致密油储层提高采收率关键理论与方法研究

The permeability of tight oil reservoir is very low, which leads to big difficulty in driving oil by natural energy or waterflooding. Therefore, unlike conventional reservoir, EOR besides natural energy and waterflooding for tight oil reservoir is a big challenge and also in urgent need before reservoir development. Aiming at the characteristic of compact matrix-fracture coupling medium that tight oil reservoir has , focusing on replenishing formation energy and improving oil migration efficiency from compact matrix to fracture, and based on previous research achievements of EOR for ultra-low permeability reservoir, this project plans to carry out study on pressure propagation in compact matrix/fracture and the coupling relationship between them; to research multi-coupling migration mechanisms for oil including seepage, diffusion and imbibition effect in compact matrix; to research matching relationship and main control factors of oil migration in compact matrix and fracture. Thus, to reveal EOR mechanisms in tight oil reservoir which is different from the case in conventional one. The breakthroughs to this study are physical models and techniques of simulation experiments for tight oil reservoir. Based on theoretical research achievements, the effective method focusing on optimizing injecting medium and injecting method is going to be explored, also oil expulsion methods in compact matrix focus on strengthening imbibition, diffusion, thermal physics and other physicochemical effects; and also the methods of increasing sweep efficiency in tight oil reservoir by combining fracture utilization and channeling prevention. All of them can provide theoretical support and new thoughts for effective development of tight oil reservoir.

致密油的储集层渗透率很低，天然能量和水驱很难将其基质中的油采出。因此，与常规油藏不同，除天然能量驱和水驱之外的“提高采收率”是致密油投入开发之时就面临的迫切需求和巨大挑战。本申请项目针对致密油储层作为基质-裂缝耦合介质的特点，以有效补充地层能量和提高致密基质中油向裂缝的运移效率为重点，以致密油储层的物理模型和模拟实验技术为突破点，基于前期对特低渗油藏提高采收率的研究成果，研究压力在致密储层基质和裂缝中的传播及其耦合关系；研究原油在致密基质中渗流、扩散、渗吸等多重耦合运移机理；研究原油在致密基质与裂缝中运移的匹配关系及主控因素，揭示致密油储层中不同于常规油藏的提高采收率机理。基于理论研究成果，探索以优化注入介质和注入方式为主要思路的有效补充能量方法；探索以强化渗吸、扩散和其他物理化学效应为重点的致密基质中原油高效排驱方法。

本项目针对当前亟待破解的致密储层异常渗流和驱油机理以及对提高采收率新技术的迫切需求开展研究，攻克了13个实验技术难点，取得了三个方面的创新性成果。.1.取得致密储层微尺度渗流的重要科学发现和理论创新。发现了常温低压条件下微圆管内奇特的非晶态固体水；发现了微管壁面单组分流体层及其厚度与管径的负相关规律。依据这些科学发现，破解了致密-低渗储层中“启动压力”和非线性渗流之谜；创建了致密储层液体微尺度渗流机理模型（Y-MS）。发现了微管中与气体滑移理论相悖的高压气体“负滑移”流动现象；发现了致密岩心中与高压气体微尺度流动效应一致的“负滑移”渗流现象，其“视渗透率”随压力梯度单调升高，并趋向于一个极值。以Y-MS模型和高压气体“负滑移”渗流规律为原理，研发出致密岩心渗流能力评价方法和视渗透率测试仪。.2.取得致密储层中原油排驱机理的重要科学发现和技术思路创新。发现了微管中的微尺度界面现象，油水与管壁接触角随管径的减小先降至极小值，再增大至150°的强疏水；弱亲水岩心的渗吸排油效率随渗透率降低增大至峰值后逐渐降低。据此揭示了致密-低渗储层中渗吸排油和毛管力异常的主要机理是微尺度界面效应。根据渗吸、扩散和压差驱替对致密基质中原油排驱的有效性和有限性研究结果，建立了局部压差驱动与渗吸/扩散排油效应协同的致密储层原油排驱技术思路。.3. 研发了原创性致密油藏提高采收率技术。根据致密储层原油排驱机理及其对提高采收率用剂的特殊要求，研发出就地乳化微调驱油剂和可控自聚集胶粒（CSA）调堵剂。研发了利用油井附近局部压差驱动、封堵调整吐出剖面、吐出高效驱油的堵调-吐驱技术；研发出集分段封堵、局部压差驱替、就地乳化启动基质原油、乳液微调、渗吸（扩散）排油等多种功能于一体的CSA深调-就地乳化微调驱油技术，并已成功地进行了矿场实验，其井组增油量为常规技术的46倍。