What is Oil Well Cementing?
Oil well cementing is a process of inserting casing into a wellbore and injecting cement into the annular space between the casing. As an important part of the oil drilling industry, there are typically at least two cementing operations for production wells and up to five for exploration wells. There are 5 main purposes for oil well cementing.
- Stabilizing Wellbore Integrity – To isolate unstable or fractured formations, reinforce drilled sections, and ensure smooth drilling progress.
- Supporting Wellhead Installation – To provide a foundation for blowout prevention systems and maintain proper mud return flow by elevating the drilling fluid outlet above the mud pit.
- Zonal Isolation – To prevent crossflow between oil, gas, and water layers with varying pressures, ensuring optimal hydrocarbon production conditions.
- Protecting Freshwater Resources – To shield shallow freshwater aquifers from contamination by deeper oil, gas, brines, or other formation fluids.
- Enhancing Production Potential – To establish a secure well structure for future stimulation treatments, such as acidizing and hydraulic fracturing, to boost production.
Cementing Technology Application In Russia
- In recent years, casing damage in Russian oilfields has surged from 17% to 38%, resulting in an annual production loss of approximately 7.6–16.6 million tons of oil. In 2015, Rosneft reported around 1,900 damaged wells, leading to a cumulative loss of 9.01 million tons, while Tatneft documented nearly 800 affected wells, reducing output by 1.09 million tons. Across eight major oil companies, casing failure rates ranged from 1.78% to 4.13%.
- A key countermeasure is enhanced well cementation, as demonstrated in the Romashkino Field, which operates over 40,000 production wells, 70% of which are over 30 years old. Common casing damage includes corrosion and perforation, with average external corrosion rates of 0.8–1.2 mm/year and internal corrosion at 0.9–1.5 mm/year.
How To Improve The Efficiency of Oil Well Cementing?
- Advanced Cement Placement Techniques
- Employ centralizers and pipe movement (rotation/reciprocation) to eliminate mud channels and improve uniform cement coverage.
- Utilize computational fluid dynamics (CFD) simulations to predict and optimize cement displacement efficiency.
- Robust Zonal Isolation Methods
- Implement multi-stage cementing for high-pressure or depleted zones.
- Apply expandable casing patches or resin systems in critical intervals.
- Real-Time Monitoring & Evaluation
- Use acoustic and pressure sensors to detect micro-annuli or weak spots.
- Conduct ultrasonic imaging (CBL/VDL logs) post-cementing for quality assessment.
- Corrosion & Chemical Resistance Measures
- Integrate H₂S-scavenging additives or epoxy-coated casing in sour environments.
- Apply zinc or aluminum-based coatings to mitigate electrochemical degradation.
- Precise Slurry Design & Material Optimization
- Use customized cement formulations with quality admixtures to enhance rheology, strength, and set time.
- Improve fluid loss control to prevent gas migration and ensure proper bonding.
What Additives Can Be Used In Oil Well Cementing?
1. Dispersant and Friction Reducer
When clay particles and drilling cuttings reach critical concentrations in drilling fluids, they form a three-dimensional network structure. This phenomenon is particularly exacerbated in salt-gypsum formations where dissolved electrolytes (especially polyvalent cations) in formation water intensify structural development, significantly impairing fluid mobility. Dispersants function by dismantling these network matrices, liberating bound water to reduce viscosity and yield point.
Our Solution: Polycarboxylate Superplasticizer
Our NOVASTAR Polycarboxylate Superplasticizer is a high-performance water reducer and dispersant used to optimize cement mortar properties. As one of the synthetic polymeric dispersants, it offers superior efficiency in the following aspects:
- Cement Particle Dispersion
– Reduces slurry consistency by 35-50% compared to untreated systems
– Enhances rheological parameters: lowers plastic viscosity by 40-60% while maintaining optimal yield point - Temperature Adaptability
– Effective performance spectrum: 30°C to 180°C (86°F to 356°F)
– Maintains dispersion stability under thermal cycling conditions - Salt Tolerance
– Demonstrates consistent performance in 5-10% NaCl environments
– Compatible with various water sources without purity requirements - Compatibility Profile
– Synergistic with all API-class cement additives
– No adverse interactions with fluid loss controllers/retarders/antifoams
2. Cement Fluid Loss Control Additive
Fluid loss additives (FLAs) are critical for minimizing filtrate loss in cement slurries, serving three primary purposes:
- Preventing Premature Dehydration in permeable formations is particularly critical during liner cementing operations.
- Shielding Water-Sensitive Formations from damage caused by fluid invasion.
- Enhancing Squeeze Cementing Efficiency by maintaining slurry integrity under high-pressure differentials.
Our Flagship Multi-Functional Fluid Loss Additive: HPMC
LANDERCOLL HPMC is a modified cellulose ether widely used as a water-reducing agent. As a water-soluble polymer, it helps stabilize drilling mud by reducing fluid loss into permeable formations while maintaining rheological properties. LANDU provides diverse types of HPMC for cementing applications, including:
- HPMC For Low-Density Systems
– Specifically formulated for fragile formations and lost circulation zones.
– Maintains excellent fluid loss control (<50mL/30min) at densities as low as 1.20 SG. - HPMC For High-Density Applications
– Optimized for HPHT wells and deepwater environments.
– Delivers <30mL/30min fluid loss in slurry densities up to 2.60 SG. - HPMC For Conventional Density Slurries
– Universal solution for most standard cementing operations.
– Provides reliable <50mL/30min API fluid loss control. - HPMC For Seawater Mixing Applications
– Corrosion-resistant formulation for offshore operations.
– Maintains stable performance in high-salinity environments.
An ideal cement retarder effectively prolongs and maintains the liquid state and pumpability of slurry. The best retarders exhibit the following properties:
- Broad temperature adaptability: Consistent performance across varying downhole conditions.
- Dose-proportional thickening time: Predictable retardation based on concentration.
- Compatibility: Harmonious interaction with all types of oilwell cements and additives without adversely affecting:
- Viscosity buildup
- Thixotropic gelation
- Compressive strength development
- Controllable performance: Reliable thickening time prediction and repeatability.
- Safety & environmental compliance: Non-toxic, non-flammable, pollution-free, and resistant to contamination.
Comparative Analysis of Common Retarders
- Citric Acid & Sodium Citrate
- Primary Function: Retardation (mild effect), with secondary dispersing ability.
- Dosage Sensitivity:
- Minimum effective dose: 0.5% BWOC (Below this threshold, may accelerate setting).
- Optimal dose range: Stable retardation beyond a critical concentration, with minimal sensitivity to small variations.
- Limitations:
- Weaker dispersion effect compared to specialized dispersants.
- Performance varies significantly depending on cement class.
- Tartaric Acid & Potassium Sodium Tartrate (Rochelle Salt)
- Key Features:
- Exceptional high-temperature retardation (up to 180°C+).
- Mild dispersing effect (supplements rheological improvement).
- No strength degradation in set cement.
- Practical Challenges:
- Increased free water & fluid loss – necessitates the use of fluid loss additives (FLAs).
- High sensitivity to alkaline contamination can lead to unpredictable setting behavior, making it less favored in field operations.
Our Recommendations: Amino-Based retarder
- Amino-Based Retarder is a specialized chemical additive used to delay the setting of cement slurries by slowing down the hydration reactions of Portland cement. These retarders are particularly valuable in deep, high-temperature (HT/HPHT) wells, where standard retarders (e.g., lignosulfonates or organic acids) may degrade or become ineffective.
Mechanism of Retardation
- Chelation & Adsorption:
- Amino groups (–NH₂, –NH–) form complexes with Ca²⁺ ions in the cement, inhibiting the formation of C-S-H (calcium silicate hydrate) gel, which is critical for cement hardening.
- Adsorbs onto cement particle surfaces, creating a barrier that delays water penetration and hydration.
- pH-Responsive Action:
- More effective in alkaline conditions (typical of cement slurries, pH ~12–13).
Advantages Over Conventional Retarders
| PROPERTY | AMINO-BASED RETARDER | LIGNOSULFONATES | ORGANIC ACIDS (E.G., CITRIC/GLUCONIC) |
|---|---|---|---|
| HIGH-TEMP STABILITY | UP TO 250+°C | DEGRADES >120°C | DEGRADES >150°C |
| DOSAGE EFFICIENCY | LOW (0.1-0.5% BWOC) | HIGH (0.5-2% BWOC) | MODERATE (0.3-1% BWOC) |
| SALT TOLERANCE | EXCELLENT | POOR | MODERATE |
| SLURRY COMPATIBILITY | WORKS WITH MOST ADDITIVES | MAY INTERFERE WITH DISPERSANTS | SENSITIVE TO pH SHIFTS |
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