The Experimental Study Of Steam–Air Foam Flooding In Heavy Oil Reservoir

Steam flooding is the most effective and common method for heavy oil production for the moment.However,in the process of steam drive,the gravity override and gas channeling are two difficult problems which cannot be avoided and the situation will be even worsen in the heterogeneous reservoir.To suppress gravity override and gas channeling,air foam is added to the steam drive,resulting in an enhanced oil recovery for heavy oil reservoir.In this paper,the feasibility of steam air foam drive in heavy oil reservoir is studied by means of laboratory tests.A high temperature resistance foaming agent,which was suitable for steam air foam system was screened through static evaluation experiments.Then,the blocking ability of the selected foaming agent was evaluated by testing the foam resistance factor test.The results demonstrated that the concentration of foaming agent,gas liquid ratio,temperature,permeability,injection rate and injection manner all have a great influence on the resistance factor.Eventually,the optimum gas-liquid ratio and injection manner were selected.Experiment on the effect of hot fluid on the properties of crude oil showed that injected air reacted with crude oil oxidation,leading to the increase in the heavy component of crude oil and the reduction in the light component.Consequently,the acid value and viscosity of the crude oil increased.The presence of steam may cause cracking of the heavy component of the crude oil and make more short chain hydrocarbons so that the oil may react with CO2 more likely.With the presence of steam and air,the change of physical properties caused by oxidation of crude oil was weaker than that of pure injected air.Meanwhile security was guaranteed because of more O2 was consumed.The effect of the hot fluid on the rock properties was evaluated experimentally.It is found that showed that the injection of hot fluids had nearly no influence on the mineral composition of the rock and would not cause variation of the physical property which was harmful for the formation.The flue gas,produced by the oxidation reaction between air and crude oil,can expand the volume of crude oil and occupies a certain pore space,resulting in the decrease of both thermal conductivity and permeability of the rock.However,the flue gas will not cause the blockage of the channel and thereby affect the subsequent exploitation.EOR experiment was done by single and double pipe model.By adding air foam to steam drive,it is found that recovery can be improved as more hot fluid will be transferred to low permeability core while viscosity of steam can also be reduced via heating.Steam air foam drive played the roles of oil recovery and profile controlling.The steam consumption of steam air foam drive was far less than that of pure steam drive.At the same time,the heat generated by the oxidation reaction of air and oil compensated the heat loss during the process of steam injection.By cooperation effect of steam drive and air foam drive,ideal recovery efficiency has been achieved with a small the energy consumption.