Borehole Stability in Shale: Beyond Mud Weight
- Ewerton Araujo (BHP) | Darren Kisinger (BHP) | Daniel Vidal (BHP) | Barry Cresap (BHP)
- Document ID
- Society of Petroleum Engineers
- IADC/SPE International Drilling Conference and Exhibition, 3-5 March, Galveston, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2020. IADC/SPE International Drilling Conference and Exhibition
- Borehole stability, Osmosis, Shale activity, Mud activity, Shale-mud interaction
- 56 in the last 30 days
- 132 since 2007
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Several wells in the Gulf of Mexico were analyzed to understand the source of shale instability during drilling and wireline operations. In spite of the mud weight being above the borehole collapse pressure, the wells still exhibited signs of shale instability. As such, it was evident that another mechanism was playing a role in the failure of the shales. This study investigated the drilling fluid properties that are known to affect shale stability. One fundamental property investigated was the water phase salinity, as shales can act as osmotic membranes, allowing fluid diffusion through the porous space while restricting the movement of salt ions. This establishment of an osmotic pressure can either preserve or destroy the mechanical integrity of the shale.
The analysis compared the water phase salinity (WPS) and mud weight (MW) of several wells, in the context of geomechanics, to understand their relationship with the actual borehole stability condition. In one particular case, the data revealed the impact of mud salinity on shale stability, where three different boreholes penetrated the same shale: the original hole (OH) and two sidetracks. In the OH, there was no indication of shale instability during the eight days the hole was exposed, no cavings were reported, and the caliper log showed an in-gauge hole. The first sidetrack (ST1) was completely different where the salinity level was reduced by 7% while the MW remained the same as the OH. During the first ten days of shale exposure in ST1, there was no significant indication of shale sloughing. However, after ten days, it was challenging to maintain a stable wellbore, which led to a stuck pipe event, and an unsuccessful attempt to regain wellbore stability by raising the MW. In the second sidetrack (ST2), the salinity concentration and MW were the same as in the OH, and after fourteen days of exposure to the mud system, there were no signs of instability. The caliper from ST2 confirmed that an in-gauge hole was maintained the entire time of drilling and wireline operations.
These observations were used to calibrate a borehole stability model, which was used to plan a subsequent infill well in the field drilled at a higher inclination and with a long open hole section through the same shales. The model successfully predicted the optimum combination of MW and WPS to maintain a stable wellbore throughout drilling and wireline operations. The results show that a scientifically-driven modeling approach based on offset wellbore observations and appropriate model selection and calibration can result in a significant improvement in drilling operational uptime by minimizing shale instability.
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Dusseault, M. B. (2004). Coupled Thermo-Mechano-Chemical Processin Shales: The Petroleum Borehole. In O. Stephanson (Ed.), Coupled Thermo-Hydro-Mechanical-Chemical Process in Geo-Systems: Fundamentals, Modelling, Experiments and Applications. 2, pp. 573-580. Stockholm: Elsevier. doi:https://doi.org/10.1016/S1571-9960(04)80101-0
Ewy, R. T. (1999, June). Wellbore-Stability Predictions by use of Modified Lade Criterion. SPE Drilling & Completion, 14 (2), 85-91. doi: 10.2118/56862-PA
Al-Bazali, T. M., Zhang, J., Chenevert, M. E., & Sharma, M. M. (2006). Factors Controlling the Membrane Efficiency of Shales when Interacting with Water-Based and Oil-Based Muds. SPE International Oil & Gas Conference and Exhibition in China (Paper SPE 100735). Beijing: Society of Petroleum Engineers. doi:10.2118/100735-MS
Araujo, E. M. P., Pastor, J. A. S. C., & Fontoura, S. A. B. (2006). Incorporating Thermochemoporoelastic Effects in Wellbore Stability Design in Shales. Golden Rocks 2006, The 41st U.S. Symposium on Rock Mechanics (USRMS): "50 Years of Rock Mechanics - Landmarks and Future Challenges (Paper ARMA/USRMS 06-964). Golden: American Rock Mechanics Association.
Chen, G., & Ewy, R. T. (2005). Thermoporoelastic Effect on Wellbore Stability. SPE Journal, 121-129. doi: 10.2118/89039-PA
Colmenares, L. B., & Zoback, M. D. (2001). Statistical evaluation of six rock failure criteria constrained by polyaxial test data. In D. Elsworth, J. P. Tinnuci, & K. A. Heasley (Ed.), Rock Mechanics in the National Interest: Proceedings of the 38th U.S. Rock Mechanics Symposium: DC Rocks 2001 (pp. 1251-1258). Washington DC: A.A. Balkema.
Lomba, R. F., Chenevert, M. E., & Sharma, M. M. (2000). The ion-selective membrane behaviour of native shales. Journal of Petroleum Science, 25(1-2), 9-23. doi:https://doi.org/10.1016/S0920-4105(99)00028-5
McLean, M. R., & Addis, M. A. (1990). Wellbore Stability: The Effect of Strength Criteria on Mud Weight Recommendations. 65th Annual Technical Conference and Exihibtion (Paper SPE 20405). New Orleans: Society of Petroleum Engineers. doi: 10.2118/20405-MS
Mody, F. K., & Hale, A. H. (1993). Borehole Stability Model to Couple the Mechanics and Chemistry of Drilling Fluid/Shale Interactions. Journal of Petroleum Technology (November), 1093-1101. doi: 10.2118/25728-PA
Muniz, E. S., da Fontoura, S. A., & Lomba, R. F. (2004). Development of Equipment and Testing Methodology to Evaluate Rock-Drilling Fluid Interaction. Gulf Rocks 2004, the 6th North American Rock Mechanics Symposium (NARMS): Rock Mechanics across Borders and Disciplines (Paper ARMA/NARMS 04-599). Houston: American Rock Mechanics Association.
Oleas, A. M., Osuji, C. E., Chenevert, M. E., & Sharma, M. M. (2010). Entrance Pressure of Oil-Based Mud into Shale: Effect of Shale Water Activity, and Mud Properties. SPE Drilling & Completion, 39-44. doi:10.2118/116364-PA
Santos, H., & da Fontoura, S. A. (1997). Concepts and Misconceptions of Mud Selection Criteria: How to Minimize Borehole Stability Problems. SPE Annual Technical Conference and Exhibition (pp. 781-796). San Antonio: Society of Petroleum Engineers. doi: 10.2118/38644-MS
van Oort, E. (2003). On the physical and chemical stability of shales. Journal of Petroleum Science and Engineering, 38(3-4), 213-235. doi:https://doi.org/10.1016/S0920-4105(03)00034-2
van Oort, E. (2018). How to test for Compatibility Between Fluids and Shales. IADC/SPE Drilling Conference and Exhibition (Paper IADC/SPE 189633-MS). Forth Worth: Society of Petroleum Engineers. doi: 10.2118/189633-MS
Zhang, J., Rojas, J. C., & Clark, D. E. (2008). Stressed-Shale Drilling Strategy - Water Activity Design Improves Drilling Performance. SPE Drilling & Completion, pp. 385-393. doi: 10.2118/102498-PA