Abstract: The micro-scale flow behavior in glass microtubes has aroused the interest of a wide variety of researchers in recent years. The glass microtubes with different inner diameters were used in this paper to simulate the porous oil reservoir, and the experiments conducted on the chemical reactions between microemulsified acid and mud acid within these microtubes. Microscope observation results show that the reaction velocity of mud acid in microtube is larger than that of microemulsified acid. Deposition produced after the mud acid entered the microtube and reacted for a period of time, while only corrosive spot appeared during the microemulsified acid reaction in it. The less the inner microtube diameter, the more ready the coalescence of bubble produced to happen and form gas-liquid annular distribution. The mud acid reaction rate, which was various at different positions in the micro tube, reaches the maximum at the position of gas-liquid interface and declines with the increase of the distance from the interface. The flow rate in a microtube(ID=50 and 25 μm), which indicates its flow ability(permeability), increases to different degrees after it reacts with both the acid solution(reaction time 24 h). And the rate increase is more obvious in the microtube after acid-etched by microemulsified acid than mud acid. These experiments not only show secondary precipitation as mud acid reacting with sand reservoir, but also interfacial effect during the reaction process. Microemulsified acid is an optimum acidizing fluid for it can eliminate pecipitation and interficial effect during the process of acid-etching.

Key words: Mud acid, Microemulsified acid, Microtube, Low permibility reservoir, Acid-etching