Mechanism Research And Technology Optimization Of Balanced Steam Injection For Thermal Recovery Of Horizontal Wells

In the course of steam stimulation and steam injection development,the horizontal wells heavy oil thermal recovery due to the steam flow pressure drop and heat loss,formation heterogeneity,technology of steam injection and the structure of tube,make the layer around the horizontal wells absorb steam unbalanced.According as the measured data in field and laboratory experiments show that the conventional steam injection technology can only make layer within the distance of horizontal well with 1/3 absorb steam well,other parts could not produce.It has the impact on heavy oil recovery.Aiming at the above problems,based on the investigation of the uniform steam injection technology of horizontal wells in thermal recovery of heavy oil at home and abroad,in order to Henan oil field,including Jinlou oil field,Gucheng oil field and Xinzhuang oil field,Yanglou oil field and Chunguang oil field as the research object,analyzed the reason of layer absorbed steam unbalanced,established a mechanical method of balanced steam injection(including the optimization of completion parameters,single string and throttle,dual-string steam injection,segmented steam injection)of wellbore fluid pressure,temperature,and dryness and heat loss calculation model,string force model and well completion string throttling model.And using reservoir numerical simulation software and calculation the software,to study the mechanism of balanced steam injection,to compare and analyze the effect of steam injection and production of frequently used balanced steam injection technology.The results show that thin reservoir,loose cementation,formation heterogeneity,lower injection speed,and heat loss is the main reason leading to the formation absorb steam unbalanced in the Jinlou oil field,Gucheng oil field,Xinzhuang oil field,Yanglou oil field and Chunguang oil field.The calculation model of wellbore steam temperature,pressure and dryness and measured data of the average relative error was 1.91%,4.76%,11.58%,to meet the needs of the engineering calculation.Analysis the influence of perforation completion and screen completion parameters on the throttling pressure drop and uneven coefficient.For the perforation completion,hole depth,hole density are the main influence factor,the bore diameter has little effects,and along with hole depth,hole density and bore diameter increased,throttling pressure drop and uneven coefficient decreased,and the decrease rate becomes smaller,the layer absorbs steam balance better.For the screen completion,slot width and slot density are the main influence factor,slot length has little effects,and slot length,slot width,slot density increased,throttling pressure drop and uneven coefficient decreased,the layer absorbs steam balance better.According to the numerical simulation of reservoir,the cumulative liquid of different steam injection technology is not significant,but the cumulative oil has obvious difference,the effect of the segmented steam injection is the best,followed by multipoint steam injection and steam injection pipe,recommended Henan oil field using segmented steam injection technology can effectively improve steam stimulation effects of the horizontal well thermal recovery.The sensitive analysis of impact of steam injection effect parameters and optimization the technology parameters considered that for horizontal wells in Henan Oil field from 200~300m,using three or four injection section,steam quality is 0.7~0.8,steam injection rate is 200~250t/d,steam injection pressure should be controlled below 90% of the formation breakdown pressure,steam temperature is the saturated steam temperature of the steam injection pressure,can effectively improve the development effect and benefits of steam stimulation for thermal recovery horizontal wells.