TY - JOUR
T1 - Discrete micro-physics interactions determine fracture apertures
AU - Couples, Gary Douglas
N1 - Funding Information:
I thank the Royal Society for a Theo Murphy Blues Skies Award, which supported my derivation of the micro-mechanics of fluid//geomechanics interactions in 2017-19. Many students and colleagues are acknowledged for developing a range of simulation models that inform my present understanding of fracture-involved geomechanics; of note in this regard are: the late Mark Reynolds, Jean-Marie Questiaux, Khalid AlRuwaili, Helen Lewis, Jingsheng Ma. I have spoken on fractured reservoirs at multiple Workshops, in training events, at many conferences, and this was also the topic of an SPE Distinguished Lecture tour in 2013-14. I recognise and appreciate the many instances of valuable feedback and vigorous discussions associated with these public events.
Publisher Copyright:
© 2022, The Author(s).
PY - 2022/10/5
Y1 - 2022/10/5
N2 - An important question arises in relation to a rock-mass that is disrupted by an array of fractures, namely: how to quantify the evolving spatial arrangement of fracture apertures that are a major factor in bulk fluid flow processes. The approach herein employs a discrete micro-physics model of the rock texture, enabling the formulation of analytical expressions that explicitly define the fluids//geomechanics interactions that occur at the micro-scale. The resulting macro-scale responses of the model define the stress, bulk strain, and pressure states that characterise the porous rock. Via extending the discrete model by introducing a planar discontinuity, the fracture-normal bulk strain determines the status of the fracture aperture, as a consequence of the movement of the rock//fracture interface. The micro-physics model shows that a closed fracture cannot change to an open fracture by pressure changes alone; instead, bulk strain must elongate the porous rock in a direction normal to the fracture. Once opened, fracture apertures respond to changes in fluid pressure. A realistic context, within which the required bulk strain occurs, is the discontinuum geomechanics of fractured rock-mass systems, for which previous simulations exhibit a range of emergent local states that relate to the conditions, identified via the micro-physics, as being the essential controls on aperture evolution.Article highlights:- Discrete rock-texture model underpins micro-physics expressions that lead to macro-scale material response of matrix//fracture- Closed fracture cannot open without local elongation normal to fracture; high pressure alone does not open fracture- Open fracture changes aperture with changing pressure.
AB - An important question arises in relation to a rock-mass that is disrupted by an array of fractures, namely: how to quantify the evolving spatial arrangement of fracture apertures that are a major factor in bulk fluid flow processes. The approach herein employs a discrete micro-physics model of the rock texture, enabling the formulation of analytical expressions that explicitly define the fluids//geomechanics interactions that occur at the micro-scale. The resulting macro-scale responses of the model define the stress, bulk strain, and pressure states that characterise the porous rock. Via extending the discrete model by introducing a planar discontinuity, the fracture-normal bulk strain determines the status of the fracture aperture, as a consequence of the movement of the rock//fracture interface. The micro-physics model shows that a closed fracture cannot change to an open fracture by pressure changes alone; instead, bulk strain must elongate the porous rock in a direction normal to the fracture. Once opened, fracture apertures respond to changes in fluid pressure. A realistic context, within which the required bulk strain occurs, is the discontinuum geomechanics of fractured rock-mass systems, for which previous simulations exhibit a range of emergent local states that relate to the conditions, identified via the micro-physics, as being the essential controls on aperture evolution.Article highlights:- Discrete rock-texture model underpins micro-physics expressions that lead to macro-scale material response of matrix//fracture- Closed fracture cannot open without local elongation normal to fracture; high pressure alone does not open fracture- Open fracture changes aperture with changing pressure.
KW - Effective stress
KW - Fluid–solid interaction
KW - Fracture aperture
KW - Micro-physics
KW - Micro-to-macro
UR - http://www.scopus.com/inward/record.url?scp=85139441090&partnerID=8YFLogxK
U2 - 10.1007/s40948-022-00484-1
DO - 10.1007/s40948-022-00484-1
M3 - Article
SN - 2363-8419
VL - 8
JO - Geomechanics and Geophysics for Geo-Energy and Geo-Resources
JF - Geomechanics and Geophysics for Geo-Energy and Geo-Resources
IS - 5
M1 - 170
ER -