Temperature-pressure Fields And Hydrocarbon Phase Evolution Of The Shahejie Formation In North Of Dongpu Depression

This paper utilized fluid inclusion analysis and basin simulation to restore the antient temperature and pressure field during the accumulation period in the north part of Dongpu depression and to analyze the phase evolutionary type of the hydrocarbon during its migration and accumulation and to study the relationship between the temperature pressure field and the phase evolution.The formation pressure of Es3 during accumulation period were controlled by structural framework, centre of subsidence and centre of hydrocarbon generation, and were largest in the subsag area, and were relatively large in the central uplift belt and were smallest in the west slope area. The area between Puwei and Wenliu controlled by the salt layer, the residual pressure are relatively high. Due to the difference of later compensation thickness the present day residual pressure in Qiaobai area and Qianliyuan area is higher than it was during late Ed.The hydrocarbon phase evolution during its migration and accumulation from deeper to shallower layers can be divided into oil cracking into gas, oil retrograde evaporating into gas and exsolution of oil soluble gas, the hydrocarbon phase evolution in the deeper layers was mainly oil cracking into gas and oil retrograde evaporating into gas while the hydrocarbon phase evolution in the middle layers was mainly exsolution of oil soluble gas. The hydrocarbon phase evolution sequences in different area are coordinate but the depth of different evolutionary stage differentiate from each other. The depth of the exsolution of oil soluble gas in Puwei area, Wenliu area and Qiaobai area are 1900 m, 2500 m, 2900 m respectively and the depth of oil cracking are 3900 m, 3850 m and 4000 m.The maternal material type of the source rocks and temperature environment are the controlling factors of the hydrocarbon evolution in the study area. The maternal material type source rocks and the thermal evolution degree of kerogen controlled the phase of the hydrocarbon when it was generated primarily while the temperature and pressure environment influenced the change of hydrocarbon phase during its migration and accumulation. During the vertical migration of hydrocarbon in the uplift belt and slope belt, along with the decrease of buried depth, temperature and pressure oil soluble gas is easy to fall off while the crude oil which only experienced lateral migration of short distances near hydrocarbon generation subsag or experienced on migration or accumulation with the increase of buried depth and temperature the crude oil is easy to split and gas enrich.