Calculation of thermodynamic properties of water by the CPA equation of state
An appreciable amount of formation water exists inevitably in the porous media of reservoirs, but the existence of water is often neglected in the usual calculation of phase equilibrium. The commonly used equation of state is simple, but may have large deviations in estimating some thermodynamic pro...
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| Format: | Article |
| Language: | English |
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KeAi Communications Co., Ltd.
2017-07-01
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| Series: | Natural Gas Industry B |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352854017301146 |
| _version_ | 1797287520433602560 |
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| author | Ping Guo Hanmin Tu Zhouhua Wang Qian Wang |
| author_facet | Ping Guo Hanmin Tu Zhouhua Wang Qian Wang |
| author_sort | Ping Guo |
| collection | DOAJ |
| description | An appreciable amount of formation water exists inevitably in the porous media of reservoirs, but the existence of water is often neglected in the usual calculation of phase equilibrium. The commonly used equation of state is simple, but may have large deviations in estimating some thermodynamic properties. The existing equation of state, which has been modified, is not very suitable for the system containing polar substances (e.g. hydrocarbons, water, and alcohols). In this paper, the CPA (Cubic-Plus-Association) equation of state which considers both physical and association interactions between molecules was used to calculate the thermodynamic properties of water under the saturated and unsaturated states. Moreover, the disadvantages of the commonly used equation of state in the calculation were analyzed. The following results were obtained. First, the commonly used equation of state can be used to effectively calculate the saturated vapor pressure of water, but it presents certain differences in calculating water density and enthalpy, and the enthalpy calculation is not affected by volume modification. Second, the average absolute/relative deviations between the thermodynamic properties of water calculated by the CPA equation of state and the experimental data are approximately 1%. For the system containing polar substances, the CPA equation of state is preferred in calculating the thermodynamic properties. The accurate estimation of the thermodynamic properties of water is fundamental in identifying the fluid state in the water-bearing gas reservoirs, and it is of great significance in the development and production of such gas reservoirs. |
| first_indexed | 2024-03-07T18:35:33Z |
| format | Article |
| id | doaj.art-afbc48e7e87046d2b532c32295037030 |
| institution | Directory Open Access Journal |
| issn | 2352-8540 |
| language | English |
| last_indexed | 2024-03-07T18:35:33Z |
| publishDate | 2017-07-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Natural Gas Industry B |
| spelling | doaj.art-afbc48e7e87046d2b532c322950370302024-03-02T05:05:10ZengKeAi Communications Co., Ltd.Natural Gas Industry B2352-85402017-07-014430531010.1016/j.ngib.2017.08.014Calculation of thermodynamic properties of water by the CPA equation of statePing Guo0Hanmin Tu1Zhouhua Wang2Qian Wang3State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, ChinaState Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, ChinaState Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, ChinaCNOOC Tianjin Company, Tianjin 300452, ChinaAn appreciable amount of formation water exists inevitably in the porous media of reservoirs, but the existence of water is often neglected in the usual calculation of phase equilibrium. The commonly used equation of state is simple, but may have large deviations in estimating some thermodynamic properties. The existing equation of state, which has been modified, is not very suitable for the system containing polar substances (e.g. hydrocarbons, water, and alcohols). In this paper, the CPA (Cubic-Plus-Association) equation of state which considers both physical and association interactions between molecules was used to calculate the thermodynamic properties of water under the saturated and unsaturated states. Moreover, the disadvantages of the commonly used equation of state in the calculation were analyzed. The following results were obtained. First, the commonly used equation of state can be used to effectively calculate the saturated vapor pressure of water, but it presents certain differences in calculating water density and enthalpy, and the enthalpy calculation is not affected by volume modification. Second, the average absolute/relative deviations between the thermodynamic properties of water calculated by the CPA equation of state and the experimental data are approximately 1%. For the system containing polar substances, the CPA equation of state is preferred in calculating the thermodynamic properties. The accurate estimation of the thermodynamic properties of water is fundamental in identifying the fluid state in the water-bearing gas reservoirs, and it is of great significance in the development and production of such gas reservoirs.http://www.sciencedirect.com/science/article/pii/S2352854017301146CPA equation of stateThermodynamic properties of waterDensityEnthalpyHigh temperatureHigh pressureGas reservoirDevelopment |
| spellingShingle | Ping Guo Hanmin Tu Zhouhua Wang Qian Wang Calculation of thermodynamic properties of water by the CPA equation of state Natural Gas Industry B CPA equation of state Thermodynamic properties of water Density Enthalpy High temperature High pressure Gas reservoir Development |
| title | Calculation of thermodynamic properties of water by the CPA equation of state |
| title_full | Calculation of thermodynamic properties of water by the CPA equation of state |
| title_fullStr | Calculation of thermodynamic properties of water by the CPA equation of state |
| title_full_unstemmed | Calculation of thermodynamic properties of water by the CPA equation of state |
| title_short | Calculation of thermodynamic properties of water by the CPA equation of state |
| title_sort | calculation of thermodynamic properties of water by the cpa equation of state |
| topic | CPA equation of state Thermodynamic properties of water Density Enthalpy High temperature High pressure Gas reservoir Development |
| url | http://www.sciencedirect.com/science/article/pii/S2352854017301146 |
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