Subsurface Water Purification Using Ultrafiltration and Electrochemical Backwashing
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Solution Overview
Problem
Current methods for producing low salinity water for enhanced oil recovery (EOR) in subsurface environments face challenges due to high costs and limited operational time caused by high particulate matter, necessitating a more robust and efficient system for purifying water in these conditions.
Innovation Solution
A subsurface water treatment system utilizing ultrafiltration membrane units, an electrochemical unit to generate hypohalous acid species for backwashing, and additional filtration steps like nanofiltration and reverse osmosis to produce purified water with reduced sulfate levels, while maintaining low fluid flux to minimize maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filtration systems are used in subsurface environments, then water purification is achieved, but operational duration is severely limited due to high particulate matter causing frequent maintenance needs
Solution Approach 1:
The filtration system is divided into multiple membrane units that can be independently backwashed. This segmentation allows one unit to be cleaned while others continue operating, extending the overall operational duration without interruption to water production.
Solution Approach 2:
The system implements periodic backwashing cycles where filtration membranes are reversely flushed at scheduled intervals. This periodic maintenance action removes accumulated particulates, restoring filtration efficiency and enabling continuous long-term operation in high-particulate subsurface environments.
2Productivity
If high flux rates are used through ultrafiltration membranes, then water production efficiency increases, but maintenance frequency increases due to faster membrane fouling
Solution Approach 1:
The system employs periodic backwashing at optimized intervals that balance flux rate with membrane fouling accumulation. By reversely flushing membranes periodically, the system maintains high productivity while preventing excessive fouling that would require frequent maintenance shutdowns.
Solution Approach 2:
Multiple membrane units operate in parallel, allowing the system to maintain continuous water production. When one unit requires maintenance, others continue operating, ensuring uninterrupted useful action and minimizing overall maintenance time impact on productivity.
3Ease of manufacture
If subsurface water treatment systems are installed on the sea floor adjacent to injection wells, then piping costs and platform space requirements are reduced, but operational reliability decreases due to high subsurface particulate matter
Solution Approach 1:
The system uses multiple independent membrane units that can be individually backwashed and maintained. This segmentation isolates fouling to specific units, allowing localized maintenance without compromising the entire system's reliability in the challenging subsurface environment.
Solution Approach 2:
The system incorporates automated backwashing capabilities that allow the membranes to clean themselves periodically. This self-service feature reduces the need for manual intervention and external support, enhancing system reliability for remote subsurface deployment where maintenance access is limited.
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
The system effectively produces purified water with low particulate and sulfate content, enhancing EOR efficiency and reducing maintenance requirements, thereby improving hydrocarbon recovery and operational autonomy in subsurface environments.
Implementation Method 1
introducing ambient subsurface source water into and through one or more ultrafiltration membrane units and producing thereby an ultrafiltrate substantially free of solid particulates having a largest dimension greater than 0.1 microns
Implementation Method 2
preparing in an electrochemical unit in fluid communication with at least one ultrafiltration membrane unit an aqueous solution comprising one or more hypohalous acid species
Implementation Method 3
delivering an ultrafiltrate-rich backwash fluid and at least a portion of the aqueous solution comprising one or more hypohalous acid species to at least one non-producing ultrafiltration membrane unit during a backwash cycle
Implementation Method 4
subjecting a portion of the ultrafiltrate to a nanofiltration separation step in a nanofiltration unit
Implementation Method 5
subjecting a portion of the ultrafiltrate to a reverse osmosis separation step in a reverse osmosis membrane unit
Data Source
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AI summary
A method of producing purified water in a subsurface environment is provided in which ambient subsurface source water is introduced into and through one or more ultrafiltration membrane units of a subsurface water treatment system and producing thereby an ultrafiltrate substantially free of solid particulates having a largest dimension greater than 0.1 microns. An electrochemical unit in fluid communication with at least one ultrafiltration membrane unit provides an antifoulant solution. An ultrafiltrate-rich backwash fluid and at least a portion of the antifoulant solution are delivered to at least one non-producing ultrafiltration membrane unit during a backwash cycle. A flux of source fluid through each of the ultrafiltration membrane units of less than thirty gallons per square foot per day limits the need for backwash cycles. A reduction in the number of backwash cycles enhances system autonomy and useful life, and limits the need for intervention for maintenance and component replacement.