岩石氯盐含量的测定方法优选及应用

Methods to measure chloride content in rock and their application

岩石氯盐含量是研究岩心的重要参数之一,结合含水饱和度参数可以预测地层含水性。测定岩石氯盐含量执行行业标准SY/T 5503-2009《岩石氯盐含量测定方法》推荐的硝酸银滴定法和电量法。研究增加了离子色谱法,并讨论了这3种方法的利弊。研究结果表明:①电量法受外界干扰因素多,测定的数据重现性不好,耗时长,方法不普及;②硝酸银滴定法适用于较清洁水样的测定,适合现场快速检测,但标准溶液配制繁琐,且由于受浸泡液颜色、pH值、过渡金属及其他干扰因素影响,滴定终点判断误差大;③离子色谱法与硝酸银滴定法的比对试验表明,两种方法分析结果均满足行业标准要求;④将离子色谱法作为岩石氯盐含量的测定方法,更为简单快捷,干扰少,且可同时分析出多种阴阳离子含量;⑤综合利用岩石氯盐含量、含水饱和度实验数据,可预测碳酸盐岩地层含水性。岩石中氯盐含量小于300 mg/kg、含水饱和度小于40%时,通常为非水层。

Chloride content,as one of the most important parameters in core analysis,and water saturation can jointly used to estimate water content in rock.Besides two methods of both silver nitrate titrimetry and coulometry,which are recommended from the petroleum industry standards SY/T5503-2009"Methods to Measure Chloride Content in Rocks",the third one of ion chromatography can also be used to measure the chloride content.So,these three methods were discussed in terms of advantages and disadvantages.Results show that(1)coulometry method often suffers from many external interferences,poor repeatability,large time consumption,and unpopularity;(2)silver nitrate titrimetry is a rapid on-site detection method applying to clean water samples,but its application is limited due to complicated preparation of standard solutions and large error to determine the end point of titration caused by the color and pH value of the soak solution,transition metals in the solution,and other interferences;(3)as per the contrast tests,the results from ion chromatography and silver nitrate titrimetry methods are in line with industry standards;(4)ion chromatography method is a good candidate due to simple and fast measurement or a few interferences.Besides,the content of anion and cation can also be examined simultaneously;and(5)formation-water content may be estimated jointly by using experimental data on chloride content and water saturation.A non-aquifer is usually characterized by the chloride content and water saturation below 300 mg/kg and 40%,respectively.