从热力学理论讨论烃类的演化

地质体中的石油,处于一种特殊的介质内,在漫长的地质历史时期,由于埋藏深度的增加,受着较高的温度和压力的影响,发生着改变石油成分和性质的种种演化。可以说,压力与温度是影响石油性质的主要因素。石油成分的变化,是一种化学变化。而热力学在解决化学变化方向上的正确性,已为许多化学实践所证实。本文以热力学理论为基础,侧重于压力因素的定性对比,结合我国湘中地区古生界碳酸盐岩等方面的资料,探讨石油的演化。初步研究表明,地层压力是石油演化中的一个重要因素。 

DISCUSSION ON THE EVOLUTION OF HYDROCARBONS IN THE LIGHT OF THE THEORY OF THERMODYNAMICS

Basing on the theory of thermodynamics,the influence of formation pressure on the parameters of hydrocarbons, such as enthalpy, entropy and free enthalpy,and the influence of pressure on the energy distribution in accord with the basical formula of thermodynamics AH=△G-T△S are discussed. It is pointed out that pressure is a negative factor to the pyrolysis of hydrocarbons. The reason for why there is oil still retained in Paleozoic carbonate rocks of the Xiang-Zhong district is also discussed under thermodynamic theory. According to the theoretical consideration of the gasification of oil, as low boiling-point fractions in an oil pool increasingly gasified, the probability of the destruction of the oil pool also increased. Contrarily, there is no phase change within gas pools, only the expansion of gas under heating, hence the influence of temperature and pressure on gas pool is minimized. Therefore, it is easier for gas pools than for oil pools to be presrved.Finally, some cognitions for the prospecting and exploration of areas bearing highly evolved oil and gas are suggested.