Preparing high-strength and low-density proppants with oil-based drilling cuttings pyrolysis residues and red mud: Process optimization and sintering mechanism

Abstract

This study aimed to assess the feasibility of manufacturing high-strength and low-density proppants from oil-based drilling cuttings pyrolysis residues (ODPR) and red mud (RM). The effects of ODPR and RM content on the performance of the proppants were studied, respectively. The optimum sintering condition was determined by response surface methodology (RSM), and the sintering mechanism was explored based on microstructural analysis of the proppants. The results showed that high-strength and low-density proppants with the breakage ratio of 8.6 % under 52 MPa closed pressure, bulk density of 1.45 g·cm−3, and apparent density of 2.96 g·cm−3 were obtained under the optimum preparation conditions (mass ratio of ODPR: RM: bauxite: MnO2 of 20: 8: 76: 4, sintering temperature of 1342 °C, sintering time of 1.0 h, sintering rate of 4.9 °C·min−1). The performance of the product proppants could meet the requirements of the Chinese Petroleum and Gas Industry Standard “Measurement of properties of proppants used in hydraulic fracturing and gravel-packing operations” (SY/T 5108-2014). ODPR and RM in the raw materials provided the chemical components of Al2O3, SiO2, CaO, BaO, Na2O, and K2O, which were involved in the formation of crystalline phases and molten phases during the sintering process. The performance of high-strength was primarily provided by the framework structure containing the crystalline phases and the dense structure caused by the molten phases. In addition, the Fe2O3 of RM would promote the generation of closed pores and then enhance the lightweight performance of proppants; however, excessive RM incorporation would lead to the formation of connected pores, which had a negative effect on the breakage ratio of proppants. This study not only creates a new pathway for recycling ODPR and RM within the shale gas industry but also provides a novel approach for manufacturing high-strength and low-density proppants.