Wellbore-Stability Performance of Water-Based Mud Additives
- Russell T. Ewy (Chevron Energy Technology Company) | E. Keith Morton (Chevron Energy Technology Company)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 2009
- Document Type
- Journal Paper
- 390 - 397
- 2009. Society of Petroleum Engineers
- 1.2.1 Wellbore integrity, 1.2.2 Geomechanics, 1.6 Drilling Operations, 5.1 Reservoir Characterisation, 6.5.4 Naturally Occurring Radioactive Materials, 4.3.1 Hydrates, 1.11 Drilling Fluids and Materials
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A critical property for many water-based muds is the ability to prevent near-wellbore pore pressure increase in shales. By slowing or preventing this pressure increase, a true overbalance pressure is maintained, which promotes wellbore stability. Using a device that simulates downhole rock stress and overbalance fluid pressure conditions and using preserved shale samples, we tested four different muds containing different additives. Direct measurements of shale pore pressure vs. time were obtained, representing the pore pressure inside the wall of the wellbore. All muds slowed the loss of overbalance pressure compared to a base-case brine fluid, but two muds were very effective at slowing and/or preventing the loss of overbalance. One active mechanism appears to be an increase in the osmotic membrane efficiency, but permeability measurements conducted during these same tests show that physical plugging of the pore space is also an important mechanism for these two fluids. Measurements of fluid-induced swelling were also conducted in this same set of tests, and all four muds resulted in less swelling than the base-case brine. The most effective fluid was repeat tested using completely different shales; it again was found to be very effective at preventing near-wellbore pore pressure increase for one of the shales, but not for all shales.
One of the main shale instability mechanisms that occurs with water-based drilling fluids is that the wellbore pressure penetrates into the shale pore space. This raises the near-wellbore pore pressure and reduces the true overbalance. This reduction of true overbalance, which acts like a support pressure for the hole, can result in shale failure and wellbore instability. The pressure penetration cannot be prevented with standard filtration additives, because shale pores are extremely small (approximately 0.01 micron) and shale permeability is extremely low (typically ~0.01 microdarcy or less); therefore, a filter cake does not develop on shales.
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Chenevert, M.E. 1989. Diffusion of water and ions into shales. In Rock atGreat Depth: Rock Mechanics and Rock Physics at Great Depth--Proceedings of anInternational Symposium, Pau, 28-31 August 1989, Vol. 3, ed. V. Maury andD. Fourmaintraux, 1177-1184. London: Taylor & Francis.
Dye, W., d'Augereau, K., Hansen, N., Otto, M., Shoults, L., Leaper, R.,Clapper, D., and Xiang, T. 2006. New Water-Based Mud BalancesHigh-Performance Drilling and Environmental Compliance. SPE Drill &Compl 21 (4): 255-267. SPE-92367-PA. doi:10.2118/92367-PA.
Ewy, R.T. and Stankovich, R.J. 2000. Pore pressure change due to shale-fluidinteraction: Measurements under simulated wellbore conditions. Proc.,Pacific Rocks 2000, 4th North American Rock Mechanics Symposium, Seattle,Washington, USA, 31 July—3 August, 147-154.
Ewy, R.T. and Stankovich, R.J. 2002. Shale-Fluid Interactions MeasuredUnder Simulated Downhole Conditions. Paper SPE 78160 presented at theSPE/ISRM Rock Mechanics Conference, Irving, Texas, USA, 20-23 October. doi:10.2118/78160-MS.
Ewy, R.T., Bovberg, C.A., and Stankovich, R.J. 2008. Shale triaxial strengthalteration due to brine exposure. Paper ARMA 08-304 presented at San Francisco2008, 42nd U.S. Rock Mechanics Symposium, 2nd U.S.-Canada Rock MechanicsSymposium, San Francisco, California, USA, 29 June-2 July.
Fritz, S.J. and Marine, I.W. 1983. Experimental support fora predictive osmotic model of clay membranes. Geochimica et CosmochimicaActa 47 (8): 1515-1522. doi:10.1016/0016-7037(83)90310-1.
Mody, F.K. and Hale, A.H. 1993. Borehole-Stability Model To Couplethe Mechanics and Chemistry of Drilling-Fluid/Shale Interactions. J. PetTech 45 (11): 1093-1101. SPE-25728-PA. doi:10.2118/25728-PA.
Mody, F.K., Tare, U.A., Tan, C.P., Drummond, C.J., and Wu, B. 2002. Development of Novel MembraneEfficient Water-Based Drilling Fluids Through Fundamental Understanding OfOsmotic Membrane Generation in Shales. Paper SPE 77447 presented at the SPEAnnual Technical Conference and Exhibition, San Antonio, Texas, USA, 29September-2 October. doi: 10.2118/77447-MS.
Schlemmer, R., Friedheim, J.E., Growcock, F.B., Bloys, J.B., Headley. J.A.,and Polnaszek, S.C. 2003a. Chemical Osmosis, Shale, and DrillingFluids. SPE Drill & Compl 18 (4): 318-331. SPE86912-PA. doi: 10.2118/86912-PA.
Schlemmer, R., Patel, A., Friedheim, J., Young M-I, S., and Bloys, B. 2003b.Progression of Water-Based Fluids Based on Amine Chemistry--Can the Road Leadto True Oil Mud Replacement? Paper AADE-03-NTCE-36 presented at the AADE 2003National Technology Conference, Houston, 1-3 April.
Simpson, J.P. and Dearing, H.L. 2000. Diffusion Osmosis--An UnrecognizedCause of Shale Instability. Paper SPE 59190 presented at the IADC/SPEDrilling Conference, New Orleans, 23-25 February. doi: 10.2118/59190-MS.
Simpson, J.P., Walker, T.O., and Jiang, G.Z. 1995. Environmentally AcceptableWater-Based Mud Can Prevent Shale Hydration and Maintain WellboreStability. SPE Drill & Compl 10 (4): 242-249.SPE-27496-PA. doi: 10.2118/27496-PA.
Steiger, R.P. 1993. Advanced triaxialswelling tests on preserved shale cores. Int. J. Rock Mech. Min. Sci& Geomech Abstr. 30 (7): 681-685.doi:10.1016/0148-9062(93)90005-X.
Stowe, C., Halliday, W., Xiang, T., Clapper, D., Morton, K., and Hartman, S.2001. Laboratory Pore Pressure Transmission Testing of Shale. Paper AADE01-NC-HO-44 presented at the AADE 2001 National Drilling Conference, Houston,27-29 March.
van Oort, E., Hale, A.H. Mody, F.K., and Roy, S. 1996. Transport in Shales and the Design ofImproved Water Based Shale Drilling Fluids. SPE Drill & Compl11 (3): 137-146. SPE-28309-PA. doi: 10.2118/28309-PA.
van Oort, E., Hale, A.H., and Mody, F.K. 1995. Manipulation of Coupled Osmotic Flowsfor Stabilisation of Shales Exposed to Water-Based Drilling Fluids. PaperSPE 30499 presented at the SPE Annual Technical Conference and Exhibition,Dallas, 22-25 October. doi: 10.2118/30499-MS.