Downhole Pump Control via Saturation Pressure Estimation
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Solution Overview
Problem
Traditional methods for capturing formation fluid samples in oil and gas exploration often result in contaminated samples due to drilling fluid infiltration, and the pressure reduction in downhole tools can cause state changes in the fluid, leading to inefficient sampling and inaccurate pumping rates.
Innovation Solution
A system and method for operating a downhole tool that uses sensors to measure fluid properties, such as optical density, to estimate saturation pressure and control the pump to maintain pressure above the estimated saturation pressure, ensuring efficient sampling of representative formation fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pressure is reduced in the downhole tool to capture formation fluid samples, then sampling efficiency is improved, but state changes in the fluid occur leading to contamination and inaccurate measurements
Solution Approach 1:
The system continuously monitors fluid properties (optical density, temperature, pressure) during pumping and uses this feedback to dynamically adjust pump operations. Saturation pressure is estimated in real-time based on measured fluid properties, and pump rate is adjusted to maintain pressure above this estimated saturation pressure, preventing phase changes and ensuring representative samples.
Solution Approach 2:
The system changes operational parameters (pump rate, pressure maintenance level) based on real-time fluid property measurements. By monitoring optical density and temperature to estimate saturation pressure, the system dynamically adjusts the pressure parameter to prevent fluid state changes while maintaining efficient sampling operations.
2Productivity
If pump rate is increased to improve sampling speed, then productivity is improved, but pressure drops below saturation pressure causing fluid state changes and contamination
Solution Approach 1:
The system uses real-time feedback from fluid property sensors to adjust pump rate. When fluid properties indicate approaching saturation pressure, the system reduces pump rate to maintain pressure above the saturation point, preventing contamination while optimizing sampling speed.
Solution Approach 2:
The pump operation transitions from static fixed-rate pumping to dynamic variable-rate pumping. The pump rate is continuously adjusted based on real-time fluid property measurements and estimated saturation pressure, allowing the system to optimize sampling speed while preventing fluid state changes.
3Reliability
If traditional pumping methods are used to reduce contamination, then sample purity is improved, but pumping rates become inaccurate and sampling efficiency decreases
Solution Approach 1:
The system changes from fixed parameter pumping to variable parameter pumping. By continuously monitoring fluid properties and adjusting pressure and pump rate parameters based on real-time conditions, the system maintains sample purity while optimizing pumping efficiency for each specific formation fluid encountered.
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 allows for the capture of uncontaminated, representative fluid samples by maintaining pressure above the saturation point, reducing contamination and improving the accuracy of pumping rates, even as fluid properties change during sampling.
Implementation Method 1
uses sensors to measure fluid properties, such as optical density
Data Source
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AI summary
A method includes pumping fluid from outside of a downhole tool through a flowline of the downhole tool with a pump and taking first measurements, using at least one sensor, within the flowline during a first stage of pumping the fluid. The method further includes estimating a saturation pressure of the fluid, via a processor, based on the first measurements and a saturation pressure model generated based on second measurements taken using the at least one sensor during a second stage of pumping the fluid, and operating the pump to maintain a fluid pressure in the flowline greater than the estimated saturation pressure.