Shale TOC Measurement via Thermal Roughness

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Solution Overview

Problem

Conventional methods for measuring total organic carbon (TOC) in shale formations are inadequate due to high variability in mineral constituents and lack of depth information in shale cuttings, making it difficult to accurately assess the economic potential of shale reservoirs.

Innovation Solution

A tool with an energy source and surface roughness measurement device is used to heat a sample, measuring the change in surface roughness to infer TOC, exploiting the thermal expansion difference between organic and inorganic materials, and can be deployed in a wellbore with packers or a hydraulic seal for precise measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional TOC measurement methods (sonic or density logs) are used, then TOC can be derived, but accurate measurement requires prior knowledge or accurate estimate of matrix properties which is not trivial for shale formations due to high variability of constituent minerals

Engineering Contradiction:

ImproveTOC measurement accuracyVSAvoidrequirement for prior matrix property knowledge

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention extracts the organic material from the rock matrix through selective thermal decomposition. By heating the sample to temperatures that decompose organic matter (typically 200-500°C) while leaving the inorganic matrix intact, the method isolates the organic component for measurement. This extraction approach eliminates the need to know matrix properties, as the organic carbon is measured directly after separation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The method applies local heating to specific regions of the rock sample containing organic material. By targeting only the organic patches within the inorganic matrix through controlled thermal exposure, the measurement process focuses on the relevant component (organic carbon) without being influenced by the variable mineral constituents of the surrounding matrix.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If high resolution measurements with short spacing between sampling points are used, then evaluation of shale lamination and quality can be improved, but measurement time and complexity increase

Engineering Contradiction:

Improveshale lamination evaluation accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The invention replaces complex mechanical sampling and multiple physical measurements with a simplified thermal-chemical approach. Instead of taking multiple core samples at different locations and performing separate analyses, a single heated sample provides comprehensive TOC information that reflects the heterogeneous lamination structure, reducing both time and operational complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If LIP measurement on shale cuttings is used, then high resolution map of lamination can be obtained, but depth information is lost due to turbulent flow mixing during transport to surface

Engineering Contradiction:

Improvelamination mapping resolutionVSAvoiddepth information

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The method performs preliminary measurement and analysis of TOC content before the cuttings are transported to the surface. By conducting the thermal decomposition and measurement while the cuttings are still in the wellbore or immediately upon retrieval, the system captures the lamination characteristics at their original depth positions before turbulent mixing occurs, preserving both spatial and depth information.

Inventive Principle:

Principle #10Preliminary 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

This method provides an independent and accurate estimation of TOC, insensitive to inorganic mineralogy, enabling high-resolution mapping of kerogen content and maturity, essential for evaluating shale gas or oil reservoirs.

Implementation Method 1

The sample is then exposed to energy from the energy source, causing the temperature of the sample to increase

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The energy source may be a laser that produces radiation that selectively heats a particular component of the sample constituent material

Methodology Applied

Scientific EffectLaser heating: Laser

Data Source

PatentUS10101494B2Measuring total organic carbon of shales using thermal expansion

Publication Date: 2018.10.16 SCHLUMBERGER TECH CORP

AI summary

A tool having an energy source and a surface roughness measurement device is provided. A baseline measurement of surface roughness of a sample is made. The sample is then exposed to energy from the energy source, causing the temperature of the sample to increase. A second measurement of surface roughness of the sample is made. The change in surface roughness of the sample is determined. Formation properties such as the total organic carbon in the sample is inferred based on the determined change in surface roughness of the sample. The tool may be disposed in a wellbore and may use packers to isolate a portion of the wellbore, or it may use a hydraulic seal on an extendible member to isolate a sample portion of the wellbore wall. The energy source may be a laser that produces radiation that selectively heats a particular component of the sample constituent material.