NMR Sensors for Real-Time Fracture Volume and Orientation Tracking
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Solution Overview
Problem
Current downhole tools are unable to measure the initiation and propagation of formation fractures or the movement of fluids within fractures in real-time, providing limited information on fracture volume and orientation.
Innovation Solution
Integration of nuclear magnetic resonance (NMR) sensors with downhole tools to monitor fluids during injection processes, using contrast agents and MRI techniques, along with pressure monitoring, to provide real-time measurements of near-borehole fracture orientations and volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional downhole tools are used, then basic formation parameters can be measured, but real-time fracture initiation and propagation cannot be measured
Solution Approach 1:
The patent combines NMR logging tool capabilities with formation testing capabilities into a single integrated tool. This merging allows the tool to both inject fluids into the formation and simultaneously measure fracture properties using NMR, enabling real-time detection of fracture initiation and propagation that neither tool could achieve alone
Solution Approach 2:
The patent uses NMR contrast agents as intermediaries to enhance the detectability of injected fluids within fractures. These contrast agents modify the NMR relaxation times of the injected fluid, creating a detectable signal that allows real-time tracking of fluid movement and fracture propagation
2Loss of information
If formation testing is performed without NMR, then pressure data can be collected, but fluid movement within fractures cannot be tracked
Solution Approach 1:
The patent replaces conventional pressure-based fluid tracking with NMR-based detection. Instead of relying solely on pressure transients to infer fluid movement, the system uses NMR signals to directly detect the presence and movement of contrast agents in the injected fluid, providing direct observation of fluid movement within fractures
Solution Approach 2:
The patent uses NMR contrast agents that create detectable signal changes (analogous to color changes in visual detection) to track injected fluids. The contrast agents alter the NMR relaxation characteristics of the fluid, making it detectable against the background of formation fluids and enabling real-time tracking of fluid movement
3Measurement precision
If NMR tool provides sequence of radio frequency pulses to enhance measurement accuracy, then relaxation time measurement precision improves, but measurement time increases
Solution Approach 1:
The patent employs periodic radio frequency pulse sequences (such as CPMG sequences) to repeatedly invert and refocus spin phases. This periodic action generates multiple spin echo signals that can be averaged to improve measurement precision while the repeated measurements provide temporal information about fracture development
Solution Approach 2:
The patent maintains continuous NMR monitoring during the fluid injection process by continuously acquiring relaxation time data. This continuous measurement approach allows the system to track fracture initiation and propagation in real-time without interrupting the injection process, minimizing measurement time while maintaining precision
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 real-time measurement of fracture properties such as orientation and volume, enhancing the accuracy of formation and fracture property estimation by correlating NMR signal strength with pressure-time curves.
Implementation Method 1
nuclear magnetic resonance (NMR) logging tool. NMR tools operate by using an imposed static magnetic field, B0, to preferentially align certain nuclei and thereby produce a bulk magnetization
Implementation Method 2
using contrast agents and MRI techniques
Data Source
AI summary
Formation testing systems and methods may inject fluids into a formation to initiate fractures and facilitate measurements of various formation properties. In accordance with certain disclosed embodiments, the injection tools are further provided with nuclear magnetic resonance (NMR) sensors to monitor the injected fluids and provide measurements of near-borehole fracture orientations and volumes. Contrast agents and/or magnetic resonance imaging (MRI) techniques may be employed. The fluid injection may occur via an extendible isolation pad, via a fracturing jet, or via an injection port in an isolated region of the borehole. The systems may employ pressure monitoring in conjunction with the NMR sensors to further enhance estimates of formation and fracture properties.