Seepage Characteristics of Emulsion with Phase Transition Behaviors

Abstract

Petroleum resins have excellent thermal tolerance and selective plugging capability. As the environment temperature exceeds their softening point, petroleum resins transform from a solid into a viscous Newton fluid, accompanied by the transformation of the system from particle dispersoid to emulsion. The presence of phase transition decides that the seepage regularity and plugging characteristics of petroleum resins are different from either particle dispersoid or emulsion. Herein, rheological measurements and physical model flooding experiments were performed to investigate the injection and plugging performance of petroleum resins. A correlation chart of the injection pressure, formation permeability, and the ratio of resin particle size to pore diameter is established. The dispersoid is demonstrated to present good injectivity when the ratio of the resin particle size to the pore‐throat diameter of the porous media is lower than 0.35. Moreover, when the environment temperature is lower than or around the petroleum resin softening point, the injection performance of the dispersoid is not affected by temperature. Comparably, while the environment temperature is 30 °C higher than the resin softening point, the injection pressure increases due to phase transition. As indicated by the plugging experiment, the presented petroleum resin dispersoid plugging agent manifests excellent performance even in the case that the permeability of water‐channeling paths is up to 20 μm2, reaching a water plugging efficiency of over 85%. For water‐channeling fractures with widths of 0.05–0.5 mm, the plugging pressure gradient can exceed 5 MPa m−1. As suggested by combined analysis of injection and plugging performance, the disperse system should be optimized in accordance with the formation condition during field practice. Specifically, the ratio of the resin particle size to the formation pore diameter should be kept lower than 0.35, while the softening point of the petroleum resin should be 10–20 °C lower than the formation temperature.