Optimization of Breaker Schedules for Stimulation of Tight Gas Reservoirs

Open Access
Author:
Li, Hang
Graduate Program:
Petroleum and Natural Gas Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 03, 2012
Committee Members:
  • Yilin Wang, Thesis Advisor
Keywords:
  • stimulation
  • breaker
  • fracturing fluid
  • optimization
Abstract:
The optimal breaker selection and breaker schedule design may achieve the purpose to maximize conductivity by cleaning out most pores of the proppant bed which are filled with the fracturing fluid. However, due to many complex reasons and chemical limits, optimization of breaker selection and schedule design still remains challenging. Extensive investigations are conducted in this study. Breaker selection guidelines and breaker schedule optimization are presented at last and field cases are followed as practical examples. Gel breakers are generally grouped into three classes: oxidizers, enzymes, and acids. All of these materials reduce the viscosity of the gel by breaking connective linkages in the guar polymer chain. Oxidizing agents decompose to produce “free radicals” which attack the polymer chains and bring about degradation. For enzymes, they will then attach to that polymer strand until it can completely degrade the polymer. The enzymes will ride to wherever the polymer travels. Acid breakers often act as a necessary component to reverse the fracturing fluid crosslinking process in matrix acidizing. They tie up the crosslinking ions and break the polymer crosslink bondings. The performances of breakers which are influented by formation temperature, fracture fluid pH and formation mineral. These selection criteria need to be carefully concidered in fracture job design. Summarization of what needs to be taken into account for any breaker selection, and the flow chart for the entire selection process, are presented. After selecting the proper type, determine the optimal breaker concentration is an important step for entire breaker design, no matter for the remediation treatment of fracturing wells or the producing wells. For fracturing wells, calculation method of the optimal breaker concentration is developed based on viscosity test data. As for the producing wells that are suffering from severely gel damage, breaker selection procedures and breaker schedule optimization are also proposed.