Liliia Reddy

Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Ebrahim Fathi

Committee Co-Chair

Samuel Ameri

Committee Member

Ali Takbiri

Abstract

This research has been dedicated to the optimization of multi-stage hydraulic fracturing by providing a more thorough understanding of fracture and reservoir stress behavior. This work was accomplished by the use of a fully coupled fracture propagation simulator (HFWVU2D developed under RPSEA (Grant/Contract No. #9122-06)) that couples fracture mechanics and fluid dynamics, unlike past studies, which observe only simple interactions. The underlying objective is to eliminate the misappropriated energy caused by inter-fracture stress interaction and stress reorientation surrounding the induced fracture network by assessing stress magnitude as a function of operation conditions.;This study is based upon an in-house numerical simulation model developed for hydraulic fracture propagation referring to the linear elastic fracture mechanics model "LEFM" using finite element method. The elastic response of the 2-D solid medium and the fluid flow within the fracture is coupled to provide a more realistic depiction of these interactions. The magnitude of stress variation and reorientation is calculated in surrounding areas of simultaneous and sequential hydraulic fracturing of a horizontal well for a wide range of hydraulic fracturing propagation regimes for both homogenous and compositional models.;The results clearly show that there is an optimum distance between hydraulic fractures below which, the change (variation) in magnitude and orientation of stresses leads to significant change in fracture geometry and propagation rate. This change has been impacted mainly through mechanical interaction that leads to higher compressive stress concentrations between fractures. The mechanical interaction becomes stronger by increasing the number of fractures or altering the fracture spacing. The effects have also been investigated in a composite reservoir model with different mechanical properties (i.e., Young's modulus and Poisson's ratio), and operational conditions, such as injection rate and volume. Mechanical properties of different layers in a composite reservoir model significantly impact the fracture geometry and propagation rate when the fracture intercepts different layer boundaries. The magnitude of change in stresses and stress reorientation is also quantified in cross sections with respect to the fracture plane as the fracture propagates.;This work provides an advanced understanding of multiple hydraulic fracturing stimulation and dynamics of fracture geometry, propagation rate and stress change in surrounding using our unique fully coupled hydraulic fracturing simulator. Moreover, it provides quantitative analysis of induced stresses and in-situ stress reorientation. The work is important for the optimization of multi-stage hydraulic fracturing in unconventional reservoirs.

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