原油状态方程和黏度模型适应性分析

Evaluation of equation of state and viscosity model for crude oil PVT analysis

油藏工程专业常用的状态方程有Soave-Redlich-Kwong(SRK)和Peng-Robinson(PR),常用的黏度模型有Lorentz-Bray-Clark(LBC)和Pedersen。不同的模型对于不同区域的原油其适应性存在差别。文章分析了状态方程和黏度模型对某非洲原油和国内渤海原油的拟合效果,发现该非洲原油拟合效果较好,PR3和SRK3状态方程均能很好的拟合实验数据,Pedersen黏度模型的预测及拟合精度高于LBC。而渤海稀油和稠油的气油比用状态方程均不能得到很好的拟合结果,LBC黏度模型拟合精度高于Pedersen。LBC黏度模型更适合于曲线形态变化较缓、较圆滑的黏度数据,难以捕捉黏度随压力降低的突变。Pedersen黏度模型能够模拟黏度随压力降低的突变,而对于曲线圆滑的数据拟合精度相对较低。这些认识有助于提高渤海原油的PVT拟合精度,提升对原油流体物性的理解,同时可以指导提高PVT实验数据的准确性。

The common EOS used in reservoir engineering are Soave-Redlich-Kwong(SRK)and Peng-Robinson(PR)and the common viscosity model are Lorentz-Bray-Clark(LBC)and Pedersen.The adaptability of equations varies among different area.This paper analyzed the matching results of different EOS and viscosity models with an African crude oil and Bohai crude oil.The result shows that the African crude oil data can get a better match.Both PR3 and SRK3 EOS can match the experiment data.The Pedersen viscosity model has higher prediction and matching accuracy than LBC.While for Bohai crude oil,no matter light or heavy,EOS cannot match the GOR curve.LBC viscosity model has more matching accuracy than Pedersen.LBC viscosity model is more suitable for gradually changing viscosity curve.It is hard to capture the abrupt viscosity change while the pressure goes down.Pedersen model can capture this behavior,however,it has lower accuracy for smooth viscosity curve with gradual viscosity change.These understanding can help increase the PVT matching accuracy of Bohai crude oil,better understand the physical behavior,and improve the PVT experiment data analysis.