The Mechanism And Technology Screening Of Multi-fluid Thermal Recovery For Heavy Oil

The reservoir in the area of center of central region 2 of Gudao O il-field is buried deeply under the ground with a very high formation pressure,which make it very inappropriate for steam flooding.However,gas and chemical agents assisted thermal recovery has been proved to be a effective substituted recovery method for this reservoir by laboratory experiments and numerical simulations.In this thesis,thermal methods of hot water flooding which is assisted by CO2,nitrogen foam and viscosity reducer are simulated.After that,the mechanism of this method has been studied and screening criteria for it has been built,which indicates a significant value for the app lication of the method as well as a higher recovery factor for heavy oil.Based on the parameters of gas,chemical agent and reservoir acquired through experimental fitting and production history matching,a numerical model aiming at evaluating effect of different multi-thermal fluid recovery methods is built,.Injection mode of single gas or chemical agent has been optimized from the view of enhanced oil recovery,while that of more than one kind of gas and chemical agent is optimized by using orthogona l design.The enhanced oil recovery factor of combined injection of foam with viscosity reducer is even higher than sum of that by injecting only foam or viscosity reducer.This illustrates there is strong synergy of gas and chemical agent only after profile control.In order to study the characteristics of enhanced oil recovery for multi-fluid thermal method,the responding remaining oil distribution is studied by using numerical simulation.From the analysis on the migration and distribution of gas and chemical agent,temperature distribution and oil viscosity reduction by multi-fluid,the oil recovery mechanism of multi-fluid thermal method has been studied.The analysis suggests that by using only CO2 or viscosity reducer,the effect of viscosity reduction can not contribute to the recovery of extra oil,while their reducing viscosity play a main charactor in oil recovery when they are used together with other chemical agents.With the assosiation of foam,the effect of chemical agent migration can recovery more oil and although the effect of reservoir heating by co-using foam and other agent is less than that by using foam only,it generally make a greater contribution to extra recovered than by using hot water only.To determine what reservoirs can be applied to multi-fluid thermal recovery method,the effect of reservoir parameters on its performance has been studied.Based on the influence of different reservoir parameters on multi-fluid thermal recovery method and the dynamically economic evaluation method,the adaptability boundary plates of reservoir parameters have been achieved.Moreover,the adaptability boundaries applied to multi-fluid thermal recovery method have been established,so that it would be convenient to conduct multi-fluid thermal recovery economically,especially when oil price would fluctuate unexpectedly.