煤系有机质演化过程中CO_2对流体黏度的影响

The Impact on Fluid Viscosity of CO_2 during the Evolution of the Coal

通过压力下黄金管封闭体系热模拟实验,获取了民和盆地侏罗系煤系有机质各演化阶段的流体组成后,结合软件PVT-sim中的CS黏度计算模型对煤成烃的黏度演化进行了计算,并着重讨论了煤系有机质产生的CO2对煤成烃黏度的影响。研究表明烃类流体黏度与其相态密切相关,地质条件下液相黏度要较伴生的气相黏度高出一个数量级。随着演化程度的上升,煤成烃的气液黏度都在逐渐降低。压力为10～30MPa,温度为25～125℃条件下,Easy%RO值达到0.86%以后液相黏度小于1.0mPa·s,最低可以下降至0.13mPa·s,气相黏度在不考虑近临界态时,最大黏度不超过0.1mPa·s,最低可低至0.013mPa·s。煤系有机质演化过程中产生的CO2含量变化对煤成烃黏度的影响也十分重要,不同温压条件下,受到气液两相中CO2分配比例不同的影响,气液两相的黏度呈规律性变化。总体表现为,气相和液相的黏度均随着总组分中CO2含量的降低而降低,CO2对液态烃中短碳链组分的萃取作用是造成上述变化的根本原因,在低温情况或低演化阶段会出现黏度随着CO2减少而上升的现象。

By the pressurized sealed gold tube pyrolysis experiments,the fluid composition of Jurassic coal from the Minhe Basin at different maturity was analyzed.Combined with the Corresponding States Method in software PVT-sim,the fluid viscosity was calculated and the impact on fluid viscosity of CO2 during the evolution of the coal was discussed.The study showed that the fluid viscosity was closely related with the fluid phase,the viscosity of the liquid phase would be an order of magnitude higher than that of the associated gas under geological conditions.With increasing maturity,viscosity of the gas and liquid phases both decreased.After the Easy%ROreaches 0.86%,at 10-30 MPa and 25-125℃,the maximum value of liquid viscosity was less than 1.0mPa·s,and the minimum value would reach 0.13mPa·s.For the gas viscosity,it was 0.1mPa·s and 0.013mPa·s,respectively.CO2 generated from coal has important influence on the petroleum viscosity.Under different temperature and pressure conditions,the distribution ration of the CO2 in gas-liquid phases affects the viscosity directly.Overall,the viscosity of both liquid and gas phases decreases with the decrease of CO2 content in total component,which is because CO2 could extract short carbon chain component in the liquid hydrocarbon Viscosity increases with the decrease of CO2 only when it is at low temperature or with low maturity.