Study On Logging Response Characteristics And Evaluation Method Of Complex Reservoir In Nanpu Sag

With the petroleum exploration and development deepening, exploration target has been diverted from simple high amplitude structural hydrocarbon reservoir to complex reservoir. The Hydrocarbon logging response of complex reservoir is character with complexity and stealthiness, which leads to great difficulty in well logging recognition and evaluation. Therefore, the research on effective well logging evaluation in complex reservoir provides advantageous support to exploration and development and has greatly important significance.Nanpu Sag is a typical complex faulted block oilfield and there exists a lot of complex reservoirs, which occupy a great proportion of oil and gas reserves and have considerable productivity. The reservoir in Nanpu Sag is character with great variation of lithology and physical property, strong heterogeneity, low and variable formation water salinity. The reservoir recognition ability decreases because of little electric difference between hydrocarbon layer and water layer. The recognition effect based on conventional log interpretation theory is bad and interpretation cocidence rate is low. Based on research objectives of Guantao and Dongying formation in Nanpu Sag, this paper comprehensively analyzes the data of mud logging, drilling, coring, and well logging, and further studies the interpretation and evaluation method in complex reservoir.The genetic mechanism of complex reservoir in Nanpu Sag is further researched and the electric logging response characteristics of various origin complex reservoirs is hackled by analyzing petrophysical experimental data, logging environment and geologic background, which lays a foundation for logging evaluation of complex reservoir in Nanpu Sag. The complex lithology, physical property and logging environment are considered as major factors that lead to complex electric property. The complex water disturbs the electric comparing basis of oil-gas layers and water layers. The complex lithology results in high bound water saturation and cation exchange capacity, and then enhances conductivity of oil-gas layers. Thin sand shale interbedding reduces the sensitivity of electric logging response to true formation resistivity. The complex logging environment, such as brine mud invasion and deviated well, further complicates electric logging response.According to the strong heterogeneity of complex reservoir, this paper introduces flow unit theory to classify reservoir and build logging interpretation models. The flow index reflects the lithology, physical property and pore structure characteristics. The reservoirs in Nanpu Sag are divided into four types through flow unit index method, and the permeability model based on flow unit has obviously improved interpretation precision, which indicates the rationality of flow unit classification. The flow unit index model is built with GR, AC and DEN in coring intervals, and applied into non-coring intervals to classify the flow units of Guantao and Dongying reservoir. The interpretation accuracy of water saturation model, irreducible water saturation model and oil and water layer identification chart based on flow unit are improved obviously and application effect is good.The Archie parameters m and n vary in a large range and the lithology, physical properties and water are key factors which affect the Archie parameters greatly. The m and n models are built on cation exchange capacity, pore structure and formation water resistivity according to different bed sets, which improves the selection method of Archie parameters. Based on three-water conduction model, this paper proposes a method to correct bound water saturation of centrifuged experiment and applies semi permeable membrane data to verify its correctness and reliability. The actual application results show that the bound water saturation calculated by this method is in good agreement with mercury injection and relative permeability results, and compared with irreducible water saturation before correction, the accuracy is obviously improved. It provides reliable data for the establishment of irreducible water model.Through analyzing mud logging information and well logging information comprehensively, the oil-water layer identification chart is established using multi-information fusion technology. For different logging environments, the sensible parameters reflecting fluid property are researched, and the differences between oil-gas and water layers are enlarged by reasonable collocation of characteristic parameters after analyzing the effects of lithology, irreducible water saturation and gas logging characteristic. The interpretation standards are quantified. The electric logging response is corrected effectively for complex logging environments, such as brine mud invasion, deviated well. The application shows that the three kinds of oil-water identification charts obtain good results. The electric logging responses corrected by inversion are closer to true formation resistivity. All of methods provide dependable technical support to further exploration and development in Nanpu Sag.