Downhole Pump Control via Saturation Pressure Estimation
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Solution Overview
Problem
Existing oil and gas exploration methods face inefficiencies in capturing representative fluid samples from geological formations due to contamination from drilling fluids and pressure changes that can cause state changes in the fluid, leading to inaccurate pumping rates and space constraints in downhole tools.
Innovation Solution
A downhole fluid testing system that uses an optical spectrometer to measure optical density and estimate saturation pressure, adjusting the pump flow rate to maintain pressure above the estimated saturation pressure, thereby reducing contamination and optimizing sampling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump operates at high flow rate to reduce sampling time, then productivity improves, but the pressure drops below saturation pressure causing fluid state changes and contamination
Solution Approach 1:
The pump flow rate is dynamically adjusted based on real-time pressure measurements and saturation pressure estimates. The controller continuously modifies the pump operation to maintain pressure above saturation pressure while optimizing sampling speed, transitioning from static to dynamic control to resolve the contradiction between high productivity and sample accuracy.
Solution Approach 2:
The system changes the operating parameters (flow rate, pressure) based on the estimated saturation pressure and uncertainty. By adjusting these parameters dynamically and incorporating uncertainty margins, the system maintains reliable fluid sampling while improving productivity through optimized pump operation.
2Reliability
If the pump operates conservatively to maintain pressure above saturation pressure, then fluid sample accuracy improves, but sampling time increases
Solution Approach 1:
The system uses feedback from pressure sensors and optical spectrometer measurements to continuously estimate saturation pressure and adjust pump operation. This closed-loop control allows the system to operate efficiently near the saturation pressure boundary rather than conservatively far from it, reducing sampling time while maintaining sample accuracy.
Solution Approach 2:
The system performs preliminary estimation of saturation pressure using the optical spectrometer and saturation pressure model before and during sampling. This preliminary action allows optimization of pump flow rate in advance, enabling faster sampling without compromising fluid sample accuracy.
3Measurement precision
If downhole tools are designed with larger capacity to accommodate sampling equipment, then measurement precision improves, but device complexity increases
Solution Approach 1:
The optical spectrometer is designed to serve multiple functions: measuring optical density for saturation pressure estimation, analyzing fluid composition, and monitoring fluid properties during sampling. This multi-functionality improves measurement precision without requiring separate dedicated equipment, thereby limiting the increase in device complexity.
Solution Approach 2:
The system combines the optical spectrometer, pressure sensors, pump, and controller into an integrated downhole tool assembly. By merging these components into a unified system rather than separate tools, the patent achieves improved saturation pressure estimation accuracy while managing device complexity through integrated design.
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 faster reduction in contamination levels, reduced pump operating time, and more accurate fluid sampling by maintaining flow line pressure above the estimated saturation pressure, enhancing the representativeness of the fluid samples and improving the efficiency of the sampling process.
Implementation Method 1
an optical spectrometer comprising at least one sensor. The optical spectrometer is configured to receive a first plurality of measurements output by the at least one sensor and to analyze portions of the fluid to obtain a fluid property of the fluid, including an optical density
Data Source
AI summary
A method includes positioning a downhole acquisition tool in a well-logging device in a wellbore in a geological formation, where the wellbore or the geological formation, or both contain a reservoir fluid. The method includes performing downhole fluid analysis using a downhole acquisition tool in the wellbore to determine a plurality of fluid properties associated with the reservoir fluid. The method includes generating a nonlinear predictive control model representative of the plurality of fluid properties based at least in part on the downhole fluid analysis. The method includes adjusting the nonlinear predictive control model based at least in part on an output representative of a pump flow control sequence at a first time interval and the plurality of fluid properties.