Development of Proppants from Ion Exchanged Recycled Glass And Metabasalt Glass-Ceramics

Open Access
Author:
Hartwich, David G.
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 07, 2011
Committee Members:
  • John Richard Hellmann Jr., Thesis Advisor
  • Barry Earl Scheetz, Thesis Advisor
Keywords:
  • Ion Exchange
  • Glass-Ceramics
  • Hydrofracturing
  • Proppants
  • Glass
Abstract:
Proppants are used in the hydrofracturing process by the oil and natural gas industry. The purpose of the proppant is to hold fractures in rocks open providing a path of permeability for hydrocarbons out of the well. Demand for proppants has increased 400% in the last decade with the worldwide demand currently claiming 5 million metric tons of proppant per year. This number is estimated to increase by another 1 million metric tons as the Marcellus Shale in Pennsylvania is developed. Shortages of high strength spherical ceramic proppant material, such as bauxite and kaolin, are forcing well service companies to use angular quartz sand which has insufficient crush strength and allows poor gas permeability. Two alternative raw materials, recycled soda-lime silicate glass and metabasalt, that are widely available and come at a low cost will be studied for use as a proppant material. Soda-lime silicate glass was successfully spheroidized for use as proppant. Ion exchange processing was performed on the proppants in an attempt to increase fracture strength, narrow the strength distribution, and cause the proppant to fail into large pieces instead of bed blinding glass powder. An initial exchange, using K+ ions to produce a region of compression on the surface of the glass proppant, showed an increase in fracture strength from un-exchanged proppants when diametrally compressed. A reverse exchange performed after the initial exchange, using Na+ ions to produce a region of tensile stress along the very surface of the proppant, showed a decrease in failure strength from the initial exchanged proppants and a narrowing of the strength distribution when diametrally compressed. Reverse exchanges could shift the strength distribution to lower failure strengths such that an increase in the number of large fracture pieces occurred. The reverse exchanges did not however alter the fracture mechanism of the proppants. Little difference was seen in the crush stress and fragment size analysis between the ion exchanged and un-exchanged proppants during the industry standard, proppant crush-resistance test. Due to these results, ion exchanging soda-lime silicate glass spheres is not believed to be economically viable for the proppant application. Metabasalt was successfully fused and spheroidized for use as proppant. Controlled devitrification was performed through heat treatment to develop crystal phases that would toughen the material through crack deflection, thereby increasing the propensity of large fracture pieces. A time-temperature-transformation (TTT) diagram was constructed from x-ray diffraction data with the magnetite, augite, labradorite, and hematite phases identified. Phase morphology, diametral compression strength, Weibull modulus, fracture type, hardness, and fracture toughness were correlated to the TTT diagram. A region of the TTT diagram, where samples showed a combination of a high propensity for large failure pieces, high failure strength, and a consistent microstructure, was chosen for further study. A sample heated according to the favorable time and temperature identified was produced and tested according to the industry standard proppant crush-resistance test and found to have an improved crush stress and size of fracture pieces, over the original metabasalt glass and soda-lime silicate glass of similar size. These results predict that the hydraulic conductivity of the heat treated metabasalt proppant pack should improve over un-modified glass proppants.