ESP Motor Control Using Fluid Density to Prevent Gas Lock
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Solution Overview
Problem
Existing ESP systems lack accurate flow rate and fluid density measurement capabilities, leading to inefficiencies and increased risk of gas lock due to high gas content, as they rely on surface measurements that do not account for downhole pressure and temperature variations.
Innovation Solution
Implementing a system with sensors to measure intake and discharge pressures, current and voltage at the ESP, and a processor to calculate shaft speed, torque, and fluid density, using efficiency and head curves to determine flow rate and density accurately, and adjust motor speed based on density thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface measurements are used to estimate flow rate and density, then the system is simpler, but measurement precision is insufficient due to not accounting for downhole pressure and temperature variations
Solution Approach 1:
The patent introduces an intermediary computational model that uses measured pressure and temperature data along with efficiency and head curves to calculate flow rate and density. This intermediary layer translates raw sensor measurements into accurate fluid property estimates without requiring direct complex downhole instrumentation for every parameter.
Solution Approach 2:
The patent replaces direct mechanical measurement devices (such as downhole flow meters and density meters) with an electrical/computational system that uses pressure and temperature sensors combined with mathematical models (efficiency curves, head curves, and thermodynamic relationships) to derive flow rate and density indirectly.
2Productivity
If motor speed is increased to maximize production, then productivity improves, but gas lock risk increases due to high gas content in the fluid
Solution Approach 1:
The patent implements a feedback control system where the calculated fluid density is continuously monitored and used to adjust motor speed. When density drops below a threshold indicating high gas content, the system automatically reduces speed to prevent gas lock, creating a closed-loop control that balances productivity with reliability.
Solution Approach 2:
The patent makes the motor speed dynamic rather than fixed, allowing it to adjust in real-time based on changing fluid conditions. The speed is modulated according to the calculated density and gas content, enabling the system to optimize production while avoiding gas lock conditions as fluid properties change during operation.
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
Enables precise estimation of flow rate and fluid density, optimizing ESP operation to prevent gas lock and enhance production efficiency by dynamically adjusting motor speed based on real-time downhole conditions.
Implementation Method 1
A frequency of an electrical signal provided to the electrical submersible pump is measured. A speed of a shaft of an electric motor of the electrical submersible pump is calculated based on the frequency, wherein the frequency is induced in the electrical signal by rotation of the motor.
Data Source
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AI summary
A system, method, and computer-readable medium for determining the flow rate and fluid density in an electrical submersible pump (ESP) and controlling the ESP based on the flow rate and density. In one implementation, an ESP system includes an ESP, drive circuitry, a current sensor, a voltage sensor, and a processor. The ESP includes an electric motor. The drive circuitry is electrically coupled to the ESP and is configured to provide an electrical signal to power the ESP. The current sensor is configured to measure a current of the electrical signal. The voltage sensor is configured to measure a voltage of the electrical signal. The processor is configured to calculate speed of a shaft of the electric motor based on a frequency induced by rotation of the motor detected in the current. The processor is also configured to calculate a density of fluid in the ESP based on the speed.