Nuclear Logging Tool Gas Saturation Detection via Inelastic Capture Ratio

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Well logging techniques face complexity in detecting interrogating particles or signals, making it difficult to determine formation properties effectively, particularly in identifying gas saturation in earth formations.

Innovation Solution

A nuclear logging system using a logging tool with gamma detectors that record gamma count rate decay curves, calculating the ratio of inelastic to capture count rates to determine gas saturation, leveraging the interaction of neutrons with atomic nuclei to differentiate between inelastic and thermal gamma interactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple detectors are used to detect interrogating particles or signals, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the detection process into distinct temporal phases (burst period and post-burst period) rather than using multiple simultaneous detectors. Gamma ray detections are separated into inelastic scatter detections during the burst period and capture detections during the post-burst period, allowing accurate measurement of formation properties using a single detector over time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system uses periodic neutron source bursts to create alternating detection periods. The neutron source operates in periodic bursts, creating distinct time windows for detecting inelastic scatter gamma rays during bursts and capture gamma rays after bursts. This periodic action enables precise measurements through temporal separation rather than spatial multiplication of detectors.

Inventive Principle:

Principle #19Periodic action

2Reliability

If multiple detectors are used to determine formation properties, then reliability is improved, but ease of operation deteriorates

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidoperational simplicity

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system dynamically switches between different detection modes based on the operational phase. During neutron source bursts, the detector is optimized for inelastic scatter detection; during post-burst periods, it switches to capture detection mode. This dynamic temporal separation simplifies operations compared to managing multiple detectors while maintaining reliable formation property measurements.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If complex detection systems are used to identify gas saturation, then measurement precision is improved, but productivity decreases

Engineering Contradiction:

Improvegas saturation determination accuracyVSAvoidlogging efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The system maintains continuous useful action by performing both inelastic scatter and capture detections in an uninterrupted sequence using the same detector. Rather than requiring separate measurement passes or multiple detectors that would reduce logging speed, the system continuously alternates between detection types during normal tool operation, maintaining high productivity while achieving precise gas saturation determination.

Inventive Principle:

Principle #20Continuity of useful action

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

Simplifies the detection of formation properties by providing a reliable method to determine gas saturation, enabling accurate interpolation of saturation values based on the ratio of inelastic to capture count rates, applicable to various logging tools including wireline, MWD, and LWD.

Implementation Method 1

leveraging the interaction of neutrons with atomic nuclei to differentiate between inelastic and thermal gamma interactions

Methodology Applied

Scientific EffectNeutron interaction with atomic nuclei:

Implementation Method 2

calculating the ratio of inelastic to capture count rates to determine gas saturation

Methodology Applied

Scientific EffectInelastic gamma interactions:

Implementation Method 3

calculating the ratio of inelastic to capture count rates to determine gas saturation

Methodology Applied

Scientific EffectThermal gamma interactions:

Implementation Method 4

A nuclear logging system using a logging tool with gamma detectors that record gamma count rate decay curves

Methodology Applied

Scientific EffectGamma detection:

Data Source

PatentUS8346481B2Method and system of determining a value indicative of gas saturation of a formation

Publication Date: 2013.01.01 HALLIBURTON ENERGY SERVICES INC

AI summary

Determining a value indicative of gas saturation of a formation. At least some of the illustrative embodiments are methods including obtaining an inelastic count rate and a capture count rate of a gamma detector for a particular borehole depth, calculating a ratio of an inelastic count rate to a capture count rate for the particular borehole depth, determining a value indicative of gas saturation based on the ratio of the inelastic count rate to the capture count rate for the particular borehole depth, repeating the obtaining, calculating and determining for a plurality of borehole depths, and producing a plot of the value indicative of gas saturation of the formation as a function of borehole depth.