Low-Field NMR Module Using Gradient Magnetic Fields
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Solution Overview
Problem
Nuclear magnetic resonance (NMR) tools face challenges in accurately sampling reservoir fluids, especially in low permeability formations and unconsolidated sand formations, due to difficulties in replicating native formation fluids and maintaining sample integrity during extraction.
Innovation Solution
A flexible, low-field NMR module using magnetic gradient fields is designed, allowing for a robust and cost-effective NMR apparatus that can provide a non-uniform magnetic field with a known gradient, suitable for various applications, including down-hole side-wall coring tools and manufacturing process controllers, enabling in situ measurements with minimal sample damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional high-field NMR apparatus are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the magnetic field parameter from uniform to non-uniform with a known gradient, enabling low-field NMR measurements while maintaining sufficient signal-to-noise ratio for diffusion and relaxation time measurements
Solution Approach 2:
Instead of using strong uniform magnetic fields as in traditional NMR, the patent inverts the approach by using weak non-uniform magnetic fields with known gradients, achieving measurements through a fundamentally different physical regime
2Device complexity
If magnetic field strength is reduced, then device cost and complexity are reduced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent changes the magnetic field configuration from uniform to non-uniform with a known gradient, allowing low-field operation while maintaining measurement capability through exploitation of the gradient for diffusion and relaxation measurements
Solution Approach 2:
The magnet assembly uses composite construction with permanent magnets and pole pieces made of different materials to generate the specific non-uniform field pattern with known gradient required for low-field NMR measurements
3Measurement precision
If uniform magnetic fields are used, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the field uniformity parameter by intentionally designing a non-uniform field with a known gradient, which is easier to manufacture using permanent magnets and pole pieces without requiring expensive precision uniformity control
Solution Approach 2:
The magnet assembly uses relatively inexpensive permanent magnets and pole pieces to create the required field configuration, avoiding the need for expensive electromagnets and precision uniformity adjustment mechanisms
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
The NMR module achieves a sufficient signal-to-noise ratio for desired measurements while maintaining a low magnetic field strength, allowing for accurate analysis of fluid properties and chemical compositions without pressure and temperature changes, thus overcoming the limitations of traditional sampling methods.
Implementation Method 1
a magnet assembly disposed about the sample chamber and constructed and arranged to provide a non-uniform magnetic field having a known magnetic field gradient inside the sample chamber
Implementation Method 2
a radio frequency (RF) coil positioned so as to substantially surround the sample chamber, and a controller coupled to the RF coil and constructed and arranged to control the RF coil to produce an RF pulse sequence
Implementation Method 3
causing the magnetic moments of nuclei ('spins') in a formation to precess about an axis. The axis about which the nuclei precess may be established by applying a strong, polarizing, static magnetic field (B0) to the sample to align the proton spins
Data Source
AI summary
A nuclear magnetic resonance apparatus that may be used in connection with a variety of different tools, including a down-hole side-wall coring tool as well as with manufacturing process controllers. In one embodiment, the nuclear magnetic resonance apparatus may include a magnet assembly constructed around a sample chamber. The magnet assembly is constructed and arranged to provide a non-uniform magnetic field having a known magnetic field gradient inside the sample chamber. The use of gradient fields may allow for a more flexible and robust magnet assembly design that may be suitable for a variety of different applications.