Diverting mechanism of viscoelastic surfactant-based self-diverting acid and its simulation
Diverting mechanism of viscoelastic surfactant-based self-diverting acid and its simulation
复制标题
粘弹性表面活性剂基自转向酸的转向机理及其模拟
DOI：
10.1016/j.petrol.2013.03.001
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发表时间：
2013-05-01
影响因子：
--
通讯作者：
Shi, Yang
中科院分区：
文献类型：
--
作者：
Liu, Ming;Zhang, Shicheng;Shi, Yang
在碳酸盐岩酸化中，酸会选择性地流入高渗透率区域溶解岩石，而低渗透率区域则未得到处理。人们发现许多技术，包括机械技术和化学技术，都在尽力避免酸的不均匀分布。在这些技术中，注入基于粘弹性表面活性剂的自转向酸（VES酸）是一种将酸转向其他低渗透率区域的有效方法。VES酸能够随着表面活性剂的胶凝在其消耗过程中自行增粘。由于高渗透率区域接收的酸更多，胶凝过程首先在该区域发生，从而使酸转向其他低渗透率区域。然而，据我们对公开文献的了解，尽管VES酸在油气田有许多成功应用，但其转向机制尚未被理解。在本文中，我们通过对以往实验结果的分析以及我们自己的实验观察，深入研究了转向机制。根据转向机制，开发了一种描述VES酸转向行为的新模型。结果表明，转向机制既取决于残酸区，也取决于残酸的粘度。随着VES酸的注入，残酸区和残酸的粘度不断增加，这导致压力差不断增大。然而，低渗透率区域的残酸区比高渗透率区域的更薄。因此，在对数 - 对数坐标系中，最大压力比与渗透率呈线性增长关系。此外，残酸粘度的不均匀分布导致突破点附近压力差急剧下降。新模型将描述常规酸化的双尺度连续介质模型与描述钙离子浓度、增粘行为和反应速率的三个方程相结合。通过一系列模拟，结果与实验结果吻合良好，这意味着新模型捕捉到了VES酸的转向机制。（c）2013爱思唯尔有限公司。保留所有权利。
In carbonate acidizing, acid selectively flows into the high permeability zones to dissolve the rock, leaving the low permeability zones untreated. Many techniques including mechanical ones and chemical ones are found to do their best to avoid the uneven distribution of acid. Among these techniques, injecting the viscoelastic surfactant-based self-diverting acid(VES acid) is an effective method to divert acid to other low permeability zones. The VES acid is able to be self-viscosified with its consumption through the gelling of the surfactant. Since the high permeability zone receives more acid, the gelling process occurs first in the zone so that the acid is diverted to other low permeability zones. However, to the best of our knowledge in the open literature, the diverting mechanism of the VES acid has not been understood in spite of many successful applications in oil and gas fields. In this paper, we thoroughly study the diverting mechanism through the analyses of the former experimental results and our own experimental observations. According to the diverting mechanism, a new model which describes the diverting behavior of the VES acid is developed. The results show that the diverting mechanism is dependent on both the spent acid zone and the viscosity of the spent acid. The spent acid zone and the viscosity of the spent acid keep increasing with the injection of VES acid, which leads to the continuous increase of the pressure difference. However, the spent acid zone is thinner for low permeability zone than for high permeability zone. As a result, the maximum pressure ratio follows a linear increase relationship with the permeability in the log-log coordinate system. In addition, the non-uniformly distributed viscosity of the spent acid leads to the sharp drop of the pressure difference in the vicinity of breakthrough. The new model couples the two-scale continuum model describing the conventional acidizing with three equations describing the concentration of Ca ions, viscosifying behavior and reaction rate. Through a series of simulations, the results are in good agreement with the experimental ones, which means that the new model captures the diverting mechanism of the VES acid. (c) 2013 Elsevier B.V. All rights reserved.