NMR Imbibition Model for Tight Reservoir Volume-Time Prediction
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Solution Overview
Problem
Existing imbibition models for tight reservoirs, such as shales, face challenges in accurately determining permeability and capillary pressure, leading to poor understanding of imbibition behavior and its impact on hydraulic fracturing processes.
Innovation Solution
A modified mathematical model using NMR T2 distributions and the Handy relationship to calculate imbibition permeability and average pore pressure, overcoming limitations of traditional methods by incorporating imbibition permeability Kimb and average pore pressure Pave.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional methods are used to calculate porosity, permeability and mineral composition data, then the calculation process is simplified, but the accuracy of physical parameters for tight reservoirs is not high
Solution Approach 1:
The patent replaces traditional mechanical experimental methods with NMR (nuclear magnetic resonance) technology to obtain porosity, permeability, and fluid distribution data. This substitution enables non-destructive, high-precision measurement of physical parameters in tight reservoirs without requiring complex physical experiments, thereby improving measurement precision while maintaining computational efficiency.
Solution Approach 2:
The patent utilizes NMR T2 relaxation time parameters to characterize pore size distribution and fluid properties. By changing from traditional physical measurement parameters to NMR-based parameters, the method achieves higher accuracy in determining porosity and permeability for tight reservoirs with low to ultra-low permeability.
2Adaptability or versatility
If Handy relationship is applied to conventional porous media, then the imbibition model is well-established, but the definition of capillary pressure and permeability is unclear for complex porous media like shales
Solution Approach 1:
The patent introduces NMR T2 distributions as an intermediary to bridge the gap between traditional Handy relationship and complex porous media characteristics. The NMR data serves as a mediator to define and quantify capillary pressure and permeability in shales, making the Handy relationship applicable to complex media while maintaining clear parameter definitions.
Solution Approach 2:
The patent applies local quality by using NMR T2 distributions to capture the heterogeneous pore structure characteristics of tight reservoirs. Instead of using bulk average properties, the method characterizes local pore size distribution and fluid properties, enabling accurate definition of capillary pressure and permeability for complex porous media.
3Measurement precision
If NMR T2 data is used to characterize porosity, permeability and fluid transport, then fluid distribution and migration characteristics are directly reflected, but the device complexity and measurement complexity increase
Solution Approach 1:
The patent replaces complex mechanical measurement systems with NMR technology, which uses electromagnetic fields to probe fluid distribution and migration. This substitution provides direct observation of fluid characteristics in porous media without requiring invasive mechanical probes or complex experimental setups, thereby improving measurement precision while the increased device complexity is offset by the non-destructive and comprehensive nature of NMR.
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
Provides a comprehensive model to simulate imbibition volume versus time, enhancing the evaluation of fracturing fluid migration and imbibition behavior in tight reservoirs, applicable to petroleum engineering and other porous media.
Implementation Method 1
nuclear magnetic resonance (NMR) have been widely used to characterize the porosity, permeability and fluid transport in porous media, and the pore size distribution analysis based on NMR T2 spectra has become a popular method to study imbibition behavior in porous media
Implementation Method 2
centrifuging the first rock core plug sample and recording changes of weight and nuclear magnetic resonance (NMR) T2 distributions to obtain water distribution characteristics
Implementation Method 3
Spontaneous imbibition is a natural phenomenon that the wetting phase fluid flows into the pores in porous media driven by capillary force
Data Source
AI summary
A method for establishing mathematical model of relationship between spontaneous imbibition volume and time of porous medium includes sample pretreatment, fully-saturation and centrifugal experiments and NMR T2 measurement. First, two rock core samples of predetermined size are selected for cleaning and drying. The first rock sample is vacuumed and injected with water to obtain a saturated sample for NMR T2 measurement. Then, spontaneous imbibition experiment is conducted on another sample, and T2 measurements are conducted to obtain the water distribution and migration characteristics during the imbibition process. Next, the calculation of the imbibition permeability, average capillary pressure and surface relaxivity are conducted based on the NMR data obtained from two samples. Finally, substitute these parameters into the Handy relationship to obtain a new NMR-based mathematical spontaneous imbibition model.