Influence Of Supercritical CO₂ Flooding On Permeability Of Low Permeability Reservoirs

The injection of CO₂ as oil displacement agent to oil and gas reservoirs can not only improve oil and gas recovery,but also realize long term storage of CO₂,which is of great significance for alleviating global warming.The process of CO₂ injection is due to the interaction of particle migration,inorganic scale precipitation?calcium carbonate precipitation?,asphaltene precipitation and the interaction between CO₂ and formation rock and water,thus affecting the physical property and percolation capacity of the reservoir.At present,there are few studies on the influence of supercritical CO₂ flooding on permeability of low permeability reservoirs,so on the basis of relevant theories and experiments,this paper studies the change of permeability of low permeability reservoirs caused by CO₂ displacement.Taking the W reservoir of S gas field as the research object,the potential damage factors of the reservoir are analyzed and evaluated through the analysis of core porosity and permeability test,scanning electron microscope analysis and mercury pressure test.The results show that W reservoir in S gas field belongs to low permeability tight reservoir.And through the core speed sensitivity test to determine the speed sensitive damage degree is strong speed sensitive.We completed the experimental study of supercritical CO₂ flooding in the saturated formation water core,and measured the permeability of core before and after the reaction.Through microscopic analysis,it is known that the migration of particles and the formation of calcium carbonate scale are the main reasons leading to the decrease of core penneability.The experimental study of supercritical CO₂ flooding for saturated kerosene cores has been completed,and the permeability of cores has been measured before and after the reaction.Microcosmic analysis shows that asphaltene precipitation and particle migration in core are the main reasons leading to the decrease of core permeability.The experimental study of core displacement with supercritical CO₂ was carried out under nitrogen condition,and the permeability of core before and after reaction was measured.Microscopic analysis shows that particle migration and blockage of pore and throat by filamentous organic matter extracted by supercritical CO₂ are the main reasons for the decrease of core permeability.The effect of different fracturing fluid?filtrate?on core permeability is studied,and the experimental study of supercritical CO₂ displacement core is carried out under the conditions of different fracturing fluid?filtrate?.The changes of core permeability before and after the reaction are measured,and the fracture fluid?filtrate?and CO₂ are attached to the surface of rock and calcium carbonate on the surface of the rock.Fonnation is the main reason for the decrease of core permeability.