溶气原油体积系数、密度的预测模型

Predictive models of formation volume factor and density of gas dissolution crude oil

从理论上探讨了天然气在原油中的溶解过程。溶气原油的体积变化主要与两个因素有关:(1)由于温度升高引起的体积膨胀,这种变化可用温度系数f(t)来描述;(2)由于气体溶解在原油中导致体积膨胀,这部分体积的变化可用天然气中各组分的液态表观摩尔体积(Vgmi)及各组分在原油中的摩尔溶解度(Ci)或气油比(RSi)来描述。利用理想溶液的体积加和原理,推导出了计算饱和原油的体积系数(B)和密度(dp)的理论方程。研究表明,将饱和原油的体积系数和密度表示为温度和各组分溶解度的函数比其他模型只用一个气体相对密度和一个总溶解气油比RS更为合理。新模型适用于常规天然气和高含非烃气的非常规天然气。

Course of dissolution of natural gas in crude oil is investigated theoretically. It is found that the volume change of crude oil is mainly related to two factors: one is the volume expansion caused by the increase of temperature, which can be described by temperature coefficient f(t), and the second is volume expansion caused <IMG SRC='IMAGE/12300317.JPG' HEIGHT=11 WIDTH=15>by the dissolution of gas in crude oil, which can be described by the liquid apparent molal volume () of each constituent of gas and their solubility in crude oil (Ci) or gas oil ratio (<IMG SRC='IMAGE/12300318.JPG' HEIGHT=11 WIDTH=11>). Based on the volume addition principle of ideal solution, three theoretical models on formation volume factor (B)and density (dp) of saturation crude oil have been deduced. Our study shows that these models in which formation volume factor and density of saturation crude oil are expressed as the function of temperature and solubility of each constituent of gas or gas oil ratio are more reasonable than others in which only the relative density of gas and overall gas oil ratio are used. The new models are appropriate for conventional gas and unconventional gas rich in inorganic gas.