砂岩地层低盐水驱过程中pH升高机理研究

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• 英文论文题名：Chemical Mechanism of pH Increase in Sandstone during Low Salinity Waterflooding
• 论文作者：陈晨 ; 董朝霞 ; 林梅钦 ; 杨杰
• 英文论文作者：Chen Chen ; Zhaoxia Dong ; Meiqin Lin ; Jie Yang ; Enhanced Oil Recovery Institute ; China University of Petroleum
• 年：2016
• 作者机构：中国石油大学(北京)提高采收率研究院;
• 论文关键词：低盐水驱 ; pH升高 ; 驱替实验 ; Zeta电位
• 会议召开时间：2016-07-01
• 会议录名称：中国化学会第30届学术年会摘要集-第三十一分会：胶体与界面化学
• 语种：中文
• 分类号：TE357.6
• 学会代码：ZGHY
• 会议名称：中国化学会第30届学术年会-第三十一分会 ; 胶体与界面化学
• 会议地点：中国辽宁大连
• 主办单位：中国化学会
• 学会名称：中国化学会
• 页数：1
• 文件大小：181k
• 原文格式：D
• 会议级别：全国

摘要

在低盐水驱过程中,室内和矿场实验都发现采出液pH升高是提高采收率的一个关键因素。本文研究了低盐水驱过程中的pH升高机理。研究应用驱替实验,两根岩心分别用MgCl_2(KCl)的高盐水驱替,再用MgCl_2(KCl)的低盐水驱替,测量前后流出液pH的变化,结果表明:两根岩心的流出液pH都升高。这是由于在高盐水条件下,金属阳离子(K~+或Mg~(2+))吸附在原本带负电的砂岩矿物表面,低盐水注入后,这些金属阳离子由于低盐水的注入而从矿物表面脱附,从而在砂岩矿物表面产生空位,而具有很强离子交换能力的H~+将吸附在砂岩矿物表面,产生剩余的OH~-,从而导致采出液pH升高。研究还用Zeta电位仪测量盐水/砂岩矿物界面电势,结果表明:随着盐水矿化度的降低,界面电势变得更负。pH升高的原因是由砂岩矿物表面金属阳离子的脱附引起。
During low salinity waterflooding,laboratory and field test results have always shown a rise in pH of effluents in sandstone which was a key factor for improved oil reocovery(IOR).This paper investigated chemical mechanism of pH increase in order to provide a better understanding of IOR by low salinity water.In coreflooding experiments,two sandstone cores were water flooded successively with high salinity water(MgCl_2 or KCl)-low salinity water(MgCl_2 or KCl),pH of all effluents was recorded.As a result,pH of all effluents was increased.We propose that this is because during high salinity injection,metal cations(K~+ or Mg~(2+)) of brine can adsorb on negative mineral surfaces,when changing to low salinity water,metal cations pre-adsorbed on mineral surfaces will diffuse from rock surfaces to water due to the difference of concentration of cations between rock surface and injected low salinity water,then vacant places were created on rock surfaces.The protons,H~+,from water will adsorb onto those vacant sites due to the strong ion exchange capacity,leading to surplus hydroxyl in-situ,as a result,pH increase.This suggestion was also demonstrated by zeta potential measurements.As salinity decreased,zeta potential of brine/rock surfaces became more negative,resulting from the desorption of metal cations from rock surfaces.

引文

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