Study On Oil And Gas Migration And Oil-water Distribution Characteristics Of Cha He Ji Reservoir

Cha He Ji Oilfield,located in Jizhong depression of Western Sag,is connected with Niu Dong large fault and Niu Tuo Town Bulge in the west.According to the previous studies,the relation of deposition in this oilfield is complicated.Cha He Ji Oilfield,for example,by the analysis in its plane change of formation thickness from Ed₃ to Upper Es₁,it is concluded that the characteristics of this area are gentle paleotopographic,spreading braided river,clustering swamps and lowlands,and thus forming the geological characteristic of alternation between fluvial facies and inundant plain-marsh facies.Such pattern leads to the complex oil-water distribution,and the unclear awareness in laws of oil-gas accumulation,while Cha He Ji Oilfield is abundant in oil and gas reservoirs.This phenomenon further results in a low proved ratio in oil and gas reservoir and an undesirable impact on use of proved reserves.As a result,this dissertation utilizes current reservoir data,fluid property data and development data to research the geological characteristics,hydrocarbon migration paths and oil-water distribution characteristics on both plane and vertical directions in Cha He Ji Oilfield.The main research achievements are as follows:?1?It is feasible to determine the migration directions of oil-gas by using the characteristics of fluid properties,which is simple and clearly.It can be believed that the oil-gas migration has two directions?from south to north and from west to east?and the main migration pathway is faults.Among these faults,the ones in Cha He Ji are quite developed,which contains Cha-39 and Cha-15 in the south,and Cha-19,Cha-30 and Cha-31 in the north,and Cha-12 in the middle.The high degree of development in faults provides a favorable channel for hydrocarbon migration.?2?The characteristics of oil and gas distribution on plane in Cha He Ji Oilfield are: high oil saturation and many oil-bearing series are along the long axis direction;more closer to the oil sources,the greater the oil saturation becomes,which conforms to the hydrocarbon migration directions;after the analysis of oil-bearing layers in 8 faults,it is suggested that the layers with high quantities of oil are Cha-15,Cha-39,Cha-12,Cha-19,Cha-30 and Cha-31,and the south areas on plane are the largest followed by the north and the middle.?3?The characteristic of oil and gas distribution on vertical in Cha He Ji Oilfield is that the upper series of high uplifts are much richer in oil than those in the lower series of low positions.?4?The main reasons for the characteristics mentioned above are: sedimentary microfacies on plane distribution are directional and complicated,and have a growing number of isolated sand bodies;the isolated sand bodies and interlayers are better developed;the areas is gentle paleotopographic,spreading braided rivers,clustering swamps and lowlands,and thus forming the geological characteristic of alternation between fluvial facies and inundant plain-marsh facies;there exist very large differences in reservoir physical property on both plane and vertical direction.