Unconventional Core Resaturation via Porous Plug Mediator
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Solution Overview
Problem
The analysis of unconventional core samples is hindered by the loss of formation fluids during transportation to the surface, leading to non-representative measurements, and existing resaturation methods are inadequate due to high capillary pressure in small pores.
Innovation Solution
An apparatus and workflow for resaturating unconventional core samples with formation fluids at high pressures, combined with petrophysical analysis using 2D NMR T1-T2 experiments, to accurately characterize the core sample and reservoir rock properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high pressure resaturation is used to overcome capillary pressure in small pores, then fluid saturation is improved, but equipment complexity and operational difficulty increase
Solution Approach 1:
A porous plug is introduced as an intermediary component between the core sample and the resaturation system. The porous plug has pore sizes larger than the core sample pores, allowing it to be saturated at lower pressures while still enabling fluid to enter the core sample's small pores through capillary action, thus mediating the high pressure requirement
Solution Approach 2:
The patent replaces direct high-pressure mechanical injection into the core sample with a two-stage process: first saturating the porous plug at lower pressure, then allowing capillary forces to drive fluid into the core sample. This substitutes direct mechanical forcing with a combination of lower-pressure mechanics and capillary action
2Device complexity
If conventional low pressure resaturation methods are used, then equipment complexity is reduced, but fluid saturation of small pores is insufficient
Solution Approach 1:
The porous plug acts as an intermediary that can be saturated at conventional low pressures, then serves as a fluid source that delivers saturation to the core sample through capillary action, enabling low-pressure equipment to achieve high-pressure resaturation results
Solution Approach 2:
The patent changes the pore size parameter of the saturation medium by using a porous plug with larger pores than the core sample. This parameter change allows the plug to be saturated at lower pressures while still enabling fluid transfer to the smaller pores of the core sample through capillary pressure gradients
3Measurement precision
If formation fluids are lost during transportation, then measurement accuracy deteriorates, but resaturation procedures are needed to restore in-situ conditions
Solution Approach 1:
The core sample is saturated with formation fluids before transportation and analysis. This preliminary saturation action ensures that the sample is in its in-situ fluid state during measurements, eliminating the need for post-transportation resaturation procedures and maintaining measurement accuracy
Solution Approach 2:
The patent applies a coating or protective treatment to the core sample before transportation to prevent fluid loss. This beforehand cushioning protects the sample from the harmful effect of fluid depletion during transport, maintaining its in-situ fluid content for accurate measurements
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 representative analysis of unconventional core samples by effectively resaturating them with formation fluids at in-situ conditions, allowing for accurate determination of petrophysical properties and improved characterization of tight hydrocarbon reservoirs.
Implementation Method 1
the high capillary pressure of the core sample due to the presence of relatively small pores. Therefore, routine core resaturation methods at low pressures, such as centrifuge-based techniques used for conventional cores, are inadequate to introduce the formation fluid into the small pores of the unconventional core sample
Implementation Method 2
Nuclear magnetic resonance (NMR) core analysis applications have been shown to be useful for the characterization of fluids in shale formations
Data Source
AI summary
A method for testing an unconventional core sample is provided. The method involves loading the unconventional core sample into a sample holder and introducing fluid into the sample holder at an elevated pressure such that fluid is injected into the internal pore space of the unconventional core sample in order to resaturate the unconventional core sample with the fluid, wherein the fluid is selected from the group including a hydrocarbon fluid and a water-based formation fluid. An apparatus and a system used in combination with the method are also provided.