开关型气溶性起泡剂的构建及其对二氧化碳驱的调控行为研究

It is a new method to control gas channeling and improve gas mobility by injecting the carbon dioxide with a carbon dioxide-soluble foaming agent, which can generate foam in situ whenever flowing through water formation. Most of carbon dioxide-soluble foaming agents are non-ionic surfactants, which have limited solubility in supercritical carbon dioxide and poor tolerance to high temperature. For the last two years a polyoxyethylene alkyl amine with straight chain, wihch is a switchable surfactant having a favorable solubility in carbon dioxide as well as good foaming ability,has been investigated at the University of Texas at Austin and the University of Rice . However, this surfactant is easy to dissolve in water while ionized with H+, and thus cannot transfer into the deep reservoir with carbon dioxide. According to the characterstic structure of carbon dioxide-soluble surfactant, a series of alkoxy polyoxy ethylene (or propylene) propylamine surfactants with methylation tail groups, branched tail groups or tert-butyl terminated tail groups will be designed. Based on that, some methods to control the partition coefficient of carbon dioxide-soluble surfactant in carbon dioxide/water will be probed. Besides, the foaming behavior of carbon dioxide with carbon dioxide-soluble surfactant in porous medium and the effect of carbon dioxide-soluble surfactant on the miscible behavior of carbon dioxide flooding will be illustrated by physical simulation. The results can provide some guidances for the applications of carbon dioxide-soluble surfactants in low permeability carbonate reservoirs in China.

在二氧化碳中加入气溶性起泡剂，使超临界二氧化碳通过含水地层时适时、就地生成泡沫是一种抑制气窜、改善气驱效果的新方法。目前所用气溶性起泡剂多为非离子表面活性剂，存在气溶性差、使用温度不高等问题。近2年来美国德克萨斯大学、莱斯大学提出的开关型表面活性剂聚氧乙烯直链烷基胺虽然具有较好的气溶性、起泡性，但质子化后易溶于水相，无法满足被二氧化碳携带向地层深部运移的要求。课题借鉴亲二氧化碳表面活性剂分子结构特点，首次设计了含甲基化尾基、分支型尾基、叔丁基封端的尾基等结构的支链烷氧基二(聚氧乙烯基)丙胺类活性剂。以此为基础，探索调控气溶性起泡体系二氧化碳/水分配系数的方法，并设计物理模拟试验揭示携带气溶性起泡剂的二氧化碳在孔隙介质中的起泡行为、考察气溶性起泡剂对二氧化碳驱混相行为的影响。研究结果可为气溶性表面活性剂在我国低渗透率碳酸盐岩油藏的应用提供指导。

二氧化碳（CO2）驱技术目前在就范围内备受关注，但较高的流度导致气体易于指进或重力超覆，限制了驱替流体的波及体积及提高采收率效果。在超临界二氧化碳中溶解低分子气溶性表面活性剂，使其在通过含水储层时可以就地生成泡沫以增加表观粘度，是一种有效调控CO2流度的新方法。本课题在合成新型支链烷氧基胺聚醚体系的基础上，系统研究了该类开关型表面活性剂在超临界二氧化碳中的气溶性及分配性，探究了其在多孔介质中的起泡行为以证实其降低CO2流度效果。研究结果表明合成的新型支链烷氧基胺聚醚可以在超临界二氧化碳中溶解度达到0.2wt%以上，十二烷基胺聚醚、异构十三烷氧基胺聚醚在超临界CO2中的浊点压力明显低于相同聚氧乙烯数的十八烷基胺聚醚；泡沫稳定性随烷基链长的增加、压力增大而增加；气相携带表面活性剂注入含水多孔介质可生成泡沫使表观粘度增加30倍以上，从而有效降低CO2流度，以达到延缓气体突破、增大波及体积效果；气相携带活性剂注入方式生成强泡沫所需的最小临界流速较小。课题研究结果能够为气溶性表面活性剂在我国低渗透碳酸盐岩油藏的CO2驱开发提供一定的理论支撑。

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