Research On Petroleum Reservior-forming Conditions In The West Of Biyang Depression. Nanxiang Basion

Under the guidance of the non-marine sequence stratigraphy, the petroleum system theory and the hydrocarbon pool-forming assemblage theory, and on the basis of available seismic, drilling and geological data, studies on tectonics, sedimentation, and pool-forming process and regular pattern of hydrocarbon accumulation in the west of Biyang sag are performed systematically, and the characteristics of reservoirs, distribution of sedimentary facies, key factors and phases of pool generation are ascertained, and the models of pool generation are established. The following are the obtained results:1. There exist Gucheng meandering river delta and Changqiao fan delta in the west of Biyang sag, with the favorite sedimentary facies for hydrocarbon accumulation as subaqueous distributary channel subfacies and mouth bar subfacies. Gucheng oilfield and Gaozhuang Block in the north of the study are supplied with sedimentary material by Gucheng meandering delta with homogeneous lithology and favorite physical properties. Jinlou oilfield in the western part is supplied by Changqiao fan delta. And Sediments in the north of Jinlou oilfield and Qianduliu area not only come from the north, but also from the west with superior physical properties.2. Thanks to Tanghe-Liyuan fault and Biyang-Liyuan fault, the palaeostructure in the study area appears as a monocline that is upwarp towards the northwest and plunges towards the west. Tectonic movement in the last period when Liaozhuang formation is deposited is an important period for the generation of faulted nose structure and faulted structure, and is also the key period to the migration and accumulation of hydrocarbon.3. Study on hydrocarbon generation in the study area is performed for the first time. The kerogen belongs to humosapropelic--sapropel type with relatively favorite type and low degree of thermal evolution, thus an immature source rock. The oil source in Jinliu oilfield and Gaozhuang block comes primarily from the lower section of H3 formation, while the oil source in Gucheng oil field is combined with the upper and the lover sections of H3 formation. The natural gas in the study area is of the biogenic origin.4. Key factors of pool generation in the west are faults and faults and the model consists of the sand bodies in Gucheng and Changqiao, source rocks in the southeast and the migration path as reservoir and fault or reservoir plus fault. Hydrocarbons migrate laterally with few as vertically, that is, hydrocarbons are admitted into the faulted area along the reservoir stretched in the center of the sag from the oil source in the southeastern part, and then accumulated in the traps of faulted block or the traps of faulted block plus lithology along the migration path in reservoirs.5. The source-reservior-caprock arrangement in the study area is relatively ideal, resulting in superior sedimentary facies, numerous faulted block, faulted nose and unconformity traps and many lithological traps in Jinliu oil field and Qiandulou area. Hydrocarbons mainly are accumulated in the high position of faulted blocks, faulted nose traps and nosing structures. Jinlou oil field and Gucheng oil field are the best in the pool-forming conditions, and Gaozhuang block takes the second places. The pool types can be classified into four types and ten categories.