Analyse On The Reservoir-Formation Condition And Predictions Of Favorable Structure Zone In The Huizhou Sag

The Pear River Mouth Basin is the maximal Meso-Cenozoic depositional basin in the north of South China Sea and an important base of marine hydrocarbon resources. The Huizhou Sag lies in Zhu I depression, which is in the east of the Pear River Mouth Basin and in Huizhou Sag some good Reservoir has been discovered. With additional exploration of Neocene, the research on Early Teriary is the primary task of current exploration. The dissertation is the research on hydrocarbon-bearing condition and law in Cenozoic of Huizhou sag. The dissertation includes the evaluatation of hydrocarbon-bearing condition, the reservoir-formation characteristic and model of typical reservoir, the characteristic and fastigium of hydrocarbon-generating, the characteristic of hydrocarbon migration and accumulation. Finally, several favorable structures is optimized.There are good hydrocarbon-generating condition, reservoir condition, cap condition and trap condition etc in Huizhou Sag: there are Wenchang and Enping Formations source rocks, which is mainly mudstone of middle-deep lack facies and river-paludal facies. The source rocks have high organic content, and were the material base for hydrocarbon generation; there are good reservoir bed and cap rock, and reservoir bed is mainly sandstone. The cap rock is mainly mudstone and there is extensive regional cap; there are some good reservoir and seal assemblages; there are many structural traps, the type of which are mainly drape and reverse drag anticline.Basin modeling is an important method of studying the characteristic hydrocarbon-generating and hydrocarbon migration. The results of basin modeling show that: the distribution of reservoir is controlled by hydrocarbon-generating low-lying, and the reservoirs mostly lie in effective trap around the hydrocarbon-generating low-lying. The main hydrocarbon-generating centers lie in the western Huizhou Sag; the main hydrocarbon-generating period is 0-18Ma(from the middle deposition period of Zhujiang Formation in Early Miocene to now),and fastigium of hydrocarbon-generating is 0-10Ma(form the beginning deposition of Yuehai Formation to now); the fluid potential of layer is mainly convergent-type, and there are many high fluid potential belts and low fluid potential belts, which make hydrocarbon migrate to some different directions and form some cells of hydrocarbon migration and accumulation.The reservoir-forming model of Huizhou Sag is almost two-step according to reservoir-forming stage, and there are single-source and two-source reservoir according to oil sources. There are three reservoir-forming models of abrupt slope type, apophysis type and gentle slope type according to structural form. Based on the relation of second order structure zone and the characteristic hydrocarbon-generating, the characteristic of the fluid potential, it is analyzed that XJ24 fault zone, HZ21 fault zone and HZ13S structure zone are the most favorable oil-bearing structure zones in Huizhou Sag.