Geothermal Well Cement Composite Thermal Shock Resistance

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Solution Overview

Problem

Geothermal wells face challenges with thermal shock resistance, corrosion, and thermal insulation due to the limitations of Ordinary Portland Cement (OPC)-based formulations, which are not effective at high temperatures and are susceptible to acid degradation, leading to inefficiencies in energy recovery and storage.

Innovation Solution

A well cement composite is developed using calcium aluminate cement (CAC), fly ash cenospheres, sodium metasilicate, and polymethylhydrosiloxane, mixed in specific ratios and alkaline environments to create a superhydrophobic, thermally insulating, and lightweight cement with improved mechanical properties and water repellency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Ordinary Portland Cement (OPC)-based formulations are used, then mechanical support and corrosion protection are provided, but thermal shock resistance and acid degradation resistance are insufficient at high temperatures

Engineering Contradiction:

Improvethermal shock resistanceVSAvoidacid degradation susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters by replacing OPC with calcium aluminate cement (CAC) and adjusting the cement slurry formulation to include specific additives and admixtures. This parameter change enables the cement to withstand thermal shocks and acid degradation at high temperatures up to 300°C, directly resolving the reliability issue with conventional OPC formulations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite cement system by combining calcium aluminate cement with various admixtures, additives, and optional components in specific formulations. This composite approach enhances thermal shock resistance and acid degradation resistance while maintaining mechanical properties, overcoming the limitations of single-component OPC-based cements.

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If low density cement slurries are used to minimize lost-circulation problems, then thermal insulating properties are improved, but mechanical strength may be reduced

Engineering Contradiction:

Improvethermal insulationVSAvoidmechanical strength

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The patent optimizes the density parameter of cement slurry by incorporating lightweight materials and adjusting the water-to-cement ratio. This creates a low-density cement with enhanced thermal insulation properties while the CAC base and formulation adjustments ensure adequate mechanical strength is maintained, resolving the trade-off between insulation and strength.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes porous or lightweight aggregate materials in the cement slurry formulation to reduce overall density. This creates voids and porous structures that improve thermal insulation by trapping air pockets, while the CAC matrix provides sufficient mechanical strength to compensate for the reduced density, simultaneously achieving both insulation and strength requirements.

Inventive Principle:

Principle #31Porous materials

3Ease of operation

If water is used to prepare cement slurries, then workability is improved, but thermal conductivity increases due to free water and cement hydrates

Engineering Contradiction:

Improveslurry workabilityVSAvoidthermal conductivity

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent changes the water content parameter and water-to-cement ratio in the slurry formulation, using optimized amounts of water along with chemical admixtures to maintain workability. This reduces the quantity of free water and potential hydrate formation in the set cement, thereby lowering thermal conductivity while preserving adequate slurry flowability for placement.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces chemical admixtures and additives as intermediaries that allow reduced water content while maintaining slurry workability. These additives improve fluidity and placement characteristics without requiring high water content, enabling the formulation to achieve both operational ease and reduced thermal conductivity by minimizing free water in the hardened cement.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If conventional cement formulations are used, then zonal isolation and mechanical support are achieved, but thermal insulation of carrier fluid is insufficient

Engineering Contradiction:

Improvezonal isolationVSAvoidheat loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent modifies the thermal conductivity parameter of the cement sheath by using calcium aluminate cement base and incorporating lightweight materials, air-entraining agents, or porous aggregates. This creates a thermally insulating cement sheath that maintains zonal isolation and mechanical support functions while significantly reducing heat loss from the carrier fluid, improving overall thermal efficiency of the geothermal well system.

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 composite exhibits enhanced thermal shock resistance, lower thermal conductivity, high compressive toughness, and excellent water repellency, reducing thermal conductivity to less than 0.7 W/mK and maintaining strength and ductility under hydrothermal conditions, thus addressing the limitations of existing cements in geothermal applications.

Implementation Method 1

The composite exhibits enhanced thermal shock resistance, lower thermal conductivity, high compressive toughness, and excellent water repellency

Methodology Applied

Scientific EffectSuperhydrophobicity: Hydrophobe

Implementation Method 2

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 3

Methodology Applied

Scientific EffectThermal shock resistance: Thermal Shock

Data Source

PatentUS11912927B2Super-hydrophobic, thermally insulating, thermal-shocks resistant well cement composites for completion of geothermal wells at hydrothermal temperatures of up to 300° C

Publication Date: 2024.02.27 BROOKHAVEN SCIENCE ASSOCIATES LLC

AI summary

A well cement composite and a method for making a well cement composite includes a mixture of calcium aluminate cement (CAC) and fly ash cenospheres (CS) in a weight ratio of from 30:70 to 80:20 CAC to CS; sodium metasilicate (SMS) in an amount of from 1 to 10% of the total weight of the mixture of CAC and CS; polymethylhydrosiloxane (PMHS) in an amount of from 0.5 to 6.0% of the total weight of the mixture of CAC and CS; and water in a weight ratio of from 0.5:1.0 to 1.2:1.0 of water to CAC and CS.