Downhole NMR Calibration Using Digital Rock Physics on Cuttings
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Solution Overview
Problem
Current downhole nuclear magnetic resonance (NMR) logging methods require extensive and costly laboratory calibration using well cores, which is time-consuming and may not accurately represent in-situ conditions, especially for shale reservoirs where core analysis can be damaged and permeability estimates are uncertain.
Innovation Solution
Combining NMR analysis with digital rock physics (DRP) analysis using drilling cuttings to validate and characterize rock properties, allowing for rapid calibration of porosity, pore size distribution, and permeability estimates without the need for core extraction, by segmenting digital images of cuttings and comparing them with in-situ NMR measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If well core extraction and laboratory analysis are used for NMR calibration, then measurement precision is improved, but loss of time and productivity deteriorate significantly
Solution Approach 1:
The patent performs digital rock physics simulations and virtual core analysis in advance to establish calibration relationships before actual NMR logging. By pre-processing rock samples digitally and creating lookup tables or calibration curves beforehand, the system eliminates the need for time-consuming physical core extraction and laboratory analysis during field operations, thus resolving the time-loss contradiction while maintaining measurement precision.
Solution Approach 2:
The patent creates digital copies of rock cores through high-resolution scanning and 3D reconstruction, then performs virtual analysis on these digital replicas. This digital copying approach replaces physical core handling and laboratory transport with computational simulations, achieving the same calibration precision without the time loss associated with physical sample processing and shipping.
2Measurement precision
If multiple well cores are extracted for calibration, then measurement precision improves, but device complexity and operational difficulty increase
Solution Approach 1:
The patent replaces the mechanical core extraction and handling system with a digital simulation system. Instead of physically extracting, transporting, and processing multiple rock cores through complex laboratory equipment, the system uses computational models and digital rock physics to perform virtual calibration, thereby eliminating the mechanical complexity while maintaining or improving measurement precision through repeated virtual simulations.
3Measurement precision
If large sized core samples are used for laboratory analysis, then measurement precision is improved, but ease of operation and productivity worsen due to handling difficulties
Solution Approach 1:
The patent creates digital replicas of large core samples through scanning technology, allowing virtual analysis of the complete sample structure without physical handling. This digital copying enables precise measurement of pore structures and rock properties while eliminating the operational difficulties of transporting and manipulating large, heavy core samples in the laboratory.
Solution Approach 2:
The patent transitions from physical three-dimensional core sample handling to digital three-dimensional virtual space analysis. By converting physical samples into digital models, the system maintains the full spatial resolution and measurement precision of large samples while operating in a virtual dimension where handling, storage, and analysis become computationally efficient rather than physically cumbersome.
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 enables rapid turnaround of NMR logging results, reducing the need for core extraction and providing more accurate and timely characterization of rock properties, improving the interpretation and value of NMR logs, and allowing for optimized logging speed based on real-time data.
Implementation Method 1
nuclear magnetic resonance (NMR) tools have been used to explore the subsurface based on the magnetic interactions with subsurface material. Some downhole NMR tools include a magnet assembly that produces a static magnetic field, and a coil assembly that generates radio frequency (RF) control signals and detects magnetic resonance phenomena in the subsurface material.
Implementation Method 2
The magnetic moments of the nuclei tend to align along the direction of the applied magnetic field (B0). The nuclei then precess around at a characteristic rate defined by: ω=−γB0 where ω is referred to as the Larmor frequency and γ is the gyromagnetic ratio
Implementation Method 3
This is done by using an antenna to apply a radio frequency (rf) pulse at the Larmor frequency to tip the magnetic moments away from B0. As the nuclei's magnetic moments precess around the applied magnetic field, they induced a voltage in an antenna (either the same one that excited the system or a different one specifically for detection) that is measured as the NMR signal.
Implementation Method 4
The nuclei then precess around at a characteristic rate defined by: ω=−γB0 where ω is referred to as the Larmor frequency and γ is the gyromagnetic ratio, a fundamental constant specific to each NMR active isotope.
Data Source
AI summary
A method for combining nuclear magnetic resonance (NMR) analysis and digital rock physics (DRP) analysis based on drilling cuttings or other rock samples for improved downhole nuclear magnetic resonance validation and characterization. A system for performing the method also is provided.