Work

Characteristics and influencing factors of spontaneous imbibition in deep tight conglomerate reservoirs in the Mahu Sag

Year: 2025

Type: article

Abstract: Research on spontaneous imbibition in deep tight conglomerate reservoirs of the Mahu Sag is vital for enhancing oil recovery and optimizing development. This study employs porosity-permeability tests, CT scanning, contact angle measurements, volumetric imbibition experiments, and NMR T₂ spectrum/imaging to investigate impacts of core properties, size, temperature-pressure conditions, and contact modes. Findings reveal strong heterogeneity in porosity (5.4%-15.8%) and permeability (0.11-8.99 mD), poor porosity-permeability correlation, and weak connectivity with low coordination numbers (≤ 5 predominant); macroscopic connected porosity strongly correlates with permeability (r = 0.92). Reservoirs show strong hydrophilicity: interstitial clays < 10° contact angle, detrital grains averaging 30°. Imbibition recovery factors range 29.6%-50.9%, influenced by higher porosity/permeability and shorter cores. Reservoir conditions (95 °C, 56 MPa) increase recovery by ~ 8%, with temperature reducing oil viscosity for faster rates and pressure enhancing drive for longer duration. Microscopically, imbibition favors sub-micropores/micropores (up to 50% recovery), while macropores exhibit counter-imbibition and oil redistribution. Results provide insights into imbibition mechanisms, refine experimental methods, guide shut-in timing, and support efficient reservoir development.

Source: Scientific Reports

DOI: 10.1038/s41598-025-21543-z