3D Physical Modelling And Gas Channeling Characteristics Of Fire Flooding In Large Scale THAI Process

Toe-to-Heel-Air-Injection(THAI)is an in-situ combustion(ISC)process that has substantial in-situ upgrading effect during heavy oil production.The oil drainage mechanism of THAI,however,is very complicated and many challenges exist in physical experiment under high temperature and high pressure conditions.In this work,a large scale 3-D fire flooding experimental system which contains a vertical gas injection well and a horizontal production well as well as a funnel well is constructed to realize the THAI process.Jiang heavy oil,a heavy oil sample from China,is used to perform fire flooding experiments under the back pressure of 0.8-2.8MPa.The temperature profiles and post-mortem pictures of coke zones during THAI process are presented in this paper.The results indicate that the oil can be ignited when the temperature close to the igniter reaches above 200°C under the back pressure of about 1MPa.The highest temperature of the fire chamber is positively correlated with the air flux and injected oxygen concentration.With the fixed distance(X,Y)between the horizontal well and vertical injection well,the air flow rate is found to be the most sensitive factor,with the flow rate to sustain a stable combustion front being around 5-10L/min in this experiment.Shapes of the fire chamber for the eight experiments clearly exhibit significant combustion front override.The coke zone adhered to the horizontal well are beneficial to inhibit oxygen breakthrough.Temperatures of coke formation vary in the range of 190-340°C,with the properties of the coke being different according to different temperatures,oil saturations,and also the different corresponding degrees of oxidation and coke deposition.Change of the flue gas concentration is discussed as well as the change of viscosity of the produced heavy oil.Gas channeling characteristics of fire flooding and gas channeling depressing method are shown in this paper.The relationship between the gas injection rate and the propagation of the combustion front was mainly introduced in this work.The results of this study will be significantly referential for the following THAI fire flooding physical simulation.