Pulsed Neutron Logging Vertical Resolution Thin Beds
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Solution Overview
Problem
Conventional oil well logging methods provide insufficient vertical resolution for accurately identifying thinly bedded formations, as neutron logging typically offers a coarse vertical resolution that cannot locate boundaries of thin beds less than one foot in thickness.
Innovation Solution
The method enhances the vertical resolution of radiation-based logging tools by using a pulsed neutron generator and a single scintillation detector with neutron shielding, distributing inelastic and capture spectra into 256 channels to obtain elemental yields and convert them into dry elemental weight fractions, combining mineralogical and sedimentological information to create high-resolution mineralogy logs, matrix density logs, and total porosity logs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional neutron logging tools are used, then the tool structure is simple and easy to operate, but the vertical resolution is coarse and cannot locate boundaries of thin beds less than one foot in thickness
Solution Approach 1:
The patent segments the borehole into multiple depth intervals and assigns different detector configurations to different segments. Standard resolution detectors are used in intervals with thick beds, while high resolution detectors are deployed in intervals containing thin beds, optimizing both resolution and operational simplicity across the entire borehole.
Solution Approach 2:
The patent employs a dynamic detector system that can change its configuration during logging operations. The tool can switch between standard resolution and high resolution detector modes, and can dynamically adjust detector spacing and positioning to match the geological characteristics of different depth intervals, thereby adapting resolution to operational needs.
2Measurement precision
If high resolution measurements are obtained throughout the entire borehole, then the vertical resolution is improved, but the logging time and data processing complexity increase significantly
Solution Approach 1:
The patent applies high measurement quality (high resolution) only to specific local intervals where thin beds are present, while using standard resolution in intervals with thick beds. This localized approach to quality enhancement reduces overall logging time and data processing complexity while maintaining high resolution where it is most needed for accurate thin bed identification.
Solution Approach 2:
Instead of applying high resolution measurements throughout the entire borehole (excessive action), the patent uses high resolution measurements only partially in intervals where thin beds are detected or suspected. This partial application of high resolution measurement reduces time loss and processing complexity while still achieving the goal of accurate thin bed characterization where required.
3Measurement precision
If multiple detectors are used to improve resolution, then measurement precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent uses a dynamic detector system where the number and configuration of detectors can change during logging operations. The tool can deploy multiple detectors in high resolution mode when thin beds are detected, and reduce to fewer detectors in standard resolution mode for thick bed intervals, thereby managing device complexity dynamically rather than statically.
Solution Approach 2:
The patent designs detectors with multi-functional capabilities that can operate in different modes (standard resolution and high resolution) depending on the geological context. This universality allows the same detector hardware to serve multiple functions, reducing the need for specialized detectors for different scenarios and thereby controlling overall device complexity.
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 evaluation of petroleum potential in thinly bedded formations by providing high-resolution images of lithological compositions, enabling the identification of multiple lithologies within thin intervals and improving the estimation of net-to-gross and net pay in these formations.
Implementation Method 1
The radiation may be induced by neutron irradiation
Implementation Method 2
a single scintillation detector with neutron shielding
Implementation Method 3
a single scintillation detector with neutron shielding
Implementation Method 4
using radiation from the formation measured in the borehole
Data Source
AI summary
Methods, systems, and devices for evaluating an earth formation intersected by a borehole using information from standard resolution measurements. Methods include generating an image representative of the formation over an interval of borehole depth, the image having a second resolution greater than the first resolution. Generating the image may be carried out by identifying layers corresponding to lithotype facies within the interval, the layers defined by boundaries having boundary locations along the borehole; and using a unified characterization of the formation within the interval determined from the standard resolution measurements and the boundary locations within the interval to solve for a value for the formation parameter corresponding to each layer consistent with the unified characterization of the interval. The unified characterization may be an average value for the formation parameter within the interval.