SPE Drilling & Completion
Volume 27, Number 1, March 2012, pp. 103-112

SPE-146979-PA

Decreasing Water Invasion Into Atoka Shale Using Nonmodified Silica Nanoparticles

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DOI  More information 10.2118/146979-PA http://dx.doi.org/10.2118/146979-PA

Citation

  • Cai, J., Chenevert, M.E., Sharma, M.M., and Friedheim, J. 2012. Decreasing Water Invasion Into Atoka Shale Using Nonmodified Silica Nanoparticles. SPE Drill & Compl 27 (1): 103-112. SPE-146979-PA. http://dx.doi.org/10.2118/146979-PA

Discipline Categories

  • 1.4.2 Drilling Fluids, Handling, Processing and Treatment
  • 5.5.4 Rock/Fluid Interactions

Keywords

  • shale, silica nanoparticle, fluid invasion, pressure penetration test, permeability

Summary

Fluid penetration from water-based muds into shale formations results in swelling and subsequent wellbore instability. Particles in conventional drilling fluids are too large to seal the nano-sized pore throats of shales and to build an effective mudcake on the shale surface and reduce fluid invasion. This paper presents laboratory data showing the positive effect of adding commercially available, inexpensive, nonmodified silica nanoparticles (NP) (particle sizes vary from 5 to 22 nm) to water-based drilling muds and their effect on water invasion into shale.

Six brands of commercial and nonmodified nanoparticles were tested and screened by running a three-step pressure penetration (PP) test (brine, base mud, nanoparticle mud). Two types of common water-based muds, a bentonite mud and a low-solids mud (LSM), in contact with Atoka shale were studied with and without the addition of 10 wt% nanoparticles. We found that a large reduction in shale permeability was observed when using the muds to which the nonmodified nanoparticles had been added. For the bentonite muds, the permeability of Atoka shale decreased by 57.72 to 99.33%, and, for the LSMs, the permeability of Atoka shale decreased by 45.67 to 87.63%. Higher plastic viscosity (PV) and lower yield point (YP) and fluid loss (FL) of the nanoparticle muds compared with base muds were also observed. We also found that nanoparticles varying in size from 7 to 15 nm and a concentration of 10 wt% are shown to be effective at reducing shale permeability, thereby reducing the interaction between Atoka shale and a water-based drilling fluid.

This study shows for the first time that it is possible to formulate water-based muds using inexpensive nonmodified and commercially available silica nanoparticles and that these muds significantly reduce the invasion of water into the shale. The addition of silica nanoparticles to water-based muds may offer a powerful and economical solution when dealing with wellbore-stability problems in troublesome shale formations.

© 2012. Society of Petroleum Engineers

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History

  • Original manuscript received: 21 June 2011
  • Meeting paper published: 30 October 2011
  • Revised manuscript received: 6 December 2011
  • Manuscript approved: 21 December 2011
  • Published online: 27 February 2012
  • Version of record: 15 March 2012