Abstract

We present a method for modeling drilling induced fractures dynamic growth through a porous medium in the near wellbore region. Understanding the early time fracture growth behavior, and related near wellbore stress state, can provide an effective tool to improve the treatment selection through parameters such as particle size distribution and ideal drilling fluid rheology. Also, it will help with field diagnostics for various lost circulation treatments and lost return events.

ExxonMobil Upstream Research Company and SIMULIA® co-developed fully-coupled hydraulic fracturing modeling capabilities. The method is based on Cohesive Zone Modeling (CZM) elements, with pore pressure degrees of freedom, which were recently implemented into SIMULIA® Abaqus finite element package. The model was benchmarked with known solutions to analytical fracture growth regimes and validated with a laboratory scale experimental setup of hydraulic fracturing. The model allows for fluid leak-off from the wellbore and fracture faces into the porous medium, as well as an arbitrary injection schedule. Additionally, the physics of dynamic fracture growth and a variety of material properties and constitutive models for both the solid and liquid, are also captured in the model. The time-dependent fracture growth and interaction between the stress concentration region near the fracture tip and the wellbore result in a non-linear behavior of the near-wellbore stress state during early time fracture propagation, which was not possible to capture with static models. The model generation, execution, and post-processing are part of an automated workflow which requires minimal user time.

This analysis allows for recommendation of optimum fracture width for maximum increase in wellbore integrity in the target formation. This is done by selecting the fracture width at the mouth, at which a necessary increase in the near-wellbore tangential stresses has been achieved as to prevent initialization of further fractures.

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