| dc.description.abstract | To effectively produce from resource shale, a stimulation method is required. Typically, hydraulic fracturing is utilized for stimulation. Hydraulic fracturing methods range in size, cost, and effectiveness. Once a hydraulic fracture network has been generated, the fractures must be propped open using proppant to allow flow through the fractures. Sand is currently the most commonly used proppant in fracture treatments. Large quantities of sand are required to effectively prop the generated and natural fractures. Sand can be a costly expense in the completion stage of a well. With low oil and gas prices, cutting costs, but not jeopardizing the success of the well is critical. The goal of this study is to find a cheap and abundant material which can act as a sand substitute to provide equal or superior fracture conductivity to that of sand proppant, and serve as an adequate proppant material.
Glass, taconite tailings, coal, and various proppant mixtures’ geometry, conductivity, and strength were all evaluated and compared to conventional sand proppants currently being used in industry to evaluate the novel proppant’s potential to serve as a sand substitute in hydraulic fracturing treatments. The proppant’s geometry was evaluated qualitatively under a microscope. The most favorable proppant geometry was seen in sand proppant followed by taconite, and the least favorable particle geometry was observed in the glass proppant.
Fracture conductivity is an effective means of measuring a fracture treatment’s effectiveness. For that reason, the API RP 61 procedure was followed using the modified API cell available in the Texas A&M University Fracture Conductivity Laboratory to evaluate the conductivity of the various proppant packs. API RP 61 is a well-established procedure set forth by the American Petroleum Institute for measuring conductivity of proppant packs. For a given proppant size, sand had the largest conductivity, followed by taconite, then glass, and finally coal which did not result in any measurable conductivity.
Proppant strength was measured by evaluating proppant crushing. Each conductivity test was conducted at the same six closure stresses starting at 1,000 psi and ending at a maximum closure stress of 6,000 psi. Before the proppant conductivity was tested, a sieve test was conducted to determine the particle distribution of each proppant type and size. Upon conclusion of each conductivity test, after the proppant pack had been exposed to 6,000 psi closure stress, the proppant was sieve tested once again. The particle distributions of the crushed and uncrushed samples were compared side by side to determine how severely the proppant had crushed. For a given proppant size, the glass proppant had the most severe crushing followed by the taconite and sand proppants.
The proppant geometry and strength evaluations were used to support the large variation in conductivity results observed in this study. A dimensionless conductivity evaluation was conducted to determine the potential for each proppant to serve as a sand substitute in hydraulic fracture treatments based on the proppant pack conductivity tested in this study. The dimensionless conductivity values calculated for each proppant based on ideal lab testing conditions for short term conductivity evaluation using a dry gas test fluid revealed that glass, taconite, and the three proppant mixtures tested all have the potential to replace sand in fracture treatments | en |
