Methods for Estimating Fracture Abundance and Size From Borehole Observations
- Charles R. Berg (Resdip Systems)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- November 2019
- Document Type
- Journal Paper
- 1,399 - 1,425
- 2019.Society of Petroleum Engineers
- fracture porosity, fracture size, fracture density, natural fractures, fracture intensity
- 32 in the last 30 days
- 93 since 2007
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This study develops deterministic, exact equations relating fracture frequency (P10), density (P32), and length and width dimensions of rectangular and elliptical fractures from borehole observations. These general equations are applicable to both image logs and cores. A Monte Carlo type of simulation model generated the stochastic data used to derive the equations. The equations use five basic parameters relating frequency to density: borehole diameter, fracture length, fracture width, fracture angle with borehole axis, and the rotation angle of the long fracture axis within the fracture plane. For both general equations, density corrections can be applied to individual fractures to find density. Fracture porosity is calculated on a per-fracture basis by applying aperture to density corrections. Both equations match the model to within the small standard deviation between simulations. In addition, the elliptical equation generally agrees with the existing exact theory.
The study also develops methods for calculating fracture height (width) and length for rectangular fractures. Fracture height and length are calculated by observing the borehole-enclosed height and length and comparing them with the borehole-enclosed area. The calculation of fracture size is extended to estimate block height and length (block-face size.)
These relationships cover a wide range of fracture size and orientation vs. borehole diameter. The theory is valid from small boreholes to tunnels. The general equations consider fractures as planar objects with length and width dimensions and negligible aperture compared with the other dimensions. Fracture aperture is applied, on a per-fracture basis, after the density correction to calculate fracture porosity. In addition to density and porosity calculations, an existing method for fracture-frequency prediction is improved by applying the general relationships.
The methods described here are demonstrated using an image log from a vertical well from British Columbia, Canada. In this well, an image log was run over the Triassic section, including the zone of interest, the Montney Formation. Although the average fracture size in the Montney was very large, possibly on the order of tens of meters, they had a much smaller block-face size, on the order of a few meters, which could explain some of the production aspects from this formation.
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Barthélémy, J.-F., Guidon, M. L. E., and Daniel, J.-M. 2009. Estimates of Fracture Density and Uncertainties From Well Data. Int J Rock Mech Min Sci 46 (3): 590–603. https://doi.org/10.1016/j.ijrmms.2008.08.003.
Dershowitz, W. S. and Herda, H. H. 1992. Interpretation of Fracture Spacing and Intensity. Presented at the 33rd US Symposium on Rock Mechanics, Santa Fe, New Mexico, 3–5 June. ARMA-92-0757.
Excel is a registered trademark of Microsoft Corporation, One Microsoft Way, Redmond, Washington 98052.
Fullbore Formation Microimager is a service mark of Schlumberger Limited, 300 Schlumberger Dr., Sugar Land, Texas 77478. https://www.slb.com/services/characterization/geology/wireline/fullbore_formation_microimager.aspx.
Hooker, J. N., Laubach, S. E., and Marrett, R. 2013. Fracture-Aperture Size—Frequency, Spatial Distribution, and Growth Processes in Strata-Bounded and Non-Strata-Bounded Fractures, Cambrian Mesón Group, NW Argentina. J Struct Geol 54 (September): 54–71. https://doi.org/10.1016/j.jsg.2013.06.011.
Joubert, T. G. 1998. Optimal Drilling Direction in Folded Fractured Triassic Carbonates in Northeastern British Columbia Determined by Applying Fracture “Occurrence” to Frequency Intercept and Flow Diagrams. Master’s thesis, University of Calgary, Calgary, Alberta, Canada (September 1998).
La Pointe, P. R. 1988. A Method to Characterize Fracture Density and Connectivity Through Fractal Geometry. Int J Rock Mech Min Sci 25 (6): 421–429. https://doi.org/10.1016/0148-9062(88)90982-5.
La Pointe, P. R., Wallmann, P. C., and Dershowitz, W. S. 1993. Stochastic Estimation of Fracture Size Through Simulated Sampling. Int J Rock Mech Min Sci 30 (7): 1611–1617. https://doi.org/10.1016/0148-9062(93)90165-A.
Lacazette, A. 1991. A New Stereographic Technique for the Reduction of Scanline Survey Data of Geologic Fractures. Comput Geosci 17 (3): 445–463. https://doi.org/10.1016/0098-3004(91)90051-E.
Laubach, S. E., Lamarche, J., Gauthier, B. D. M. et al. 2018. Spatial Arrangement of Faults and Opening-Mode Fractures. J Struct Geol 108 (March): 2–15. https://doi.org/10.1016/j.jsg.2017.08.008.
Luthi, S. M. and Souhaité, P. 1990. Fracture Apertures From Electrical Borehole Scans. Geophysics 55 (7): 821–833. https://doi.org/10.1190/1.1442896.
Mauldon, M. and Dershowitz, W. 2000. A Multi-Dimensional System of Fracture Abundance Measures. Presented at the Geological Society of America Annual Meeting, Reno, Nevada, 9–18 November.
Mauldon, M. and Mauldon, J. G. 1997. Fracture Sampling on a Cylinder: From Scanlines to Boreholes and Tunnels. Rock Mech Rock Eng 30 (3): 129–144. https://doi.org/10.1007/BF01047389.
Narr, W. and Lerche, I. 1984. A Method for Estimating Subsurface Fracture Density in Core. AAPG Bulletin 68 (5): 637–648.
Narr, W. and Suppe, J. 1991. Joint Spacing in Sedimentary Rocks. J Struct Geol 13 (9): 1037–1048. https://doi.org/10.1016/0191-8141(91)90055-N.
Narr, W., Schechter, D. S., and Thompson, L. B. 2006. Naturally Fractured Reservoir Characterization. Richardson, Texas: Society of Petroleum Engineers.
Olson, J. E., Laubach, S. E., and Lander, R. H. 2009. Natural Fracture Characterization in Tight Gas Sandstones: Integrating Mechanics and Diagenesis. AAPG Bull. 93 (11): 1535–1549. https://doi.org/10.1306/08110909100.
Ortega, O. J., Marrett, R. A., and Laubach, S. E. 2006. A Scale-Independent Approach to Fracture Intensity and Average Fracture Spacing. AAPG Bull. 90 (2): 193–208. https://doi.org/10.1306/08250505059.
Ozkaya, S. I. 2003. Fracture Length Estimation From Borehole Image Logs. Math Geol 35 (6): 737–753. https://doi.org/10.1023/B:MATG.0000002987.69549.ba.
Palmstrom, A. 2005. Measurements of and Correlations Between Block Size and Rock Quality Designation (RQD). Tunn Undergr Sp Tech 20 (4): 362–377. https://doi.org/10.1016/j.tust.2005.01.005.
Pollard, D. D. and Aydin, A. 1988. Progress in Understanding Jointing Over the Past Century. GSA Bull. 100 (8): 1181–1204. https://doi.org/10.1130/0016-7606(1988)100%3C1181:PIUJOT%3E2.3.CO;2.
Priest, S. D. 1993. Discontinuity Analysis for Rock Engineering. London: Chapman & Hill.
Stevenson, B. and Coffin, K. 2015. Guidelines for the Handling of Natural Fractures and Faults in Hydraulically Stimulated Resource Plays. Presented at the SPE/CSUR Unconventional Resources Conference, Calgary, 20–22 October. SPE-175910-MS. https://doi.org/10.2118/175910-MS.
Terzaghi, R. D. 1965. Sources of Errors in Joint Surveys. Géotechnique 15 (3): 287–304. https://doi.org/10.1680/geot.1918.104.22.1687.
Wang, X. 2005. Stereological Interpretation of Rock Fracture Traces on Borehole Walls and Other Cylindrical Surfaces. PhD dissertation, Virginia Polytechnic Institute and State University, Blacksburg, Virginia (September 2005).
Wang, X., Mauldon, M., Dunne, W. et al. 2004. Using Borehole Data To Estimate Size and Aspect Ratio of Subsurface Fractures. Presented at Gulf Rocks 2004, the 6th North America Rock Mechanics Symposium (NARMS), Houston, 5–9 June. ARMA-04-570.