Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated. Degradable materials (fibers and solid particles) have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation. Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism, it was observed that the volume of the base fluid and the loading of the particles are not optimized. The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product. It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters. Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development, new applications of existing products or usage optimization. In this work, we develop a numerical model to study fiber dynamics in fluid flow. We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres. The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions. The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates. The trends of the dynamic fiber behavior under various operating conditions including fiber loading, flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations. The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading, selecting fibers with higher stiffness, reducing the injection flow rate, reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.

中文翻译：

---

钻井中流体桥接中的纤维建模

酸的准确放置是基质增产的主要考虑因素，因为酸倾向于渗透阻力最小的区域，同时不处理地层的低渗透率区域。可降解材料（纤维和固体颗粒）最近表现出良好的流体导流能力，可以克服与基质刺激有关的问题。尽管在最近的酸刺激工作中取得了成功，这是由于使用了一些依靠纤维絮凝作为主要转移机理的产品而引起的，但据观察，基础流体的体积和颗粒的负载并未得到优化。当前行业缺乏科学的设计指南，因为所使用的方法是基于特定产品在特定领域的经验或经验研究。然后，重要的是要了解在具有不同转向机制和转向器的碳酸盐中，酸转移原理的基本原理。数学建模和计算机仿真是发展这种理解的有效工具，并有效地应用于新产品开发，现有产品的新应用或使用优化。在这项工作中，我们开发了一个数值模型来研究流体流动中的纤维动力学。我们采用离散元素方法，其中纤维由相互连接的球体的多刚体系统表示。离散纤维模型与流体流动求解器耦合以解决固有的同时相互作用。研究的重点是当纤维与悬浮液相互作用并遇到可能代表碳酸盐岩裂缝或虫洞的限制时，纤维易于絮凝和桥接的趋势。从数值模型获得的包括纤维载量，流速和流体粘度在内的各种工况下的动态纤维行为的趋势表明与实验观察结果一致。目前的数值研究表明，通过增加纤维载荷，选择具有更高刚度的纤维，降低注射流速，降低悬浮液粘度或增加纤维之间的吸引力内聚力，可以增强纤维-流体系统的桥接能力。使用粘性纤维。从数值模型获得的包括纤维载量，流速和流体粘度在内的各种工况下的动态纤维行为的趋势表明与实验观察结果一致。目前的数值研究表明，通过增加纤维载荷，选择具有更高刚度的纤维，降低注射流速，降低悬浮液粘度或增加纤维之间的吸引力内聚力，可以增强纤维-流体系统的桥接能力。使用粘性纤维。从数值模型获得的包括纤维载量，流速和流体粘度在内的各种工况下的动态纤维行为的趋势表明与实验观察结果一致。目前的数值研究表明，通过增加纤维载荷，选择具有更高刚度的纤维，降低注射流速，降低悬浮液粘度或增加纤维之间的吸引力内聚力，可以增强纤维-流体系统的桥接能力。使用粘性纤维。