Dynamics of hydrofracturing and permeability evolution in layered reservoirs

Ghani, I., Koehn, D. , Toussaint, R. and Passchier, C. (2015) Dynamics of hydrofracturing and permeability evolution in layered reservoirs. Frontiers in Physics, 3, 67. (doi:10.3389/fphy.2015.00067) (PMID:25798109) (PMCID:PMC4351591)

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Abstract

A coupled hydro-mechanical model is presented to model fluid driven fracturing in a porous material that is structured as a layered reservoir. In the model the solid elastic continuum is described by a hybrid lattice-particle model based on a discrete element approach coupled with a fluid continuum lattice that is used to solve Darcy pressure diffusion. The model assumes poro-elastic effects and yields real time dynamic aspects of the fracturing and effective stress evolution under the influence of excess fluid pressure gradients. The model is used to study the formation of different fracture patterns in heterogeneous geological settings. We show that the formation and propagation of hydrofractures is highly sensitive to different mechanical and tectonic conditions. In cases where fluid pressure is the driving force, sealing layers induce permutations between the principal directions of the local stress tensor, which regulates the growth of vertical fractures and may result in irregular pattern formation or sub-horizontal failure below the seal. Stiffer layers tend to concentrate differential stresses and lead to vertical fracture growth, whereas the layer-contact tends to fracture if the strength of the neighboring rock is high. The stress field at the onset of fracturing becomes anisotropic, which eventually leads to the development of large-scale failure in the system by linking isolated tensile fractures. If the model is under extension for a long time, large-scale hydrofractures develop by linking up confined tensile fractures in competent layers. This leads to the growth of large-scale normal faults in the layered systems, so that subsequently the effective permeability is highly variable over time and the faults drain the system. The simulation results are well consistent with some of the field observations carried out in the Oman Mountains, where abnormal fluid pressure is reported to be a crucial factor in the development of several generations of regional fracture and fault sets, including bedding-normal and bedding-parallel fracturing.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Koehn, Dr Daniel
Authors: Ghani, I., Koehn, D., Toussaint, R., and Passchier, C.
Subjects:Q Science > QC Physics
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Geography
Journal Name:Frontiers in Physics
Publisher:Frontiers Research Foundation
ISSN:2296-424X
ISSN (Online):2296-424X
Copyright Holders:Copyright © 2015 Ghani, Koehn, Toussaint and Passchier
First Published:First published in Frontiers in Physics 3:67
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
UNSPECIFIEDUNSPECIFIEDFRACSIIKoehnDGMKUNSPECIFIEDUNSPECIFIED
594831Flow and Transformation in Porous Media (FlowTrans)Daniel KoehnEuropean Commission (EC)UNSPECIFIEDGES - GES ADMINISTRATION