Azimuthal Elemental Imaging Using Pulsed Neutron Logging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current geological exploration methods in wellbores provide limited information about the mineral composition of earth formations, which is crucial for complete lithologic characterization, especially when using measurement-while-drilling (MWD) techniques.
Innovation Solution
A logging tool with a pulsed neutron source and gamma ray detectors that processes measurements to estimate elemental composition and determine the fraction of possible mineral constituents, such as dolomite, limestone, and shale, without requiring a shale volume estimate, using constrained optimization and spectral decomposition techniques to produce detailed mineral composition images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If conventional imaging methods (electrical, acoustic, gamma ray, density measurements) are used to produce borehole wall images, then structural information about the earth formation is revealed, but little or no information about the formation mineral composition is provided
Solution Approach 1:
The measurement process is segmented into multiple discrete neutron energy groups (thermal, epithermal, fast neutrons) and multiple gamma-ray energy windows. Each segment captures specific nuclear interactions with different elements, allowing mineral composition to be determined through composited measurements without requiring a single complex instrument
Solution Approach 2:
The logging tool is designed with multi-functional capabilities: it measures neutron moderation (for hydrogen content), neutron capture gamma rays (for elemental identification), and inelastic scattering gamma rays (for mineralogical information). This universal tool replaces multiple separate logging tools and provides both structural and compositional information simultaneously
2Loss of time
If measurement-while-drilling (MWD) techniques are used to obtain formation information during drilling, then information is available earlier before formation damage by drilling mud invasion, but complete lithologic characterization including mineral composition remains limited
Solution Approach 1:
The logging tool performs preliminary measurements of neutron-gamma interactions and gamma-ray spectra during the drilling process itself, before the wellbore is completed and before any wireline logging is conducted. This preliminary action captures formation composition data at the optimal time when formation damage has not yet occurred
Solution Approach 2:
The system measures changes in neutron energy parameters (moderation from fast to thermal) and gamma-ray energy spectra characteristics. By analyzing how these parameters change with different mineral compositions, the system achieves complete lithologic characterization during drilling without requiring separate post-drilling logging runs
3Loss of information
If separate wireline logging runs are conducted after drilling to obtain complete formation evaluation data, then comprehensive formation parameters are obtained, but time and cost are increased
Solution Approach 1:
The patent merges the drilling operation with the logging operation by integrating the logging tool into the bottomhole assembly. Multiple measurement functions (neutron moderation, capture gamma-ray spectroscopy, inelastic scattering) are combined into a single tool that operates during drilling, eliminating the need for separate wireline logging runs and providing complete formation evaluation data in real-time
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 more complete lithologic characterization of earth formations during drilling, providing valuable information for reservoir navigation, diagenesis analysis, and potential reservoir identification, thereby improving hydrocarbon recovery and reducing the need for separate wireline logging.
Implementation Method 1
a pulsed neutron source configured to propagate neutrons into the earth formation, and the measurements are made by at least one detector spaced apart from the source of neutrons configured to measure gamma rays resulting from interaction of the neutrons with nuclei in the earth formation
Implementation Method 2
The at least one processor is configured to determine the elemental composition by further determining (i) a capture spectrum of gamma rays, and (ii) an inelastic spectrum of gamma rays
Implementation Method 3
The at least one processor is configured to determine the elemental composition by further determining (i) a capture spectrum of gamma rays, and (ii) an inelastic spectrum of gamma rays
Data Source
AI summary
Measurements made by a pulsed neutron tool with two or more gamma ray detectors are used to provide a mineralogical and/or elemental image of the formation. This may be used in reservoir navigation and in furthering the understanding of the geology of the prospect. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).