Rock Sample Characterization Using Combined NMR and IR Spectroscopy
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Solution Overview
Problem
Current methods for characterizing subterranean formations, particularly in highly-deviated wells, are challenging due to the length and conditions of these wells, leading to incomplete reservoir characterization and poor completion quality assessments.
Innovation Solution
The proposed solution involves performing Nuclear Magnetic Resonance (NMR) measurements and Infrared (IR) spectroscopy measurements on rock samples from subterranean formations to determine properties such as pore volume, matrix density, and porosity, which are then used to assess reservoir quality and completion quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional wireline logging tools are used in highly-deviated wells, then reservoir parameters can be measured, but the length and conditions of these wells make measurements challenging and not economically viable
Solution Approach 1:
The patent replaces traditional mechanical wireline logging tools with a drilling while logging (DWL) system that integrates measurement capabilities directly into the drilling apparatus. This substitution eliminates the need to convey complex logging tools through highly-deviated wellbores, as measurements are taken during the drilling process itself when the drill string is already in place.
Solution Approach 2:
The drilling apparatus is equipped with multiple measurement tools that can characterize reservoir properties including porosity, permeability, mineralogy, and fluid saturation. This multi-functional system performs both drilling and comprehensive reservoir characterization in a single operation, eliminating the need for separate logging operations.
2Loss of information
If multiple vertical wells are placed across the extent of the basin, then formation properties can be determined, but this indirect method fails to capture the variation in porosity and fluid types, insoluble hydrocarbon concentrations, mineralogy, and clay-volumes laterally
Solution Approach 1:
The patent transitions from a vertical well approach to a lateral well approach, utilizing the horizontal dimension to traverse through the reservoir. This allows direct sampling and measurement of lateral variations in reservoir properties including porosity, fluid types, and mineralogy across the basin extent, rather than inferring lateral variations from multiple vertical well data.
Solution Approach 2:
The system performs reservoir characterization measurements during the drilling process itself, before completion operations. This preliminary characterization provides accurate lateral variation data that informs subsequent completion and stimulation strategies, eliminating the need for multiple vertical wells to map reservoir heterogeneity.
3Measurement precision
If NMR measurements are performed on rock core samples, then pore volume and porosity can be determined, but the samples must be trimmed and surface ground to fit in the NMR probe, resulting in a high filling factor requirement
Solution Approach 1:
The patent uses small rock fragments or cuttings (e.g., 0.5-5 mm particles) instead of large core samples. This segmentation allows the use of smaller NMR probes that do not require extensive sample preparation, trimming, or surface grinding, while still providing accurate porosity and pore volume measurements representative of the bulk rock.
Solution Approach 2:
The patent employs low-field NMR technology operating at lower frequencies (e.g., 1-10 MHz) compared to traditional high-field systems. This parameter change allows for smaller probe sizes and reduced sample preparation requirements, as the lower field strength penetrates smaller samples effectively and provides sufficient signal-to-noise ratio for accurate measurements.
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 allows for accurate and efficient characterization of reservoir properties, even in data-poor environments, providing valuable insights into reservoir quality and completion quality, thereby optimizing well performance.
Implementation Method 1
performing an NMR measurement on the rock sample
Implementation Method 2
performing an IR spectroscopy measurement on the rock sample
Data Source
AI summary
Methods and systems are provided that combine NMR and IR spectroscopy measurements on a rock sample to determine data representing at least one property of the rock sample. In one embodiment, cuttings can be split into first and second lots. Results of an NMR measurement performed on the first lot of cuttings without cleaning can be analyzed to determine pore volume of the cuttings. Results of an IR spectroscopy measurement performed on the second lot of cuttings after solvent cleaning can be analyzed to determine matrix density of the cuttings. Porosity can be determined from the pore volume and matrix density of the cuttings. In another embodiment, combined NMR and IR spectroscopy measurements can be performed on an unprepared rock sample (without solvent cleaning) to characterize properties of kerogen in the rock sample and porosity. In another aspect, a method is provided that employs multi-nucleic NMR measurements to determine porosity.