酸性天然气生成水合物条件实验测定与应用

doi:10.3969/j.issn.1006-6535.2021.05.022

摘要/Abstract

摘要： 针对酸性天然气藏开发易生成水合物,堵塞井筒及生产管线的问题,运用定温搜索压力法,对中国西部地区2个高含CO₂的天然气藏气样进行水合物生成条件实验测定。研究表明:天然气中高CO₂含量提高了地层水中HCO^-₃的离子含量,从而增加了地层水的矿化度;与纯CH₄气体相比,相同温度条件下,CO₂的存在显著降低了天然气水合物生成所需的地层压力。对于目标天然气流体,在低矿化度地层水中,生成水合物条件与在纯水中没有明显差别;在较高矿化度(16 970.7 mg/L)地层水中生成天然气水合物压力显著高于纯水体系。进一步基于Clausius-Clapeyron方程计算所合成水合物的分解焓为62 kJ/mol,生成的天然气水合物为Ⅰ型结构。最后结合实验数据和生产动态数据,对目标气藏开发过程水合物生成特征进行分析,预测井筒内是否生成水合物以及出现水合物的井筒位置,该研究为现场生产预防水合物生成具有借鉴意义。

关键词: 水合物, 酸性天然气, 高CO₂含量, 生成条件, 水合物堵塞, 地层水

Abstract: To address the problem that hydrate generation is prone to blocking wellbores and production pipes in the development of sour natural gas reservoirs, the hydrate formation conditions were experimentally determined with constant-temperature pressure search method for gas samples taken from two natural gas reservoirs with high CO₂ content in Western China. It was found in the study that high CO₂ content in natural gas increased the HCO₃^- ion content of formation water, thereby improving the salinity of formation water; compared with pure CH₄ gas, the existing CO₂ significantly reduced the formation pressure required for gas hydrate generation under the same temperature conditions compared with pure CH₄ gas. For the target gas fluid, there was no obvious difference in hydrate formation conditions between low-salinity formation water and pure water; the pressure of gas hydrate formation in formation water with high salinity (16 970.7 mg/L) was significantly higher than that in pure water system. Further, the decomposition enthalpy of the synthesized hydrate was calculated based on the Clausius-Clapeyron equation as 62 kJ/mol, and the gas hydrate formed was of Type I structure. Finally, the characteristics of hydrate formation in the target gas reservoir development process were analyzed in combination with experimental data and production performance data, and the hydrate formation in the wellbore and the location of the wellbore where the hydrate formed were predicted. There is much for reference of the results of the study to the prevention of hydrate formation in field production.

Key words: hydrate, sour natural gas, high CO₂ content, formation conditions, hydrate blockage, formation water

中图分类号:

TE135

刘煌, 李瑞景, 汪周华, 王庆文. 酸性天然气生成水合物条件实验测定与应用[J]. 特种油气藏, 2021, 28(5): 154-160.

Liu Huang, Li Ruijing, Wang Zhouhua, Wang Qingwen. Experimental Determination and Application of Hydrate Formation Conditions for Sour Natural Gas[J]. Special Oil & Gas Reservoirs, 2021, 28(5): 154-160.

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