ENHANCED OIL RECOVERY METHOD BY NANOFLUID-ASSISTED CO2 HUFF-N-PUFF

摘要

The present invention provides an enhanced oil recovery method by nanofluid-assisted CO₂ huff-n-puff. A nanofluid is injected into an injection well in an oil reservoir formation having hydrophilic wetting characteristics, and soaking is performed; in the soaking stage, after the nanofluid tends to replace crude oil to occupy dead-ends of fractures and pores, and liquid CO₂ is injected; and in the process of production, CO₂ originally dissolved in the formation fluid reaches a supersaturated state. As a result, CO₂ preferentially nucleates at the nanofluid side to generate CO₂ bubbles, grows and expands with the continuous reduction of formation pressure, and pushes crude oil near the dead-ends of fractures and pores to move outward, thereby improving the recovery efficiency.