Preparation of low-temperature expandable graphite as a novel steam plugging agent in heavy oil reservoirs

Steam channeling is a commonly occurring phenomenon during steam flooding in heavy reservoirs. In this study, low-temperature expandable graphite was prepared to be employed as a steam plugging agent to resolve this problem. The preparation process was divided into two stages: (1) preoxidation and (2) deep oxidation and intercalation. The effects of the reagents and expansion temperature on the expansion capability were studied. An improved preparation formula for expandable graphite employed a mass ratio of graphite: H 2 O 2 :HClO 4 :KMnO 4 : acetic acid (HAc) as 1:2:6:0.5:1, and the expansion volume at 300 °C was 273 mL/g. Moreover, the initial expansion temperature was approximately 140 °C. In a water environment, the graphite particles demonstrated an expansion, which is less than that in a dry environment, and most layers maintained a good connection to ensure that the graphite sheets exhibited better anti-breaking strength. The Fourier transform infrared spectroscopy and X-ray diffraction analysis indicated that the intercalation reagents (HClO 4 and HAc) successfully entered the graphite layers, and the crystallinity of graphite decreased gradually during the reaction process. The oxidants (H 2 O 2 , KMnO 4 ) oxidized the edges of the graphite layers and slightly opened them, which provided the channels for the intercalation agents to enter the interlayer space. After expanding at 300 °C, a worm-like particle was formed. Through direct plugging, bridge plugging, and expansion capability, the low-temperature expandable graphite can control steam channeling. This study established a complete preparation technique of low-temperature expandable graphite that can be used for controlling steam channeling. This may serve as a reference for the preparation of steam plugging agents and an efficient development of heavy oil.