NMR Echo Time Analysis for Shale Organic Content
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional NMR techniques are unable to accurately determine parameters such as kerogen content, bitumen content, and total organic content (TOC) in unconventional reservoirs like shale formations due to short T2 relaxation times, which are below the detection limit of conventional methods.
Innovation Solution
The use of high-field NMR systems capable of detecting NMR signals with echo times of less than or equal to 100 microseconds, allowing for the analysis of T2 relaxation time spectra to determine organic hydrogen content, including kerogen, bitumen, and oil content, through specific pulse sequences and processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional NMR techniques are used, then the equipment complexity is low and ease of operation is maintained, but the measurement precision is insufficient for detecting short T2 relaxation times below 0.03 seconds
Solution Approach 1:
The patent applies parameter changes by modifying the echo time parameter to 100 microseconds or less, which enables detection of short T2 relaxation times in unconventional reservoirs. This parameter adjustment allows conventional NMR equipment to detect signals that were previously undetectable, thereby improving measurement precision without requiring fundamentally new equipment
Solution Approach 2:
The patent uses partial action by focusing NMR measurement on specific short echo time ranges (≤100 microseconds) rather than attempting to measure all relaxation times. This selective approach enables detection of kerogen and bitumen signals without requiring the full capabilities of advanced NMR systems, resolving the contradiction between measurement precision and device complexity
2Measurement precision
If conventional NMR techniques with longer echo times are used, then the signal detection is easier, but the ability to characterize organic constituents in unconventional reservoirs is lost
Solution Approach 1:
The patent changes the echo time parameter to extremely short durations (≤100 microseconds), which matches the short T2 relaxation times of kerogen and bitumen in unconventional reservoirs. This parameter change enables accurate characterization of organic constituents that were previously undetectable with conventional longer echo times
Solution Approach 2:
The patent replaces conventional NMR measurement approaches with a modified pulse sequence design that uses short echo times. This substitution of the measurement mechanism enables detection of fast-relaxing signals from organic matter without requiring more complex detection hardware
3Measurement precision
If short echo times of 100 microseconds or less are used, then the detection of organic hydrogen content is enabled, but the measurement process becomes more difficult and requires specialized processing
Solution Approach 1:
The patent applies preliminary action by using specific pulse sequences designed to generate detectable echoes at very short times (≤100 microseconds). These pre-planned pulse sequences account for the short relaxation times of organic constituents, enabling accurate measurement of organic hydrogen content before standard processing is applied
Solution Approach 2:
The patent uses specialized processing techniques as intermediaries to bridge the gap between short echo time measurements and accurate organic hydrogen content determination. These processing methods translate the difficult-to-detect short echo signals into reliable quantitative measurements of kerogen, bitumen, and oil content
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 accurate characterization of organic hydrogen content in shale formations by detecting short T2 relaxation times associated with kerogen and bitumen, improving the evaluation of unconventional reservoirs and their producibility.
Implementation Method 1
An NMR measurement includes applying a static magnetic field to the substance. The static magnetic field generates an initial magnetization of atomic nuclei within the substance.
Implementation Method 2
an oscillating magnetic field is applied at a particular frequency to the substance. The oscillating field is composed of a sequence of radio frequency (RF) pulses that tip the magnetization of the atomic nuclei away from the initial magnetization.
Implementation Method 3
The sequence of pulses can be arranged so that the pulses and the static field interact with the nuclei to produce a NMR signal composed of 'echoes' within at least a portion of the substance. The NMR signal is detected
Data Source
AI summary
Methods for analyzing a formation samples using nuclear magnetic resonance (NMR) are described herein. One method includes performing an NMR measurement of the formation sample to obtain NMR data. The NMR measurement detects NMR signals with echo times of less than or equal to 100 microseconds. The NMR data is analyzed to determine a measure of organic hydrogen content of the formation sample, such as (i) total organic hydrogen content, (ii) kerogen content, (iii) bitumen content, and/or (iv) oil content.