Study On Sedimentary Facies And Reservoir Of Pingbei Area Chang7-chang10

Ordos Basin is the second big sedimentary basin in china, and has rich oil and gas. Pinbei area is located at the middle-south of Shanbei slope of Ordos Basin, which has been explored and developed for more than a decade. The exploring of petroleum is made constantly progress, but the whole exploring extent is still low. Based on regional well cores, logging and analytical data, completly the analysis of sedimentary facies and sand body ultimate distribution, as well as some studies about reservoir features are made, geological characteristics in this area is recognized clearly.Through regional key beds, combined with the methods of sedimentary cyclical control and stratigraphic thickness similarity, stratigraphy correlation of Yanchang Formation in Pinbei area are made. At the same time, obeying to practice, Chang7-10are subdivided to8sand group and further into29layers. On the above study, the well section profile is selected and isochronous stratigraphic framework is established in the study area.Sedimentary facies and depositional systems about Yanchang Formation in the south-eastern of Pinbei area has been researched, through sedimentary characteristics, rocks and other electrical characteristics. The study shows that ChanglO stage developed mainly river sedimentary facies, which are consisted of braided river channel sand dam and flood plain microfacies; Chang7,Chang8and Chang9stage developed delta-lacustrine depositional system and mainly developed microfacies such as underwater distributary channel, inter-distributary bay, debouch bar, sheet sand, distal bar. Shallow-semi deep lake facies are developed, but lake mud microfacies and prodelta clay in Pinbei area can not been distinguished. Distributary channel sand body are the main reservoir sand body. The development of sand body is controlled by sedimentary distributes in the direction of NE-WS.According to reservoir rock characteristics, physical characteristics and pore structure, reservoir characteristics are studied. The results show that Chang7oil-bearing formation is belonging to low-porosity and extra-low permeability reservoir; Chang8extra-low porosity and extra-low permeability; chang9extra-low porosity and extra-low permeability; changlO mid-porosity and mid-permeability reservoir. Through the factors analysis that affected reservoir properties, reservoir evaluation standard is established. Four levels of reservoir in the area are set up:good reservoir, middle, bad and non reservior. The good and middle reservoir mainly developed in the distributary channel microfacies. The bad and non reservoir mainly exists in the sheet sand and inter-distributary bay sedimentary micro-facies.The inter-relationship of reservoir, sediment, trap condition and oil/gas enrichment is clarified. The rule of oil/gas enrichment is summarized that oil play in the planar distribution are affected by reservoir, but not controlled by reservoir; oil play are obviously affected by sedimentary facies in study area and there are more lithological trap in the area. Finally, sediment and reservoir is taken as the prediction index; explaining results as the evaluation standard; test results as the implementation index. Favorable reservoir evaluation standard in Pinbei area are set up. Four trap types are identified:real area, evaluation area, prospective area, invalid trap. The favorable areas of Chang7-10oil-bearing formation in Pinbei area are predicted.