Construction and phase transition characteristics of nano‐graphite‐induced rapid growth self‐generated proppants

Abstract

Abstract To solve the problem that the self‐generated proppant in fractures grows slowly and cannot support the fractures in time, nano‐graphite (NG) was introduced into a phase change liquid (PCL) composed of “styrene‐divinylbenzene (SDB)” and the resulting self‐generated proppants were constructed with a high growth speed. The NG/PCL started the phase transition from liquid to solid after 8 min at about 55°C in the wellbore section, and the phase transition was completed for only 2.5 min at a constant temperature of 65°C in fracture. Moreover, due to the high thermal conductivity and heterogeneous nucleation of the NG powder, the maximum strength of self‐generated proppant in the NG‐containing system can reach about 56.2 N during its growth process, which is 34.4% higher than that of pure SDB. The yield of the well‐dispersed spherical self‐generated proppants NG/SDB under the completely static condition can reach about 80%, of which the proppants with a particle size of 0.4 ~ 0.7 mm account for about 80%. NG/SDB exhibited an ultra‐low apparent density of approximately 1.004 g/cm 3 , high compressive strength, and a crushing ratio of less than 1% at a closure pressure of 52 MPa, which is lower than that of commercial quartz sand and ceramsite proppants. Highlights Self‐generated proppants with rapid growth were developed by the introduction of NG. Positive effects of NG in PCL system are obvious on phase transition and growth. NG/SDB is qualified in phase transition timing and compressive strength. The single‐microsphere yield of NG/SDB is about 80%. The crushing ratio of NG/SDB as low as 3.92% at a closure pressure of 69 MPa.