基于显微红外光谱技术的岩石微观渗流特性研究

Study on microscopic seepage characteristics of rock based on micro infrared spectra technology

岩石的渗流特性决定了石油开采效率,对于储层的定量评价具有重要意义。为了解岩石中孔洞裂缝以及不同介质对其渗流性能的影响规律,利用显微红外光谱成像技术,对岩石样品进行光谱成像试验,根据样品的光谱图像和吸光度A值,将该岩石截面划分为孔隙裂缝区域、孔隙与岩石介质过渡区域、白云岩介质区域;据此建立能够精确表征真实岩石结构的有限元模型,对其微观渗流特性进行数值模拟研究。研究结果表明:(1)该岩石样品的特征吸收波段为2 500~2 700 cm^(-1),说明样品介质主要为白云岩;(2)同一平面的二维流动中流体的动力黏度越大,流体在孔道中的流动速度越小;(3)多孔白云岩介质的渗透率较小时,流体主要以沿裂隙孔道的自由流动为主,而介质中渗流运动较弱;随着介质渗透率的增大,多孔介质中的流体渗流运动逐渐明显;(4)孔喉尺寸较小的孔道,毛细管阻力较大,孔道中流体不发生流动;孔喉尺寸扩大后,优势水流路径数量增加,岩石截面中流体流动范围增大,流动速度变大。此研究结果可以为石油开采中储层改造方案的制定提供科学依据,从而有效提高石油开采效率。

The seepage characteristic of rock determines the efficiency of oil exploitation and it has important significance for the quantitative evaluation of reservoirs. In order to figure out the influence of the pores, cracks and different mediums in rocks on its seepage performances, spectral imaging experiment was carried out on rock sample by using the microscopic infrared spectral imaging technology. The rock section can be divided into pore and crack regions, transition regions of pore and rock medium, and dolomite medium regions according to the spectral image and absorbance value A. Based on this, a finite element model in which the real structures of the rock sample could be described precisely was established and numerical simulation researching the rock＇s micro seepage characteristics was carried out. The results show that： （1） the spectral absorption band of the sample is at 2 500 - 2 700 cm^-1, showing that the sample medium is mainly dolomite. （2） the greater the dynamic viscosity of the fluid in the two-dimensional flow of the same plane is, the smaller the flow rate of the fluid in the channel is. （3） When the permeability of porous dolomite medium is small, the fluid flow is mainly dominated by the free flow along the crack channels, and the seepage movement in rock medium is weak. With the increasing of the medium permeability, fluid seepage in porous medium is gradually obvious. When the pore throat size is small, the capillary resistance is big, and the fluid does not flow. （4） When the pore throat size is enlarged, the number of preferential flow path increases, the fluid flow range in the rock section increases, and the flow rate becomes large. The results can provide a scientific basis for the development of reservoir reconstruction project, so as to improve the efficiency ofoil exploitation.