During the development of low-permeability oil fields, high-pressure water injection is employed as a means of increasing reservoir pressure and enhancing oil recovery. This process features an interplay between pressure-driven flow and spontaneous imbibition, which exerts a pivotal influence on the distribution of oil and water. To describe the dynamics of this interplay, pore-scale visualization experiments and core flooding online nuclear magnetic resonance experiments were conducted in the present work. The results demonstrate that after water flooding, residual oil predominantly exists in clustered forms. Initially, during high-pressure water injection and the early stages of well shut-in, crude oil movement is driven primarily by pressure. As the process continues, however, a spontaneous imbibition mechanism driven by capillary forces becomes the predominant force, which results in the transformation of clustered residual oil into various mobilizable forms. This reorganization of residual oil is a migration pattern from smaller to larger pores, facilitated by spontaneous imbibition.
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Capillarity 2024, 13(2): 29-36
Published: 10 September 2024
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