Experimental Study On Oil Displacement Efficiency And Seepage Mechanism Of Marine Low Permeability N Reservoir

With the exploration of offshore oil and gas, more and more high-quality reserves have been developed, so it is urgent to enlarge the low-grade reserves and improve the development effect. It already has a mature development theory and technology of the low permeability oil fields onshore which can provide offshore low permeability oilfield development with a certain reference significance. However, developing the offshore oil and gas fields of low permeability reservoirs, it is not only to face buried deep reservoir, poor reservoir properties, high heterogeneity, pressure gradient, stress sensitivity and fast decline of production, but also the challenges of the offshore environment, the limited space and bearing, and many other adverse conditions brought about by high development costs. In addition, the cost of offshore oil and gas field is much higher than the onshore fields, which has a higher requirement of single well production and oil extraction rate. So, when researching reasonable development mode of offshore low permeability oilfield, it is necessary to learn from the experience of onshore low permeability reservoir development, and combine the characteristics of offshore oilfield development with it.This paper, based on the basic geological characteristics of offshore low permeability N reservoir, analyzed the basic geological characteristics of reservoir, and according to the experiment method and principle, did the start-up pressure gradient, oil displacement efficiency, wettability and stress sensitive experiment by the use of natural cores. This paper had made the following achievements:(1) Done seepage experiments of the reservoir, obtained the relationship between start-up pressure gradient and mobility equation and the relationship under the condition of single phase water and single-phase oil of bound water saturation; done water flooding experiment, obtained the relative permeability curves of8cores and obtained the relationship of oil displacement efficiency and wettability and the change of the injection ratio under the two displacement modes of constant speed and variable speed.(2) Done wettability and stress sensitive experiments, obtained the wettability of8cores and the relationship of permeability and effective stress.(3) By using reservoir engineering and seepage mechanics, researched the rule of two typical heterogeneity modes of nonlinear seepage, researched the production capability of different well types, and done the parameter optimization of the fracturing horizontal well.(4) Researched the seepage characteristics of the development pattern of vertical water injection wells and fracturing horizontal production wells by the use of reservoir engineering and simulation software; analyzed the influence factors of area sweep efficiency and vertical sweep efficiency under the development pattern of vertical water injection wells and fracturing horizontal production wells.