Core Sample Preservation Using Hydrogen-Free Fluid Displacement
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Solution Overview
Problem
Existing methods for obtaining core samples from reservoirs often stress the rocks and fluids, causing changes in rock and fluid properties, and result in altered fluid compositions, especially for low permeability rocks, making accurate analysis challenging, particularly for tight shale gas and tight shale oil reservoirs.
Innovation Solution
A rock and fluid sampling tool with a vessel filled with a hydrogen-free fluid is used to collect and preserve core samples, maintaining original reservoir pressure and preventing fluid expulsion by displacing the hydrogen-free fluid with the core samples and sealing the vessel with a gas, allowing for imaging and analysis at reservoir conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing techniques are used to obtain core samples from reservoirs, then core samples can be retrieved for analysis, but the rocks and fluids in the sample are stressed causing changes in rock properties, fluid properties, and fluid compositions
Solution Approach 1:
The patent uses a hydrogen-free fluid (such as fluorocarbon-based fluid) as an inert environment to displace native fluids during core sample retrieval. This inert fluid prevents chemical reactions and maintains the stability of original rock and fluid properties while allowing the core sample to be brought to the surface for analysis without alteration of its compositional characteristics
Solution Approach 2:
The hydrogen-free fluid acts as an intermediary substance between the core sample and the external environment. It replaces native fluids in the pore spaces during retrieval, serving as a mediator that protects the original fluid compositions from stress-induced changes while enabling safe transport and analysis of the core sample
2Measurement precision
If core samples from tight shale gas and tight shale oil reservoirs are retrieved to the surface, then analysis can be performed, but volatile fluids and highly compressible gases expand during depressurization further impacting analysis
Solution Approach 1:
The hydrogen-free inert fluid provides a stable environment that prevents expansion and phase changes of volatile fluids and compressible gases during retrieval. By maintaining reservoir pressure conditions through this inert medium, the original fluid compositions remain unchanged, enabling accurate determination of gas-in-place and other fluid properties
Solution Approach 2:
The patent applies beforehand cushioning by pre-filling the retrieval system with hydrogen-free fluid at reservoir pressure before core sample insertion. This creates a pressure buffer that cushions against sudden expansion of volatile fluids and gases during depressurization, maintaining compositional stability throughout the retrieval process
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 method effectively preserves original pore fluids and rock properties, enabling accurate imaging and analysis of core samples, including hydrocarbons-in-place determination, while minimizing contamination and depressurization effects.
Implementation Method 1
The vessel is filled with a hydrogen-free fluid. The one or more core samples are deposited in the vessel such that a portion of the hydrogen-free fluid is displaced by the one or more core samples and the one or more core samples are immersed in the hydrogen-free fluid
Implementation Method 2
transferring a gas into the vessel to fill the unoccupied space and sealing the vessel via a cap on an end of the vessel. Sealing the vessel via the cap produces a pressurized vessel at a pressure value
Implementation Method 3
imaging at least one of the one or more core samples in the pressurized vessel using at least one of neutron imaging, X-ray imaging, and nuclear magnetic resonance imaging
Implementation Method 4
The vessel includes a eutectic metal component
Data Source
AI summary
Provided herein are methods and apparatus for collecting and preserving core samples from a reservoir. In some embodiments, a method includes obtaining core samples from a reservoir using a rock and fluid sampling tool and depositing the core samples in a vessel filled with a hydrogen-free fluid such that a portion of the hydrogen-free fluid is displaced by the core samples and the core samples are immersed in the hydrogen-free fluid. The method also includes transferring a gas into the vessel to occupy a space in the vessel and sealing the vessel via a cap on an end of the vessel. Methods of analyzing the core samples core samples collected from a reservoir and a rock and fluid sampling tool are also provided.