Preparation and Field Test of Double-Shell Coated Proppant (DSCP)

The fracturing development of deep shale gas wells requires that proppants should have good compressive strength and flow conductivity. Therefore, phenol-formaldehyde resins, polyol polymers, and curing agents were taken as raw materials to prepare the double-shell coated proppant (DSCP) by a certain mass ratio with the combination of physical surface coating and chemical modification methods. The effort was to find a proppant with high compressive strength, good flow conductivity, and moderate costs. It could be applied to the fracturing of oil and gas wells with high closure pressure. For the prepared DSCP, its inner shell was mainly made of phenol-formaldehyde resins to enhance the compressive strength, and the outer shell was mainly made of inert synthetic resins to further improve the compressive strength and strengthen the flow conductivity. Laboratory experiments were carried out to evaluate the performance of DSCP, such as compressive strength and flow conductivity. The experimental results indicated that the crushing rates of DSCP at 69 and 86 MPa were 1.21% and 2.35% respectively, its flow conductivity was 3.12 mD•cm at 90 ℃ and 90 MPa. In other words, DSCP had good compressive strength and flow conductivity. Field tests showed that compared with the case of horizontal wells fractured with ceramisite, the cost of proppants could be reduced by about 30% on the premise of the same fracturing scale and technical parameters. The research result suggests that DSCP can be applied to the fracturing of wells with high closure pressure and has good prospects of popularization and application.