Restricted (Penn State Only)
Cai, Yuzhe
Graduate Program:
Energy and Mineral Engineering (PHD)
Doctor of Philosophy
Document Type:
Date of Defense:
June 16, 2021
Committee Members:
  • Gregory King, Major Field Member
  • Ali Borhan, Outside Unit & Field Member
  • Derek Elsworth, Major & Minor Field Member
  • Arash Dahi Taleghani, Chair & Dissertation Advisor
  • Mort D Webster, Program Head/Chair
  • Flowback
  • dfit
  • diagonostic fracture injection test
  • infill well
  • parent well
  • Fracture driven interaction
  • FDI
  • Fracture closure
Unconventional resources, such as tight gas, shale gas and shale oil, have become an essential source of energy in North America. Advances in hydraulic fracturing and horizontal completions have made exploration of these reservoirs profitable. My study can be broadly divided into three parts. After the hydraulic fracturing, the fracturing fluid needs to be produced back to the surface and the period is called flowback. After the hydraulic fracturing, the fracturing fluid needs to be produced back to the surface and the period is called flowback. In the first part of the study, a semi-analytical model is developed for the purpose of inverse analysis. A coupled fluid flow and geomechanics flow model is also presented to investigate potential reasons for low flowback recovery. Diagnostic fracture injection tests (DFITs) have been broadly used in unconventional reservoirs to derive properties such as initial formation pressure, formation permeability, and closure pressure. The first focus of the dissertation is utilizing DFITs data to obtain formation permeability, and closure pressure. The obtained properties are very crucial for hydraulic fracturing design. A semi-analytical model is proposed for early flowback, and the model can be used for inverse analysis to determine the properties of the hydraulic fracture. The obtained fracture properties can then be used for long-term reservoir production forecast. The last focus of the dissertation is fracture-hits modeling and analysis. Completion of child wells (or infill wells) has received significant attentions in the last few years as a strategy to increase ultimate recovery from unconventional shale plays specially in shale oil reservoirs. However, fracture driven interferences (FDI) between the child wells and the parent wells have been observed, which harm their ultimate recovery. As a result, the interferences between the parent wells and child wells are modeled. By analyzing the pressure response of the parent wells, the FDI can be mitigated. Throughout the study, both coupled geomechanics and fluid flow numerical models and analytical/semi-analytical models are developed. The numerical models can simulate the development of non-planar fractures and non-uniform fracture closure patterns. The analytical/semi-analytical models can be used for quick inverse analysis for estimating fracture or formation properties.