Semester

Summer

Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Petroleum and Natural Gas Engineering

Committee Chair

Ebrahim Fathi

Committee Co-Chair

Kashy Aminian

Committee Member

Ali T. Borujeni

Abstract

Hydraulic fracturing is a widely used technique in industry to enhance oil and gas recovery. The process involves the injection of fracking fluid with high pressure into the wellbore to propagate initial fractures generated during well perforation. It is a coupled process of fluid and rock mechanics one controlling the fluid movement and other fracture propagation. There is a lack of reliable and robust simulation technique that can couple these two processes at the same time being practical for large domain size of hydraulic fracturing in the field scale. In hydraulic fracturing, multiple fractures are also created within one cluster in a stage which increases the dimension of the problem. In addition to simulation difficulties of the process, there are concerns from operational point of view to choose the best technique to be able to place as many effective fractures as possible considering mechanical interactions between fractures that can impact the fracture geometries and ultimately production performance. The objectives of this thesis work therefore are to model multi-fracture hydraulic fracturing process in heterogeneous tight formations and optimize the process by sensitivity analysis on parameters such as fracture number and fracture spacing during hydraulic fracturing operations.;In this study, a fully coupled finite element model was built to simulate multiple hydraulic fracturing and possible fault reactivation zones are determined based on the slip-tendency analysis. Cases with different fracture number, fracture spacing and heterogeneity (materials number, Poisson's ratio, Young's modulus) are simulated. The results show that the number of hydraulic fractures and their spacing significantly impacts fractures geometry. The fracture number has positive relationship with propagation rate and negative relationship with fracture width while fracture spacing has negative relationship with propagation rate and positive relationship with fracture width.;The composite reservoir simulations indicate that heterogeneous condition in reservoir has minimum effect on fracture propagation if the fracture does not cross the boundary. However, if fracture passes through the interface between two materials distinguished by different Young Modulus both magnitude and rate of fracture propagation would change significantly. Slip-tendency analysis performed clearly show the possible fault reactivation zones are around edge fractures tips. This study provides us understanding of multiple hydraulic fracturing investigating fracture geometry and stress change, and it is important for the development of sound numerical hydraulic fracturing optimization models.

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