Multiscale Imaging of Fixed-Cutter-Drill-Bit-Generated Shale Cuttings
- Reza Rahmani (National Oilwell Varco) | Ray E. Ferrell (Louisiana State University) | John Rogers Smith (Louisiana State University)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- April 2016
- Document Type
- Journal Paper
- 196 - 204
- 2015.Society of Petroleum Engineers
- imaging , cuttings, PDC bit , drilling , shale
- 3 in the last 30 days
- 510 since 2007
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Shales account for more than 75% of the formations drilled worldwide, and fixed-cutter bits are used to drill most of the footage. Cutter/rock interactions after the initial failure of rock are shown to be a major source of drilling inefficiency. Analytical and numerical modeling was implemented to understand these interactions and their controlling factors, but a comprehensive model does not exist. This is mainly because of the complex nature of the problem that depends on several factors that include rock characteristics, pressure-and-temperature environment, bit design, and drilling-fluid properties. Having such a large range of factors requires a cross-disciplinary approach to tackle the problem. This paper is focused on fabric analysis of the rock cuttings. Recent developments in fabric-analysis techniques allow the study of the size, shape, composition, and spatial arrangement of particles and matrix constituents in finegrained rocks. This has led to an increased understanding of compaction phenomena, shear strength, porosity, permeability, fracturing, electrical propagation, and seismic properties of the rock. Despite this, the changes in rock fabric during interaction with the drill bit are not well-understood. This work takes advantage of those techniques by analyzing the shale cuttings at the macro-, micro-, and nanolevels to understand how shales break and deform under confining pressure to better understand drill-bit/rock interactions. Cuttings recovered from a well in Tuscaloosa, Louisiana, drilled with fixed-cutter bits were analyzed in multiple scales: macro, micro, and nano. Shallower and deeper sections were drilled with water-based mud and oil-based mud (OBM), respectively. Samples were gathered from seven depth intervals ranging from 13,500 to 21,320 ft. The microscale analysis was performed with a X-ray computed-tomography scanning technique, whereas nanoscale analysis was performed with a scanning electron microscope (SEM). Shale-cuttings fabric was characterized by images produced by energy-X-ray-descriptive spectroscopy (EDS) and backscattered-electron microscopy of ion-milled samples. Cuttings were generally formed in the shape of layered ribbons in which the mud-facing side is uneven and serrated whereas the cutter side is smooth and has a darkened clay film. The size of the ribbons and thickness of the layers were larger in areas drilled with OBM. Cuttings accumulation in the form of a ball attached to some of the ribbons from drilling in OBM provided evidence that cutter balling can occur during field drilling operations. SEM-EDS analysis of cuttings showed significant accumulation of barite, a component in the drilling fluid, on the external surface of the serrated sides of the ribbons. In addition, scattered barite zones were found inside the cuttings. X-ray diffraction analyses indicated a mixed mineral assemblage dominated by quartz and smectite with minor illite, kaolinite, chlorite, mixed-layered materials, and traces of calcite and pyrite. It was hypothesized that the absence or scattered appearance of barite in some zones of produced cuttings, particularly the cutter side of the ribbon and the cutter ball, may relate to higher deformation of cuttings at those zones. In addition, the mechanism of cutter balling was explained with an analogy with metal-cutting theories. This was supported by comparison between the geometry of shale cuttings from this field and copper cuttings from single-cutter experiments. Structural analysis of cuttings from actual field drilling reinforced the relevance of the observations made during laboratory experiments. It also provided unique insights, observations, and incentives for additional investigation of how cuttings are formed and what influences dysfunctions or inefficiencies. This is a significant step in understanding shale/cutter interactions that severely affect the bit penetration rate, especially under high confining pressure.
|File Size||1 MB||Number of Pages||9|
Astakhov, Viktor P. 2006. Tribology of Metal Cutting. Vol. 52. Elsevier.
Block, G. and Jin, H. 2009. Role of Failure Mode on Rock Cutting Dynamics. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, USA, 4–7 October. SPE-124870-MS. http://dx.doi.org/10.2118/124870-MS.
Day-Stirrat, R. J., Schleicher, A. M., Schneider, J. et al. 2011. Preferred Orientation of Phyllosilicates: Effects of Composition and Stress on Resedimented Mudstone Microfabrics. J. Structural Geology 33 (9): 1347–1358. http://dx.doi.org/10.1016/j.jsg.2011.06.007.
Fawad, M., Mondol, N. H., Jahren, J. et al. 2010. Microfabric and Rock Properties of Experimentally Compressed Silt-Clay Mixtures. Marine and Petroleum Geology 27 (8): 1698–1712. http://dx.doi.org/10.1016/j.marpetgeo.2009.10.002.
Gerbaud, L., Menand, S., and Sellami, H. 2006. PDC Bits: All Comes From the Cutter/Rock Interaction. Presented at the IADC/SPE Drilling Conference, Miami, Florida, USA, 21–23 February. SPE-98988-MS. http://dx.doi.org/10.2118/98988-MS.
Josh, M., Esteban, L., Delle Piane, C. et al. 2012. Laboratory Characterisation of Shale Properties. J. Petrol. Sci. & Eng. 88: 107–124. http://dx.doi.org/10.1016/j.petrol.2012.01.023.
Judzis, A., Black, A. D., Curry, D. A. et al. 2007. Optimization of Deep Drilling Performance; Benchmark Testing Drives ROP Improvements for Bits and Drilling Fluids. Presented at the SPE/IADC Drilling Conference, Amsterdam, 20–22 February. SPE-105885-MS. http://dx.doi.org/10.2118/105885-MS.
Ledgerwood III, L. W. 2007. PFC Modeling of Rock Cutting Under High-Pressure Conditions. Presented at the1st Canada-US Rock Mechanics Symposium, Vancouver, Canada, 27–31 May. American Rock Mechanics Association (ARMA-07-063).
Loucks, R. G., Reed, R. M., Ruppel, S. C. et al. 2012. Spectrum of Pore Types and Networks in Mudrocks and a Descriptive Classification for Matrix-Related Mudrock Pores. AAPG Bull. 96 (6): 1071–1098. http://dx.doi.org/10.1306/08171111061.
Oil and Gas J. 2007.
Potential Gas Committee. 2003. Potential Supply of Natural Gas: 2002.
Rahmani, R. 2013. Analytical Modeling and Diagnosis of Penetration Rate Performance of PDC Bits. PhD dissertation, Baton Rouge, Louisiana State University.
Rahmani, R., Smith, J. R., and Dahi Taleghani, A. 2012. Analytical Modeling of PDC Single Cutter-Rock Interaction Under Confining Pressure. Presented at the 46th US Rock Mechanics/Geomechanics Symposium. American Rock Mechanics Association, Chicago, USA, 24–27 June. ARMA-2012-341.
Shaughnessy, J. M., Romo, L. A., and Soza, R. L. 2003. Problems of Ultra-Deep High-Temperature High-Pressure Drilling. Presented at the SPE Annual Technical Conference and Exhibition, Denver, USA, 5–8 October. SPE-84555-MS. http://dx.doi.org/10.2118/84555-MS.
Smith, R. H., Lund, J. B., Anderson, M. et al. 1996. Drilling Plastic Formations Using Highly Polished PDC Cutters. Presented at the SPE Annual Technical Conference and Exhibition, Dallas, 22–25 October. pp. 29–44. SPE-30476-MS. http://dx.doi.org/10.2118/30476-MS.
Smith, J. R. 1998. Diagnosis of Poor PDC Bit Performance in Deep Shales. PhD dissertation, Baton Rouge, Louisiana State University.
Snead, M. C. 2005. The Economics of Deep Drilling in Oklahoma. Center for Applied Economic Research: Oklahoma State University.
Van Oort, E., Bland, R., and Pessier, R. 2000. Drilling More Stable Wells Faster and Cheaper With PDC Bits and Water Based Muds. Presented at the IADC/SPE Drilling Conference, New Orleans, USA, 23–25 February. SPE-59192-MS. http://dx.doi.org/10.2118/59192-MS.
Warren, T. M. and Armagost, W. K. 1988. Laboratory Drilling Performance of PDC Bits. SPE Drill Eng 3 (2): 125–135. SPE-15617-PA. http://dx.doi.org/10.2118/15617-PA.