Low-Field NMR Pore Volume Compressibility Measurement
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Solution Overview
Problem
Conventional methods for measuring pore volume compressibility in inhomogeneous, fractured, and vuggy rocks are inaccurate due to their inability to apply different compressibilities to various secondary porosities, leading to unsatisfactory results and destructive testing.
Innovation Solution
A method involving saturation of rock samples with deuterium oxide (D2O) followed by centrifugation and low-field 1H nuclear magnetic resonance (NMR) measurements to determine pore volumes associated with secondary porosities, allowing for accurate characterization of pore volume compressibility in naturally fractured reservoirs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods (USC testing, PPD, CPP protocols, hydrostatic tests) are used to measure pore volume compressibility, then the measurement process is simple and straightforward, but the accuracy is reduced in inhomogeneous, fractured, and vuggy rocks
Solution Approach 1:
The patent segments the pore space into primary porosity and secondary porosity components, allowing separate measurement and characterization of each. This segmentation enables accurate measurement of pore volume compressibility in inhomogeneous, fractured, and vuggy rocks by treating different pore types independently rather than as a homogeneous system.
Solution Approach 2:
The patent uses mercury as an intermediary fluid to infiltrate and measure secondary porosity. By injecting mercury at controlled pressures and measuring its intrusion into secondary pores, the system can accurately characterize pore volume compressibility without directly measuring the complex heterogeneous pore structure itself.
2Measurement precision
If conventional destructive testing methods are used, then the measurement can be completed, but the rock sample is destroyed and cannot be reused
Solution Approach 1:
The patent replaces destructive mechanical testing methods with non-destructive nuclear magnetic resonance (NMR) imaging and mercury injection techniques. These methods allow measurement of pore volume compressibility and secondary porosity characterization without physically destroying the rock sample, enabling sample preservation and potential reuse.
3Ease of operation
If conventional methods are applied to inhomogeneous, fractured, and vuggy rocks, then the testing process is straightforward, but the results are unsatisfactory due to inability to account for different secondary porosities
Solution Approach 1:
The patent segments the pore system into primary and secondary porosity components, with secondary porosity further divided into fractures and vugs. This segmentation allows the application of different compressibility values to different pore types, significantly improving measurement accuracy in inhomogeneous rocks while maintaining a systematic testing approach.
Solution Approach 2:
The patent applies different compressibility parameters to different pore types based on their geological characteristics. By assigning specific compressibility values to fractures, vugs, and primary pores separately, the method accurately reflects the heterogeneous nature of the rock system while maintaining operational simplicity through standardized measurement protocols.
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 provides accurate and non-destructive measurement of pore volume compressibility, enhancing the characterization of secondary porosity and improving the prediction of recovery rates in oil and gas reservoirs, particularly in heterogeneous fractured reservoirs.
Implementation Method 1
saturating a rock sample with deuterium oxide (D2O)
Implementation Method 2
centrifuging the rock sample at a first selected rotational speed in the presence of a second fluid to displace a portion of the D2O in the rock sample with the second fluid
Implementation Method 3
measuring the rock sample with low-field 1H nuclear magnetic resonance (NMR) to determine a first volume of the second fluid within the rock sample
Data Source
AI summary
Systems, methods, and apparatuses for determining pore volume and pore volume compressibility of secondary porosity in rock samples is disclosed. In some implementations, determining a pore volume of a secondary porosity in a rock core sample may include saturating the rock sample with deuterium oxide (D2O) by applying a vacuum to the core sample covered by D2O; centrifuging the saturated rock sample at a selected rotational speed in the presence of a second fluid to displace a portion of the D2O from the rock sample with the second fluid; measuring the rock sample with low-field 1H nuclear magnetic resonance (NMR) to determine a volume of the second fluid within the rock sample; and determining a pore volume associated with a secondary porosity based on the volume of the second fluid within the rock sample.