UCG Cement Mix with Graphite and Metakaolin for Thermal Isolation

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Solution Overview

Problem

Existing cementitious materials used in underground coal gasification (UCG) fail to set effectively at low bottomhole static temperatures and maintain integrity at high combustion front temperatures, leading to zonal isolation failures and increased costs due to the need for specialized equipment and additives.

Innovation Solution

A cement mix containing graphite and aluminum silicate, which sets at low temperatures and withstands extreme heat, providing zonal isolation and thermal conductivity to dissipate heat away from the wellbore, compatible with standard Portland cement additives and equipment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If Portland cement is used in UCG wells, then it is compatible with standard additives and equipment, but it disintegrates around 450°C and cannot withstand combustion front temperatures

Engineering Contradiction:

Improvecompatibility with standard cementing additives and equipmentVSAvoidwithstand combustion front temperatures

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies composite materials by combining Portland cement with high-alumina cement and calcium aluminate phosphate cement to create a multi-component cementitious composition. This composite approach allows the system to benefit from the ease of manufacture and compatibility of Portland cement while incorporating the high-temperature resistance of the other cement types, thereby resolving the contradiction between ease of manufacture and reliability at high temperatures.

Inventive Principle:

Principle #40Composite materials

2Reliability

If high alumina phosphate cement is used to withstand high temperatures, then it can resist combustion front temperatures, but it requires specialized equipment and additives, increasing cost and complexity

Engineering Contradiction:

Improvewithstand combustion front temperaturesVSAvoidspecialized equipment and additives required

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges multiple cement types into a single integrated cementitious composition that can be handled as one material system. By combining Portland cement, high-alumina cement, and calcium aluminate phosphate cement in specific proportions, the invention allows the use of standard cementing equipment and procedures while achieving the high-temperature resistance normally requiring specialized CaP cement systems, thereby reducing device complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If CaP cement is used for high temperature resistance, then it can withstand combustion temperatures, but contamination with Portland cement residues causes unpredictable setting times

Engineering Contradiction:

Improvewithstand combustion temperaturesVSAvoidpredictable setting times

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies homogeneity by creating a uniformly mixed cementitious composition where Portland cement, high-alumina cement, and calcium aluminate phosphate cement are combined in controlled proportions. This homogeneous mixture ensures consistent chemical reactions and predictable setting times throughout the cement slurry, eliminating the unpredictability caused by contamination while maintaining high-temperature resistance.

Inventive Principle:

Principle #33Homogeneity

4Ease of manufacture

If cement slurry is designed to set at low bottomhole static temperatures, then it sets effectively in shallow coal beds, but it may not provide adequate high-temperature resistance

Engineering Contradiction:

Improvesets at low bottomhole static temperaturesVSAvoidresistance to high combustion temperatures

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent applies parameter changes by carefully controlling the proportions of different cement components and adjusting slurry formulation parameters such as water-to-cement ratio and additive concentrations. These parameter adjustments enable the cement slurry to set effectively at low bottomhole static temperatures in shallow coal beds while the embedded high-alumina and CaP cement components provide the necessary high-temperature resistance once set.

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

The cement mix effectively maintains zonal isolation and reduces syngas temperature, enhancing processing and handling, while being less costly than high alumina phosphate cement systems, with superior mechanical properties and reduced internal stresses.

Implementation Method 1

providing zonal isolation and thermal conductivity to dissipate heat away from the wellbore

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

aluminum silicate... withstands extreme heat

Methodology Applied

Scientific EffectHeat absorption: Absorption (EM radiation)

Implementation Method 3

graphite and an aluminum silicate in the production of synthesis gas by underground coal gasification

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentUS8596356B2Method of producing synthesis gas by the underground gasification of coal from a coal seam

Publication Date: 2013.12.03 BAKER HUGHES CO

AI summary

Synthesis gas is more effectively produced from the underground gasification of coal from a coal seam when the casing lining is cemented with a cementitious slurry containing a cementitious material, graphite and an aluminum silicate, such as metakaolin. The cementitious slurry of the cement mix sets as a cement sheath at bottomhole static temperatures less than or equal to 65° C. The set cement may withstand extreme dry heat temperatures which are greater than or equal to 800° C.