吉木萨尔页岩油乳化原因及对策

Causes and countermeasures of shale oil emulsification in Jimusar

吉木萨尔原油压裂开采过程中常出现乳化增黏现象,影响了原油正常生产。为明晰原油乳化原因,考察了原油组分、压裂液组分与pH等对乳状液稳定性和对界面性质的影响;采用醇碱萃取得到石油酸,通过高分辨质谱分析了石油酸分布和组成。结果表明,胍胶压裂液破胶液比聚合物滑溜水压裂液更易乳化。引起吉木萨尔原油乳化的主要原因:一是原油中含有较多的环烷酸、芳香酸、脂肪酸等界面活性物质;二是压裂液组分中的碱及弱碱性地层水与原油中的酸性物质长时间作用,形成界面活性较强的皂类;三是在生产过程中强烈的搅拌促进原油乳化。在原油与胍胶压裂液破胶液混合液中加入质量分数为0.5%的JN-1降黏剂后,30℃时混合液黏度由2232 mPa·s降至155 mPa·s,表明JN-1降黏剂的加入可有效降低混合液黏度。因此,可采用不含碱的聚合物滑溜水压裂液,并在压裂液中加入降黏剂以解决吉木萨尔原油压裂乳化增黏的问题。

Emulsification and viscosity increase often occur during fracturing production of crude oil in Jimusar,which affects the normal production of crude oil.In order to clarify the cause of crude oil emulsification,the effects of crude oil composition,fracturing fluid composition and pH on emulsion stability and interface properties were studied.Petroleum acid was obtained by alcohol alkali extraction.The distribution and composition of petroleum acid were analyzed by high resolution mass spectrometry.The results showed that guanidine gum fracturing fluid gel breaking liquid was more emulsified than polymer slickwater fracturing fluid.The main reasons for the emulsification of crude oil in Jimusar were as follows:First,there were many interfacial active substances such as naphthenic acid,aromatic acid and fatty acid in the crude oil.Second,the alkali and weakly alkaline formation water in the fracturing fluid components interacted with the acidic substances in the crude oil for a long time to form soaps with strong interfacial activity.Third,strong stirring in the production process promoted crude oil emulsification.The addition of mass fraction 0.5%JN-1 viscosity reducing agent made the viscosity of the mixture of crude oil and guanidine gum fracturing fluid gel breaking liquid decreased from 2232 mPa·s to 155 mPa·s at 30℃,indicating that JN-1 viscosity reducing agent could effectively reduce the viscosity of the mixture.Therefore,the alkali free polymer slickwater fracturing liquid could be adopted and adding viscosity reducer into fracturing fluid to solve the problem of fracturing emulsification and viscosity increase of crude oil in Jimusar.