Study on the preparation of a free-sintered inorganic polymer-based proppant using the suspensions solidification method

In this paper, a novel type of free-sintered inorganic polymer proppant with a particle size of 2-3 mm was prepared based on the features of alkali-activated slag materials (an inorganic polymer material) by using the suspension solidification method, and using slag and sodium silicate as the main raw materials. By adding quartz sand and silica fume, as well as by adopting a steam curing treatment and a Ba2+exchange treatment, the performances of inorganic polymer proppants were improved. The testing data showed that the volume density was 1.91 g/cm3, roundness and sphericity≧0.9, turbidity = 45 NTU, crushing rate = 21% under a closed pressure of 52 MPa, and acid solubility = 4%. This means that all of the indices met the industrial requirements. Moreover, this preparation process was simple and did not use high-temperature sintering, saving a significant amount of energy. The properties of high roundness, sphericity and low volume density, are helpful for the suspension and transportation of the proppants in cracks; in addition, these features reduce the demand of the fracture liquid. Compared with traditional natural quartz sand proppants and ceramic proppants, inorganic polymer proppants have the advantages of a low density, low raw material cost, simple preparation process and low energy consumption. Further research on inorganic polymer proppants is warranted.