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An equivalent circulating density prediction model for extended-reach horizontal wells considering drill strings
Zhao Huang1, Yanfei Li1, Kun Jiang2
1Drilling & Completion Project Team, Pinghu Oil & Gas Field in the East China Sea, CNOOC (China) Limited, Shanghai, 200335, China.
Scientific Reports
|July 22, 2025
Summary
Sinusoidal buckling in drill strings causes depth measurement errors in extended-reach wells. A new model corrects equivalent circulating density (ECD) calculations, improving well control accuracy.
Area of Science:
- Petroleum Engineering
- Drilling Mechanics
Background:
- Extended-reach horizontal wells (ERHWs) face challenges with drill string sinusoidal buckling.
- Buckling leads to inaccurate well depth and vertical depth measurements.
- These errors significantly impact Equivalent Circulating Density (ECD) calculations and well control.
Purpose of the Study:
- To develop a corrected ECD calculation model for ERHWs.
- To account for well depth and vertical depth measurement errors caused by drill string buckling.
- To enhance the accuracy of ECD control during drilling operations.
Main Methods:
- Corrected a traditional ECD calculation model.
- Incorporated measurement errors from sinusoidal drill string buckling.
- Established a new ECD model specifically for ERHWs.
- Validated the model using field data from the East China Sea.
Main Results:
- The proposed model's predictions closely matched recorded ECD values during sinusoidal buckling.
- The new model predicts lower ECD values when buckling occurs due to increased drill string length.
- Increased drill string buckling degree resulted in smaller predicted ECD values.
Conclusions:
- The developed model provides more accurate ECD predictions for ERHWs with sinusoidal drill string buckling.
- This improved accuracy reduces drilling risks and enhances well control operations.
- The model offers reliable reference data for fine ECD control in challenging wellbores.
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