原油裂解对油包裹体均一温度和捕获压力的影响及其地质意义

通过原油裂解动力学和石油包裹体热动力学模拟方法系统阐述了地质条件下原油裂解过程对油包裹体均一温度及捕获压力的影响.结果表明:初始裂解阶段(T_R＜13%，T＜160 ℃)，油包裹体均一温度随原油裂解呈增大趋势，捕获压力呈减小趋势；随着裂解程度增大(T_R＜24%，T＜190 ℃)，油包裹体均一温度随原油裂解呈减小趋势，捕获压力呈增大趋势，但此阶段油包裹体均一温度仍高于初始捕获时均一温度，捕获压力仍小于初始捕获压力；此后，随着原油裂解程度不断增大，油包裹体均一温度持续减小甚至到负值，捕获压力则持续增大甚至超过静岩压力.封闭条件下低程度的原油裂解(T＜160 ℃，T_R＜13%)只会形成常压或者低压；而较高程度的原油裂解(T_R＞40%)才会形成超压，甚至超过上覆静岩压力(T_R＞70%).深部原油裂解气勘探中要特别注意地层温度位于160~190 ℃范围内的常压到低压油气藏，而地层温度高于190 ℃原油裂解气勘探应以找超压-超高压油气藏为主. 

Effects of Oil Cracking on Homogenization Temperature and Trapping Pressure of Oil Inclusion and Its Geological Significance

This paper systematically elaborates the effects of oil cracking on homogenization temperature and trapping pressure of oil inclusion using crude oil crack kinetic and petroleum inclusion thermodynamics modeling. The results demonstrate that homogenization temperature shows a trend of increase and the trapping pressure shows a trend of decrease at the initial stage of oil cracking (T_R < 13%, T < 160 ℃); with the progressing of oil cracking (T_R < 24%, T < 190 ℃), homogenization temperature shows a trend of decrease and the trapping pressure shows a trend of increase, however, the homogenization temperature still exceeds the initial homogenization temperature and the trapping pressure is still below the initial trapping pressure at this stage of oil cracking. After that, the homogenization temperature continues to decrease or even turns negative values in some severe oil cracking processes; at the same time, trapping pressure continues to increase or exceed litho static pressure. In addition, oil cracking only results in normal pressure or under pressure during the initial stage of oil cracking (T_R < 13%, T < 160 ℃), while oil cracking will lead to overpressure (T_R > 40%) or even exceeding litho static pressure (T_R > 70%) during the high level of oil cracking. Therefore, deeply buried reservoirs with pressure systems from under pressure to normal pressure should be paid more attention especially when formation temperature ranges from 160 ℃ to 190 ℃, and oil cracking gas exploration should be focused on the reservoirs with overpressure or ultrahigh pressure when formation temperature is over 190 ℃.