Dual Piston Pumping System for Formation Evaluation
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Solution Overview
Problem
Existing downhole pumping systems for formation testing face challenges in maintaining accurate fluid sampling and pressure control due to exposure to harsh environmental conditions, which affects reliability and sample representativeness, and often introduce contamination through common pumping chambers and pistons.
Innovation Solution
A dual piston pumping system with separate working and pumping chambers, connected by a rod, and controlled by hydraulic and valve modules, allows for independent management of working and process fluids, maintaining isolation and controlling flow rates and pressures effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common pumping chamber and piston is used for both working fluid and process fluid, then the device complexity is reduced, but the sample representativeness and measurement precision deteriorate due to contamination and chemical scavenging
Solution Approach 1:
The pump is divided into two separate pumping chambers: a first pumping chamber for working fluid and a second pumping chamber for process fluid. This segmentation prevents contamination between fluids while maintaining separate control over each fluid's handling, thereby preserving sample accuracy without excessive complexity increase
Solution Approach 2:
The harmful interaction between working fluid and process fluid is eliminated by extracting them into separate chambers. The working fluid chamber is isolated from the process fluid chamber, preventing H2S absorption in oil films and chemical scavenging that would otherwise contaminate formation fluid samples
2Power
If seals and cavitation-prone pump designs are used, then the pumping capability is enhanced, but the sample purity and formation fluid representativeness deteriorate due to chemical scavenging and mineral breakdown
Solution Approach 1:
A displacement rod acts as an intermediary mechanism to transmit force from the working fluid chamber to the process fluid chamber without direct fluid contact. This allows pumping capability to be maintained through mechanical force transmission while avoiding seals and cavitation that would contaminate the formation fluid sample
Solution Approach 2:
The pump uses hydraulic principles where working fluid pressure moves a piston that connects via a displacement rod to another piston in the process fluid chamber. This hydraulic-mechanical-hydraulic transmission provides pumping power without direct mechanical seals contact with formation fluid, preventing chemical scavenging
3Adaptability or versatility
If H2S exposure occurs in oil film within the pump, then the pump can operate in harsh environments, but the measurement precision and H2S detection accuracy deteriorate
Solution Approach 1:
The working fluid containing H2S-absorbing oil film is completely separated from the process fluid path. By extracting the working fluid handling into an isolated first pumping chamber, the system maintains adaptability to harsh environments while preventing H2S absorption that would interfere with formation fluid H2S measurements
Solution Approach 2:
Different parts of the pump have different fluid handling characteristics: the first pumping chamber handles working fluid with H2S-absorbing properties isolated from formation fluid, while the second pumping chamber handles process fluid with minimal H2S interaction. This local differentiation allows harsh environment operation without compromising measurement accuracy
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 configuration ensures accurate and representative fluid sampling by minimizing contamination and maintaining formation pressure, while allowing for controlled operations such as sampling and pressure management, enhancing the reliability and efficiency of downhole testing.
Implementation Method 1
the working piston forms a first working chamber and a second working chamber in the first cylinder and where the pumping piston forms a first pumping chamber and a second pumping chamber in the second cylinder
Data Source
AI summary
A double piston positive displacement pumping system and methods are disclosed. The pump has a working bore with a first piston defining a pair of working chambers and a separate pumping bore having a second piston defining a pair of pumping chambers. The pistons are coupled together by a connecting rod such that the translate together axially within their respective bore. Working fluid is controllably introduced into and out of the working chambers to force the axial translation of the piston pair and wherein a process fluid is drawn into and out of the pumping chambers. The working fluid and the process fluid are confined to their respective bores and pistons.