算,形成一种不同压力下估算饱和岩石裂隙结构参数的计算模型。基于该模型可分别得到裂隙密度与有效压力预测曲线及裂隙孔隙度与有效压力预测曲线。三块岩石样本的超声波实验数据表明,该估算模型能有效地描述岩石弹性特征的压力依赖性。采用高压状态下的岩石来近似代替仅含硬孔隙的岩石主相并不精确,且裂隙-硬孔隙间存在一定的相互关系。The distribution of rock fracture parameters can be retrieved from the relationship between elastic wave velocity and pressure dependence.However,in the ultrasonic frequency band,the Gassmann equation cannot effectively explain the non-relaxation phenomenon of pressure gradient.In order to obtain the fracture structure parameters from the wave velocity of saturated rocks,a rock skeleton model of two-pore(fracture and pore)structure is constructed to obtain the relationship between fracture structure parameters and effective pressure.The Gurevich relation is used to explain the non-relaxation phenomenon of the pressure gradient un-der high frequency conditions,and the elastic characteristics of the rock skeleton under high-frequency saturation state are formed.Combined with the rock skeleton model,the fracture structure parameters are estimated by the elastic wave velocity of saturated rocks,and a calculation model is formed to estimate the fracture structure parameters of saturated rocks under different pressures.The prediction curve of fracture density and effective pressure and that of fracture porosity and effective pressure can be obtained respectively based on the model.The ultrasonic experimental data of three rock samples show that the proposed model can effective-ly describe the pressure dependence of rock elastic characteristics.It is not accurate to use rocks under high pressure to approximate the main phase of rocks containing only hard pores,and there is a certain relationship between fractures and hard pores.

关 键 词：双孔结构 裂隙结构参数 有效压力 弹性波速度 压力依赖性 

分 类 号：TU45[建筑科学—岩土工程]