| 摘要: |
| CO2地质封存技术是实现碳减排的有效措施，对鄂尔多斯盆地马家沟组马五1亚段地层水特征进行研究，是下一步实施工程化CO2封存的首要前提。本文依据对深部钻井取样的直观观察与实验测试，采用单项指标分类评价和多项指标综合评价的方法深入分析了马家沟组马五1亚段地层水的物理性质、化学性质、地层水类型和水化学特征参数。结果表明：马家沟组马五1亚段地层水密度较大、矿化度极高，属于卤水，含量最多的离子是Cl−，其次是Ca2+，地层水是CaCl2型。钠氯系数、氯镁系数、脱硫系数和镁钙系数的分析表明马五1亚段地层水封闭性极好，处于较强的还原环境。综合分析认为马家沟组马五1亚段地层水具备实施CO2封存的良好条件，非常适宜进行CO2封存。 |
| 关键词: 马五1亚段 矿化度 卤水 CO2封存 鄂尔多斯盆地 |
| DOI：10.7515/JEE182060 |
| CSTR： |
| 分类号: |
| 基金项目:国家重点研发计划项目（2016YFE0102500） |
|
| Water characteristics of Majiagou formation Ma51 submember in Ordos Basin and the significance for CO2 geological sequestration |
|
SUN Yujing, ZHOU Lifa, HUO Feifei
|
1. Department of Geology, Northwest University, State Key Laboratory of Continental Dynamics, Xi’an 710069, China
2. National & Local Joint Engineering Research Center of Carbon Capture and Storage Technology, Xi’an 710069, China
|
| Abstract: |
| Background, aim, and scope Global warming caused by emission of greenhouse gases dominated by CO2 has become a severe challenge to human being. Many measures have been taken to combat global warming all over the world. What is worth mentioning is the CO2 geological sequestration, it is an effective and burgeoning measure to achieve carbon emission reduction. The CO2 sequestration potential is very huge in Ordos Basin. So, in this paper the formation water characteristics in Ma51 submember of Majiagou formation are systematically studied, which is the precondition for further engineering design of CO2 sequestration in Ordos Basin. Materials and methods Based on the direct observations and experimental tests of deep drilling samplings, the method of “single index classification evaluation and multiple index comprehensive evaluation” is adopted. The physical properties, chemical properties, formation water types and hydrochemical characteristic parameters of the Majiagou formation Ma51 submember are analyzed in detail. Results The results indicate that the pH of the water ranges from 3.5 to 8.6, mainly from 4.5 to 6.5; the water density ranges from 1.0 g·cm−3 to 1.5 g·cm−3, mostly 1.1—1.3 g·cm−3; the mineralization degree is generally greater than 50 g·L−1, and average mineralization degree is 166 g·L−1; the highest concentration ion is Cl−, followed by Ca2+; the concentration order of the ions is rCl−1＞rCa2+＞r(Na++K+)＞rMg2+＞rHCO3−＞rSO42−, and the formation water is CaCl2 type. The analysis results of water chemical characteristic parameters show that Na/Cl factor (rNa+/rCl−1) ranges from 0.18 to 0.55, 0.34 on average; Cl/Mg factor (rCl−/rMg2+) ranges from 11.04 to 165.16, 32.11 on average; desulfurization factor (100×rSO42− rCl−) ranges from 0 to 0.45, 0.09 on average; Mg/Ca factor (rMg2+/rCa2+) range from 0.01 to 0.30, 0.17 on average. Discussion Most samples have a pH of 4.5—6.5, which does not meet the drinking water standard (6.5—8.5). The density is generally 1.1—1.3 g·cm−3, indicating that the salinity may be high. The sample salinity is generally greater than 50 g·L−1 and the average salinity is 166 g·L−1 further explains that the water is not suitable for drinking. The ion composition and concentration, the “salinity classification” and “Sulin’s classification” together indicate that the water with high salinity is brine and it belongs to the CaCl2 type. The comprehensive analysis of the Na/Cl factor (rNa+/rCl−), Cl/Mg factor (rCl−/rMg2+), desulfurization factor (100×rSO42−/rCl−) and Mg/Ca factor (rMg2+/rCa2+) show that the content of Cl− and Ca2+ is relatively high, and the content of Na+, Mg2+ and SO42− is low. Overall, the reduction reaction is complete and the formation water is in a closed environment. Conclusions The conclusions that can be drawn from the above results and discussion are as follows: the water can not serve as drinking water and the implement of CO2 sequestration in Ma51 submember will not cause contamination to fresh water we live on; formation water of Ma51 submember is under a very strong reducing environment, which is very good for CO2 sequestration and can greatly reduces the risk of CO2 leakage; the ion with the highest content is Cl−, and the second content is Ca2+, which can weaken the chemical reactions and help to generate CaCO3 precipitation in the end, thus prolonging the CO2 sequestration time and reducing the risk of CO2 leaking. Recommendations and perspectives CO2 sequestration is a comprehensive environment protection issue that involves the combination of geology and engineering. So, only studying the significance of formation water characteristics for CO2 sequestration is far from enough. The industrial CO2 sequestration still has many problems to deal with. For example, laboratory tests of CO2 sequestration mechanisms; analysis on affecting factors of CO2 geologic sequestration; blocks selection and evaluation for CO2 sequestration; evaluation on sequestration potential of a region or layer; leakage risk assessment after CO2 sequestration; improvement in public recognition and research of relevant laws and regulations. The process of CO2 sequestration still has a long and hard way to go. |
| Key words: Ma51 submember mineralization brine CO2 sequestration Ordos Basin |
