碳酸盐岩多尺度三维酸蚀蚓孔立体延伸动态模拟

Dynamic simulation of 3-D multiple-scale wormhole propagation in carbonate rocks

在双重尺度模型基础上建立了多尺度三维酸蚀蚓孔延伸模型并阐述了其数值求解方法。同时,利用地质建模方法建立了孔隙空间关联分布模型,成功解决了孔隙空间突变问题,使模拟结果更加真实可靠。通过模拟发现,注入速度是影响蚓孔形态的主要因素,随着注入速度的增大,溶蚀结构可分为面溶蚀、锥形结构、主蚓孔、分支结构和均匀溶蚀5类。当扩散速度与对流速度相当时会产生主蚓孔通道,越靠近注入端口的蚓孔越粗,而越接近出口端的蚓孔越细。主蚓孔在延伸过程中大致会经历以下4个阶段:蚓孔竞争发育、形成优势通道、主蚓孔突破岩心和蚓孔内径扩宽。其次,孔隙空间联通性是蚓孔扩展路径的决定因素,蚓孔最终沿初始高孔渗分布轨迹突破岩心。最后,通过现场算例验证了该模型及方法用于模拟碳酸盐岩储层酸化、酸压中蚓孔扩展的可行性与正确性,并为该研究领域的精细化模拟预测提供了新的手段。

Three dimensional （3-D） simulation of wormhole propagation is crucial for predicting stimulation effects of acidizing or acid fracturing in carbonate reservoirs.This paper presented a 3-D multiple-scale wormhole propagation model built based on the double-scale model,and its solving details.Meanwhile,geological modeling method was used to establish the geology model of porosity correlation distribution in 3-D space,which deals with the saltation of porosity successfully and makes the simulation results more realistic and reliable.Through the simulations,we found that the injection rate is the key factor affecting wormhole patterns.With the increase of the injection rate,five dissolving patterns may be observed,namely face dissolution,conical wormhole,dominant wormhole,ramified wormhole and uniform dissolution.When the convection and dispersion are comparable,the dominant wormhole may form with a thick root and a thin tip.The do-minant wormhole propagation can be divided into the following successive four stages,including competition stage,dominant stage,breaking stage and broadening stage.Most importantly,we found that the wormhole propagation pathway is highly correlated with the spatial correlation of porosity,since the wormhole breaks the core through those large pores with well connectivity.Finally,the field simulation results verified that the models and methods proposed in this paper are feasible and reliable for wormhole simulation of acidizing and acid fracturing in carbonate reservoirs.Those works could provide theoretical support for fine simulation and prediction in the relevant research areas.