The Experimental Test Of Solid Deposition In Low Permeability Reservoirs CO₂ Flooding

CO₂ flooding is an effective method to enhance oil recovery,it's suitable for burial depth,poor physical property and low permeability,high viscosity and high condensate difficult to exploit.However,in the process of CO₂ flooding,due to changes in temperature,pressure,PH and oil dissolved gas loss,CO₂ reacts with reservoir rocks or fluid cause soild deposition,blocking pore,increase the flow resistance,make the oil well productivity decrease.With the rapid development of CO₂ flooding technology,research and solve this problem is more and more urgent.Based on principle investigation of the CO₂ flooding enhanced oil recovery and solid deposition,a series experiment was carried out focused on HongHe oil field.After the evaluation of the rock property,fluid property and the high-pressure physical properties for crude oil before and after the injection of CO₂,and the the minimum miscible pressure,the core damage caused by precipitation produced by the reaction of formation water with different concentrations of CO₂ and rock mineral was tested through displacement experiment.Solid deposition quantity of oil after the injection of CO₂ was tested by transmittance.Through single core,long core displacement experiment,the influence of oil composition and production mode on solid deposition was studied.The experiment result expresses that core permeability declined to various degrees in value after contact with formation water with different concentrations of CO 2,and along with the increase of CO₂ concentration and back pressure,and the decrease of permeability,the permeability decreased more.Using the the PVT equipment with observation window and fluid laser densitometer,the generation of precipitation after CO 2 was injected into crude oil was confirmed.Refering to the oil industry standards ?SY/T7550-2004 Content test of wax,colloid and asphaltene in oil?,the quantity of asphaltene precipitation quantity of simulated oil was measured,it was 7.57 % of the total oil.After the injection of CO 2,oil recovery was increased nomatter for mixed oil or formation oil,and in the same conditions,oil recovery factor is higher for mixed oil than formation oil,the recovery efficiency difference between the two kinds oil increased before decreasing with the increase of injecting pressure.Core permeability declined caused by generating of solid deposition after CO 2 injected,and the decrease amplitude increases with the increase of the back pressure until back pressure equals to the miscible pressure.Co mpared to CO₂ huff-puff in low permeability reservoir,CO₂ flooding cost more gas,has better effect in enhancing oil recovery.Along with the increase of injection pressure,the higher oil recovery,the greater the permeability reduction caused by precipitation.