论文部分内容阅读
基于数字岩心的透射超声波模拟是数字岩石物理的重要组成部分,可用于研究波在孔隙岩石中的传播规律,计算岩石的等效速度等。在三维数字岩心中模拟超声波传播时,沿波传播方向在数字岩心两侧附加均匀的镶边层,设置震源和检波器。震源激发后检波器记录数字岩心的入射波和透射波,拾取两者波峰时间的差值,计算超声波在数字岩心中的传播速度(即数字岩心的速度)。为评估透射超声波模拟的精度,将一个数字岩心的孔隙分别饱和气、油和水,计算它们的速度。当震源频率较高时,速度随频率的降低而升高,这应当是波场散射的结果。当孔隙流体按气→油→水方向变化时,不同频率对应的速度具有相似的变化规律,并与线弹性静力学模拟输出的速度的变化规律相似,但数值有差异。考虑到线弹性静力学模拟已被广泛应用,若将其作为基准,则可认为透射超声波模拟具有较高的相对精度。
Transmitted ultrasonic simulation based on digital core is an important part of digital rock physics. It can be used to study the wave propagation in porous rock and calculate the equivalent velocity of rock. When simulating the propagation of ultrasonic waves in a three-dimensional digital core, a uniform edging layer is attached to both sides of the digital core along the wave propagation direction to set the source and the detector. After excitation, the geophone records the incident and the transmitted waves of the digital core, picks up the difference between the peak times and calculates the propagation velocity of the ultrasonic wave in the digital core (ie, the velocity of the digital core). To assess the accuracy of the transmitted ultrasonic simulation, the porosity of a digital core was saturated with gas, oil and water, respectively, to calculate their velocities. When the source frequency is high, the velocity increases with decreasing frequency, which should be the result of wavefield scattering. When the pore fluid changes in the direction of gas → oil → water, the velocities corresponding to different frequencies have similar variation rules, which are similar to those of linear elastic statics output, but the values are different. Considering that the linear elastic statics simulation has been widely used, if it is taken as a reference, it can be considered that the transmission ultrasonic simulation has higher relative accuracy.