Numerical Study of Fracture Initiation, Propagation, and Sealing to Enhance Wellbore Fracture Gradient
This paper presents finite-element simulation results for hydraulic fracture's initiation, propagation and sealing in the near wellbore region. The main objective of these simulations was to investigate the hypothesis of wellbore hoop stress increases when fractures are wedged and/or sealed during lost circulation control. To address this objective three-dimensional poro-elastic models were solved with finite-element simulations. Three analytical solutions were also reviewed to investigate other mechanisms of increasing fracture propagation pressure by fracture sealing, these models then were used to predict a new fracture gradient and compare it to the numerical simulation results. The situation was also investigated from a fracture mechanics perspective where analogous bridging and toughening mechanisms were applied to increase fracture resistance in other materials. Cohesive zone modeling was used as the primary methodology for simulating fractures, this enabled us to assign individual criteria for fracture initiation and propagation in each model. Our results demonstrate that fracture wedging is not able to increase wellbore hoop stress more than its ideal state where no fracture exists, however this will help to restore part or all of the wellbore hoop stress lost during fracture propagation which can act as secondary mechanism for increasing wellbore fracture gradient. The alternative mechanism can be explained the existence of a strong barrier and/or non-invading zone inside the fracture which prevents further communication between wellbore and propagated fracture.
S. H. Salehi and R. Nygaard, "Numerical Study of Fracture Initiation, Propagation, and Sealing to Enhance Wellbore Fracture Gradient," Proceedings of the 45th US Rock Mechanics / Geomechanics Symposium (2011, San Francisco, CA), American Rock Mechanics Association (ARMA), Jun 2011.
45th US Rock Mechanics / Geomechanics Symposium (2011: Jun. 26-29, San Francisco, CA)
Geosciences and Geological and Petroleum Engineering
Keywords and Phrases
Analytical Solutions; Cohesive-Zone Modeling; Finite Element Simulations; Fracture Gradient; Fracture Initiation; Fracture Propagation Pressure; Fracture Sealing; Hoop Stress; Hydraulic Fracture; Lost Circulation Control; Near-Wellbore Region; Numerical Studies; Poroelastic Model; Secondary Mechanisms; Toughening Mechanisms; Wellbore; Finite Element Method; Fracture Mechanics; Hydraulic Fracturing; Oil Field Equipment; Residual Stresses; Rock Mechanics; Three Dimensional
Article - Conference proceedings
© 2011 American Rock Mechanics Association (ARMA), All rights reserved.
01 Jun 2011