Oil-Water Interface Sensor for Automatic Tank Dewatering

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Solution Overview

Problem

Existing automatic tank dewatering apparatuses for hydrocarbon storage tanks require major modifications, frequent calibration and maintenance, and are costly, while they do not effectively measure water presence or quantity, leading to hydrocarbon losses during dewatering.

Innovation Solution

A method using an oil-water interface sensor with two probes, an analytics sensor, a control system, and a controllable valve to automatically drain water from hydrocarbon storage tanks by measuring the vertical displacement of the oil-water interface and controlling the valve accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If automatic tank dewatering apparatuses are implemented, then manual labor and safety risks are reduced, but device complexity and installation costs increase due to requiring major modifications in the tank or drain piping

Engineering Contradiction:
Improvemanual labor requirementVSAvoidinstallation complexity
Core Design Contradiction:
Ease of operationVSDevice complexity

Solution Approach 1:

The dewatering system is segmented into independent functional modules: interface detection sensors (capacitive or radar), control logic unit, and valve actuation system. This modular segmentation allows each component to be installed and calibrated independently, reducing overall installation complexity while maintaining automatic operation capabilities

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The control system is designed to be universal and adaptable to different tank configurations and existing drain piping systems. The interface detection mechanism can operate with various sensor types (capacitive, radar) and the control logic can be programmed to work with different valve types, making the system widely applicable without requiring major custom modifications

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Ease of operation

If automatic tank dewatering apparatuses are implemented, then operational safety is improved, but maintenance requirements and calibration frequency increase

Engineering Contradiction:
Improveoperational safetyVSAvoidmaintenance frequency
Core Design Contradiction:
Ease of operationVSEase of repair

Solution Approach 1:

The system incorporates self-diagnostic and self-calibration capabilities where the control unit continuously monitors sensor readings and valve positions, automatically detecting drift or failures. The interface detection system uses reference measurements and compensation algorithms to maintain accuracy without manual intervention, reducing maintenance frequency while ensuring operational safety

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system implements continuous feedback loops where sensor measurements of the oil-water interface are constantly compared against target values, and valve actuation is adjusted in real-time based on this feedback. This closed-loop control ensures accurate dewatering operation and automatically detects when calibration or maintenance is needed, reducing manual maintenance requirements

Inventive Principle:
Principle #23Feedback

3Device complexity

If dewatering cycle is initiated based on manual determination, then operational simplicity is maintained, but hydrocarbon losses occur due to fluids flowing in the drain pipe

Engineering Contradiction:
Improvesystem simplicityVSAvoidhydrocarbon loss
Core Design Contradiction:
Device complexityVSLoss of substance

Solution Approach 1:

The interface detection sensors continuously monitor the oil-water interface position before the dewatering cycle is initiated. The control system uses these preliminary measurements to determine the optimal start timing and duration of dewatering operations, ensuring that hydrocarbons are not lost while still achieving complete water removal. The system can predict when water accumulation reaches critical levels based on historical data and continuous monitoring

Inventive Principle:
Principle #10Preliminary action

4Extent of automation

If existing automatic dewatering systems are used, then dewatering automation is achieved, but measurement precision of water presence or quantity is insufficient

Engineering Contradiction:
Improvedewatering automationVSAvoidwater quantity measurement
Core Design Contradiction:
Extent of automationVSMeasurement precision

Solution Approach 1:

The system merges multiple measurement approaches (capacitive sensing, radar detection, or other interface detection methods) to simultaneously detect both the presence and quantity of water. By combining these measurement techniques, the system achieves high precision in water quantity measurement while maintaining full automation of the dewatering process

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The system transitions from simple presence/absence detection to multi-dimensional measurement by detecting interface position, water layer thickness, and volume calculations. This dimensional expansion of measurement capabilities provides precise water quantity information while maintaining automation, allowing the control system to optimize dewatering operations based on actual water volumes

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 method allows for efficient and automatic removal of water build-up in hydrocarbon storage tanks, preventing hydrocarbon losses and reducing the need for manual labor and frequent maintenance.

Implementation Method 1

The first probe generates the first input data stream. The second probe generates the second input data stream. The method includes the step of processing the first input data stream and the second input data stream to determine a vertical displacement of the oil-water interface.

Methodology Applied
Scientific EffectHydraulic pressure measurement: Pascal's Law

Implementation Method 2

The analytics sensor is a sound velocity sensor located on a vertical section of the drain line. The sound velocity sensor measures the sound velocity of a transmitted sound wave travelling across the drain line.

Methodology Applied
Scientific EffectSound wave propagation: Speed of Sound

Implementation Method 3

The controllable valve is fluidly connected to a drain line. The drain line is fluidly connected to the bottom portion of the hydrocarbon storage tank. The water build-up is removed via the drain line as the controllable valve is maintained in the open position.

Methodology Applied
Scientific EffectFluid flow control: Valve

Implementation Method 4

The oil-water interface sensor includes a first probe and a second probe. The first probe is located at a bottom portion of the hydrocarbon storage tank. The second probe is located above the first probe. The method includes the step of processing the first input data stream and the second input data stream to determine a vertical displacement of the oil-water interface.

Methodology Applied
Scientific EffectDensity difference separation: Density Gradient

Data Source

PatentEP4090444B1Method for controlling the oil/water interface in an oil reservoir
Publication Date: 2025.05.07 SAUDI ARABIAN OIL CO
  • EP4090444B1 patent drawingFigure 1
  • EP4090444B1 patent drawingFigure 2
  • EP4090444B1 patent drawingFigure 3

AI summary

Embodiments of the disclosure provide a method and system for removing water build-up in a hydrocarbon storage tank. An oil-water interface sensor is located in the hydrocarbon storage tank (220) and includes a first probe (240) and a second probe (242). The first probe (240) is located at a bottom portion of the hydrocarbon storage tank. The first probe generates a first input data stream. The second probe (242) is located above the first probe. The second probe generates a second input data stream. The first and second input data streams are processed (30) to determine a vertical displacement of an oil- water interface, which is compared against a predetermined value. An output data stream responsive to the comparison is generated including instructions to maintain a controllable valve (226) either in an open position or in a closed position. The output data stream is communicated to the controllable valve, fluidly connected to a drain line connected to the bottom portion of the hydrocarbon storage tank to be in the open position or in the closed position. Water build-up is removed via the drain line as the controllable valve is maintained in the open position.