What is Oil Well Cementing?
Oil well cementing is one of the most critical stages in oil and gas well drilling engineering. This is to isolate the oil, gas, and water layers within the wellbore, protect the casing, extend the well’s lifespan, and enhance hydrocarbon production efficiency. According to the American Petroleum Institute, cementing additives account for 38% of the chemicals used in oilfield operations. The application of water-reducing agents in oilfield cement has become a pivotal technical approach to addressing various complex cementing challenges, enhancing cementing quality, and safeguarding oil and gas reservoirs.
Oil Well Cementing in the Russian Polar Regions
Arctic oil and gas reservoirs are predominantly located in permafrost zones with temperatures ranging from -5°C to -18°C, ice content up to 80%, and depths up to 500 meters. For traditional cement mortars, the thick permafrost in polar regions and the low temperatures slow down the setting and strength development. When the temperature drops below 0°C, the water in the cement mortar condenses and does not participate in the hydration reaction. As a result, the mortar is unable to set adequately, thus failing to cement the well. Additionally, the heat released during the cement slurry’s hydration process can cause the permafrost to thaw. The natural gas hydrates in the permafrost can trigger extensive decomposition, posing risks such as well kicks or blowouts during drilling operations.
Russia has adopted a lightweight cement mortar system due to its low thermal conductivity. It stops heat transfer between the wellbore and the formation. In this cement mortar formulation, Polycarboxylate Superplasticizer plays a key role in reducing the exothermic heat generated during the hydration reaction while ensuring that the slurry sets within the required timeframe and attains adequate strength.
What is a Polycarboxylate Superplasticizer in Oil Well Cementing?
As a third-generation high-performance water-reducing agent, polycarboxylate-based superplasticizers are designed to improve the workability, strength, and durability of cementitious systems by reducing the water-to-cement or water-to-gypsum ratio. LANDU Novastar Polycarboxylate Superplasticizer is highly compatible with other additives, such as gypsum retarders, air-entraining agents, or accelerators, and various base materials, such as PST-1-50 Cement. In oil well cementing, it serves as:
Dispersant
The lay and drill cuttings in the drilling fluid can form a spatial network if their concentration is too high. This network structure can be intensified by dissolved salts, particularly polyvalent cations, in the water in salt-gypsum formations. This finally undercuts the fluidity of the drilling mud. Another versatile additive is gypsum, especially suitable for reducing the setting time of cement mortar in permafrost regions. However, it also substantially increases the slurry’s viscosity.
LANDU NOVASTAR Polycarboxylate Superplasticizer effectively disrupts this network structure, releasing trapped water and thereby adjusting the viscosity and shear stress of the drilling fluid. This is because the negatively charged carboxyl groups (-COOH) on PCE molecules repel cement particles, preventing flocculation. Also, the long side chains of PCE molecules create a physical barrier between cement particles, reducing friction and improving fluidity.
Water Reducing Agent
LANDU NOVASTAR Polycarboxylate Superplasticizer water-reducing agent optimizes the particle size distribution (PSD) of cement and supplementary materials, increasing the solid particle content per unit volume and minimizing the water-cement ratio of the slurry. It significantly shortens the initial setting time of cement and enhances the compressive strength of the cement while reducing its porosity and permeability.
Workability Enhancer
In oil well cementing, slump retention (maintaining fluidity over time) is crucial to ensure the cement can be pumped smoothly through long distances and complex well geometries. PCE molecules are less prone to adsorption by cement particles compared to traditional superplasticizers (e.g., sulfonated naphthalene formaldehyde – SNF). It significantly improves the workability of cement mixtures. It maintains the fluidity of the mixture over extended periods, preventing slump loss. Ensures smooth and efficient pumping of cement slurries, even in high-pressure, high-temperature (HPHT) environments. PCE superplasticizers are thermally stable and can maintain their performance even at elevated temperatures and pressures.
Acetone Formaldehyde Sulfite vs. PCE Superplasticizer
- In oil well cementing, the acetone-formaldehyde-sulfite(AFS) dispersant is still acting as a monopoly. However, PCE Superplasticizer has begun to emerge in recent years for the following advantages.
| Feature | PCE Superplasticizers | AFS Dispersant |
|---|---|---|
| Efficiency | High efficiency at low dosages. | Lower efficiency, requiring higher dosages. |
| Slump Retention | Excellent slump retention over extended periods. | Limited slump retention due to cement absorption. |
| Water Reduction | Up to 30% or more water reduction. | Typically 15–20% water reduction. |
| Environmental Impact | Low toxicity and biodegradability. | May contain sulfonate groups, posing environmental concerns. |
| Compatibility | Highly compatible with other additives. | May have compatibility issues with certain additives. |
