RESEARCH PROGRESS ON THRESHOLD PRESSURE GRADIENT IN HEAVY OIL RESERVOIRS

Polymer flooding is one of the key technologies for enhancing oil recovery. Partially Hydrolyzed Polyacrylamide (HPAM) is widely used due to its excellent viscosity-increasing properties. However, the adsorption and retention behavior of HPAM in reservoir porous media presents a dual effect: on one hand, it improves sweep efficiency by increasing flow resistance; on the other hand, it leads to a loss in effective polymer concentration and viscosity, reducing displacement efficiency and increasing costs. Therefore, a systematic understanding and control of HPAM adsorption behavior are crucial for improving the effectiveness of polymer flooding. This work systematically reviews seven main measurement methods for HPAM adsorption quantity, comparing their applicable conditions and limitations. It summarizes the key factors influencing HPAM adsorption and retention behavior from three aspects: polymer properties, rock mineral characteristics, and reservoir environmental conditions. Furthermore, it outlines chemical anti-adsorption methods, represented by competitive adsorption and nanofilm protection, along with their mechanisms. Finally, future research directions are proposed, focusing on building adsorption prediction models, deepening the understanding of adsorption mechanisms under multi-field coupling conditions, and developing novel functional polymers with anti-adsorption capabilities.

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