| As a kind of unconventional and hidden special oil formation,low resistance oil formation has great exploration potential.A set of low-resistance oil reservoirs is commonly developed in the Pavilion Tao Formation of the Bohai A Oilfield,and it has been proved through long-term practice that these reservoirs have large reserves and production.However,because the formation of such low-resistance reservoirs is influenced by multiple factors,the contrast of log response characteristics in the oil-water layer is low,which leads to very great difficulties in their quantitative identification and low log interpretation compliance rate.In this thesis,firstly,from the geological background,combined with petrophysical experiments and logging response characteristics analysis,we deeply analyze the formation mechanism of low resistance oil formation from both macroscopic and microscopic perspectives,and clarify the main controlling factors of low resistance oil formation in the study area.Secondly,based on the data of hydrocarbon components from gas logs,we established Pixler plates and triangle plates,and improved the traditional method of hydrocarbon abundance based on the effect of biodegradation on the target layer,which resulted in small or even incomplete heavy hydrocarbon components.For the difficult interpretation section,we have carried out research work on new logging techniques and established geochemical logging identification,Flair formation fluid logging identification and 3D quantitative fluorescence identification standards.In addition,based on the drilling NMR logging data,we analyzed the response characteristics of drilling NMR logging in different fluid reservoirs for key wells,collared wells and difficult wells,and proposed an innovative drilling NMR T2water spectrum reconstruction and fluid identification technique based on microscopic pore structure constraints.The study concludes that the weak hydrodynamic depositional environment,mechanical compaction during rock formation and tectonics are the macroscopic causes of this type of low resistance reservoir,the high bound water saturation due to complex pore structure is the main microscopic cause of low resistance in the study area,and the difference in mineralization of oil and water reservoirs due to natural freshwater flooding pattern is another microscopic cause.Among the new logging techniques,geochemical logging,Flair logging and 3D quantitative fluorescence can effectively identify difficult formations;conventional logging identification plates can only distinguish conventional oil and water formations,while the water spectrum reconstructed by the microscopic pore structure-constrained method is basically consistent with the measured T2spectrum in standard water formations,and the low resistance oil formations can be effectively identified by comparing the reconstructed water spectrum with the measured T2spectrum.Finally,the method of oil and gas abundance method and water spectrum method are tested,and the actual data application shows that the low resistance oil layer identification accuracy based on nuclear magnetic water spectrum method is higher,and the identification compliance rate is 89%.The above research results provide an important reference and interpretation basis for the subsequent exploration and development of the Bohai A oil field and the tapping of old wells. |
