Shale geomechanics

Shale (or mudrock) geomechanics as well as natural and hydraulically induced fractures in shale continue to be areas of intense Structural Diagenesis Initiative research.

Already in 2019, the Initiative has published 10 papers covering specific aspects of these topics. Additionally, a forward-looking overview paper in Reviews of Geophysics, Laubach et al., 2019, points to future research directions that could help solve some of the fundamental challenges in accurately predicting subsurface fracture attributes and responses to engineering operations.

Shale outcrop

A key initiative is direct observation of hydraulic fractures in the Hydraulic Fracture Test Site in the Midland Basin. This ongoing study is providing insights into the types and patterns of fractures in the subsurface, including in-depth analysis of natural fracture and hydraulic fracture interaction. Two papers by Gale et al. summarize recent findings.

Hydraulic and natural fracture interactions are also being systematically analyzed with numerical and physical models. Yue et al. describe numerical results investigating layering effects on hydraulic fracture growth and Wang et al. describes how physical modeling throws light on the hydraulic fracture process.

Four papers describe recent findings in our systematic analysis of shale mechanical properties. These results take advantage of a range of specialized testing capabilities within the group. Papers by Chen et al. provide an account of recent advances in understanding controls on fracture mechanical properties. Papers by Ramos et al. describe recent progress in unraveling the controls on static and dynamic properties of shale.

Initiative scientists are also involved in worldwide core and outcrop studies of shales. Ukar et al. and McCay et al. provide two recent examples.

Further work on all these topics is in press or in preparation.

Direct observation & modeling

Gale, J.F.W., Elliott, S.J., Laubach, S.E., 2019. Direct observation of hydraulic fractures in the Hydraulic Fracture Test Site (HFTS) slant core, Reagan Co., Midland Basin, Texas: Insights into distribution, morphology, intensity and interaction with natural discontinuities. William C. Gussow Geoscience Conference, New Directions in Geosciences for Unconventional Resources. | view | blog post

Gale, J.F.W., Elliott, S.J., Li, J.Z., and Laubach, S.E., 2019. Natural fracture characterization in the Wolfcamp Formation at the Hydraulic Fracture Test Site (HFTS), Midland basin, Texas. SPE/AAPG/SEG Unconventional Resources Technology Conference, URTEC-644. doi: 10.15530/urtec-2019-644 | view

Yue, K., Olson, J.E., Schultz, R.A., 2019. The effect of layered modulus on hydraulic-fracture modeling and fracture-height containment. SPE Drilling & Completions. doi.org/10.2118/195683-PA | view

Wang, W., Wu, K., and Olson, J.E., 2019. Characterization of hydraulic fracture geometry in shale rocks through physical modeling. International Journal of Fracture, 216 (1), 71-85. | view

Mechanical properties

Chen, X., Eichhubl, P., Olson, J.E., Dewers, T.A., 2019. Effect of water on fracture mechanical properties of shale. JGR Solid Earth doi.org/10.1029/2018JB016479 | view

Chen, X., Eichhubl, P., Olson, J.E., Dewers, T., 2019. Salinity, pH, and temperature controls on fracture mechanical properties of three shales and their implications for fracture growth in chemically reactive fluid environments. Geomechanics for Energy and the Environment. doi:10.1016/j.gete.2019.100140 | view

Ramos, M.J., Espinoza, D.N., Laubach, S.E., and Torres-Verdin, C., 2019. Quantifying static and dynamic stiffness anisotropy and nonlinearity in finely laminated shales: experimental measurement and modeling. Geophysics 84 (1), MR25-MR36. doi.org/10.1190/geo2018-0032.1 | view

Ramos, M.J., Espinoza, D.N., Goldfarb, E.J., Tisato, N., Laubach, S.E., Torres-Verdin, C., 2019. Microstructural controls on elastic anisotropy of finely laminated Mancos Shale. Geophysical Journal International, 216 (2), 991-1004. doi.org/10.1093/gji/ggy474 | view

Outcrop and core studies

Ukar, E., Lopez, R.G., Gale, J.F.W., and Manceda, R., 2019. Outcrop to core comparison of natural fractures in the Vaca Muerta Formation, Argentina. Sixth EAGE Shale Workshop, 28 April 2019. doi: 10.3997/2214-4609.201900284 | view

McCay, A.T., Shipton, Z.K., Lunn, R.J., and Gale, J.F.W., 2019. Mini thief zones: sub-centimeter sedimentary features enhance fracture connectivity in shales. AAPG Bulletin, 103 (4), 951-971. doi.org/10.1306/0918181610617114 | Featured in AAPG Explorer | view

Overview and future directions

Laubach, S.E., Lander, R.H., Criscenti, L.J., et al., 2019. The role of chemistry in fracture pattern development and opportunities to advance interpretations of geological materials. Reviews of Geophysics doi:10.1029/2019RG000671 | view | blog post