Impact Of Co2 On Fracture Complexity When Used As A Fracture Fluid In Rock

Open Access
Author:
Culp, Brian Michael
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 19, 2014
Committee Members:
  • Chris J Marone, Thesis Advisor
  • Derek Elsworth, Thesis Advisor
  • Charles James Ammon, Thesis Advisor
Keywords:
  • Rock Mechanics
  • Fracturing
  • Unconventional
  • Bluestone
  • PMMA
  • hydraulic fracture
  • hydrocarbon
  • geology
Abstract:
With the development of horizontal drilling and hydraulic fracturing, the field of unconventional resources is becoming the dominant source of hydrocarbons in the United States. Hydraulic fracturing uses a water based mix of chemicals and proppants to create and prop open fractures within a shale matrix. This matrix of propped fractures provides a pathway for hydrocarbon recovery. The greater the fracture complexity, the greater amount of reservoir being accessed. Understanding the most efficient and effective way of exploiting these resources, early in play development, is essential. This research has explored the impact of different fracture fluids on fracture complexity within Polymethyl methacrylate (PMMA) and Pennsylvania Bluestone (Sandstone). Water (H2O), Nitrogen (N2), Carbon Dioxide (CO2), Super Critical Carbon Dioxide (SC CO2), and Breathable Air (~20% 02) were the fluids tested. Experiments were done in an unconfined setting where fluid temperature, sample temperature, and fluid flow rates were controlled and measured. This research confirms that fracture (or breakdown) pressure is a function of the fracture fluid type and its state (Alpern, 2013). It was determined that the Standard Sample Design (blind borehole) fractures as if it was a Plugged Through Borehole PMMA Design; further, installing a plug can seed a fracture initiation point. The location of this fracture initiation point controls the fracture geometry and complexity in this sample size. A dual fitting Through Borehole PMMA Block Design removes the borehole termination initiation point and minimizes the membrane effect, which reduces the number of CO2 failure pressures that approach the tensile strength of the PMMA Block. Bluestone experiments show that there is a similar relationship between average CO2 failure pressures and other Super Critical failure pressures. Although the difference between Saturated and Unsaturated experiments showed an overall slight drop in failure pressure, the range of failure pressures is not significant enough to declare there is an impact. Post failure examination of Bluestone indicates that the pore water may be pushed out of the immediate pore space surrounding the borehole during the experiment; further, the permeability of the Bluestone may be too high to test if the pore water will control the fracture pressures.