Study On Hydrocarbon Accumulation Mechanism And Models Of Cambrian-ordovician Buried Hills In The Eastern Part Of North China

In the guidance of hydrocarbon accumulation theories of petroleum geology, usingvarious data and the results of previous studies to classify the multiple types ofCambrian-Ordovician buried hills in the Eastern part of North China, and using manymethods and techniques to carry on research on the hydrocarbon accumulation conditions,mechanism and models of the buried hills systematically, and established multiple kinds ofburied hills hydrocarbon accumulation models.1. Focusing on the structure of the buried hills, we carried on detailed research ontheir geological structure and tectonic evolution in Indo-china, Yanshannian, Himalayanmovements, and divided the buried hills into Indo-china Buried Hills, Early YanshanianBuried Hills, Middle Yanshanian Buried Hills, and Early Himalayan Buried Hills whichexperienced single movement and those which experienced two or more movements’superimosition, totally11categories.2. Carried on detailed study of multiple buried hill reservoirs, and then put them in tothe classification scheme, counting up to6buried hills of4categories. Early YanshanianBuried Hills were shaped in the early stage of the Yanshan era, which could accept there-migration of oil and gas from the transformed early reservoirs, and they could still savesome early hydrocarbon after suffering from secondary alteration, accessed to mainaccumulation period in Paleogene. Middle Yanshanian Buried Hills were shaped in themiddle stage of the Yanshan era, which were covered by Mesozoic group, if there washydrocarbon sources, they could experience an accumulation process, after Paleogene, theycontinued to be buried and then accessed into main accumulation period, the Mesozoicgroup could be also used as reservoirs. Early Himalayan Buried Hills were shaped in Paleogene, the main period of hydrocarbon generation and expulsion of source rocks werein the same time, so this kind of buried hill are most favourable to the hydrocarbonaccumulation, and the Paleogene fault blocks could accept the hydrocarbon from the lowerburied hills. Early Yanshanian+Early Himalayan Buried Hills were shaped in the earlystage of the Yanshan era and after buried in the cap rock some periods, transfomed in theearly stage of the Himalayan era, the main hydrocarbon accumulation stage was inPaleogene.3. The study on hydrocarbon accumulation conditions of buried hills reveals:Paleogene source rocks are most important in the study area, followed by Lower Paleozoicand Carboniferous-Permian; the migration pathways are permeable rock formation, faults,unconformity and their combinations; there can be many source-reservoir-cap rockassociations among Cambrian-Ordovician internal layers and combined with overlyinglayers. The research in hydrocarbon accumulation mechanism of buried hills suggests:abnormal pressure is the main driving force in the oil and gas migration; there areOil-source-faults the Unconformity two ways for hydrocarbons to supply; Buried hills’reservoir heterogeneity and the displacement pressure of storing space affect theaccumulation and distribution of oil and gas.4. Comprehensive analysis indicates that the buried hills those were experience theEarly Himalayan movement are most favorable to hydrocarbon accumulation, whichmainly develop in the central fault of each depression, followed by steep slope zone thengentle slope belt; the exploration of Paleozoic primary petroleum accumulation should aimat those stable and deeper paleostructure. Buried hills which are related to the Indo-Chinamovement develop mainly in Jiyang depression; Buried hills which are affected mainly bythe Yanshanian movement develop mostly in Huanghua Depression; In Jizhong Depression,most of the buried hills’ developments are mainly affected by the Himalayan movement.