Low-Salinity Water Injection for Carbonate Oil Recovery
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Solution Overview
Problem
In subterranean carbonate formations, existing water flood methods face challenges due to high salinity connate water leading to reduced oil recovery, as high ionic strength and dissolved minerals in injection water can precipitate and plug formation passageways, reducing porosity and permeability.
Innovation Solution
A method involving nano-filtration to reduce the ionic strength and sulfate concentration of seawater or brine to create a low-salinity aqueous displacement fluid, which is injected into the formation, along with additives like surfactants or viscosifying polymers to enhance oil recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high salinity seawater or brine is injected into the formation, then fluid injection for oil displacement is achieved, but ionic strength and dissolved minerals precipitate and plug formation passageways, reducing porosity and permeability
Solution Approach 1:
The patent extracts and removes harmful dissolved minerals and ions from injection water through filtration systems before injection into the formation. This prevents mineral precipitation that would otherwise plug formation passageways and reduce permeability, while still maintaining the fluid injection function for oil displacement.
Solution Approach 2:
The patent applies preliminary filtration and treatment to the injection water before it is injected into the formation. By pre-removing dissolved minerals and adjusting chemistry, the system prevents future plugging issues rather than dealing with them after they occur, maintaining formation permeability throughout the waterflood operation.
2Ease of manufacture
If conventional water flood methods are used, then injection operations are simple, but oil recovery is reduced due to high ionic strength effects on rock wettability
Solution Approach 1:
The patent changes the chemical parameters of the injection water, specifically reducing ionic strength and adjusting mineral content, to alter rock wettability from oil-wet to more water-wet conditions. This enhances capillary imbibition and oil displacement efficiency, significantly improving oil recovery compared to conventional high-salinity water flooding.
3Quantity of substance
If nano-filtration and chemical treatment are applied to reduce ionic strength, then oil recovery is enhanced by altering rock wettability, but water treatment complexity and cost increase
Solution Approach 1:
The patent introduces filtration systems and chemical treatment processes as intermediary steps between the injection water source and the formation. These intermediaries remove harmful components and adjust water chemistry to achieve the desired low ionic strength, enabling enhanced oil recovery while managing the complexity through systematic treatment stages.
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 increases oil recovery by altering rock wettability, reducing plugging issues, and improving fluid flow, allowing for higher oil extraction rates, potentially exceeding 15% of the original oil in place.
Implementation Method 1
passing sea water through a nano-filtration membrane to provide an aqueous displacement fluid having an ionic strength from 0.1 to less than 0.5% of the ionic strength of the connate water
Implementation Method 2
This approach increases oil recovery by altering rock wettability
Data Source
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AI summary
There is disclosed a method for enhancing recovery of crude oil from a porous subterranean carbonate formation of which the pore spaces contain crude oil and connate water, the method comprising determining an ionic strength of the connate water; and injecting an aqueous displacement fluid having a lower ionic strength than the connate water into the formation.