Nuclear Spectroscopy Background Ratio Correction

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Solution Overview

Problem

Nuclear spectroscopy in drilling operations faces challenges in accurately determining formation type due to environmental variations and interference from tool and mud elements, leading to inaccurate elemental concentration measurements.

Innovation Solution

A method and system that utilize a nuclear spectroscopy tool with a neutron source and gamma ray detector to perform environmental measurements, calculate a background ratio, and subtract spectral components to isolate formation-specific signals, thereby improving the accuracy of elemental concentration estimates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If neutron-gamma spectroscopy is used to determine formation type, then elemental concentration information can be obtained, but tool and mud elements interfere with formation element detection

Engineering Contradiction:

Improveelemental concentration measurement accuracyVSAvoidbackground spectrum interference

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent segments the total gamma ray spectrum into multiple components: formation element spectra, tool element background spectra, and mud element background spectra. By separating these components and measuring them independently, the system can subtract the background contributions to isolate the formation element signals, thereby resolving the interference problem.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces environmental parameters (borehole size, formation density, borehole fluid density, hydrogen index, neutron slowing-down length, thermal neutron capture cross section) as intermediaries that characterize the measurement environment. These parameters are used to calculate background ratios that represent the relative contributions of tool and mud elements, enabling accurate background subtraction without directly measuring the interfering elements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If environmental parameters vary from well to well and with depth, then formation conditions change, but this causes variations in measured spectra that affect measurement accuracy

Engineering Contradiction:

Improveenvironmental condition variationVSAvoidspectral measurement consistency

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent implements a dynamic background subtraction method where the background ratio is calculated based on environmentally-dependent parameters measured during each specific logging operation. Rather than using fixed background corrections, the system adapts the background subtraction to the actual environmental conditions (borehole size, formation density, fluid properties) present at each depth and location, thereby maintaining measurement accuracy across varying conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameters used for background correction from fixed values to environmentally-dependent variable parameters. By measuring borehole size, formation density, borehole fluid density, hydrogen index, neutron slowing-down length, and thermal neutron capture cross section, the system dynamically adjusts the background ratio to account for environmental variations, ensuring consistent measurement precision across different wells and depths.

Inventive Principle:

Principle #35Parameter changes

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 accuracy of elemental concentration measurements by effectively accounting for environmental impacts and tool-related interference, leading to more reliable formation type determination and drilling decisions.

Implementation Method 1

neutrons are emitted from the nuclear spectroscopy tool such that some of the neutrons generate gamma rays from a formation adjacent the nuclear spectroscopy tool

Methodology Applied

Scientific EffectNuclear reaction: Nuclear Fission

Implementation Method 2

An energy spectrum of gamma rays induced by the emitted neutrons can be detected

Methodology Applied

Scientific EffectGamma ray detection: Photoelectric Effect

Data Source

PatentUS9541668B2Environmental corrections in nuclear spectroscopy using variable element ratio

Publication Date: 2017.01.10 SCHLUMBERGER TECH CORP

AI summary

A method for estimating an aspect of a formation using a nuclear spectroscopy tool includes placing a nuclear spectroscopy tool into a borehole and emitting neutrons such that some of the neutrons generate gamma rays from a formation adjacent the nuclear spectroscopy tool and some of the neutrons generate gamma rays from elements within the nuclear spectroscopy tool. An energy spectrum of gamma rays induced by the emitted neutrons can be detected. The energy spectrum includes a background having a plurality of measured spectral components. A background ratio between at least one spectral component of the background and another measured spectral component can be determined or estimated in accordance with environmental measurements. The detected gamma ray spectra can be analyzed using a combination of standard spectra and subtracting at least one spectral component of the background in accordance with the background ratio.