Experimental Research On Expansion Limits Of Steam Chamber In Oil Sand SAGD Development

Based on the proven heavy oil reserves in China is very considerable,and with the consumption and reduction of conventional oil and gas resources,the efficient development of heavy oil becomes more and more important to alleviate the energy demand.SAGD technology is an important technology for heavy oil development,and the interlayer inside the reservoir has an important impact on the expansion of steam cavity in SAGD development.At present,there are relatively few indoor simulation experiments and field applications to study the expansion limit of steam chamber in SAGD development at home and abroad,so it is of great significance to study the expansion limit of steam chamber in SAGD development.Based on the actual geological conditions of Long Lake Reservoir in Canada,this paper studies the influence of interlayer on the expansion limit of steam cavity and its mechanism in the process of SAGD development.Firstly,the basic physical properties of reservoir fluid are analyzed,and the percolation ability of heated crude oil is tested to study the possibility of crude oil flowing through the interlayer under the action of gravity.Then,through the derivation and determination of similarity criteria,the three-dimensional physical model of oil sand SAGD is designed,and the field production parameters of long lake reservoir are transformed into experimental basic parameters.The temperature field,saturation field and production parameters of different types of interlayer were analyzed by using the laboratory three-dimensional physical simulation experiment,and the expansion mechanism of steam chamber was further studied.Finally,numerical simulation is used to supplement the laboratory physical experiment.Finally,the boundary of steam cavity expansion under different types of interlayer is determined.The results show that the crude oil of Long lake reservoir can be approximately Newtonian fluid when the temperature rises to above 80℃.When the crude oil is heated to above 200℃,the viscosity decreases to below 8.966 m Pa·s.at this time,the heated crude oil can overcome the start-up pressure gradient of the interlayer and start to flow.In the SAGD development process,the oil production rate in the rising stage of steam chamber is increasing.In the transverse development stage,the shape of the steam chamber is close to the inverted triangle,and the oil production rate reaches the maximum in this stage,and the oil production rate is basically stable.In the falling stage of the steam chamber,the oil production rate decreases rapidly.Through SAGD development steam cavity expansion limit experiment,when the permeability of mudstone interlayer is 20×10^-3μm²,the expansion thickness limit of steam cavity is 1 cm,which is equivalent to 0.5 m interlayer in actual reservoir;when the permeability of thin conglomerate interlayer is 150×10^-3μm²,the expansion thickness limit of steam cavity is 4 cm,which is equivalent to 2 m interlayer in actual reservoir.