Study On Optimum Design For Common Heavy Oil Chemical Flooding

With the abundant crude oil resources,the development has long-term strategic significance for stable production and stimulation.Thermal recovery technology is widely used in many crude oilfields.However,due to heat loss,limited heating radius,steam channeling and so on,there are large numbers of remaining oil.Aiming at the broad application prospect of crude oil chemical flooding,with mass laboratory experiments for polymers,viscosity reducer,surfactant and composite systems,the paper provides a forceful basis for the application to field.Firstly,the static evaluation for chemical agents is carried out,such as salt tolerance,thermal resistance and rheological behavior.The results show that hydrophobically associating polymer has good viscosification property and thermal resistance,but the thermal stability is poor.However,optimized HPAM has better solubility and thermal resistance compared with hydrophobic associated polymer.In the case of low oil-water ratio(≤7:3)and appropriate salinity(≤15000mg/L),viscosity reducer shows excellent effect of viscosity reduction.As for surfactant,its oil-water IFT can reach ultra-low status.And with higher concentration and lower salinity,oil-water IFT would be much lower.Secondly,the feasibility in crude oil reservoir is analyzed with a series of core chemical flooding experiments.The results show that viscosity reducer can reduce crude oil viscosity and enhance oil recovery effectively by emulsification.The recovery of viscosity reducer flooding is 26.00%.Due to mobility control,polymer flooding recovery is 24.71%.In relative terms,surfactant flooding recovery is only 22.22%,slightly above 20.75% of water flooding recovery.Although the oil-water IFT can reach ultra-low status,it is still hard for crude oil flooding.Based on the above research results,the slug combination of polymer and viscosity reducer is proposed.Through the physical simulation experiments,the injection parameters are optimized,such as slug sequence,size and agent concentration.The results show that the slug combination of polymer and viscosity reducer can exploit the remaining oil obviously.Meanwhile,because of lower oil-water mobility ratio,priority to polymer injection is in favor of heavy oil recovery.The subsequent viscosity reducer can reduce flowing resistance and enhance oil recovery by emulsification.The optimum slug combination is 0.3PV polymer of 3000mg/L and 0.2PV viscosity reducer of 0.5%,which can increase recovery by 5.29% and 4.00% respectively compared to polymer flooding and viscosity reducer flooding.As to water flooding,the combined slug flooding can enhance recovery by 9.25%.The slug combination of polymer and viscosity reducer proposed in this paper is of great significance to guide the actual production in oilfield,and improves the oil displacement effect,which leads recovery enhanced.