Coupled processes in wellbore stimulation
Restricted (Penn State Only)
- Author:
- Wang, Rui
- Graduate Program:
- Energy and Mineral Engineering (PHD)
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 21, 2024
- Committee Members:
- Jeremy Gernand, Program Head/Chair
Corina Drapaca, Outside Unit & Field Member
Gregory King, Major Field Member
Derek Elsworth, Major Field Member
Arash Dahi Taleghani, Chair & Dissertation Advisor - Keywords:
- Wellbore stimulation
Coupled processes
Flowback rate
Pump-in/flowback test
Fracture closure
Sandstone acidizing
Post-flush period
Breakdown pressure
High-porosity channels - Abstract:
- Wellbore stimulation is a typical operation to enhance or recover the injectivity or productivity of a well. Three primary wellbore stimulation techniques are hydraulic fracturing, acid fracturing, and matrix acidizing. The models used to simulate these stimulation treatments usually couple several processes, such as fluid flow, geomechanics, and chemical reaction. My study can be broadly divided into two parts. Hydraulic fracturing is used to enhance recovery in unconventional reservoirs. Injection tests are broadly used to derive formation properties crucial for hydraulic fracturing design. The accuracy of properties estimation, such as closure stress, depends on the fracture closure behavior. Among these tests, the pump-in/flowback test, also called DFIT-flowback has some advantages in terms of running time and accuracy over typical injection tests such as conventional DFITs, especially in low permeability formations. The success of this test is dependent largely on choosing an appropriate flowback rate to achieve meaningful results. The first focus of the dissertation is to propose an optimal range for the flowback rate achieving uniform fracture closure during the pump-in/flowback test. A coupled geomechanics and fluid flow model is presented to investigate the effect of fracture closure behavior on the accuracy of formation property estimation. By employing the suggested optimal range of flowback rates, operators in the field can obtain accurate estimation of closure stress without trial and error. It aids in the attainment of desirable fractures during the main frac job and enhances oil and gas production. Sandstone acidizing is commonly designed for cleaning perforation, recovering perforation functions, and improving injectivity during completion operations such as frac-pack, aiming to reduce the fracturing pressure and enhance productivity. However, recent field cases have shown unexpected breakdown pressure increases after the post-flush period of acid treatment in sandstone reservoirs. The second focus is to understand this problem, a coupled fluid flow and chemical reactions model is proposed to simulate the acidizing process through a perforation hole, and then the subsequent post-flush resulting in precipitant transport. Finally, the breakdown process where fluid is injected into the rock is modeled to compare breakdown pressures in different cases. Understanding the influencing factors behind the unexpected high breakdown pressure following the acidizing treatments enables field operators to adjust acidizing treatment parameters. These adjustments benefit subsequent main frac job, optimizing stimulation performance, and ultimately enhancing oil and gas production in the field.