Doped Proppant Neutron Logging for Fracture Detection
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Solution Overview
Problem
Current methods for locating induced subterranean fractures in hydraulic fracturing operations are limited by the need for radioactive materials, complex detection equipment, shallow investigation depth, potential hazards, and high costs, which hinder effective identification of fractured zones and their extent.
Innovation Solution
A method using a pulsed neutron capture tool or compensated neutron tool with proppants doped with thermal neutron absorbing materials like boron carbide or gadolinium oxide, allowing for the differentiation of propped and unpropped fractures through changes in neutron count rates and capture cross-sections, enabling deeper investigation and cost-effective fracture location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radioactive materials and complex detection equipment are used to locate induced fractures, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the detection function from complex radioactive equipment and implements it using simple neutron capture tools with doped proppants. The proppants are doped with thermal neutron absorbing materials like boron carbide or gadolinium oxide, which can be detected by standard neutron capture tools, eliminating the need for specialized radioactive detection equipment while maintaining fracture location accuracy.
Solution Approach 2:
The patent uses inexpensive doped proppants that can be easily prepared and disposed of after the fracturing operation. These proppants contain thermal neutron absorbing materials that provide detectable signals during the logging process, replacing expensive radioactive tracers with cost-effective alternatives that achieve the same detection purpose.
2Measurement precision
If radioactive materials are used for fracture identification, then measurement precision is improved, but safety hazards increase
Solution Approach 1:
The patent converts the potentially harmful radioactive materials into beneficial thermal neutron absorbing materials. By using boron carbide or gadolinium oxide-doped proppants, the system achieves fracture identification through neutron capture rather than radioactive decay, eliminating radiation safety hazards while improving detection capability through the unique neutron absorption properties of the dopant materials.
3Length of stationary object
If conventional neutron tools are used, then investigation depth is limited, but if doped proppants are used with pulsed neutron capture tools, then investigation depth increases and fracture extent can be better determined
Solution Approach 1:
The patent changes the physical parameter of the proppants by doping them with thermal neutron absorbing materials. This modification alters the neutron capture characteristics, enabling pulsed neutron capture tools to detect fractures at greater depths. The dopant materials create distinct neutron capture signatures that enhance the detection signal and extend the effective investigation depth beyond conventional tool capabilities.
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 eliminates the need for radioactive materials and complex equipment, providing deeper fracture investigation and cost savings while accurately identifying fractured zones and their extent, facilitating more effective hydraulic fracturing operations.
Implementation Method 1
emitting neutrons from the neutron source into the borehole and formation and detecting in the borehole region thermal neutrons or capture gamma rays resulting from nuclear reactions of the source neutrons with elements in the borehole region and subterranean formation
Implementation Method 2
a proppant in which all or a fraction of such proppant includes a thermal neutron absorbing material... having a macroscopic thermal neutron capture cross-section exceeding that of elements normally encountered in subterranean zones to be fractured
Data Source
AI summary
Methods are provided for determining the locations and heights of fractures in a subterranean formation using a neutron-emitting logging tool. Utilizing predetermined relationships (1) between logging tool count rates and associated apparent formation hydrogen index values and (2) between logging tool count rate ratios and associated apparent formation hydrogen index values, the methods detect the presence and heights in the formation of proppant containing high thermal neutron capture cross section material in a manner substantially eliminating proppant determination uncertainty resulting from a prior change in formation hydrogen index values. A second, associated, method employing logging tool count rates and count rate ratios to determine the presence of proppant containing high thermal neutron capture cross section absorbers utilizes a crossplot of count rate versus ratio. Logged intervals containing no proppant will fall on a trend/trendline on the crossplot, whereas logged intervals containing proppant will fall off from this trend/trendline.