白云岩储层酸岩反应控制模式界限

为明确白云岩储层酸岩反应控制模式界限,以中亚某区块白云岩储层岩心为对象,开展酸岩反应动力学试验和数值模拟研究,并通过扫描电镜对比分析灰岩与白云岩酸蚀机制的差异;建立不同因素控制下的白云岩酸岩反应动力学方程,明确温度90℃、转速500 r/min为表面反应控制模式、表面反应和传质共同控制模式的界限。结果表明相同试验条件下,随着白云质体积分数的升高,酸岩反应速度迅速降低;当白云质体积分数超过75%时,酸岩反应速度降到最低并趋于稳定;白云岩储层的酸压改造方向应区别于灰岩储层,在允许范围内可以适当提高酸岩反应速度,以改善裂缝壁面的非均匀刻蚀程度,增大酸蚀裂缝的导流能力。

Limitation on acid-rock reaction and its control mode in dolomite formation

In order to define the limitation of acid-rock reaction and its control mode of dolomite reservoirs,the kinetics experiments of acid-rock reaction and numerical simulation were carried out,using rock cores from a dolomite reservoir in Central Asia.The difference of acid erosion mechanisms on limestone and dolomite was analyzed by scanning electron microscope.An acid-rock reaction kinetics model in dolomite cores under different conditions was established.The limits of surface reaction and mass transfer control mode were defined at 90℃,with stirring rate of 500 r/min.The results show that,under the same testing conditions and with the increase of the dolomite content,the acid-rock reaction rate decreases rapidly.When the dolomite content exceeds 75%,the acid-rock reaction rate decreases to a lowest level and tends to be stable.Therefore,the acid fracturing transformation direction in dolomite reservoirs should be different from that in limestone reservoirs,and acid-rock reaction rate can be appropriately increased within an allowable range in order to enhance the uneven erosion on the fracture wall and increase the conductivity of acid eroded fractures.