1、 Technical Introduction
The binary composite oil displacement technology system is based on the P+N additive enhancement theory. This technology overcomes the shortcomings of a single oil displacement agent and utilizes the super additive enhancement effect of the binary (surfactant+polymer) composite system oil displacement agent, greatly improving the oil displacement efficiency. Injecting petroleum sulfonate, surfactant additives, and polymers into the ground in different proportions can greatly reduce the interfacial tension between oil and water, and better improve oil washing efficiency. The composite system utilizes the chemical synergistic effect of polymers and surfactants to increase the swept volume of water flooding and reduce the oil-water mobility ratio, thereby "strongly washing" the residual oil in the reservoir and improving the oil recovery rate. Binary composite flooding can expand the swept volume and improve oil washing efficiency, with a greater increase in recovery rate than single polymer flooding; Compared with ternary composite flooding, it can reduce the production of emulsion, make treatment easier, and lower treatment costs; At the same time, it can prevent alkali scaling, facilitate on-site operation and normal injection, and is an effective tertiary oil recovery technology.
Deshi Group is one of the earliest enterprises in China to participate in the research of binary composite drive. In the past decade of research and practice, the company has established a comprehensive reservoir rock flooding data model, studied various oil-water systems at home and abroad, accumulated hundreds of surfactant products, and formed surfactant systems with different characteristics.
2、 Mechanism of enhancing oil recovery efficiency
The active agent in the binary composite flooding system can greatly reduce the interfacial tension between crude oil and water in the formation, improve the oil recovery rate, and the polymer can play a role in deep profile control, expanding the affected volume, and controlling the flow rate of subsequent chemical agents. The two have a good synergistic effect on increasing oil production.
（1） Compared with single polymer flooding, binary flooding can increase the recovery rate by about 5% under the same economic conditions.
（2） Compared with active water flooding, it can prevent fluid channeling.
（3） Compared with ternary drive, it also has obvious advantages:
1. Reduce the production of emulsion, make it easier to handle, and lower processing costs;
2. Prevent alkali scaling, easy on-site operation and normal injection;
3. Reduced the damage of scale to the formation.
From the perspective of oil displacement mechanism, binary composite flooding, as a type of chemical flooding, has technical advantages.
3、 Surfactants required to enhance oil recovery efficiency
Surfactants for oil recovery have been extensively studied both domestically and internationally. One of the key issues in promoting the application of chemical composite oil recovery technology is the use of surfactants for composite oil recovery. The development of low-cost and efficient surfactants for oil recovery is the main issue for reducing costs and increasing efficiency in chemical composite oil recovery. The main task of composite flooding is to select active agents with high interfacial activity and utilize the synergistic effect between chemical agents to minimize the interfacial tension between oil and water.
4、 Types of surfactants and related product indicators for oil displacement
Due to the different structures and types of lipophilic and hydrophilic groups, there are currently thousands of types of surfactants used for oil displacement. Anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, in addition to these four categories, there are also fluorine-containing, silicon-based surfactants, and polymer surfactants.
5、 Technical application cases
