注水倍数对储层微观孔隙结构影响实验研究

目前针对大庆油田某区块水驱倍数对储层微观孔隙结构特征的研究还不系统，缺少岩心微观孔隙结构参数、孔渗以及矿物含量等参数随不同水驱倍数变化规律的量化研究，严重制约了对储层水驱微观机理的揭示。基于核磁共振技术和压汞相结合的方法，建立了随岩石物性变化而变化的核磁共振转换系数C值的确定方法，充分克服压汞法不能重复利用相同位置样品而造成的误差，以及核磁法不能准确确定转换系数C值的弊端。利用该方法分析了岩心在不同水驱倍数下孔径大小及岩心矿物成分的变化规律。不同物性岩心的孔隙度和渗透率随水驱倍数增加均出现不同程度的增大；岩心原始孔隙度和渗透率越大，岩心孔径增加的幅度越大。水驱后黏土含量降低，高岭石的相对含量降低幅度最大，黏土矿物变化和微粒运移是导致岩石物性和孔径变化的主要原因。 

The influence of water flooding multiples on reservoir micro pore structure

Recent research on the micro-pore structure characteristics of reservoirs during long-term water flooding in a block of the Daqing Oilfield is non-systematic and falls short on the quantitative research on the micro-pore structure parameters at different water flooding multiples. This poses a challenge for revealing the mechanism of reservoir alteration. To resolve this problem, this paper develops and presents a method, combining nuclear magnetic resonance (NMR) with mercury intrusion, to determine the value of nuclear magnetic resonance conversion coefficient (C) with corresponding changes of rock physical properties. Utilizing high pressure mercury intrusion to calibrate the pore diameter by NMR overcomes the shortcomings that the samples in the same position are unable to be reused by mercury intrusion and the conversion coefficient, C value, of NMR can not be accurately determined. By the new method the core diameter and the change of core mineral composition under different water injection multiples, the porosity and permeability of all experimental cores increase to different degrees during long-term water flooding. Long term water flooding of the core increases the pore size and lowers the clay content. Furthermore, the experiments show that kaolinite is affected most. Clay mineral variation and particle migration are the main reasons for the change of rock physical properties and pore size.