Analysis Of Characteristics Of Chemical Flooding Process Based On Thermodynamics

The dependence on crude oil imports of our country has exceeded 73%,and the contradiction between supply and demand has intensified.How to build a national oil and gas safety supply system,meet China's huge oil and gas demand for modernization in the future,and ensure oil and gas supply is one of the important issues that my country's energy supply needs to pay attention to.As far as crude oil extraction is concerned,most of my country's major oilfields have entered the middle and late stages of exploitation,and they are facing many difficulties in stabilizing and high yielding.They have entered the tertiary oil recovery stage mainly focused on enhanced oil recovery(EOR).As an important tertiary oil recovery method,chemical flooding has received extensive attention due to its large range of enhanced oil recovery,wide application range,and huge development potential.At present,the research of chemical flooding mechanism is mostly based on the knowledge of reservoir engineering and seepage mechanics.It is still in the qualitative and semi-quantitative stage,and some basic science and application issues have not been fully elucidated.Using thermodynamics,reservoir engineering,heat and mass transfer and other interdisciplinary methods to study the changing laws of surfactant solutions at the oil-water interface is of great significance for in-depth analysis of surfactant flooding characteristics.This paper analyzes the interfacial phenomenon in the chemical flooding process and discusses the oil displacement mechanism of surfactants.Aiming at the adsorption phenomenon on the phase interface and the process of micelle molecule association during the oil displacement process of surfactants,based on the interface theory and thermodynamic method,according to the energy conversion phenomenon on the interface during the adsorption process,a thermodynamic energy model of the adsorption process is established.The relationship between the change of molecular aggregation morphology and the change of free energy in the process of micellization was analyzed.The free energy change during the process of micelle aggregation was obtained through the"hydrophobic effect",a thermodynamic model of micelleization was constructed,and the micelles were deduced.Enthalpy,entropy,free energy and other energy change equations in the process of aggregation.Taking C₁₁H₂₃(OC₂H₄)y OH non-ionic surfactant as an example,the surface activity and thermodynamic changes of its surface activity and thermodynamic changes are calculated and analyzed by numerical calculation methods.It is found that under normal circumstances:the increase in the length of the EO group will lead to a decrease in the interfacial activity and the ability to reduce surface tension of the C₁₁H₂₃(OC₂H₄)y OH type surfactant,while the increase in temperature will cause the ability of C₁₁H₂₃(OC₂H₄)y OH type surfactant to reduce the interfacial tension and increase the interfacial activity.The thermodynamic calculation results show that the interface energy is continuously reduced during the adsorption process,and the interface free energy is continuously reduced.In the process of adsorption,the entropy change and energy continue to decrease,indicating that the interface adsorption causes the molecular arrangement on the interface to be more orderly,and at the same time the free energy of the interface decreases,and the crude oil is more easily displaced by water.The micellization process is a spontaneous endothermic process.The increase in temperature is conducive to the progress of the micellization.The entropy drive is the main driving force of the micellization.The micellization process has a linear enthalpy-entropy compensation relationship.For the C₁₁H₂₃(OC₂H₄)y OH type nonionic surfactant,the shorter EO group and the increase in temperature are conducive to the progress of micellization,better stability,and better interfacial activity at the oil-water interface.In the calculation range,C₁₁H₂₃(OC₂H₄)₆OH at313.15K has the best interfacial activity and ability to reduce surface tension.