微观孔隙结构对致密砂岩渗吸影响的试验研究

An Experimental Study on the Effect of Microscopic Pore Structure on Spontaneous Imbibition in Tight Sandstones

韦青 李治平 白瑞婷 张甜甜 南珺祥

WEI Qing LI Zhiping BAI Ruiting ZHANG Tiantian NAN Junxiang

中国石油勘探开发研究院, 北京 100083; 中国地质大学(北京)能源学院, 北京 100083; 中国科学院地质与地球物理研究所, 北京 100029; 低渗透油气田勘探开发国家工程实验室, 陕西西安 710018; 中国石油长庆油田分公司勘探开发研究院, 陕西西安 710018

PetroChina Research Institute of Petroleum Exploration & Development, Beijing, 100083, China; School of Energy and Resource, China University of Geosciences(Beijing), Beijing, 100083, China; Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China; State Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields, Xi’an, Shaanxi, 710018, China; Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Xi’an, Shaanxi, 710018, China

目前对于渗吸的研究多集中于润湿性和界面张力，微观孔隙结构作为影响自发渗吸的主要因素之一常被忽略。利用核磁共振技术对致密砂岩渗吸过程中的油水分布变化进行了研究，同时采用恒速压汞、氮气吸附、高压压汞等试验手段求取了平均孔喉比、比表面、孔隙尺寸等表征微观孔隙特征的参数，并在此基础上分析研究了微观孔隙结构对渗吸的影响。试验结果表明：在致密砂岩渗吸过程中，中等尺寸的孔隙采出程度最大；孔隙度与渗吸采收率相关性不大，而渗透率越大，储层品质越好，渗吸采收率越高；平均孔喉比和比表面均与渗吸采收率负相关，比表面越大，中小喉道分布越多，孔喉比越大，越不利于渗吸流体的吸入和非润湿相的排出；中等孔隙比例越大，渗吸采收率越高，而由于黏滞力的作用部分小孔隙无法进行有效的渗吸，小孔隙比例增大对于渗吸采收率的提高不利。因此，储渗性能较好、中等孔隙占比较高的致密砂岩储层更适宜采用渗吸采油。

Experimental studies of spontaneous imbibition mostly focus on wettability and interfacial tension, while the microscopic pore structure as one of the primary factors affecting spontaneous imbibition is usually neglected. Nuclear magnetic resonance (NMR) technology was used to investigate the change of oil and water distribution in tight sandstone during spontaneous imbibition; in addition, constant-speed mercury injection, high pressure mercury injection, nitrogen adsorption and other test methods were adopted to obtain characteristic parameters of microscopic pore such as average pore throat ratio, specific surface area and pore size. On this basis, the effect of microscopic pore structure on spontaneous imbibition was analyzed and studied. Experimental results showed that medium pores achieved the highest recovery rate in the process of spontaneous imbibition; the porosity was correlated less with the imbibition recovery rate while the imbibition recovery rate was proportional to the permeability and reservoir quality; the average pore throat ratio and specific surface area were negatively correlated with the imbibition recovery rate, medium and large throats increased with the specific surface area and the higher pore throat ratio was more adverse to absorption of imbibition fluids and non-wetting phase discharge; the imbibition recovery rate was proportional to the medium pore ratio and the small pore ratio increase was adverse to the improvement of the imbibition recovery rate, because some small pores could not achieve effective imbibition under viscous forces. Therefore, tight sandstones with the highest reservoir permeability and medium pore ratio were more suitable for imbibition oil recovery.

国家自然科学“CO2驱油对储层的伤害机理研究”（编号：51174178）、中国石油长庆油田分公司科学研究与技术开发项目“致密油储层定量评价技术研究”（编号：技2014-18）联合资助。

https://doi.org/10.11911/syztjs.201605019