Research On Technology Of Steam Flooding And Gravity Drainage Development In The Late Period Of Steam Soaking Of Super Heavy Oil Reservoir

The development effect of steam soaking in super heavy oil reservoirs has been deteriorating,steam assisted gravity drainage technology?SAGD?becomes the main development replacement technology,but the application of SAGD reservoir needs to meet certain geological conditions with limitations.Z411 block belongs to super heavy oil reservoir,the viscosity of crude oil can reach 12×10⁴mPa·s,initially developed by the huff and puff exploitation,mining to a lesser extent,however,due to the deep reservoir depth and thin thickness,it can not be developed by SAGD development technology.Based on the geological characteristics of the reservoir and the current underground fluid distribution characteristics,the concept of steam flooding and gravity drainage development was proposed.Therefore,this paper mainly studies the feasibility of the development of target reservoirs and the main factors affecting the effects of steam flooding and gravity drainage development,and provides experience for the development of similar reservoirs.Based on the current development status of the Z411 block,this paper establishes a numerical simulation model for the steam flooding and gravity drainage development pilot test area,which is based on the study of the remaining oil distribution law of the target block.The feasibility of steam flooding and gravity drainage development mode was tested around the pilot test area well network.On the basis of phase equation,the subsurface conditions of steam and N₂ and the parameter calculation methods under different temperature and pressure were studied;the flow vector diagram was used to characterize the evolution of the steam chamber during the development of steam flooding and gravity drainage development.The effects of reservoir structure characteristics,horizontal well injection method,injection velocity,injection dryness,and N₂ injection volume on the formation of steam chamber were studied,and the role of multivariate thermal fluids in the development of steam flooding and gravity drainage was analyzed.Finally,compared the development results of different development programs and conducted an analysis of the net present value of investment returns,optimized the best development plan.The results of the study indicate that there are three stages in the steam flooding and gravity drainage development process:steam preheating stage,steam chamber expansion stage,and the steam flooding and gravity drainage development stage.In the implementation of development,it is preferable tha the formation dip angle is less than 2°,and the injection is carried out in sections,and the steam velocity,dryness,and certain dryness of non-condensate gas should be maintained in order to ensure the formation of an optimal steam chamber.Economic evaluation shows that steam flooding and gravity drainage development technology can significantly improve the development revenue of Z411 block reservoirs.