The Analyse Of The Change And Function Of Clay Mineral In Waterflood Development In The Low-permeability Reservoir

In order to prevent and treat reservoir damages such as reservoir permeability plugging and water absorbing capacity decline, which are caused by a series of physical-chemical reactions and hydration expansion in waterflood development in the low-permeability reservoirs involving changes of clay mineral to produce particulate precipitation or migration, and to enhance recovery ratio, It is analyzed that the basic structure of clay minerals and the mechanism of clay mineral particles migration, hydration expansion and shown in theory the central causes of clay minerals on the reservoir damage.In order to better explain the reason for the reservoir pore structure and properties, it is studied in this article the effect of content and different occurrence of clay minerals on property of pore structure, capillary pressure curve, relative permeability curve and reservoir wettability and so on. It is found that on the impact of pore characteristics, the main seepage pore radius of dispersed particle clay occurrence of sandstone is larger, pore radius of membrane clay occurrence is smaller, and for bridge tycle clay occurrence, there are micro-pore among clays, the most is irreducible pore, only a handful of pores are larger and have certain permeability in the reservoir; on the impact of the relative permeability, the permeability of sandstone, under the same porosity, is dropping as the different occurrence of clay minerals, the order is dispersed particle, membrane and bridge tycle. In addition, the different occurrence have varied degrees impact on capillary pressure curve, the variational law of capillary pressure curve characteristics between different sandstone clay occurrence is that with different clay occurrence, expulsion pressure,saturation median pressure and the minimum non-saturation pore volume increase in the order of dispersed particle, membrane and bridge type clay occurrence, especially the expulsion pressure and median pressure of bridge type occurrence is greatest.With nuclear magnetic resonance technology, It is analyzed that the relationgship between clay minerals and movable fluids under different sedimentary environments. Then combined with the field data and the results of theoretical analyses ,the ties between the structure and occurrence of clay minerals and reservoir performance variation are given.