CO2气体物性参数精确计算方法研究

Research on the precise calculation method of physical parameters for CO2

王海柱 沈忠厚 李根生 王芳 郎淑敏

WANG Haizhu SHEN Zhonghou LI Gensheng WANG Fang LANG Shumin

中国石油大学油气资源与探测国家重点实验室，北京　102249 华北油田公司勘探开发研究院，河北任丘　062552

State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Research Institute of Petroleum Exploration and Development of Huabei Oilfield Co., Renqiu 062552, China

压力和温度对CO2气体的物性参数影响较大，尤其在靠近临界区域附近。利用Span-Wagner（S-W）状态方程计算了CO2气体在不同状态条件下的密度、定压热容、定容热容等参数，与现有文献报道的实验值进行对比，其误差范围在2%以内。利用计算精度较高的P-R状态方程，对CO2气体的密度进行了计算，并给出了计算误差，与S-W状态方程计算误差相比，P-R状态方程计算误差较大，最大值高达11%以上，不能满足工程计算要求，而S-W状态方程计算误差仅在0.5%以内。S-W 状态方程将为CO2气井生产、CO2提高采收率等井筒温度和压力精确预测提供基础。

The pressure and temperature affect in the physical property parameters of CO2 greatly, especially near to the surrounding of critical zone. The parameters of density, heat capacity at constant pressure, heat capacity under constant volume, et al. were calculated at different state conditions for CO2 using the Span-Wagner equation of state (S-W EOS). The results were compared with the experimental data reported in the reference, and the conclusion was that the error range is no more than 2% which means that the precision of calculation results is higher. At the same, the density of CO2 was calculated using the P-R EOS which has higher precision, and the calculation error was given; then the result was compared with that of S-W EOS, and the calculation error of P-R EOS was higher than that of the S-W EOS. The maximum value of the former was up to 11% or more, which can not meet the engineering calculation demand, however, the calculation error of S-W EOS was within 0.5%. S-W EOS will provide the basis for accurate prediction of borehole temperature and pressure in CO2 gas well production, CO2 enhanced oil recovery and other projects.