To address the challenges in developing ultra-low permeability tight oil reservoirs,the mechanism of gas flooding to enhance oil recovery was systematically investigated through experimental and numerical simulation methods.The results indicated that the adsorption capacity of CO2 and N2 on core samples increased with increasing of pressure.At 25 ℃ and 15 MPa,the adsorption capacities of CO2 and N2 reached 1.5 mmol·g-1 and 0.45 mmol·g-1,respectively,with CO2 exhibiting significantly higher adsorption capability than N2.Core flooding experiments demonstrated that at the pressure gradient of 2.5 MPa·m-1,the flow rate of CO2 reached 3.0 m·d-1,while that of N2 was only 1.2 m·d-1,proving that CO2 had higher transmission efficiency in tight media.Displacement efficiency analysis revealed that at 15 MPa and 25 ℃,the displacement recovery rate of CO2 could reach 71.4%,compared to 45.1% for N2.The techno-economic evaluation showed that although the cost of high-pressure CO2 injection was relatively high,it brought the most significant increase in oil production revenue,demonstrating its economic advantage.This study provides important theoretical and practical guidance for enhancing oil recovery in ultra-low permeability tight oil reservoirs through gas flooding,contributing to improved development efficiency and economic benefits.
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