Overview
EN ISO 10426-6:2008 (ISO 10426-6:2008) defines standardized methods for determining the static gel strength (SGS) of cement slurries and related materials used for well cementing in the petroleum and natural gas industries. Published by CEN as an endorsed version of the ISO document, this part of the ISO 10426 series specifies test requirements and procedures to measure SGS under simulated well conditions and to support cement design and quality control.
Key topics and requirements
- Scope and purpose: Test methods for evaluating SGS development of cement slurries to simulate downhole conditions (temperature, pressure, placement).
- Terms and definitions: Clear definitions such as static gel strength (SGS), critical static gel strength (CSGS) and critical static gel-strength period (CSGSP). SGS is expressed in pascals (Pa) (or pounds force per 100 ft²).
- Sampling and preparation: Guidance to sample dry cement, additives and mixing water using best available sampling methods and to prepare slurries per ISO 10426-2 procedures; laboratory temperatures should match anticipated field conditions (or use 23 °C ± 2 °C if unknown).
- Test apparatus types: Procedures for three instrument classes are provided:
- Rotating-type SGS apparatus - torque measurement on a paddle at very low continuous rotation (example stirring speed in SGS portion: 0.0000092 r/s (0.2°/min); initial placement stirring typically 2.5 r/s ± 0.25 r/s).
- Ultrasonic-type SGS apparatus - non-mechanical monitoring of gel-strength development (method described in the standard).
- Intermittent rotation-type SGS apparatus - periodic shear/disturbance protocol (method described in the standard).
- Calibration and accuracy: Instrument and temperature-measurement calibration requirements (e.g., thermocouples calibrated at least every three months; thermometers checked annually). The standard notes possible variance between instrument types due to sample size and configuration.
- Cautionary note: SGS results should not be used as the sole engineering parameter for cement design - interpret together with other test data.
Applications
- Designing cement slurries for specific well scenarios (shallow-water flow mitigation, plugging operations, annular flow conditions)
- Laboratory quality control and validation of cement formulations
- Pre-job verification of cement behavior under simulated bottom-hole temperature and pressure
Who uses this standard
- Cementing and drilling engineers
- Completion engineers and well design teams
- Laboratory technicians and test houses
- Cement and additive manufacturers
- Operators performing wellbore integrity and plugging work
Related standards
Keywords: EN ISO 10426-6:2008, ISO 10426-6:2008, static gel strength, SGS, well cementing, cement slurry testing, petroleum industry, CEN.
