Fluid Sample Quality Quantification via Pressure History Reconstruction
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Solution Overview
Problem
Current well/formation testing methods face challenges in obtaining high-quality fluid samples due to contamination from mud filtrates and unwanted phase changes during sampling, as the pressure history of fluid samples is complex and difficult to quantify accurately.
Innovation Solution
A method to quantify fluid sample quality by measuring bottom-hole pressure, obtaining formation properties, reconstructing the pressure history of fluid samples, and determining if the pressure has dropped below the bubble or dew point, using integrated simulation models of fluid transport in the reservoir and wellbore, and tracking the pressure history of fluid parcels from the formation to the sampler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wireline formation tester is used to take fluid samples, then real-time pressure monitoring and single phase sampling capability are improved, but mud filtrate contamination is worsened
Solution Approach 1:
The invention divides the fluid sampling process into distinct stages: initial filtrate removal phase and subsequent formation fluid sampling phase. The system segments the flowline into different functional zones and uses sequential pumping operations to first clear mud filtrates, then capture representative formation fluids, thereby resolving the contradiction between maintaining single-phase conditions and avoiding contamination
Solution Approach 2:
The invention performs preliminary action by conducting a pre-sampling pumpout operation to remove mud filtrates before actual formation fluid sampling. This preliminary step ensures that the flowline is cleared of contaminants, allowing subsequent samples to be free from mud filtrate contamination while maintaining the pressure control capabilities of the WFT
2Object-affected harmful factors
If Drill Stem Test is used to take fluid samples, then mud filtrate contamination is reduced, but real-time pressure monitoring and phase change control are worsened
Solution Approach 1:
The invention applies feedback by continuously monitoring bottom-hole pressure during the DST operation and using this information to control flow rates and maintain pressure above bubble or dew point. This real-time feedback loop enables the system to achieve both low contamination (like DST) and pressure control (like WFT) by adjusting operational parameters based on measured pressure conditions
3Reliability
If flow rate is reduced to maintain pressure above bubble point, then single phase sampling is improved, but sampling time is worsened
Solution Approach 1:
The invention applies partial action by using reduced flow rates only during critical sampling intervals when pressure control is essential, rather than maintaining low flow rates throughout the entire operation. This allows the system to achieve single-phase sampling during sample capture while minimizing the time penalty, by switching to higher flow rates during non-critical phases like initial pumpout or between samples
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 accurate quantification of fluid sample quality, ensuring representative samples by reconstructing the pressure history and identifying phase changes, thereby improving the reliability of reservoir fluid properties and management.
Implementation Method 1
an optical density sensor, as described in the U.S. Pat. Nos. 4,994,671, 5,266,800 and 6,966,234, may be used to distinguish the filtrates and formation fluids
Implementation Method 2
Gas vaporization or condensates drop out when the fluid pressure goes below the bubble or dew point, leading to phase change in the fluid samples
Data Source
AI summary
The invention relates to fluid sampling in a test that is used to determine physical and chemical characteristics of the fluids in a subterranean reservoir. The method reconstructs the entire pressure history of the fluid parcel that is captured in the fluid samplers during a test. Using this reconstructed pressure history of the samples, the quality of the samples, particularly, whether there is a phase change in the samples during the test, can be accurately quantified.