The physical and chemical properties of oil will change as oil production increases.Water flooding is a technique used most for oil production

the miscosity of oil increases because a lots of water enter into strata which contact with oil and bring some light crude oil components.At the same time

the water flooding will also cause emulsification of oil. As the water flooding increases

formation pressure will go up and lead to the enrichment of light components.As a result

the yield of oil also increases.The oil can also dissolve wax and cause the increase of wax content.Some asphaltene components in the pore which loosely contact with rock can be expulsed during water flooding process.This increases the asphaltene content of oil production.Combustion is another important techmique for heavy oil production.The combustion behavior is closely related to the SARA fraction of oil.Saturated hydrocarbon begin to burn first

release some energy in low temperature stage and affect the combustion front.In high temperature stage

asphaltene begin to react and release large amounts of heat

affect the succession of combustion bed.The third technique is CO

2

flood used in some oil fields.These processes will increase in oil API gravty with precipitation of heavy components from oil phase due to CO

2

injection.