Researches on the PAM／Cr^3＋ Gel for Deep Profile Control

STP强凝胶调堵剂由聚丙烯酰胺、交联剂及延缓剂组成。其中,聚丙烯酰胺的相对分子量为4.00×106—7.00×106、水解度为17.6%;交联剂为Na2Cr2O7 NH4Cl氧化还原体系;延缓剂为加入乙二醇的乳酸/丙酸/乙酸有机酸复配体系。考察了pH值、温度、矿化度及延缓剂用量等因素对STP强凝胶成胶的影响。筛选出STP强凝胶成胶的最佳条件:pH值为5.2,温度为55 ℃、矿化度小于7 g/L。在此条件下调节延缓剂用量可控制成胶时间(12—144 h)。在由3支串联高渗透率岩心和3支串联低渗透率岩心并联而成的非均质模型上,对STP液典型配方进行深部调剖驱油模拟实验研究。结果表明,在水驱饱和油之后(合层采收率为24.3%),依次用调堵剂封堵第一、第二、第三高渗岩心后水驱,合层采收率分别达46.8%、62.2%和69.1%。由此可以得出,封堵深度越大,提高采收率的幅度越大;深部调剖可增加注水对低渗透层的波及程度,未成胶的调堵剂液通过高渗层时可驱替其中的残余油。

Researches on the PAM/Cr3+ Gel for Deep Profile Control

The profile control hard-gel is composed of polyarylamide (5-6g/L), whose molecular weight is 4,000,000 - 7,000,000 and hydrolysis degree is 17.6%, and cross-linking oxidation-reduction agent (Na2Cr2O7 + NH4Cl), with an delayed organic acid crosslinker which contains lactic acid/propionic acid/ethanoic acid and ethylene glycol. After research of the influence factors, such as pH, temperature, salinity and the dosage of delayed crosslinker, the optimum condition(pH 5.2, temperature 55℃, salinity ＜ 7g/L) was found. Gelation time (12-144h) can be controlled by adjusting the dosage of the delayed crosslinker. Deep profile control experiments are carried out on heterogeneous models, which contains three serial high permeable and low permeable cores arranged in a parallel. After water flooding (total recovery, 24.3%), the first, second and third high-permeable cores each are sealed in turn by the profile control agent, and the total displacement recovery increases to 46.8%, 62.2% and 69.1% respectively. So, the greater the sealed depth, the larger the enhancing recovery will be. Finally, the oil displacement mechanisms of deep profile control are discussed.