SPE Drilling & Completion
Volume 24, Number 2, June 2009, pp. 239-248

SPE-108159-PA

Olefin-Based Synthetic-Drilling-Fluids Volumetric Behavior Under Downhole Conditions

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DOI  More information 10.2118/108159-PA http://dx.doi.org/10.2118/108159-PA

Citation

  • Demirdal, B. and Cunha, J.C. 2009. Olefin-Based Synthetic-Drilling-Fluids Volumetric Behavior Under Downhole Conditions. SPE Drill & Compl  24 (2): 239-248. SPE-108159-PA. doi: 10.2118/108159-PA.

Discipline Categories

  • 1 Drilling and Completions
  • 1.2 Drilling Design and Analysis
  • 1.3 Wellbore Design/Construction

Keywords

  • managed pressure drilling, drilling fluids, synthetic, volumetric, downhole conditions

Summary

Usual practice in drilling engineering is to determine drilling-fluid density at surface conditions assuming that drilling-fluid density does not change with changing downhole conditions. This assumption may result in inaccuracy while estimating static and dynamic pressures in the wellbore, especially when synthetic-based drilling fluids are used. Inaccurate estimation of the pressure profile in the annulus can lead to severe well problems such as kicks, drilling-fluid losses, and wellbore instability. In addition, inaccurate pressure-profile estimation can affect the success of managed-pressure-drilling (MPD) operations, which require real-time knowledge of wellbore pressures to keep wellbore pressure between formation pore and fracture pressures using a control choke placed on the return line of the annulus.

Effects of pressure and temperature on volumetric behavior of two olefin-based synthetic oils are investigated in this study using a mercury-free pressure/volume/temperature (PVT) system. The olefin-based synthetic oils used in this study are C16C18 internal olefin (IO) and C12C14 linear alpha olefin (LAO). To simulate deep offshore situations, the temperature is ranged between 25 and 175°C, while the pressure is ranged between 0 and 14,000 psig.

In addition, volumetric performances of olefin-based synthetic-oil systems under investigation are compared with those of water, brine solution, mineral oil, diesel oil, and n-paraffin-based oil under similar conditions.

The study shows that the volumetric properties of synthetic-based oils are more sensitive to pressure and temperature conditions compared to water, brine solutions, mineral oil, and diesel oil. Once emulsion systems containing synthetic-based oils are used, density change with respect to downhole conditions should be modeled to increase the reliability of pressure-profile calculations.

© 2009. Society of Petroleum Engineers

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History

  • Original manuscript received: 28 February 2007
  • Meeting paper published: 16 April 2007
  • Revised manuscript received: 7 August 2008
  • Manuscript approved: 21 August 2008
  • Published online: 1 June 2009
  • Version of record: 1 June 2009