Neutron Logging Proppant Detection Lithology Correction
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Solution Overview
Problem
Current methods for locating induced subterranean fractures in hydraulic fracturing operations are limited by logistical challenges, mechanical issues, and safety concerns associated with radioactive materials, leading to high costs and potential contamination, and lack the necessary depth and resolution for accurate fracture identification.
Innovation Solution
The use of a pulsed neutron capture tool or compensated neutron tool, which includes a thermal neutron source and detectors, to differentiate proppants in the formation from those in the wellbore by measuring changes in thermal neutron capture cross-sections and count rates before and after fracturing, allowing for the determination of fracture location and height without the need for radioactive materials or complex spectroscopy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radioactive materials are used to tag proppant for fracture location, then fracture identification capability is improved, but safety hazards and contamination risks increase
Solution Approach 1:
The patent replaces long-lived radioactive materials with short-lived isotopes (e.g., iodine-131 with 8-day half-life, sulfur-35 with 87-day half-life) that decay quickly after use. This eliminates long-term contamination risks while maintaining fracture identification capability during the measurement period. The radioactive tag is effectively disposable - used briefly then naturally eliminated.
Solution Approach 2:
The patent introduces a chemical intermediary approach using beta-emitting isotopes that can be detected through their interaction with the formation and borehole fluid. Instead of directly detecting gamma rays from strong radioactive sources, the method detects beta particles and their secondary effects, providing an intermediate detection mechanism that reduces safety hazards.
2Measurement precision
If complex spectroscopy equipment is used to detect proppant location, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the essential detection capability needed for fracture identification - beta particle detection - and eliminates complex gamma ray spectroscopy equipment. By using beta-emitting isotopes with distinct energy signatures, the method achieves accurate fracture location without requiring sophisticated spectral analysis instruments.
Solution Approach 2:
The patent employs simple, inexpensive detection equipment that can be deployed temporarily for the measurement campaign. The focus shifts from expensive, complex spectroscopy tools to simpler detectors that leverage the unique properties of short-lived radioactive isotopes, reducing both equipment cost and operational complexity.
3Length of stationary object
If conventional neutron logging is used, then investigation depth is limited, but equipment simplicity is maintained
Solution Approach 1:
The patent changes the fundamental detection parameter from gamma ray intensity (conventional neutron logging) to beta particle energy characteristics. Beta particles have different penetration and interaction properties with formation materials, enabling deeper effective investigation while maintaining equipment simplicity. The energy spectrum of beta emissions provides additional discrimination capability for fracture identification.
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 method provides a safer, more cost-effective, and deeper investigation of fracture locations, eliminating the need for radioactive materials and complex equipment, while offering improved accuracy and resolution in identifying fractured intervals and their extent.
Implementation Method 1
measuring changes in thermal neutron capture cross-sections
Implementation Method 2
measuring changes in thermal neutron capture cross-sections and count rates
Data Source
AI summary
Subterranean formation locations/heights of tagged proppant doped with a high thermal neutron capture cross-section material are determined using data obtained from before and after frac logging passes through a well of a logging tool having near and far neutron detectors. Proppant location inaccuracies arising from changes in lithology between a zone of no interest and a proppant-containing formation zone are made, after any required normalization for a between-log change in borehole fluid, using an observed difference between the near/far detector count rate ratios in the two passes to determine a count rate differential correction to be applied to the before frac detector count rate. The corrected before frac count rate log is then overlaid with the after frac count rate log such that suppression in the after frac count rate log relative to the corrected before frac count rate log indicates the presence of proppant.