Nanofluid-Assisted CO2 Huff-n-Puff for Enhanced Oil Recovery
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Solution Overview
Problem
Current CO2 huff-n-puff methods for enhanced oil recovery struggle to control CO2 supersaturation nucleation and precipitation, leading to random bubble formation and limited crude oil recovery from dead-ends of fractures and pores in the formation.
Innovation Solution
The method involves using a nanofluid to displace crude oil, followed by CO2 injection, where the nanofluid preferentially occupies dead-ends of fractures and pores, facilitating controlled CO2 nucleation and bubble growth, which then drives crude oil outward, improving recovery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CO2 is injected into the formation by huff-n-puff, then crude oil viscosity is reduced and crude oil expansion occurs, but CO2 supersaturation nucleation and precipitation cannot be controlled, causing random bubble formation in the formation fracture-matrix porous media structure
Solution Approach 1:
The patent introduces nanoparticles as an intermediary substance that mediates the nucleation process. The nanoparticles serve as preferential nucleation sites for CO2 bubbles, transforming the random nucleation process into a controlled one. The nanoparticles act as a bridge between the CO2 and the crude oil, enabling controlled bubble formation at specific locations rather than random nucleation throughout the porous media.
Solution Approach 2:
The patent changes the physical and chemical parameters of the injection fluid by adding nanoparticles. This modification alters the nucleation behavior of CO2, changing it from random supersaturation nucleation to controlled nucleation at nanoparticle interfaces. The addition of nanoparticles changes the interfacial properties and nucleation energy barriers, enabling precise control over bubble formation location and timing.
2Quantity of substance
If CO2 bubbles grow and expand randomly in the formation porous media, then formation energy is supplemented, but it becomes difficult to effectively exploit crude oil near the dead-ends of fractures and pores
Solution Approach 1:
The patent applies local quality by concentrating nanoparticles in specific regions of the porous media, particularly near dead-ends of fractures and pores. This creates localized zones with enhanced nucleation capability where CO2 bubbles preferentially form. The nanoparticle distribution is non-uniform, with higher concentrations in areas that are difficult to access, ensuring that bubble formation occurs specifically where needed rather than uniformly throughout the formation.
Solution Approach 2:
The patent performs preliminary action by injecting nanoparticles into the formation before CO2 injection. The nanoparticles are positioned and distributed in advance within the porous media, particularly in dead-end regions. This preliminary placement ensures that when CO2 is subsequently injected, the nucleation sites are already prepared and positioned optimally, enabling immediate and controlled bubble formation in the target areas without requiring random exploration.
3Duration of action of stationary object
If CO2 huff-n-puff is performed cyclically many times, then formation energy is maintained, but the effect on improving recovery of crude oil near dead-ends of fractures and pores remains limited
Solution Approach 1:
The patent enables self-service by allowing the nanoparticles to continuously serve as nucleation sites over multiple cyclic operations. The nanoparticles remain stationary in the porous media and repeatedly facilitate CO2 bubble formation during each huff-n-puff cycle. This eliminates the need for re-injection of nucleation promoters and allows the system to maintain enhanced recovery capability throughout the extended cyclic operation, with each cycle benefiting from the persistent presence of nanoparticle nucleation sites.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances crude oil recovery by ensuring CO2 bubbles nucleate and expand preferentially at the nanofluid interface, effectively exploiting oil from previously inaccessible areas, thereby improving overall recovery efficiency.
Implementation Method 1
a nanofluid is injected into an injection well of an oil reservoir formation having hydrophilic wetting characteristics
Implementation Method 2
oil reservoir formation having hydrophilic wetting characteristics
Implementation Method 3
CO2 injected into the formation will dissolve in crude oil, which can effectively reduce crude oil viscosity, cause crude oil expansion
Implementation Method 4
CO2 originally dissolved in the formation fluid reaches a supersaturated state
Implementation Method 5
CO2 preferentially nucleates at the nanofluid side to generate CO2 bubbles
Implementation Method 6
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
Data Source
AI summary
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.