Methods of Measuring Formate Content in Drilling Fluids
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摘要: 针对当前钻井液用甲酸钠、甲酸钾标准应用现状,分析了甲酸盐含量测定存在的主要问题和影响因素,并筛选优化出最佳的检测方法。对于甲酸钠含量测定结果普遍偏高甚至超百的技术难题,通过红外等分析方法确定了目前钻井用甲酸钠的均为副产法产品,其含有季戊四醇等有机杂质,适合的方法是灼烧滴定法,同时对该方法进行了优化,实验发现该方法中灼烧产物的洗涤转移过程中引入酚酞会导致滴定终点延后结果偏高,通过改进洗涤转移过程,排除了该影响;对于甲酸钾含量测定,适合用硫代硫酸钠滴定法测定,同时增加钾离子含量测定,提高了方法的科学性和准确性,解决了以单一甲酸根折算甲酸钾含量存在无法有效鉴别低成本甲酸盐掺假的弊端。以上研究成果已作为标准方法引入T/CPSI 06401—2024《钻井液用加重剂甲酸盐类》标准,该标准已于2024年4月正式发布实施。Abstract: In studying the standards concerning sodium formate and potassium formate as drilling fluid additives, the major problems existed in and factors affecting the measurement of the concentrations of formates were analyzed, and a best detection method was screened out through optimization of many methods presently in use. Methods for sodium formate detection presently in use generally give results that are higher than the true values and are sometimes higher than 100%. To solve this problem, several methods such as infrared spectrum measurement were used to detect the content of sodium formate in a drilling fluid, and it was found that the sodium formate products presently in use are all manufactured by byproduct methods, and contain organic impurities such as pentaerythritol. The method that found suitable for the detection of sodium formate is the burning titration method, which was optimized through experiment. It was found in laboratory experiment that the introduction of phenolphthalein when washing and transferring the burned product causes the titration endpoint to delay and the result obtained is thus higher than the true value. By improving the washing and transferring process, this negative effect was eliminated. It was also found that sodium thiosulfate titration method is suitable for the detection of potassium formate. Increasing the content of the potassium ions helps obtain more accurate results, eliminating the disadvantages of the old methods in which the content of potassium formate is calculated only from the content of formate radical and it is thus unable to identify the low-cost formate adulteration. The achievements of this study have been introduced into the standard T/CPSI 06401—2024 named “Weighting Agent for Drilling Fluid—Formates”, which was issued and implemented in April of 2024.
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表 1 甲酸盐含量测定方法对比
样品信息 甲酸盐含量/% 硫代硫酸钠滴定法(以甲酸根计) 灼烧滴定法(以甲酸
根计)四苯硼钾重量法(以钾离子计) 甲酸钠 2022N003 103.14 90.10 2022N007 100.41 98.26 2022N014 106.49 85.54 2022N019 97.26 87.40 分析纯 98.67 98.53 甲酸钾 2021N001 98.29 93.90 92.18 2022N021 97.19 93.45 96.51 2022N022 96.76 94.16 95.86 2022N023 97.16 94.89 96.97 分析纯 98.49 96.28 99.18 表 2 硫代硫酸钠滴定法测试条件差异点汇总
标准 T加热/
℃t加热/
min试样溶液的
酸碱环境与KI反应过程中
酸加量参与反应的
样品量HG/T 5390—2018 75 10 / 10 mL V硫酸∶V水=1∶8 0.100 g Q/28HY 06—2017 沸水浴 20 2 mL 100 g/L氢氧化钠溶液 10 mL 10%硫酸溶液 0.500 g Q/0500DST002—2019 100 15 / 10 mL V硫酸∶V水=1∶8 0.100 g QCDH 16—2018 沸水浴 30 0.2 g无水碳酸钠 5 mL V硫酸∶V水=1∶8 0.100 g Q/28HY 07—2017 沸水浴 30 0.2 g无水碳酸钠 6 mL 6 mol/L硫酸溶液 0.500 g T∕CSTM 00178—2020 100 30 3 mL 100 g/L氢氧化钠溶液 10 mL 20%硫酸溶液 0.088 g 钻井液用甲酸盐检测方法的研究_刘克清 75 10 / 10 mL 20%硫酸溶液 0.060 g 甲酸根含量测定方法研究与讨论_王仲广 75 30 7 mL 0.5 mol/L氢氧化钠 5 mL 2 mol/L硫酸溶液 0.084 g 表 3 硫代硫酸钠滴定法影响因素分析
验证条件 甲酸钾分析纯样品的
甲酸钾含量/%加热温度 75℃ 98.30 80℃ 98.23 100℃ 97.67 加热时间 10 min 98.29 20 min 98.24 30 min 98.29 试样溶液的
酸碱环境试样溶液原液 98.29 加0.1 g碳酸钠 98.30 加5 mL 20%硫酸 84.52 与KI反应过程
中酸加量3 mL 20%硫酸
(6.96 mmol)94.82 5 mL 20%硫酸
(11.6 mmol)98.30 5 mL 4 mol/L硫酸
(20 mmol)98.30 表 4 高锰酸钾草酸滴定法比对数据
平行试验 甲酸钾/% 测定机构A 测定机构B 测定机构C 测定机构D 1 83.20 88.52 77.10 93.40 2 79.09 83.97 78.27 88.60 3 87.99 101.40 91.44 94.30 4 74.98 90.50 5 85.94 98.00 平均值 82.24 91.30 82.27 92.96 极差值 13.01 17.43 14.34 9.40 表 5 2022N003甲酸钠样品红外官能团解析
峰位置/cm−1 化学键振动模式 结论 771.47 羧酸根COO变角振动 含有—COO—
羧酸根基团1353.53 羧酸根COO对称伸缩振动 1580.93 羧酸根COO反对称伸缩振动 2714.77 醛基CHO中CH伸缩振动 2828.92 醛基CHO中CH伸缩振动 1012.29 醇的C—OH伸缩振动 含醇羟基—OH 1038.08 醇的C—OH伸缩振动 3309为中心
宽谱带羟基O—H形成
氢键伸缩振动表 6 甲酸钠含量测定不同方法比对数据
样品编号 甲酸钠/% 灼烧滴定法
(以甲酸根计)高锰酸钾草酸滴定法
(以甲酸根计)硫代硫酸钠滴定法
(以甲酸根计)ICP法
(以钠离子计)热失重
(理论计算)2022N003 90.10 82.24 103.14 90.37 91.54 2022N007 98.26 90.82 100.41 98.00 97.51 2022N014 85.54 79.56 106.49 83.94 85.81 2022N019 87.40 74.06 97.26 89.92 90.00 分析纯甲酸钠 98.53 89.97 98.67 97.51 / 表 7 酚酞对测定结果的影响
测试样品 测试条件 甲酸钠含量/% 分析纯甲酸钠 不加酚酞 98.57 加酚酞 99.61 无水碳酸钠标准物质 不加酚酞 99.89 加酚酞 100.04 表 8 洗涤次数对测定结果影响
重复洗涤次数 加酚酞是否变色 甲酸钠含量/% 1次 粉红色 96.44 2次 粉红色 98.28 3次 粉红色 98.65 4次 无色 98.63 5次 无色 98.51 表 9 甲酸钾含量测定方法比对汇总数据
样品编号 甲酸钠含量/% 硫代硫酸钠滴定法
(以甲酸根计)高锰酸钾草酸滴定法
(以甲酸根计)灼烧滴定法
(以甲酸根计)ICP-OES法
(以钾离子计)四苯硼钾重量法
(以钾离子计)2021N001 98.29 70.45 93.90 93.07 92.18 2022N021 97.19 76.50 93.45 98.22 96.51 2022N022 96.76 86.18 94.16 96.71 95.86 2022N023 97.16 76.79 94.89 97.46 96.97 分析纯甲酸钾 98.49 78.61 96.28 99.95 99.18 表 10 硫代硫酸钠滴定法测甲酸钾含量比对数据
酸加量 甲酸钾/% 再现性偏差
(极差值)/%检测机构A 检测机构B 检测机构C 检测机构D 首次比对∶11.6 mmol
(5 mL 20%硫酸溶液)98.29 98.30 96.22 97.02 2.08 二次比对∶20.0 mmol
(5 mL 4 mol/L硫酸溶液)98.28 98.29 98.22 98.70 0.48 -
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