Technical Characteristics and Application Advantages of WF-3L Liquid Fluid-Loss Additive (Acrylamide Type) for Oilwell Cement

Oilwell cement used in cementing operations must withstand high-temperature and high-pressure (HTHP) environments while preventing excessive fluid loss into permeable formations. Excessive fluid loss leads to thick filter cakes, reduced cement strength, and potential formation damage. Traditional fluid-loss additives like hydroxyethyl cellulose (HEC) degrade under high temperatures, limiting their effectiveness in deep and ultra-deep wells. Acrylamide-based copolymers, such as WF-3L, have emerged as superior alternatives due to their exceptional thermal stability and salt resistance.

Molecular Structure and Mechanism of Action

WF-3L is a copolymer of acrylamide (AAm) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), with minor functional monomers like vinyl phosphonic acid (VPA). Its molecular chain contains sulfonic acid (-SO₃⁻) and phosphonic acid (-PO₃²⁻) groups, which provide strong negative charges. These charges induce electrostatic repulsion, causing the polymer chains to expand and form a three-dimensional network. This network controls fluid loss through three mechanisms:

Adsorption-bridging effect: Long-chain molecules adsorb onto cement particles, bridging them to form dense filter cakes with low permeability.

Viscosifying effect: Increases the viscosity of the cement slurry liquid phase, slowing water migration into the formation.

Thermal and salt resistance: Sulfonic and phosphonic acid groups maintain hydration under HTHP (≤180°C) and high-salinity (18% NaCl) conditions, preventing chain curling and loss of functionality.

Performance Advantages and Engineering Applications

Wide temperature range adaptability: Tests show that at 90°C and 6.9 MPa, WF-3L reduces fluid loss to ≤50 mL/30 min. At 120°C with high salinity, fluid loss remains ≤120 mL/30 min, meeting deep-well requirements.

Low free water and high compressive strength: At 90°C under atmospheric pressure, free water is ≤3.5 mL, and 24-hour compressive strength exceeds 14 MPa, preventing gas migration and formation fluid invasion.

Compatibility and ease of use: Works seamlessly with API Grade G cement, silica flour, and various retarders/dispersants. Its liquid form enables precise dosing and reduces dust pollution.

Case Study: In an offshore deep well (BHCT 165°C), WF-3L reduced fluid loss from 180 mL/30 min to 45 mL/30 min, cutting filter cake thickness by 40% and upgrading cementing quality from "acceptable" to "excellent."