微管中的酸化反应: 沉淀及界面效应

利用玻璃微管模拟孔隙性油藏, 研究了微乳酸(O/W)、土酸(即HCl/HF混合物)在不同内径的玻璃微管中的反应. 结果表明, 土酸对微管内表面的溶蚀速率较快, 且在反应过程中发现有氟硅酸钾/钠沉淀析出; 而微乳酸的反应速度较慢, 反应过程中只发现一些蚀斑. 微管内径越小, 则反应产生的气泡越易发生聚并, 形成气液环状分布. 土酸在管内不同位置处的反应速率不同, 液气界面处的反应明显较快. 在相同压力梯度下, 50及25 μm微管经两种酸液体系酸蚀后蒸馏水在其中的流速均有不同程度的增加(在管中反应 24 h), 即其流动能力明显增大; 蒸馏水在经微乳酸酸化后的微管中流动能力增加得更明显. 这不仅直观地证明了土酸在砂岩储层中酸化引起的二次沉淀反应, 而且土酸在微管中反应的界面效应也制约了酸化效果, 微乳酸在反应过程中不产生沉淀并能消除界面效应, 因而是一种较理想的酸化体系.

Acidizing Reaction in Microtubes: Deposition and Interface Effects

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.