高稳定性壳聚糖凝胶堵剂的制备与成胶性能评价

Preparation and Gelation Behavior Evaluation of Ultra-stable Chitosan Gel Plugging Agent

聚丙烯酰胺类凝胶堵剂在油田调剖堵水、井筒堵漏、修井暂堵等领域应用广泛,但其耐温、抗盐、抗剪切性能不足,在高温高盐油藏条件下难以实现高强度封堵并维持稳定。针对以上问题,以壳聚糖(CTS)、N,N'-亚甲基双丙烯酰胺(MBA)为原料制备了一种有机交联壳聚糖凝胶堵剂,研究了原料加量、pH值、温度、矿化度、剪切作用等对凝胶成胶性能的影响。结果表明,CTS与交联剂MBA可通过迈克加成反应形成共价键交联;交联后的凝胶强度及成胶时间随CTS与MBA浓度上升分别增加和降低;矿化度的增加可降低交联反应的活化能,促进交联反应的进行,使成胶时间缩短、凝胶强度增加;pH值会影响CTS的质子化程度,当pH值低于4.2时,胶凝强度急剧降低。CTS-MBA凝胶体系的抗剪切性能较好,凝胶基液在6000 r/min剪切速率下剪切30 min后的成胶强度仅降低2.4%。在120℃及矿化度为30 g/L的条件下,2.0%CTS和0.6%MBA组成的凝胶体系在老化90 d后仍可维持性能的稳定。CTS-MBA凝胶的耐温、抗盐、抗剪切性能和热稳定性好于聚丙烯酰胺类凝胶,同时降低了药剂成本。

Polyacrylamide-type hydrogels have been widely used in conformance control,circulation lost control and well workover as plugging agents.However,polyacrylamide suffers from unfavorable temperature resistance,salt resistance and shearing resistance,which makes high strength and stable plugging under high temperature and high salinity extremely difficult.Aiming at these problems,an organic crosslinking chitosan(CTS)gel system was prepared using CTS and N,N'-methylene bisacrylamide(MBA)as raw materials.The effects of chemical dosage,pH value,temperature,salinity and shearing on the gelation performance were studied.The results showed that CTS could be crosslinked with crosslinker MBA through Michael addition reaction.The gel strength increased and gelation time decreased respectively,with increasing dosage of CTS and MBA.The increase of salinity could reduce the activation energy of the cross-linking reaction,promote the gelation process,shorten gelation time,and increase gel strength.The pH value had a significant effect on the protonation degree of CTS.As a result,the gel strength decreased sharply when the pH value was lower than 4.2.The CTS-MBA gel system possessed superior shearing resistance.The gel strength only decreased 2.4% after the gellant being sheard at 6000 r/min for 30 minutes.The gel system composed of 2.0% CTS and 0.6% MBA could remain stable after aging for 90 days under the condition of 120℃ and 30 g/L salinity.CTS-MBA gel had better temperature resistance,salt resistance,shearing resistance and thermal stability than polyacrylamide gel.At the same time,the cost of chemicals was reduced.