Analysis of the Characteristics and Compatibility of Diatomite Supports with Cementing Engineering

As a natural nano-porous siliceous material, diatomite supports play an increasingly important role in modern oilfield cementing engineering. This special carrier, formed by the deposition of ancient diatom fossils, mainly consists of amorphous silica (with a SiO? content of 85-94%), and has a unique combination of physical and chemical properties: high porosity (60-90%), large specific surface area (20-70m2/g), low density (0.15-0.5g/cm3), and excellent chemical inertness. These properties of diatomite supports make them ideal functional additives and performance regulators for cementing slurry systems.

In cementing engineering, diatomite supports mainly exert their effects through three mechanisms: first, as micro-nano-scale reinforcing phases, they improve the mechanical properties of the cement stone; second, by utilizing the multi-level pore structure to regulate the filtration loss performance and rheological characteristics of the cement slurry; third, through surface active sites to carry and release cementing additives. Studies have shown that cementing slurry systems containing diatomite supports can increase the compressive strength of the cement stone by 20-40%, while maintaining excellent gas migration prevention capabilities.

Application of Diatomite Supports in Cementing Slurry Systems

Diatomite Supports in Low-Density Cementing Slurry Systems

In low-pressure and leak-prone formations, diatomite supports have significant advantages as low-density reducing materials. Compared with traditional floating beads or bentonite, diatomite supports have more balanced performance: a wide range of density adjustment (0.8-1.4g/cm3); do not affect the stability of the cement slurry; can simultaneously improve the mechanical properties of the cement stone. Experimental data show that cementing slurry systems containing 15-25% diatomite supports can achieve a 24-hour compressive strength of 14-18MPa, far exceeding API standards.

The application of diatomite supports in foam cement systems is particularly successful. Through special surface modification treatment, diatomite supports can stabilize the foam structure and improve the stability of foam cement. After applying foam cement slurry containing diatomite supports in an oilfield, the quality rate of cement ring sealing from 75% to 92% was significantly reduced, significantly reducing the frequency of subsequent well repair operations.

Diatomite Supports in Gas Migration Prevention Cementing Slurry Systems

In high-pressure gas well cementing, diatomite supports mainly play the following roles: absorbing formation fluids through the porous structure to reduce the risk of gas migration; improving the sedimentation stability of the cement slurry; enhancing the compactness of the cement stone. Optimized pore diameters (0.1-1μm) of diatomite supports can form an ideal microstructure, significantly improving the gas migration prevention ability of the cement slurry.

Studies have shown that the gas permeability of the gas migration prevention cementing slurry system developed based on diatomite supports can be reduced to below 0.01mD, and the gas migration coefficient (SPN value) <3, fully meeting the requirements of high-pressure gas well cementing. In shale gas well cementing, diatomite supports not only play the role of preventing gas migration, but also the active silicon components contained in them can react with the cement hydration products, increasing the long-term strength growth rate of the cement stone by 15-25%.

Diatomite Supports in High-Temperature Deep Well Cementing Slurry Systems

In high-temperature deep well cementing, diatomite supports demonstrate unique value. By regulating the mineral composition and heat treatment process of diatomite supports, high-temperature stable agents with a temperature resistance of up to 200℃ can be developed. Tests show that specially treated diatomite supports can effectively inhibit the strength decline of cement at high temperatures, maintaining the 28-day strength retention rate of the cement stone from 60% to above 85% at 150℃.

In the application of retarder carriers, the multi-level pore structure of diatomite supports can achieve precise release of additives, meeting the requirements of long-segment sealing construction in deep wells. After using the diatomite carrier-based retardant system in a super-deep well, the thickening time of the cement slurry can be adjusted within the range of 150-400 minutes, and the transition time is controlled within 15 minutes, ensuring high-quality sealing in the well section above 5000 meters.

Innovations and performance optimization of diatomite carriers

Surface modification technology

To improve the performance of diatomite carriers in cementing applications, various surface modification technologies have been developed in the industry:

1. Silane coupling agent treatment: Using KH-560 and other silane coupling agents to improve the interface bonding between diatomite carriers and the cement matrix, the interface strength of the treated composite material increased by more than 50%;

2. Nano modification: By depositing SiO? or CaCO? nano particles on the surface, regulating the surface activity and pore structure of diatomite carriers;

3. Organic-inorganic hybridization: Using polymer monomers to perform in-situ polymerization on the surface of diatomite carriers to achieve functional modification.

Structural regulation technology

Optimizing the microstructure of diatomite carriers through physical and chemical methods:

Acid activation treatment: Using hydrochloric acid to remove impurities, increasing the specific surface area and active silicon content;

Grading technology: Obtaining a suitable particle size distribution for the cement slurry system through wet grading (the cementing grade is usually 5-50 μm);

Pore structure design: Optimizing the pore size distribution and surface characteristics by controlling the calcination temperature (500-800°C).

Composite reinforcement technology

Combining diatomite carriers with other functional materials:

Compared with nano materials: such as nano clay/diatomite carrier composites, which synergistically improve the performance of the cement slurry;

Combined with fibers: such as carbon fiber reinforced diatomite carriers, which increase the toughness of the cement stone;

Combined with elastic materials: such as rubber particles modified diatomite carriers, which enhance the impact resistance of the cement ring.

Performance tests show that the optimized treated diatomite carriers can increase the compressive strength of the cement stone by 30-50%, reduce the elastic modulus by 20-35%, and achieve the ideal mechanical properties of "strong but not brittle". For example, the permeability of the modified diatomite carrier cement system under simulated downhole conditions can be reduced to below 0.05 mD, fully meeting the requirements for air tightness.

Application cases and effect evaluation

Offshore oilfield cementing cases

After adopting the siliceous earth carrier-based low-density cement slurry system, a certain offshore oilfield achieved remarkable results:

- The cement slurry density was stabilized at 1.30 g/cm3, and the leakage rate was reduced by 90%;

- The 7-day compressive strength of the cement stone reached 21 MPa, far exceeding the design requirement of 16 MPa;

- The quality rate of well cementing improved from 68% to 89%;

- The frequency of subsequent well repair operations decreased by 60%, and each well saved approximately 2 million yuan.

Case of Well Cementing for Shale Gas Wells

In the well cementing of shale gas horizontal wells, the siliceous earth carrier anti-gas migration cement slurry performed well:

- The gas migration coefficient (SPN value) was less than 2.5, superior to the industry standard of 3.0;

- The quality of the cement ring sealing section reached 92%;

- The incidence of external pipe leakage after fracturing was reduced by 70%;

- The test production output of each well increased by 15-20%.

Case of Ultra-deep Well Cementing

For an 8000m ultra-deep well, a siliceous earth carrier high-temperature cement system was adopted:

- The cement slurry maintained good stability at 180℃ high temperature, without sedimentation or stratification;

- The setting time was precisely controlled within 360±15 minutes;

- The temperature stability decline rate of the cement stone was less than 10%;

- The record of the deepest well cementing operation in China was successfully completed.

Performance Comparison Data

Compared with traditional cementing additives, the siliceous earth carrier product performed exceptionally well in multiple indicators:

| Performance Indicators | Siliceous Earth Carrier System | Traditional Additive System |

| Cement Stone Compressive Strength | High (Increased by 20-40%) | Varies by Type |

| Anti-Gas Migration Capability | Excellent (SPN < 3) | Average (SPN 3-5) |

| Sediment Stability | Excellent (API Free Liquid < 5 mL) | Moderate (API Free Liquid 5-15 mL) |

| High Temperature Stability | Excellent (200℃ Strength Retention > 85%) | Average (150℃ Strength Retention 60%) |

| Comprehensive Cost | Moderately High | Varies by Type | 

Industry Development Trends and Challenges

Technical Development Trends

1. Intelligent Application: Develop intelligent silica soil carrier cement systems that respond to formation conditions;

2. Nanomodification: Study the application of nano-silica soil carriers in ultra-low permeability cement;

3. Multi-functional Integration: Endow the silica soil carrier with additional functions such as corrosion inhibition and self-repair;

4. Green and Environmentally Friendly: Optimize the processing technology of silica soil carriers to reduce energy consumption and carbon emissions.

Market Development Prospects

The global market size for oilfield cementing is expected to reach 15 billion US dollars by 2025, with an annual growth rate of approximately 4.5%. Due to its superior performance, the share of silica soil carriers in the cementing additive market is expected to increase from the current 12% to 20-25%. Particularly in the following areas, the growth potential is enormous:

- Deepwater cementing;

- Shale oil and gas well cementing;

- High-temperature and high-pressure well cementing;

- Carbon dioxide sequestration well cementing.

Technical Challenges

1. Quality Control: Ensuring the batch stability of the performance of silica soil carriers;

2. Mechanism of Action: Deeply revealing the interaction mechanism between silica soil carriers and cement;

3. Standard System: Establishing evaluation standards for silica soil carrier cementing products;

4. Cost Optimization: Reducing the cost of modification processing while ensuring performance.

As oil and gas exploration and development move deeper and into more complex formations, the importance of silica soil carriers in cementing engineering will continue to increase. Through material innovation, mechanism research, and engineering practice, silica soil carriers are expected to become the core component of a new generation of high-performance cementing materials, providing key technical support for the integrity management of oil and gas wells throughout their life cycle. It is expected that the market demand for silica soil carriers for cementing will grow at an average annual rate of 6-8% in the next five years. Technological progress will enable them to play a greater role in unconventional and extreme environment cementing.