Study On Distribution And Logging Evaluation Methods Of Low Porosity And Permeability Reservoirs In Jinhu Depression

With the exploration and development of Jinhu depression, Reservoirs with low porosity and permeability have been the main exploration target at present and even in the future days. But because of their low porosity, low permeability, complex pore structure and strong heterogeneity, it is very difficult to evaluate them with logging data and oil layers are not easy to interpreate. So the research of evaluation methods and distribution of low porosity and permeability reservoirs is of great significance.The study of the characteristics of low porosity and permeability peservoirs is the base of reservoir logging evaluation. Firstly, the lithology, physical properties, electrical behavior, oil-bearing properties of low porosity and permeability reservoirs in Jinhu depression and the relationship between them were analysised and recognition methods for different lithologies were studied, on this basis, a series of models of different sections in different structural belts , such as , its porosity model , permeability model, median size calculating model and shale content model were set up with core calibrating log technology and previous research. Then, according to oil production test data, mercury injection data and results of well log interpretation,the net pay cut off of different lithologies in different sections were established with test method, displacement pressure/median pressure method and oil production test verification method.HDIL ,NMR ,FMI and XMAC logging have great advantages on evaluate low porosity and permeability reservoirs. HDIL logging can describe drilling fluid invasion characteristics and provide 2D images; a series of parameters such as porosity , permeability , movable fluid volume and irreducible fluid volume can be gained from NMR logging, which is not affected by lithologies directly; FMI logging can be used to analysis lithologies ,fractures and crustal stress;XMAC logging can also be used to analysis crustal stress,in addition,it can provide reference for fracturing and perforation.The macro- factors and micro-factors ,including sedimentation process,structure characteristics,diagenesis,petrologic characteristics and pore structure characteristics , that control low porosity and permeability reservoirs in Jinhu depression were studied in the research.Sedimentation process and diagenesis were the major factors.Based on the researchs above,19 oil layers were found by reinterpreting 13 typical wells of different structural belts in Jinhu depression . Under the control of the 19 new oil layers above and the low porosity and permeability reservoirs which were found in oil testing process , and meanwhile combining the factors that control low porosity and permeability reservoirs , the distribution of low porosity and permeability reservoirs of E1f and E2s formations were researched . This research pointed out the dominant area of low porosity and permeability reservoirs and the next exploration direction.