Recycled materials and waste products, such as glassy materials, igneous-rock tailings, and Portland cement-based materials, have been used to prepare new proppants. Both conventional recycled glass, such as plate glass, e-glass, and common bottle glass, have been explored in addition to unconventional sources, such as materials generated from the burning of sewage sludge. Undersized materials, such as fines from the processing of the minerals to make roofing-shingle granules, have been used to prepare proppants. Recycled concrete may also be used to manufacture proppants.
All of the above mentioned proppants are useful in place of conventional sand and intermediate-strength proppants in applications including gravel packing and hydraulic fracturing.
Glass-based proppants are known for their catastrophic failure and tendency to crush into fine particulates. New processing methods allow for mitigation of this shortcoming by generating proppants that closely resemble the performance of conventional sand proppants. Igneous materials can be processed to create proppants that exceed the performance of sand proppants and approach that of conventional intermediate-strength ceramic proppants. Portland cement-based proppants have been developed with a SG as low as 1.6. New processing techniques allow for lower sintering temperature compared to commercial ceramic proppants, resulting in reduced energy consumption during manufacture. Recycled concrete has been used to generate proppants that resemble conventional ceramic proppants but are also processed at reduced temperature to reduce the energy required during manufacture. API testing, such as crush and conductivity tests, are reviewed in this paper for comparison to conventional proppants. These new proppant systems are desirable because of a potential lower cost and for their sustainability during manufacture. In some aspects of performance, the new proppants exceed conventional proppants.
Several new materials systems are presented for consideration in the manufacturing of proppants. In some cases, these systems make use of recycled materials or waste materials and, in other cases, these systems are processed at reduced temperature to reduce the energy required during manufacture, compared to conventional proppants. As potential opportunities for new proppants, these materials are presented to the oilfield community to judge whether they are technically and commercially viable.