玛北高含盐采出液盐析影响因素及临界盐析模型

Influencing Factors and Critical Salt-Precipitation Model for High-Salinity Produced Water of Mabei Oilfield

摘要

高矿化度采出液在油气田集输过程中易发生盐析沉积, 影响管道输送安全与系统稳定性。针对玛北高盐高碱油藏采出液盐析问题, 基于采出液物性测试与水化学分析结果, 开展盐析影响因素、单盐临界矿化度及复盐协同盐析实验研究。结果表明：玛北采出液水相矿化度约为（2.5~3.0）×10⁴ mg/L, 水型为重碳酸钠型, 主要离子为Na⁺、CO₃^2-、HCO₃^-和Cl^-。降温约20 min后体系基本达到盐析平衡；含砂量1%~5%、含油量0%~40%对游离水相临界矿化度影响较小。NaCl临界矿化度随温度变化较小, Na₂CO₃对温度最敏感, 是引发盐析的重要因素。NaCl-Na₂CO₃-NaHCO₃复配体系临界矿化度随温度升高整体增大, 且受盐类配比显著影响。进一步建立复盐协同临界盐析模型, 交互修正后D~M复配体系平均绝对误差由10.68%降至6.76%, 表明复盐体系临界矿化度受Na⁺共同离子效应、碳酸盐平衡转化和高离子强度耦合作用控制。研究结果可为玛北高盐高碱采出液集输过程中盐析风险预测与工艺优化提供理论依据。

Abstract

High-salinity produced water is prone to salt precipitation in the gathering and transportation process of oilfields, which affects pipeline transportation safety and system stability. To address salt precipitation in produced water from a high-salinity and high-alkali reservoir in Mabei Oilfield, this study conducted experiments on salt precipitation factors, single-salt critical salinity, and mixed-salt cooperative precipitation experiments, based on produced-water property testing and water-chemistry analysis. The results showed that the salinity of the aqueous phase from Mabei Oilfield is approximately （2.5-3.0）×10⁴ mg/L. The produced water is of the sodium bicarbonate type, and the main ions are Na⁺, CO₃^2-, HCO₃^-, and Cl^-. The system basically reaches salt precipitation equilibrium after 20 min of cooling. Sand content of 1%-5% and oil content of 0%-40% have little effects on the critical salt precipitation salinity of the free water phase. The critical salinity of NaCl changes only slightly with temperature, whereas Na₂CO₃ is the most temperature-sensitive salt and is an important driver for salt precipitation. The critical salinity of the NaCl-Na₂CO₃-NaHCO₃ mixed-salt system generally grows with increasing temperature and is significantly affected by salt proportions. A cooperative mixed-salt precipitation model was further established. After interactive correction, the mean absolute error for the D-M mixed-salt system decreased from 10.68% to 6.76%, indicating that the critical salt precipitation salinity of the mixed-salt system is controlled by the Na⁺ common-ion effect, carbonate equilibrium transformation, and high-ionic-strength coupling. The findings of this study provide a theoretical basis for salt precipitation risk prediction and process optimization for the gathering and transportation of high-salinity and high-alkali produced water in Mabei Oilfield.

关键词

高含盐采出液 / 水相组成 / 盐析行为 / 临界矿化度 / 盐析模型

Key words

high-salinity produced water / aqueous-phase composition / salt precipitation behavior / critical salinity / salt precipitation model

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基金资助

新型油气勘探开发国家科技重大专项“准噶尔盆地页岩油藏CCUS-EOR混相驱技术与集成示范”(2025ZD1405006)