全三维酸液流动反应模型在酸压中的应用

酸液浓度分布计算是酸压模拟计算中的重要内容，传统的酸岩反应模型都是基于酸液的一维流动，忽略了裂缝高度方向酸液流动及酸岩纵向反应速度的变化，不考虑缝中酸液浓度随时间的变化。酸压裂缝在缝高方向延伸过程中必然引起酸液的纵向流动，酸液在缝高方向的流动必然导致缝高方向存在酸液浓度差。考虑酸液在缝高方向的流动、缝中酸液浓度随时间的变化以及同离子效应的基础上，建立了酸压过程中全三维缝中酸液流动反应模型，并给出数值求解方法。计算结果表明，缝高方向的酸液浓度和酸液流速都呈抛物线分布，越靠近裂缝中部酸浓度越高，在裂缝中部达到最大值；酸液在缝高方向的流动影响酸液有效作用距离的大小，全三维模型计算的酸液有效作用距离比二维模型计算的要小。

APPLICATION OF FULLY 3-D REACTION MODEL OF ACIDIZING FLUID IN ACID FRACTURING

Concentration distribution calculating of acidizing fluid is the major content of the acid fracturing simulation calculating works. Traditional acid/rock reaction models are established on the basis of one-dimensional flow of acidizing fluid, which omit the acidizing fluid flowing along the direction of the fracture height, and the variation of the acid/rock longitudinal reaction velocity, and never consider the variation of acidizing fluid concentration with time in the fractures. The extension of the fracture height direction must lead to the longitudinal flow of the acidizing fluid, which will inevitably result in the concentration difference of the acidizing fluid in the fracture height direction. Considering the flow of the acidizing fluid in the fracture height direction, the variation of acidizing fluid concentration with time in the fractures and the common-ionic effect, the fully 3-D reaction model of acidizing fluid flowing in the process of acid fracturing is developed and its numerical solution is provided. The calculating results show both the concentration and the flowing rate of the acidizing fluid along the direction of the fracture height appear by parabolic curve. The less the distance to the medium of the fracture is, the higher the concentration of the acidizing fluid is. The concentration reaches the maximum at the medium of the fracture. The flow of the acidizing fluid along the fracture height will influence the effective distance treated by the acidizing fluid. The effective distance calculated by the fully 3-D model is smaller than that calculated by the 2-D model.