Sdudy On The Genesis And The Filtration Characteristic Of Low Oil-saturated Reservoir

For the complex geologic structure and genetic model of the low saturated-oil reservoir, the research on the genesis and systematic study can help to evaluate reservoir and analyze the distribution of oil & gas as to make clear the further exploitation direction or development plan. The research on the reservoir filtration is the most basic work and the study to characteristics of the filtration of the low saturation as to find out the different features with normal reservoir can supply the scientific basis for the reasonable development of such reservoir.The paper made the No.1 area in the middle of the Zhunge'er Basin (Xinjiang, China) as the research object. According to the research objects and difficulties of the project, the technical line of multidisciplinary comprehensive study was made. Firstly, the physical features, fluid properties and space distribution were studied, and the reservoir structures and the historic evolved process of the fluid distribution were reduced with the help of the analytical methods for the geochemical and fluid dynamics. On base of above works, the form mechanism of the low saturation reservoir was researched from three main aspects: firstly, to research the affluence by the structure adjustment by the relationship between multi-expulsion and multi-structure and space allocation; Secondly, to research the affects by the genesis of the super low pressure system; thirdly, to research the affects by the vertical heterogeneous barrier within the layer, capillary effect of the low permeability.On base of the research on the genesis of the low oil saturation, the filtration characteristics had been studied. Through the simulation of the genetic condition and the process, the filtration characteristics and mechanism of the microscopic water drive oil were researched and the empirical equation were simulated; To the characteristics of the low permeability oil field, the damage evaluation and the starting pressure gradient were researched, especially the affects to the filtration characteristics of oil and water which had modified affects to relative permeability of oil & water.The research showed that the No.1 area is formed on premise of the adjusts of the oil&gas field and on background of the low latitude structure & low permeability. The main reasons are as follows: (1) the original reservoir was damaged by the later stage Himalayan movement and form the integrity reservoir. (2) the transition zone(oil & water) is form mainly because of the low latitude and low permeability.(3) the restraining barrier and interbed aggravates the formulation of the transition.(4) genesis dynamics is weak and the dip angle of formation is small and the separation of the oil and water is not enough. (5) The non-match of the transport and conductor lead the insufficient supplies of oil and gas. The filtration characteristics of the low saturation reservoir have two aspects: (a) the transition of oil and water in relative permeability plot turns narrow than normal reservoir; (b) the water cut have three stages:"rapidly rising; steady; slowly rising". The rising degree of water cut in early stage has close relationship with the time of oil production and the original water saturation.Lots of evaluation techniques are adapted in this paper to research the genetic mechanism and filtration characteristics. The results are very valuable for the development of the low oil-saturated reservoir.