Investigation On Recovery Principal And Improvement Technology Of Conventional Heavy Oil Recovered By Horizontal Well Steam Flooding

With the continuous development of horizontal well steam flooding,the problems of small steam sweep,steam channeling and uneven reservoir utilization in horizontal well section have become increasingly prominent.At present,the following three problems exist in the steam flooding recovery principal and improvement technology of horizontal wells:the main controlling recovery principal in different development stages is not clear and the contribution of each principal to oil production is lack of quantitative research;the expansion law of steam chamber and the influence law of yield increase factors are not clear;the implementation and scheme design of the improvement technology in the target block of the horizontal well steam flooding mainly rely on experience.To solve these problems,this paper carries out relevant research combined with laboratory experiments and reservoir numerical simulation.Through laboratory simulation experiments and reservoir numerical simulation,the contribution of horizontal well steam flooding thermal viscosity reduction,thermal expansion,steam distillation,displacement and gravity differentiation to oil production is studied,and the quantitative characterization and main controlling recovery principal analysis of each stage are carried out.The volume change of the steam chamber with equal dryness of the conceptual model is analyzed,and the expansion law of steam chamber and the influence law of yield increase factors are summarized.Based on oil displacement experiment of sand-packed model,different steam flooding improvement technologies for horizontal well are screened,and the key parameters of temperature-resistant gel profile control and water plugging improvement technologies are optimized through numerical simulation of actual model reservoirs.The optimal improvement technical scheme of steam flooding for horizontal wells in the target block is proposed.The results of the investigation on the recovery principal of steam flooding in horizontal wells show that thermal viscosity reduction and displacement are the main controlling recovery principals,and the contribution ratios in different stages reach 20%-45%and 25%-50%;The second is steam distillation,from less than 5%in the thermal connection stage to more than 30%in the distillation erosion stage;Finally,thermal expansion and gravity differentiation,the highest contribution ratio is only 10%-15%.On the basis of the investigation on the recovery principal of steam flooding in horizontal wells,through the numerical simulation of the conceptual model reservoir,it is clear that the permeability contrast,well spacing and oil layer thickness are the main factors affecting the steam flooding of conventional heavy oil with horizontal wells.The results of oil displacement experiment of sand-packed model show that both temperature-resistant gel can effectively block high-permeability channels,reduce water content,expand steam sweep range,and improve displacement pressure and oil displacement efficiency.Compared with pure steam flooding,the cumulative oil recovery can be increased by 17.21%.The reasonable injection timing of temperature-resistant gel profile control in Well Group M is 0.5 to 1 year after steam flooding,with an injection volume of 300 m~3 per round and four injection rounds per year.After 0.5 year of steam flooding,the temperature-resistant gel slug is injected for profile control.Four rounds of injection per year results in a cumulative injection of 10,800 m~3 of gel and increases crude oil production by 23,459.6 m~3,which can increase the recovery rate in the steam flooding stage of horizontal wells by 1.65%.