Mert Ozdemirtas

MSc 2008

Co-advisor: Dr. E. Kuru

Currently with TOTAL

Research topic: "Experimental and Numerical Modeling of Borehole Ballooning - Effect of Fractures Roughness"

Borehole ballooning or breathing, is commonly observed during drilling through fractured zones. It refers to the small, partial and continuous mud losses and significant rapid mud gains due to annular pressure fluctuations resulting from mud circulation and non-circulation. Better understanding of the factors controlling borehole ballooning and /or breathing is needed for correct interpretation of the symptoms obtained while drilling and avoid mixing this phenomena with lost circulation and well kicks. Limited studies in this area dealt with one-dimensional (cylindrical) models for different (Newtonian and non-newtonian) fluid types with parallel plate approximation and simplified linear fracture deformation assumptions. In my research, I introduced a two dimensional transient model of borehole ballooning and/or breathing. The model considers the effects of non-Newtonian fluid rheology, and fracture roughness on the fracture volume change as a function of transient wellbore pressure fluctuations inherent in typical drilling operations. The model has been solved numerically to investigate the effects of drilling fluid properties (i.e., drilling fluid density and rheology) and formation properties (i.e., formation pressure, fracture roughness, and rate of change of fracture aperture.) on the cumulative fluid loss and gain rate between the borehole and the fractured formation. Analyses on the importance of fracture roughness and non-linear deformation approximations were provided and situations where the degree of roughness become critical were identified. At the same time, I am also working on the experimental verification for my numerical model. 


  1. Ozdemirtas, M., Babadagli, T., and Kuru, E.: “Numerical Modeling of Borehole Ballooning/Breathing – Effect of Fracture Roughness,” CIPC 2007-038, CIM 58th Annual Tech. Meet., Canadian Int. Petroleum Conf., Calgary, Canada, 12-14 June 2007. 

  2. Ozdemirtas, M., Babadagli, T. and Kuru, E. : “Experimental and Numerical Investigations of Borehole Ballooning in Rough Fractures,” SPE 110121, 2007 SPE Annual Technical Conf. and Exh., Anaheim, CA, 11-14 Nov. 

  3. Ozdemirtas, M. and Babadagli, T. and Kuru, E.: “Effects of Fractal Fracture Surface Roughness on the Borehole Ballooning,” Vadose Zone Journal, vol. 8, No. 1, Feb. 2009. 

  4. Ozdemirtas, M., Babadagli, T. and Kuru, E.: “Experimental and Numerical Investigations of Borehole Ballooning in Rough Fractures,” SPE Drilling and Comp., June, 2009, 256-265. 

  5. Ozdemirtas, M., Kuru, E., and Babadagli, T.: “Experimental Investigations of Borehole Ballooning Due to Flow of Non-Newtonian Fluids in Fractured Rocks,” Int. J. of Rock Mech. and Min. Sci., vol. 47, 1200-1206, 2010 (Technical Note-peer reviewed). 

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