A fully coupled 3D finite element investigation of hydraulic fracture growth in elastoplastic rocks

Elias Pirayesh, Mohamed Y. Soliman, Stephen M. Morse, Hossein Emadi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Invaluable to both well stimulation and wellbore stability is the study of fracture initiation and propagation. The literature is rich with fracture tip phenomena theories. In particular, the effect of tip plasticity has been the subject of much debate. However, little has been done to investigate the effect of rock mass plasticity, a potential controlling factor in weak and compactible rocks. This paper advances a 3D dynamic computational model to replicate the growth of hydraulic fractures in elastoplastic rocks. The proposed model is based on a non-linear Finite Element formulation that couples solid deformation and fluid flow. Rock is treated as a work-hardening elastoplastic material whose plastic deformation can be found using an associated flow rule. This paper features a new computational method to find material tangent stiffness tensor in non-linear Finite Element Analysis. A meshing/remeshing scheme is employed to maintain a high mesh resolution and to reach infinite boundary effect while keeping simulation runtime reasonable. The model tested successfully against analytical solutions for pressurized cracks and radially growing hydraulic fractures. Due to the action of fracturing fluid pressure on fracture faces, normal stress increases on the fracture faces and a zone of tensile stress forms ahead of the fracture. The size of this zone dictates fracture growth rate. Due to plastic deformation, when subjected to loading, compared to elastic rocks, elastoplastic rocks experience less increase in normal stress on the fracture face and a smaller tensile zone. Combined with typically high permeability of compactible rocks, this results in slower fracture growth, larger fracture widths and higher fracture pressures. Another significant observation is that elastoplastic rocks can undergo shear localization, depending on rock properties, stress state and treatment conditions. This paper presents a unique method to account for rock mass plasticity during fracturing operations. It showcases a robust 3D computational non-linear Finite Element model with a concrete physical foundation. Simulation results are in agreement with both laboratory and field observations.

Original languageEnglish
Title of host publicationSociety of Petroleum Engineers - SPE Annual Technical Conference and Exhibition, ATCE 2016
PublisherSociety of Petroleum Engineers (SPE)
ISBN (Electronic)9781613994634
StatePublished - 2016
EventSPE Annual Technical Conference and Exhibition, ATCE 2016 - Dubai, United Arab Emirates
Duration: Sep 26 2016Sep 28 2016

Publication series

NameProceedings - SPE Annual Technical Conference and Exhibition


ConferenceSPE Annual Technical Conference and Exhibition, ATCE 2016
Country/TerritoryUnited Arab Emirates


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