A Study Of Percolation Rules Of Oil-Water Two-Phase Flow In Low-Permeability Reservoirs

Based on the three fundamental factors of fluid, porous medium and fluid condition and taking the example of Zhuang-19 Area of Changqing Xifeng oil field, the dissertation explores oil-water two-phase flow seepage rules of the low-permeability oilfields through plentiful experimental studies and theoretical analysis, and analyses the influences of low-speed non- Darcy seepage on oilfields production process and various economic indicators, from which the correspondent countermeasures are found out so as to improve the effects of this kind of oilfields' development. The researching results can provide referential theoretical basis for the researched area to be able to make injection-production program scientifically and reasonably to increase recovery efficiency. The research work and achievements of this dissertation include:1. Mercury injection method test and analysis: The capillary pressure curve is comprehensively used to describe pores and throats of reservoir rock and to analyze the main seepage channel of the reservoir. The reservoir of the researched area is dominated by medium pores and medium throats. The reservoir grading is good and the skewness is a little thin. The main seepage channel of the reservoir is 0.07μm～0.73μm.2. The stress sensitivity of low-permeability reservoirs is studied and the effective stress received by rock core is changed through changing confining pressure. The author draws the conclusion that the lower the initial permeability of rock core, the higher the loss rate of permeability after receiving pressure. The permeability stress sensitivity of extremely low-permeability rock core is stronger than medium and high-permeability rock core, the reason of which is related to starting pressure gradient in seepage.3. Unsteady experiment measurement on oil-water relative permeability. The formula of oil-water two-phase relative permeability considering starting pressure gradient is deduced. By comparison it is found that the difference between relative permeability curves before and after considering starting pressure gradient is very small. Therefore, it is thought that unsteady experiment data processing low-permeability rock core still can adopt JBN method. The characteristic of relativepermeability curve of Zhuang-19 Area is obtained and the abnormal reason of low-permeability reservoirs relative permeability curve is analyzed. Normalization processing is conducted of relative permeability curve data of each rock core and average relative permeability curve is got.4. The productivity equation of low-permeability reservoirs is deduced. Factors that influence the productivity are analyzed, including reservoir permeability, production pressure and well spacing. Several problems should be paid attention to when developing low-permeability oilfields. Non-Darcy movement equation of low-permeability reservoir fluid is used to deduce the relationship between limit injection-production well spacing and permeability. The mechanism of monomolecular film oil displacement is analyzed. After water displacement, monomolecular film displacement is done to rock cores and various formulations and programs are adopt to study its conditions of increasing recovery efficiency of low-permeability rock cores.