Supercritical carbon dioxide microemulsion capable of reducing minimum miscible pressure of carbon dioxide and crude oil

Abstract

The invention discloses a supercritical carbon dioxide microemulsion capable of reducing minimum miscible pressure of carbon dioxide and crude oil. The microemulsion consists of a CO2-philic surfactant, a cosolvent and supercritical carbon dioxide; and the microemulsion is prepared by the following steps: uniformly mixing the CO2-philic surfactant, the cosolvent and the supercritical carbon dioxide according to proportions under pressure of 8-20MPa and at temperature of 40-90 DEG C, and injecting an obtained mixture to an oil reservoir. The supercritical carbon dioxide microemulsion disclosed by the invention can be used for effectively reducing the minimum miscible pressure of carbon dioxide and crude oil by more than 20%, so that the miscible phase of the carbon dioxide and the crude oil can be achieved under relatively low pressure.

Description

technical field [0001] The invention belongs to the technical field of petroleum exploitation and oilfield chemistry, and relates to a method for reducing the minimum miscible pressure of carbon dioxide and crude oil, in particular to a method for reducing the minimum miscible pressure of carbon dioxide and crude oil by using a carbon dioxide-friendly surfactant. Background technique [0002] Miscible flooding means that in porous media, when one fluid displaces another fluid, due to the diffusion and mass transfer between the two fluids, the two fluids can dissolve each other without an interface, thus completely The interfacial tension is eliminated, the capillary quasi-number becomes infinite, and the capillary force in the porous medium is reduced to 0, thereby reducing the trapping of the displaced fluid by the capillary force, and theoretically, the microscopic displacement efficiency can reach 100%. Carbon dioxide miscible flooding means that light hydrocarbon molecul...

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Problems solved by technology

[0005] Essentially, the main reason for the high miscibility pressure of supercritical carbon dioxide and heavy oil is that carbon dioxide is a non-polar molecule with weak van der Waals force and low dielectric constant, which leads to its weak dissolving ability. Polar small molecules such as aliphatic hydrocarbons, halogenated hydrocarbons, aldehydes, ketones, esters, etc. with less than 20 carbon atoms are dissolved in it, while for polar macromolecules such as colloids and asphaltenes in crude oil, even if the pressure reaches 30MPa or more , its solubility is still limited

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