Summary This paper highlights the difference between foam injection for gas blocking in production well and injection well and emphasizes the use of polymer enhanced foam. Moreover, this paper shows systematic experimental methods for choosing suitable foam systems for gas blocking in production well considering different factors, which provides a guide regarding what kinds of foaming agents and polymer stabilizers should be used and how to evaluate them for designing a pilot application. The target in this work is the Vostochno-Messoyakhskoye field, operated by Gazpromneft, which is currently experiencing gas channeling from the gas cap in production wells because of strong heterogeneity. Foam has long been considered as a good candidate for gas blocking. However, foam injection for gas blocking in production wells is different from that in injection wells, which requires a long-term impact on gas-saturated highly permeable areas without significantly affecting the phase permeability of oil in the reservoir. Therefore, for gas blocking in production well, a long half-life time of foam is required to sustain stable foam because a continuous shear of surfactant solution/gas cannot be achieved as in injection wells. Thus, reinforced foam by polymer (polymer-foam) is chosen. Four polyacrylamide polymer stabilizers and five anionic surfactants were evaluated using bulk test to determine foaming ability, foam stability, and effect of oil by comparing foam rate and half-life time to determine the suitable foam system with optimal concentrations of reagents. Furthermore, filtration experiments were conducted at reservoir conditions to determine the optimal injection mode by evaluating apparent viscosity, breakthrough pressure gradient, resistance factor, and residual resistance factor. Polymer can significantly improve half-life time (increase foam stability), and the higher the polymer concentration, the longer the half-life time. But simultaneously, a high polymer concentration will increase the initial viscosity of the solution, which not only decreases the foam rate but also increases difficulties in injection. Therefore, an optimal polymer concentration of about 0.15–0.2 wt% is determined considering all these influences. Filtration experiments showed that the apparent viscosity in the core first increased and then decreased with foam quality (the volumetric ratio of gas to total liquid/gas flow). The optimal injection mode is coinjection of surfactant/polymer solution and gas to in-situ generate foam at the optimal foam quality of about 0.65. Filtration experiments on the different permeability cores showed that the gas-blocking ability of polymer-foam is better in high-permeability cores, which is beneficial for blocking high-permeability zone. It should also be noted that under a certain ratio of oil-to-foam solution (about lower than 1 to 1), the presence of high-viscosity crude oil slowly decreased the foam rate with increasing oil volume, but significantly increased the half-life time (i.e., foam stability which is favorable for foam treatment in production well).

中文翻译：

---

用于减少 Messoyakhskoye 油田生产井气顶气窜的泡沫试验设计的实验室研究

总结 本文重点介绍了生产井注气堵气与注气井注泡沫的区别，并强调了聚合物增强泡沫的使用。此外，本文还展示了考虑不同因素选择合适的生产井气堵泡沫体系的实验方法，为应使用哪种发泡剂和聚合物稳定剂以及如何评估它们以设计试点应用提供了指导。这项工作的目标是由 Gazpromneft 运营的 Vostochno-Messoyakhskoye 气田，由于非均质性强，该气田目前正在经历生产井气顶的气窜。长期以来，泡沫一直被认为是阻气的良好候选者。然而，生产井注气堵气不同于注气井，需要对含气饱和高渗透区进行长期冲击，同时不显着影响储层油相渗透率。因此，对于生产井的气堵，需要较长的泡沫半衰期来维持稳定的泡沫，因为不能像注入井那样实现表面活性剂溶液/气体的连续剪切。因此，选择了聚合物增强泡沫（polymer-foam）。使用本体测试评估了四种聚丙烯酰胺聚合物稳定剂和五种阴离子表面活性剂，通过比较泡沫速率和半衰期来确定起泡能力、泡沫稳定性和油的效果，以确定具有最佳试剂浓度的合适泡沫体系。此外，在储层条件下进行过滤实验，通过评估表观粘度、突破压力梯度、阻力系数和残余阻力系数来确定最佳注入模式。聚合物可以显着提高半衰期（增加泡沫稳定性），而且聚合物浓度越高，半衰期越长。但同时，高聚合物浓度会增加溶液的初始粘度，这不仅会降低起泡率，还会增加注射难度。因此，考虑到所有这些影响，确定了约 0.15-0.2 wt% 的最佳聚合物浓度。过滤实验表明，随着泡沫质量（气体与总液体/气体流量的体积比）的增加，芯中的表观粘度先升高后降低。最佳注入模式是表面活性剂/聚合物溶液和气体共注入原位产生泡沫，最佳泡沫质量约为 0.65。不同渗透率岩心的过滤实验表明，高渗岩心中聚合物泡沫的阻气能力较好，有利于封堵高渗带。还需要注意的是，在一定的油泡溶液比（约低于 1 比 1）下，高粘度原油的存在随着油量的增加而缓慢降低泡沫率，但显着增加了半寿命（即有利于生产井泡沫处理的泡沫稳定性）。不同渗透率岩心的过滤实验表明，高渗岩心中聚合物泡沫的阻气能力较好，有利于封堵高渗带。还需要注意的是，在一定的油泡溶液比（约低于 1 比 1）下，高粘度原油的存在随着油量的增加而缓慢降低泡沫率，但显着增加了半寿命（即有利于生产井泡沫处理的泡沫稳定性）。不同渗透率岩心的过滤实验表明，高渗岩心中聚合物泡沫的阻气能力较好，有利于封堵高渗带。还需要注意的是，在一定的油泡溶液比（约低于 1 比 1）下，高粘度原油的存在随着油量的增加而缓慢降低泡沫率，但显着增加了半寿命（即有利于生产井泡沫处理的泡沫稳定性）。