Hydrocarbon Accumulation Characteristics Of Ordovician In The Western Area

The Ordovician carbonate reservoirs of LunguXi in Tarim Basin is a complex reservoir controlled by both multi-stage tectonic movements and the formation of ancient karst. Grasping the summary of its accumulation characteristics and controlling factors are of great significance to the oil and gas exploration and development. Therefore, based on petroleum geology and geochemical analytical tools, combined with reservoir development characteristics and tectonic evolution history of hydrocarbon reservoir, the writer described the characteristics of the Ordovician, making the following conclusions:(1)Cambrian-Ordovieian source rocks in Tarim Basin are the most widespread source rocks Department of Tarim basin district main source rocks. Cambrian source rocks are widely distributed, high abundance of organic matter, hydrocarbon generation capacity, making a great contribution to the formation of southern area of large-scale reservoirs.(2)The reservoir lithology of Lunguxi Ordovician is grainstone and the second is micrite. Karst reservoir is the main reservoir. Carbonate reservoirs of Group eagle mountain belongs the reservoir of low porosity and permeability. And the size of the reservoir permeability is not controlled by the porosity size.(3)Comparing the geochemical characteristics of Ordovician oil of LunguXi and Cambrian-Ordovician source rocks indicates that the crude oil of LunguXi is mainly from the Ordovician Cambrian source rocks.(4)The Ordovician reservoirs of LunguXi mainly had two hydrocarbon filling process, the first phase occurred in late Caledonian-Hercynian, second phase in the Late Hercynian. Oil filling direction from south to north, there are two advantages of migration direction on the grounds. Hercynian is the main form of Lungu Western heavy oil, Yanshan late-Himalayan adjustment occurred late Hercynian generated oil rilling, forming the characteristics of biodegradable oil mixed with a small amount of normal oil.(5)The Ordovician reservoir had four controlling factors as follows:1) Cambrian source rocks provided adequate oil and gas resources to LunguXi;2) LunguXi located at favorable regional tectonic position;3) Unconformity and fault controled hydrocarbon accumulation;4) The development of vuggy karst reservoir is an important factor to the formation of large oil and gas fields.