Effect of normally distributed porosities on dissolution pattern in carbonate acidizing
Effect of normally distributed porosities on dissolution pattern in carbonate acidizing
复制标题
DOI：
10.1016/j.petrol.2012.06.021
复制
发表时间：
2012-09-01
影响因子：
--
通讯作者：
Mou, Jianye
中科院分区：
文献类型：
--
作者：
Liu, Ming;Zhang, Shicheng;Mou, Jianye
在碳酸盐岩酸化过程中，酸溶解岩石，形成一个称为虫孔的高渗透率通道。影响虫孔形成的主要因素之一是多孔介质的非均质性。以往的文献认为孔隙度场是均匀分布的，这与岩石孔隙度的真实分布并不相符。在本文中，我们使用正态分布方法来生成孔隙度。两种方法的比较表明，正态分布法的待突破孔隙体积小于均匀分布法。由于正态律的特点，引入了表征异质性的相关长度和标准差。网格间径向或周向的相关性对虫孔有影响。由于虫洞在周向的相关长度较大，虫洞倾向于远离径向，使自身变厚。由于径向相关长度大，虫孔数量增加，虫孔变薄。总注酸量随着初始孔隙度的增大而减小。标准偏差存在一个临界值，低于该临界值，待突破孔隙体积不敏感，高于该临界值，待突破孔隙体积急剧减小。无论沿射孔是否有酸漏，随着射孔长度的增加，孔隙体积减小。面溶模式末端压力的急剧下降是由于废酸锋的传播速度比反应锋快，并且两者之间的距离较短。连续的孔洞改变了虫洞的传播路径，减少了注入量。最后，建立了一个表观表皮因子模型来研究虫孔的性能。在突破损伤区之前，皮肤因子急剧下降表明改善巨大，突破后，皮肤因子缓慢下降。虫洞的长度和时间遵循幂律关系。(C) 2012 Elsevier B.V.版权所有
In carbonate acidizing, acid dissolves rock to create a high permeability channel called wormhole. One of the main factors to influence the formation of wormhole is the heterogeneity of porous medium. In former literature, uniformly distributed porosity fields were considered which are not in accord with the real distribution of porosities in rocks. In this paper, we use a normal distribution method to generate porosities. The comparison of the two methods shows that the pore volume to breakthrough for the normal distribution method is less than that for the uniform distribution method. Due to the characteristics of normal law, correlation length and standard deviation which characterize heterogeneity are introduced. The correlation in the radial or circumferential direction among girds has an effect on wormholing. Wormhole tends to propagate away from the radial direction to make itself thicker due to the big correlation length in the circumferential direction. The number of wormholes is increased and the wormholes become thinner because of big correlation length in the radial direction. The total acid injection volume decreases with the increase of initial porosity. A critical value for standard deviation exists, below which the pore volume to breakthrough is insensitive, above which the pore volume to breakthrough decreases sharply. The increase of perforation length decreases the pore volume to breakthrough whether there is acid leakoff along the perforation or not. The sharp decline of pressure at the end for the face dissolution pattern is due to the faster propagation velocity for the spent acid front than that for the reaction front and the short distance between them. Continuous vugs change the wormhole propagation path and decrease the injection volume. Finally, an apparent skin factor model is developed to study the performance of wormholing. Before the breakthrough of the damage zone, the sharply decreased skin factor indicates huge improvement, after the breakthrough, the skin factor decreases slowly. Wormhole length and time follow a power-law relationship. (C) 2012 Elsevier B.V. All rights reserved.