Identification Technology For Water-flooded Zone At Xinzhao Ultra-low Permeability Reservoir

Xinzhao Oilfield is a fractured low permeability reservoir and has been put into development in 2000 by synchronous water injection.Due to the complex lithology and thin payzones, the injected water flushing renders physical properties like pores and permeability etc. complicated and then results in poor well logging responses with great difficult to make discrimination between low oil bearing zones and water flooded zones. Throught the oilfield the interbedded water zones frequently developed and are difficult to be separated from the water flooded zones. Hence, It has become a key point to carry out the idendification technology research at the later development stage for adustment and well infilling.Here based on fine subdivision of reservoirs, Windowed Fourier transform was used to treat the well logging data with high resolution. From the definition of petrophysical properties, the classified evaluation method was put into use and has resolved the question how the well logging responds to strong reservoir heteroneneity to a certain extent, which formed the foundation for the study of the water flooding mechanism and the build-up of identification criterio. The lithology-electric log experiments were implemented to analyze the mechnism of flooded layers, which obtained the change rules of resistivity in the flooding processes of reservoirs with diffent petrophysical features. As per the sensitivity analysis of well logging response, the crossplot and multiple regression were applied to derive the formation calculation model. By Fisher Discriminant method, several curves were combined to distinguish fluid properties, which could define he highly flooded layers and reduce the interference between the water flooded zones. In view of the effect of sedimentary cycles on flooded zones, the space state model was introduced to inhance the identification precise and has build a new identification technology suitable for Xinzhao Oilfield. It has resolved the difficulty in flooded zones explanation of ultra-low permeability with good Compliance rate and provided a helpful reference for the flooded zones explanation of the same sorts of domestic reservoirs.