Neutron Porosity Modeling for Complex Geologic Formations
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Solution Overview
Problem
Existing methods for determining neutron porosity in geologic formations are limited by assumptions about the matrix and pore fluid type, leading to inaccuracies in subsurface structure interpretation and resource extraction models.
Innovation Solution
A system and method utilizing a simulation component that processes seismic and well data through a framework like PETREL, incorporating object-based modeling and meshless techniques to construct detailed geologic models, enhancing the accuracy of neutron porosity logs and improving subsurface characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional neutron porosity logging tools are used, then measurement capability is limited to basic porosity, but measurement precision and applicability to complex formations deteriorate
Solution Approach 1:
The tool segments the measurement process by using multiple independent neutron sources (fast neutron source and thermal neutron source) and multiple detectors positioned at different locations. Each source-detector pair measures specific parameters, and the results are combined to achieve comprehensive formation characterization with high precision across various formation types.
Solution Approach 2:
The tool achieves multi-functionality by integrating multiple neutron sources and detectors that can measure various formation parameters including porosity, hydrogen index, chlorine content, and lithology. This universal measurement capability allows the same tool to accurately characterize different formation types (sandstone, limestone, dolomite, anhydrite) without requiring multiple specialized tools.
2Measurement precision
If multiple neutron sources and detectors are used, then measurement capability and precision improve, but device complexity increases
Solution Approach 1:
The tool merges multiple neutron sources (fast neutron source and thermal neutron source) and multiple detectors into a single integrated logging tool assembly. The sources and detectors are positioned in specific geometric arrangements within the tool body, combining their functions to achieve comprehensive formation measurement while maintaining a unified tool structure that can be deployed as a single unit.
3Adaptability or versatility
If fast neutron source and thermal neutron source are used together, then measurement versatility improves, but energy consumption and safety concerns worsen
Solution Approach 1:
The tool employs periodic action by alternately activating the fast neutron source and thermal neutron source during the logging process. The fast neutron source is activated first to measure fast neutron parameters, then the thermal neutron source is activated to measure thermal neutron parameters. This periodic activation of different sources reduces cumulative energy consumption and minimizes safety concerns compared to continuous operation of all sources, while still achieving comprehensive measurement versatility.
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
Enhances the precision of neutron porosity measurements by accounting for various formation factors, allowing for more accurate interpretation of subsurface structures and improved resource extraction models.
Implementation Method 1
a fast neutron source positioned in the tool to emit neutrons into the formation and a first detector to detect scattered neutrons
Implementation Method 2
a thermal neutron source positioned in the tool to emit neutrons into the formation and a second detector to detect absorbed neutrons
Data Source
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AI summary
A method can include receiving neutron data and density data for a borehole in a geologic formation; determining a migration length value for a layer of the geologic formation based at least in part on the neutron data; forward modeling at least the layer based at least in part on the migration length value and the density data; and outputting, based at least in part on the forward modeling, modeled neutron data for the layer.