Enhanced oil recovery method by nanofluid-assisted CO2 huff-n-puff

Patent metadata

Field	Value
Publication number	US-11401456-B2
Application number	US-202017010938-A
Country	US
Kind code	B2
Filing date	Sep 3, 2020
Priority date	Dec 31, 2019
Publication date	Aug 2, 2022
Grant date	Aug 2, 2022

Abstract

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.

First claim

What is claimed is:

1. An enhanced oil recovery method by nanofluid-assisted CO 2 huff-n-puff, comprising:
using a nanofluid to displace crude oil from an injection well to a production well;
when the crude oil obtained by displacement contains the nanofluid, closing the injection well and the production well, and performing first soaking;
when the first soaking reaches a first set time, opening the injection well and the production well, and using liquid CO 2 to displace crude oil from the injection well to the production well;
when the crude oil obtained by displacement contains the injected CO 2 , closing the production well, and continuing to inject the liquid CO 2 into the injection well, and when a bottom hole pressure of the injection well is equal to the miscibility pressure of the liquid CO 2 and the formation crude oil, closing the injection well and performing second soaking; and
when the second soaking reaches a second set time, opening the production well to complete the exploitation of crude oil,
wherein the opening of the production well comprises opening the production well at a specific speed to reduce the formation pressure at a set rate of 0.5 MPa/h or lower.

2. The enhanced oil recovery method by nanofluid-assisted CO 2 huff-n-puff according to claim 1 , wherein the first set time is one week.

3. The enhanced oil recovery method by nanofluid-assisted CO 2 huff-n-puff according to claim 1 , wherein the second set time is two weeks.

Assignees

• Univ Tsinghua
• Shanxi Research Institute For Clean Energy Tsinghua Univ

Inventors

• Jiang Peixue
• Xu Ruina
• Huang Feng

Classifications

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title

• E21B43/16

  Enhanced recovery methods for obtaining hydrocarbons · CPC title

• C09K2208/10

  Nanoparticle-containing well treatment fluids · CPC title

• E21B43/164 Primary

  Injecting CO2 or carbonated water (in combination with organic material C09K8/594) · CPC title

• C09K8/594 Primary

  Compositions used in combination with injected gas {, e.g. CO2 orcarbonated gas}(C09K8/592 takes precedence) · CPC title