@article {Nagel2013,
	title = {{Coupled Numerical Evaluations of the Geomechanical Interactions Between a Hydraulic Fracture Stimulation and a Natural Fracture System in Shale Formations}},
	journal = {Rock Mechanics and Rock Engineering},
	volume = {46},
	number = {3},
	year = {2013},
	month = {mar},
	pages = {581{\textendash}609},
	abstract = {Due to the low permeability of many shale reservoirs, multi-stage hydraulic fracturing in horizontal wells is used to increase the productive, stimulated reservoir volume. However, each created hydraulic fracture alters the stress field around it, and subsequent fractures are affected by the stress field from previous fractures. The results of a numerical evaluation of the effect of stress field changes (stress shadowing), as a function of natural fracture and geomechanical properties, are presented, including a detailed evaluation of natural fracture shear failure (and, by analogy, the generated microseismicity) due to a created hydraulic fracture. The numerical simulations were performed using continuum and discrete element modeling approaches in both mechanical-only and fully coupled, hydro-mechanical modes. The results show the critical impacts that the stress field changes from a created hydraulic fracture have on the shear of the natural fracture system, which in-turn, significantly affects the success of the hydraulic fracture stimulation. Furthermore, the results provide important insight into: the role of completion design (stage spacing) and operational parameters (rate, viscosity, etc.) on the possibility of enhancing the stimulation of the natural fracture network ({\textquoteright}complexity{\textquoteright}); the mechanisms that generate the microseismicity that occurs during a hydraulic fracture stimulation; and the interpretation of the generated microseismicity in relation to the volume of stimulated reservoir formation. {\textcopyright} 2013 Springer-Verlag Wien.},
	keywords = {Discrete element modeling, Horizontal well, Hydraulic fracturing, Multi-stage fracturing, Natural fractures, Numerical simulation, Stimulation, Stimulation optimization, Well completion},
	issn = {0723-2632},
	doi = {10.1007/s00603-013-0391-x},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84877873776\&partnerID=tZOtx3y1},
	author = {Nagel, N. B. and Sanchez-Nagel, M. A. and Zhang, F. and Garcia, X. and Lee, B.}
}
@conference {Nagel2012b,
	title = {{A numerical evaluation of the geomechanical interactions between a hydraulic fracture stimulation and a natural fracture system}},
	booktitle = {46th US Rock Mechanics / Geomechanics Symposium 2012},
	volume = {3},
	year = {2012},
	pages = {1882{\textendash}1898},
	abstract = {Due to the low permeability of many shale gas reservoirs, multi-stage hydraulic fracturing in horizontal wells is used to increase the stimulated volume. However, each created hydraulic fracture alters the stress field around it, and subsequent fractures are affected by the stress field from the previous fractures, which results in higher net pressures, smaller fracture widths, and diminished microseismic emissions. The results of a numerical evaluation of the effect of stress shadowing, as a function of natural fracture and geomechanical properties, are presented, including a detailed evaluation of natural fracture shear failure (and, by analogy, the microseismicity) due to a created hydraulic fracture using both continuum and discrete element modeling approaches. The results show the critical impact that a created hydraulic fracture has on the shear of the natural fracture system, which in-turn, significantly affects the success of the stimulation. Furthermore, the results provide important insight into the mechanisms that generate the microseismicity that occurs during a hydraulic fracture stimulation. Copyright 2012 ARMA, American Rock Mechanics Association.},
	isbn = {9781622765140},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84873277033\&partnerID=tZOtx3y1},
	author = {Nagel, N. B. and Sanchez-Nagel, M. A. and Garcia, X. and Lee, B.}
}
