Effects and Mechanism of Gaseous Acid on Surface Microtopography of Tight Sandstone Reservoirs

Conventional reservoir acidification technology is limited by the rheology of acidic fluid, and it is difficult to penetrate deep into tight reservoirs to achieve effective stimulation. In this study, it is proposed to use gas acid to transform tight sandstone reservoirs. By carrying out the dissolution experiment of gas acid on a tight sandstone surface, the dissolution characteristics of rock surface under the action of gas acid are systematically analyzed, the change of wetting behavior after gas acid dissolution is quantitatively characterized, and the dissolution mechanism of gas acid on tight sandstone is revealed. The experimental results show that under the erosion of gas acid, the cemented minerals on the rock surface gradually dissolve, resulting in the increase of surface roughness. Among them, hydrogen fluoride gas (HF) has the most prominent effect on improving rock surface roughness, and the growth rate of surface area can reach 34%. At the same time, the contact angle of the rock surface decreases by 23.47°. The numerical simulation further shows that the concentration of gas acid, initial injection rate, molecular size, and density all have significant effects on the acidification effect. The above research results provide new ideas and theoretical basis for the efficient development of tight reservoirs.