超低渗油藏CO2驱智能响应体系构筑及流度控制机理研究

For ultra-low permeability reservoirs, the great development of natural/artificial fractures and the big differences between physical properties of the matrix and the fractures usually result in the common challenges of the serious channeling, low sweep efficiency and poor displacement efficiency in the process of CO2 flooding. In this study, CO2 typed smart responsible surfactant is proposed to solve the above challenges. Its molecular structure is designed using molecular simulation technology and the structure-activity relationship between its molecular structure and its performance in response to CO2 is studied and clarified, in order to obtain a novel smart responsible system for mobility control with the characteristics of high in-situ effective viscosity, thermal stability and low cost type intelligent. By use of chemistry and molecular simulation methods, this project studies the phase transition mechanism of CO2 typed smart responsible system for mobility control. Especially, the research is emphasized on the intrinsic relationships in the molecular-scale, micellar-scale and macro-scale during its phase transition process. Based on independently designed, visualized, heat and pressure-resistant and nano- and micro-scaled 3-D model with flow control chip, the dynamic distribution, phase transformation and gas control of CO2 typed smart responsible system, CO2 mass diffusion and its sweep efficiency, the distribution characteristics of oil phase marked by fluorescence and its migration can be investigated in the application process of the new smart responsible system for mobility control in CO2 flooding. Through the above experimental tests, the mobility control mechanism of CO2 flooding for ultra-low permeability reservoirs in the multi-scaled matrix-fracture system can be revealed. Moreover, a new smart responsible mobility control method for CO2 flooding in ultra-low permeability reservoirs can be developed to enhance oil recovery. In addition, this new method can provide the scientific basis and technical support for greatly improving the development effect of CO2 flooding and be of great significance for enhancing oil recovery of ultra-low permeability reservoirs in China.

针对超低渗油藏天然/人工裂缝发育，基质-裂缝物性差异大而导致CO2驱气窜严重，储层动用程度低、驱油效果差这一难题。本研究采用分子模拟技术设计CO2智能响应表面活性剂的分子结构，阐明分子结构与CO2响应性能间的构效关系，制备出CO2高效智能响应表面活性剂，进而构筑出用于CO2流度控制的廉价易得、CO2高效增粘、热稳定性强的智能响应体系。采用化学和分子模拟手段，着重研究相变过程中分子尺度-胶束尺度-宏观尺度的内在关系，阐明CO2智能响应体系的相转变作用机制。基于自主设计可视化耐温耐压纳-微尺度流控芯片三维模型，探究CO2驱流度控制过程中智能响应体系的动态展布、相变与控气规律、CO2扩散传质与波及规律和荧光标记油相动用与运移规律，揭示超低渗油藏CO2驱多尺度基质-裂缝系统中流度控制作用机理，形成超低渗油藏CO2驱流度控制提高采收率新方法，为改善超低渗油藏CO2驱开发效果提供科学依据。

针对超低渗油藏天然/人工裂缝发育，基质-裂缝物性差异大而导致CO2驱气窜严重，储层动用程度低、驱油效果差这一难题，本研究采用分子模拟技术设计出了CO2智能响应表面活性剂的分子结构，通过脂肪酸缩合反应和亲核取代反应分别合成了叔胺类CO2高效智能响应型黏弹性表面活性剂和羟磺基两性离子型黏弹性表面活性剂，并优化了最佳合成条件，CO2响应型：160 ℃、6 h、0.5wt%硅溶胶催化剂、物料比1：1.2；两性离子型：90 ℃、9 h，物料比1：1.1、1：1.2溶剂比、固含量50%。进而构筑出了用于CO2流度控制的廉价易得、CO2高效增粘、热稳定性强的智能响应体系：芥酸酰胺羟丙基磺基甜菜碱（EAHSB）、油酸酰胺丙基二甲胺（DOAPA）、对甲苯磺酸钠（SPTS）质量比为30：70：75，80 ℃储层用量2.0wt%，130 ℃储层用量5.0wt%。采用化学和分子模拟手段，着重研究相变过程中分子尺度-胶束尺度-宏观尺度的内在关系，阐明了CO2智能响应体系的相转变作用机制。DOAPA分子遇CO2质子化，由非离子转换为阳离子，具有优异的表面活性和自组装能力；EAHSB/DOAPA/SPTS -CO2体系以分子间静电作用和疏水作用力为主要驱动力，自组装形成囊泡、饼状胶束、层状胶束，同时囊泡和层状胶束间“黏连”形成大且粗的长柱状结构和环状结构，介观上表现为强度高、稳定性好的圆形“孔穴”状三维结构，宏观黏弹性更优。采用自主设计的基质-裂缝双重介质岩心模型和高温高压驱替装置进行流度控制实验，发现智能响应体系封堵率高达到99.2%，CO2气驱采收率提高了20.0%，表现出了体系较强的流度控制能力。借助核磁共振等装置进一步探究了CO2驱流度控制过程中智能响应体系的动态展布、相变与控气规律、CO2扩散传质与波及规律和油相动用与运移规律，并揭示了超低渗油藏CO2驱多尺度基质-裂缝系统中流度控制作用机理，形成了超低渗油藏CO2驱流度控制提高采收率新方法，为改善超低渗油藏CO2驱开发效果提供科学依据。