Subsea Isothermal Multiphase Sampling System
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Solution Overview
Problem
Current methods for sampling fluids in subsea environments face challenges in efficiently collecting representative samples at line conditions, particularly in multiphase fluids, due to difficulties in managing temperature and pressure gradients and maintaining sample integrity during collection and analysis.
Innovation Solution
A system comprising a multiphase sampling apparatus with liquid-rich and gas-rich sampling ports, connected to a subsea remotely operated vehicle (ROV) with temperature and pressure control arrangements, enabling selective sampling and enrichment of representative phases while maintaining isothermal and isobaric conditions, and allowing for subsea or surface analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluid samples are collected from subsea wellhead to surface for PVT analysis, then reservoir characterization and production optimization can be achieved, but temperature and pressure gradients cause problematic deposition of materials such as asphaltenes
Solution Approach 1:
The system performs preliminary separation of multiphase fluids into distinct phases (gas, oil, water) at the subsea sampling location before analysis. This preliminary action prevents the mixing and subsequent deposition problems that occur when multiphase fluids are transported to surface facilities, where temperature and pressure gradients cause asphaltenes to precipitate.
Solution Approach 2:
The sampling system segments the multiphase fluid stream into separate phase samples (gas-rich and liquid-rich sampling ports) that can be analyzed independently. This segmentation allows each phase to be characterized without the harmful deposition effects that occur in mixed multiphase conditions during transport.
2Measurement precision
If multiphase fluids are sampled and transported to surface facilities for analysis, then reservoir characterization can be performed, but the detection and sampling process becomes difficult and inefficient
Solution Approach 1:
The system replaces complex mechanical sampling and transport mechanisms with a streamlined subsea sampling apparatus that directly separates and collects phase-specific samples at the wellhead. This substitution eliminates the need for complex multiphase transport and surface separation equipment, making the sampling process easier and more efficient while maintaining high measurement precision.
3Measurement precision
If representative samples of multiphase fluids are collected at line conditions, then accurate production optimization data can be obtained, but maintaining isothermal conditions requires temperature control arrangements
Solution Approach 1:
The temperature control arrangement applies heating or cooling locally at the sampling points and sample lines rather than throughout the entire fluid system. This localized approach maintains isothermal conditions for the samples being collected while minimizing the overall system complexity and energy requirements.
4Measurement precision
If separate phase sampling ports are used to extract gas-rich and liquid-rich samples, then representative phase data can be obtained, but the sampling apparatus complexity increases
Solution Approach 1:
The sampling apparatus uses dynamic flow control mechanisms that allow the system to adaptively switch between gas-rich and liquid-rich sampling ports based on real-time flow conditions. This dynamic capability enables accurate phase composition measurement without requiring permanently complex multi-port configurations for all possible sampling scenarios.
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 efficient and representative sampling of multiphase fluids at line conditions without damaging or restricting flow, allowing for accurate analysis and optimization of well fluid production, suitable for a wide range of subsea fluids from lean gas to heavy oil.
Implementation Method 1
a temperature control arrangement disposed between the multiphase sampling apparatus and the vehicle sampling apparatus that minimizes the temperature difference between the representative sample and the multiphase fluid flowing through the flowline
Implementation Method 2
a pressure control arrangement that minimizes the pressure difference between the representative sample and the multiphase fluid flowing through the flowline
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A system and method for collecting a selected phase of a representative sample from a multiphase fluid flowing through a flowline, preferably located subsea. The system includes a multiphase sampling apparatus attachable to the flowline for sampling the representative sample; a vehicle sampling apparatus (e.g., ROV) locatable proximate the flowline having a power supply and a fluid sample collector for storing at least one selected phase of the representative sample; an interface for connecting the multiphase sampling apparatus and the vehicle sampling apparatus; and a temperature control arrangement disposed between the multiphase sampling apparatus and the vehicle sampling apparatus configured to minimize the temperature difference between the representative sample and the multiphase fluid flowing through the flowline.