Numerical Simulation Study Of Alkaline-surfactant-gas Alternating Injection In Block X

There are many challenging oil reservoirs in China that are difficult to develop using traditional oil recovery methods.In response to these types of reservoirs,many scholars have conducted rock core displacement experiments using different chemical agents and gas combinations,which have shown that alternating injections of chemical agents and gases can indeed improve the recovery rate.However,there is relatively little research on the reservoir scale.This article proposes an innovative Alkali-Surfactant-Gas Alternating Injection(ASAG)method for low-permeability immiscible oil reservoirs.First,we study whether the ASAG method can improve the recovery rate through laboratory rock core displacement experiments,and then conduct numerical simulation studies at the reservoir scale.We perform sensitivity analyses on more than ten influencing factors,including reservoir geological parameters,fluid parameters,and injection process parameters,to determine whether these factors affect the recovery rate under the conditions of this oil reservoir and to what extent.The laboratory rock core displacement experiments show that compared to water flooding,alternating injections of water and gas can significantly increase the recovery rate,and the addition of alkali and surfactant can further improve the effect of water-gas alternation.The experimental results show that compared with water flooding,water-gas alternation can increase the recovery rate by 15%,and when ASAG is injected and produced,the recovery rate can be increased by 30%.During the experimental fitting process,the main goal is to obtain the interfacial tension curve,pore volume,and chemical agent concentration range,which provide a reference for sensitivity analysis.In the sensitivity analysis of numerical simulation at the reservoir scale,it can be seen that some factors are very important for the recovery rate results,while others have little effect.The research results of this article show that permeability and crude oil viscosity have a considerable impact on the recovery effect of ASAG,and the higher the permeability,the better the recovery rate,while the lower the crude oil viscosity,the higher the recovery level.The volume of the injected chemical plug and the number of alternating cycles both have a certain impact on the recovery rate,and the concentration of the chemical agent directly affects the recovery level,which is a very important influencing factor.The concentration of the chemical agent is positively correlated with the recovery rate,but the recovery level is not always higher with higher concentration.There is an optimal value,and from an economic and environmental perspective,a higher concentration of chemical agent is not always better.This article uses laboratory rock core displacement experiments and numerical simulation methods to study in detail the factors affecting the improvement of the recovery rate of ASAG,providing a certain reference value for subsequent chemical agent and gas alternating injection to improve the recovery rate.