The Types And Main Controlling Factors Of Ordovician Reservoirs In Eastern Lungu

Almost one-third of wells in Sangtamu fault belt appeared the production characteristic that producing gas in earlier stage and producing oil later in recent years,this area present the geology status that the wells mainly produce condensate gas and a part of wells produce oil.Through comparative analysis the oil and gas physical properties and geochemistry characteristics,we consider that multi-stage hydrocarbon-filling and reconstructing is the main reason for “Dry gas,Heavy oil” property.We classify the types of oil-gas reservoirs,and the oil-gas phases and saturation show a regional trend from unsaturated gas reservoir,-saturated gas reservoir,to saturated oil reservoir from southeast to northwest through the PVT phases analysis.The oil-gas phases have little changes vertically.However,some wells was featured by unsaturated gas reservoir in the upper intervals,while saturated gas reservoir in the lower intervals.Combined with geological background,we have discussed the process and reason of “the lower oil” in this area.By analyzing the potential of deep oil-gas resources,we forecast that some wells near strike-slip fault will continue to appear the productive characteristics of “earlier gas and later oil”,and the retains high percentage middle-lower Cambrian may indicate that the deep reservoir having great potential for exploration.Based on liquid producing situation,characteristics of fault zone and karst reservoir,this paper has analyzed the controlling factors of faults action and karstification on migration of oil-gas and reservoir delevoping.We forcast that the cracked zone of fault and plume zone of fault are the high yield region,and the unfilling karst reservoirs which is controlled by underground river is the important exploration target at next stage.Finally,by combined with source-reservoir-caprock assemblage and characteristic of petroleum geology,it is clear that oil-gas distribution is mainly controlled by fault,reservoir characteristics,oil-gas accumulating process,gas wash degree,position of source rocks and caprock in this area.