碳酸盐岩缝洞型储层酸化的数值模拟研究

酸化是碳酸盐岩储层地质改造的主要施工工艺，厘清碳酸盐岩储层酸化机理对于提升酸化整体效果具有重要意义。限于缝洞在储层中的准确刻画，目前的研究集中于碳酸盐岩无缝洞型储层的酸化研究。为此，基于数值模拟手段，建立缝洞刻画算法，采用双尺度连续模型，研究了不同注入速度、酸浓度及表面化学反应速率等因素对酸化过程中蚓孔形成及发育的影响机理。发现：缝洞型油藏的酸蚀蚓孔过程受缝和洞共同影响，采用普通油藏进行酸化数值模拟的研究会高估缝洞型油藏酸化行为中的溶蚀量及溶蚀贯通储层的时间。随着酸浓度的增大，碳酸盐岩溶蚀量由5.7%增大为7%；注入速度的增大将影响碳酸盐岩酸蚀形态，且酸化影响范围和次生蚓孔发育数量均不断增多；酸的表面化学反应速率不是影响碳酸盐岩酸化行为的主要原因。

Numerical simulation of acidizing in fracture-vug type carbonate reservoir

Acidizing is the main construction technology of carbonate reservoir geological transformation. Clarifying the acidizing mechanism of carbonate reservoir is of great significance to improve the acidizing effect in carbonate reservoir. Limited to the accurate characterization of fracture-vug in the simulation, the current research focuses on the acidizing of carbonate reservoir without fracture-vug. Therefore, based on numerical simulation, a fracture-vug characterization algorithm was established, and a two-scale continuum model was used to study the influence mechanism of different injection rate, acid concentration and surface chemical reaction rate on the formation and development of wormhole in the process of acidification. It is found that the development of wormhole in the acid etching process of fracture-vug type reservoir is affected by both fractures and holes. The study of acidizing numerical simulation of ordinary reservoir will overestimate the amount of dissolution and the time of breakthrough reservoir in the acidizing process of fracture-vug type reservoir. With the increase of acid concentration, the dissolution of carbonate rock increases from 5.7% to 7%; The increase of injection rate will affect the acid corrosion morphology of carbonate rocks, and the influence range of acidification and the development number of secondary wormholes are increasing; The surface chemical reaction rate of acid is not the main reason affecting the acid corrosion behavior of carbonate rocks.