Imidazoline compound, mobility control system, plugging agent for gas channeling, and method for carbon dioxide flooding

Abstract

An imidazoline compound, a mobility control system, a plugging agent for gas channeling, and a method for carbon dioxide flooding. The structure of the imidazoline compound is represented by formula (1), in which R is pentadecyl, heptadecenyl, or heptadecyl. A mobility control system that contains the imidazoline compound can interact with carbon dioxide to form a plugging agent for gas channeling, and thereby attains a plugging effect for carbon dioxide channeling in a carbon dioxide flooding process.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 15 / 716,207, filed on Sep. 26, 2017, entitled “Imidazoline Compound, Mobility Control System, Plugging Agent For Gas Channeling, And Method For Carbon Dioxide Flooding”, and claims priority to Chinese Application No. 201710566128.8, filed on Jul. 12, 2017, entitled “Mobility Control System for Carbon Dioxide Flooding in Low permeability or Ultra-low Permeability Oil Reservoirs and Use Thereof”, which are specifically and entirely incorporated by reference.FIELD OF THE INVENTION[0002]The present invention relates to the field of oil recovery efficiency improvement, in particular to an imidazoline compound, a mobility control system that contains the imidazoline compound, a plugging agent for gas channeling formed by the mobility control system, and a method for carbon dioxide flooding utilizing the mobility control system.BACKGROUND OF THE INVENTION[0003]As a highly efficient ene...

AI Technical Summary

Benefits of technology

The mobility control system is a new system that can be used to increase the amount of carbon dioxide flooding in oil reservoirs. It is a safe and effective system that is easy to use and can reduce damage to non-target zones. The system is made up of all natural components and is environmentally friendly. It has very low viscosity, making it easy to inject and can plug gas channels deep inside the reservoir. This can lead to more oil being recovered through carbon dioxid flooding, improving the overall oil production.

Problems solved by technology

However, in a water injection process, a hydrated film may be formed easily, and the clay minerals in the formation swell and the pores tend to be closed when the clay minerals encounter water, resulting in rapidly increased injection pressure and severely decreased injection volume or even failure of injection; consequently, the recovery efficiency of the matrix is very low.

However, oil reservoirs with ultra-low permeability are usually accompanied with natural and / or artificial fractures.

As a result, after carbon dioxide is injected into the formation, since the viscosity of carbon dioxide is much lower than that of water, gas channeling may occur easily along the fractures; therefore, the swept volume of carbon dioxide and the oil displacement efficiency are severely decreased, so that the field experiment result is severely degraded.

However, for oil reservoirs with ultra-low permeability, the follow-up injection is very difficult, and the introduced water will hamper carbon dioxide from mixing with hydrocarbon compounds.

However, foaming agents employed by conventional foam flooding are usually water-dissoluble surfactants.

When such a surfactant is used for ultra-low permeability oil reservoirs, the solution of water-dissoluble foaming agent is difficult to inject, and consequently it is difficult to use the foam fluid to control carbon dioxide mobility.

Wherein, ordinary polymers are hydrophobic and usually have a problem of poor solubility, which results in a poor viscosifying effect; fluoropolymers have much better dissolvability in supercritical carbon dioxide, and can attain a fairly good viscosifying effect; however, such polymers have their obvious shortcomings: firstly, the production cost is too high to mass production; secondly, the environmental hazard is severe, and adverse to environmental protection.

The viscosity of the system is low and equivalent to the viscosity of water; hence, the system has a characteristic of high plugging strength; however, a certain degree of contamination to the matrix of the ultra-low permeability oil reservoir will be resulted.

However, it is necessary to note that the pH value of the solution in the actual oil reservoir or the reaction of NaOH with rocks in the oil reservoir will make it difficult to control the pH reasonably during the construction process.

Ethylene diamine belongs to small molecular organic amine, and is inflammable, toxic, and harmful to health and environment in itself; in addition, if the oil saturation is high, the plugging strength of the generated precipitate will be decreased.

Though the above-mentioned methods have certain carbon dioxide mobility control capability, they have drawbacks such as unsatisfactory effect, complex operation, environmental pollution, and formation damage, etc.

Images