Buffered Dosing Tank Control for Precise Chemical Injection
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Solution Overview
Problem
Current methods for precision dosing of chemicals in hydrocarbon production systems, such as those used in wellbores, face inaccuracies due to variable pump strokes, high costs of flow meters, and difficulties in measuring fluid volumes in non-standard tank shapes, leading to inefficiencies and overtreatment.
Innovation Solution
A system with a buffered dosing tank of known geometry, equipped with a fluid level detector (like a pressure sensor) that calculates fluid volume and adjusts the injection pump's speed/duty cycle to achieve precise chemical dosing, eliminating the need for expensive flow meters and reducing errors from non-standard tank shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pump strokes are used to measure chemical discharge, then the measurement system is simple and low-cost, but the dosing precision is poor due to variable pump stroke volumes
Solution Approach 1:
A dosing tank with known geometry is introduced as an intermediary between the pump and the chemical injection point. The tank's regular geometric shape (cylindrical, rectangular, or spherical) allows precise volume calculation from fluid level measurements, eliminating the need to directly measure variable pump stroke volumes while maintaining simple, low-cost measurement using basic level sensors
Solution Approach 2:
The mechanical measurement approach (counting pump strokes) is replaced with a geometric calculation approach. By measuring the fluid level in a tank of known geometry and calculating volume based on the level change and tank dimensions, the system achieves precise dosing measurements without relying on mechanical pump stroke consistency
2Measurement precision
If flow meters are used to measure chemical discharge, then dosing precision is improved, but the system cost increases significantly for low flow rates
Solution Approach 1:
The system replaces expensive, sophisticated flow meters with simple, low-cost fluid level sensors (such as pressure sensors, ultrasonic sensors, or capacitive sensors) that measure the liquid level in the dosing tank. These inexpensive sensors provide sufficient precision for chemical dosing applications without the high cost of industrial flow meters
Solution Approach 2:
The dosing tank with known geometry serves as an intermediary that amplifies small volume changes into measurable level changes. This geometric transformation allows simple level sensors to achieve the precision that would otherwise require expensive flow meters, particularly for low flow rate chemical injection applications
3Volume of moving object
If non-standard shaped chemical tanks are used, then space utilization is improved, but volume measurement accuracy deteriorates due to inability to calculate volume from fluid level
Solution Approach 1:
The patent deliberately adopts symmetric, regular geometric shapes (cylindrical, rectangular, or spherical) for the dosing tank. This asymmetric choice (contrary to space-optimizing non-standard shapes) enables straightforward mathematical calculation of volume from fluid level measurements using simple geometric formulas, achieving both space efficiency and measurement precision
Solution Approach 2:
The system changes the geometric parameter of the tank from non-standard shapes to regular geometric shapes with known mathematical relationships between dimension and volume. This parameter change enables direct calculation of chemical volume from fluid level measurements without requiring complex lookup tables or empirical calibration
4Reliability
If batch treatment with treater trucks is used, then chemical delivery effectiveness is improved, but operational efficiency worsens due to difficulty accessing remote locations and frequent truck deliveries
Solution Approach 1:
Chemicals are pre-loaded into the dosing tank at a known concentration and volume. The controller calculates the precise amount of chemical needed based on the dosing requirements and tank geometry, preparing the system in advance for accurate, continuous dosing without requiring frequent truck deliveries to remote locations
Solution Approach 2:
The system uses the dosing tank's known geometry and fluid level measurements to self-calculate the volume of chemical remaining and the dosing rate. The controller automatically adjusts pump operation to maintain precise dosing, enabling the system to serve itself without requiring external intervention or frequent truck deliveries for monitoring and adjustment
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 system provides highly accurate and precise chemical dosing over time, ensuring the correct amount of chemicals is delivered to the wellbore, reducing waste and the need for frequent truck deliveries, while allowing for smaller, more accurately measured dosing tanks that enhance resolution and accuracy.
Implementation Method 1
The fluid level detector measures the pressure of the dosing tank to determine a fluid level
Data Source
AI summary
A method and system to precision dose a fluid system with an injection fluid having chemicals is provided. The method and system includes providing a buffered dosing tank of a known geometry between a source tank and an injection pump. The fluid level detector measures the pressure of the dosing tank to determine a fluid level. The fluid level together with the known geometry allow for a controller to calculate a fluid volume in the dosing tank and a change of volume over time. Using the change of volume over time, the controller can calculate an actual dose rate and adjust a speed or duty cycle of the injection pump such that the actual dose rate is approximately the target dose rate.