Fractured Carbonate Rock Research

According to a  2012 review volume on carbonate exploration and reservoir analysis co-edited by an SDI researcher, it is commonly quoted that carbonate reservoirs contain some 50–60% of the world’s oil and gas reserves (Garland et al., 2012). Indeed, the world’s largest oil field (Ghawar, Saudi Arabia) and the world’s largest gas field (North Field/South Pars straddling the Qatar/Iran border) are both reservoired in carbonate rocks. Many low-matrix-porosity hydrocarbon reservoirs are productive because permeability is controlled by fractures and faults. Understanding basic fracture properties is critical in reducing geological risk and therefore reducing well costs and increasing well recovery.

Esti Ukar

Research on the origins and controls on fractures in carbonate rocks has been an abiding part of studies under the auspices of FRAC and of the SDI initiative research program, including work on the regional stratigraphic and diagenetic controls on fracture occurrence (Marrett and Laubach, 2001; Ortega et al., 2013), fracture abundance (Marrett et al., 1999; Ortega et al., 2006), spatial arrangement (Gale, 2002; Marrett et al., 2017), mechanical and fracture stratigraphy (Laubach et al., 2009), modeling cement accumulation in fractures (Gale et al., 2010), how to image carbonate minerals (Reed and Milliken, 2003: Ukar and Laubach, 2016), interaction of cement accumulation and fracture growth (Hooker et al., 2012), mechanical properties of carbonate rocks (Olson, 2004), detection of fractures using seismic methods (Marrett et al., 2007), modeling fracture patterns (Olson, 2004) modeling the role of fractures on reservoir behavior and fluid flow and upscaling to flow simulation (Philip et al., 2005), interaction of natural and hydraulic fractures (Alabbad and Olson, 2016), and mudloss while drilling analysis (Razavi et al., 2017).

Research on Fractures in Carbonate Rocks

Dr. Esti Ukar leads on SDI’s effort in natural fracture research in carbonate rocks. Leadership entails maintaining a focus within the larger FRAC and SDI effort on issues particularly germane to carbonate rocks. She also directs the new high-resolution field emission scanning electron microscope facility with a focus on cathodoluminescence imaging (SEM-CL).

Ukar’s research combines small-scale brittle structural petrology with large-scale deformation characterization and modeling on the upper continental crust. Ukar’s reseach spans from fracture scaling analyses and fracture evolution and timing modeling using commercial and in-house software, to developing paleostress indicators using twinned fracture cements.

The following papers and abstracts reflect some of Ukar’s recently published work:

  • Ukar, E. and Laubach, S.E., 2016, Syn- and postkinematic cement textures in fractured carbonate rocks: Insights from advanced cathodoluminescence imaging, Tectonophysics, v. 690 (A), 190-205. doi: 10.1016/j.tecto.2016.05.001 | publications
  • Ukar, E., Laubach, S.E., Marrett, R., 2016, Quartz c-axis orientation patterns in fracture cement as a measure of fracture opening rate and a validation tool for fracture pattern models: Geosphere, v. 12, no. 2, p. 400–438, doi: 10.1130/GES01213.1. | publications
  • Fall, A., Ukar, E., Laubach, S.E., 2016, Origin and timing of Dauphiné twins in quartz cement in fractured sandstones from diagenetic environments: insight from fluid inclusions. Tectonophysics | publications
  • Ukar, E., Ozkul, C., Eichhubl, P., 2016, Fracture abundance and strain in folded Cardium Formation, Red Deer River anticline, Alberta Foothills, Canada. Marine & Petroleum Geology 76, 210-230. doi: 10.1016/jmarpetgeo.2016.05.016 | publications
  • Ukar, E., and Cloos, M., 2014. Low-temperature blueschist-facies mafic blocks in the Franciscan mélange, San Simeon, California: Field relations, petrology, and counterclockwise PT paths. Geological Society of America Bulletin, B30876-1.
  • Ukar, E., Cloos, M., and Vasconcelos, P., 2012. First 40Ar-39Ar ages from low-T Mafic blueschist blocks in a Franciscan Mélange near San Simeon: Implications for initiation of subduction. The Journal of Geology, 120(5), 543-556.

Carbonate Rock Structural Diagenesis Initiative

In 2014 SDI began a campaign to systematically unravel fracture systems in carbonate rocks, building on our previous work [see reference list below]. The program is led by Ukar, Marrett and Laubach and includes a core group of industry experts. Initial topics of research include

  1. Timing and rate of fracture growth
  2. Role of cement in fracture size and spatial arrangement development
  3. Diagenetic evolution of mechanical and fracture stratigraphy
  4. Fracture-prone and fracture-resistant rocks (including rock properties library)
  5. Evolution of fracture porosity and permeability
  6. Prediction of fracture attributes including clustering, height distribution
  7. Subsurface (core, log, production & seismic) and outcrop-based studies
  8. Numerical modeling using JOINTS and other structural modeling approaches
  9. Review of existing knowledge of fracture systems in carbonate rocks

Starting in 2016 Ukar has led the ongoing Fracture Research Study in western China.

Carbonate Rock Fracture initiative CRSDI page

Progress reports are listed here.

Selected references of program work on fractured carbonate rocks

Selected initiative papers on fractures in carbonate rocks; for access see publications:

  • Late opening-mode fractures in karst-brecciated dolostones of the Lower Ordovician Ellenburger Group, west Texas: Recognition, characterization, and implications for fluid flow. Gale, J.F.W. and Gomez, L.A., 2007, AAPG Bulletin 91: 1005-1023.
  • Specifying lengths of horizontal wells in fractured reservoirs. Gale, J.F.W., 2002, Society of Petroleum Engineers Reservoir Evaluation and Engineering 5(3), 266-272.
  • Predicting and characterizing fractures in dolostone reservoirs: using the link between diagenesis and fracturing. Gale, J.F.W., Laubach, S.E., Marrett, R.A., Olson, J.E., Holder, J. & Reed, R.M., 2004, In: Braithwaite, C.J.R., Rizzi, G. & Darke, G., eds., The Geometry and Petrogenesis of Dolomite Hydrocarbon Reservoirs. Geological Society, London, Special Publications, 235, 177-192.
  • Modeling fracture porosity evolution in dolostone. Gale, J.F.W., Lander, R.H., Reed, R.M., and Laubach, S.E., 2010, Journal of Structural Geology 32(9), 1201-1211. doi:10.1016/j.jsg.2009.04.018.
  • Advances in carbonate exploration and reservoir analysis. Garland, J., J.E. Neilson, S.E. Laubach, & K. J. Whidden, 2012, In Garland, J., J.E. Neilson, S.E. Laubach, & K.J. Whidden (eds.) Advances in Carbonate Exploration and Reservoir Analysis, Geological Society of London Special Publications 370, p. 1-15. doi: 10.1144/SP370.15
  • Effects of diagenesis (cement precipitation) during fracture opening on fracture aperture-size scaling in carbonate rocks. Hooker, J.N., Gomez, L.A., Laubach, S.E., Gale, J.F.W. & Marrett, R., 2012, In Garland, J., J.E. Neilson, S.E. Laubach, & K. J. Whidden (eds.) Advances in Carbonate Exploration and Reservoir Analysis, Geological Society of London Special Publications 370, p. 187-206. doi:10.1144/SP370.9.
  • Stylolites in limestone: magnitude of contractional strain accommodated and scaling relationships. Benedicto, A., Schultz, R.A., 2010, Journal of Structural Geology 32(9), 1250-1256.
  • Mechanical and fracture stratigraphy: Laubach, S.E., Olson, J.E., and Gross, M.E., 2009, AAPG Bulletin 93(11), 1413-1426.
  • Genesis and controls of reservoir-scale carbonate deformation, Monterrey salient, Mexico: Marrett, R., ed., 2001, The University of Texas at Austin, Bureau of Economic Geology, Guidebook 28.
  • Anisotropy and beyond: geologic perspectives on geophysical prospecting for natural fractures. Marrett, R., Laubach, S.E. Olson, J.E., 2007, The Leading Edge 26/9, 1106-1111.
  • Extent of power-law scaling of natural fractures in rock: Marrett, R., Ortega, O.O., and Kelsey, C., 1999, Geology 27, 799-802.
  • Fracturing during burial diagenesis, Marrett, R., and Laubach, S.E., 2001, in Marrett, R., ed., Genesis and controls of reservoir-scale carbonate deformation, Monterrey salient, Mexico: The University of Texas at Austin, Bureau of Economic Geology, Guidebook 28, p. 109-120.
  • Predicting fracture swarms – the influence of subcritical crack growth and the crack-tip process zone on joint spacing in rock, Olson, J.E., 2004, in Cosgrove, J.W., and Engelder, T., eds., The initiation, propagation, and arrest of joints and other fractures, Geological Society of London Special Publication 231, 73-87.
  • Correlation analysis of fracture arrangement in space. Marrett, R., Gomez, L. Gale, J., Laubach, S., 2017. Journal of Structural Geology.
  • Fault and joint swarms in a normal fault zone. Laubach, S., Mace, R., Nance, H., 1995. Mechanics of Jointed and Faulted Rocks [Austin chalk example].
  • A scale-independent approach to fracture intensity and average fracture spacing: Ortega, O. J., Marrett, R., and Laubach, S. E., 2006, AAPG Bulletin 90(2), 193-208.
  • Quantifying diagenetic and stratigraphic controls on fracture intensity in platform carbonates: An example from the Sierra Madre Oriental, northeast Mexico, Ortega, O.J., Gale, J.F.W., Marrett, R., 2010, Journal of Structural Geology 32(12), 1943-1959. doi:10.1016/j.jsg.2010.07.004
  • Modeling coupled fracture-matrix fluid flow in geomechanically simulated fracture networks: Philip, Z.G., Jennings, J.W., Jr., Olson, J., Laubach, S.E., and Holder, J., 2005, SPE Reservoir Evaluation & Engineering 8(4), 300-309.
  • How to overcome imaging problems associated with carbonate minerals on SEM-based cathodoluminescence systems: Reed, R.M., and Milliken, K.L., 2003, Journal of Sedimentary Research 73(2), 328–332.
  • Syn- and postkinematic cement textures in fractured carbonate rocks: Insights from advanced cathodoluminescence imaging, Ukar, E. and Laubach, S.E., 2016, Tectonophysics 690(A), 190-205. doi: 10.1016/j.tecto.2016.05.001
  • Characterization of naturally fractured reservoirs using mud loss data: the effect of fluid leak-off. Razavi, O., Lee, H.P., Olson, J.E., Schultz, R.A., 2017. 51st US Rock Mechanics/Geomechanics Symposium.

Information about the SEM CL Facility

Structural Diagenesis Initiative Main Page

Fracture Research and Application Consortium