The Study On Steam Absorption Characteristics Influencing Factors And Optimized Design Of Dual-Horizontal-Well SAGD

Steam-assisted gravity drainage(SAGD),as a frontier technology of thermal recovery of super heavy oil,has been widely used in commercial exploitation of super heavy oil.Dual-horizontal-well SAGD is a typical well layout method.During the development of the dual-horizontal-well SAGD in well group A of the Liaohe Du84 Block,the horizontal section is relatively long.Steam channeling or ineffective steam operation is likely to occur between the injection and production horizontal wells,which seriously affects the development effect.Aiming at the above problems,the main influencing factors of steam absorption characteristics in dual-horizontal-well SAGD are studied by means of reservoir engineering,mathematical statistics and numerical simulation.The string structure and production parameters of well group A are also optimized.Firstly,the quantitative understanding of the steam absorption characteristics of dual-horizontal-well SAGD is obtained by theoretical calculation,and the evaluation index of steam absorption characteristics is established by reservoir engineering method.According to the reservoir characteristics of the well group,the factors affecting the steam absorption characteristics of dual-horizontal-well SAGD are divided into geological factors and production factors.By means of numerical simulation and orthogonal test,the significance of various factors affecting the steam absorption characteristics in different production stages is analyzed.The results show that the main controlling factors of preheating time in dual-horizontal-well SAGD are reservoir depth,vertical distance between dual horizontal wells,etc.The main control factors affecting the vapor absorption uniformity in dual-horizontal-well SAGD are horizontal permeability range,steam injection speed,steam dryness,etc.Then,the numerical models of different string structures are established by using the flexible well function of CMG software.The distribution of steam dryness in the wellbore is calculated and the formation steam absorption is analyzed.The depth of short pipe in the parallel double pipe structure is optimized.The results show that the steam distribution effect of parallel double-tube structure is better than that of single-tube structure.The uniformity of steam absorption in dual-horizontal-well SAGD will be further improved by extending short tube into horizontal section.The optimized length of steam injection short tube is 120?160m.Finally,the dual-horizontal-well SAGD process in A well group of Du84 block in Liaohe oilfield is tracked through numerical simulation experiments.The key parameters of production stage are optimized and the field application of process improvement measures is carried out.The optimum results are as follows: injection speed is 300?350 t/d;steam dryness is 70% or more;production-injection ratio is 1.2?1.4;sub-cool should be controlled at 5?15?.The development effect of well group A has been improved significantly since the adjustment of process measures was implemented in the field.The research results of this paper have certain guiding significance for improving steam absorption uniformity and well group development effect in dual-horizontal-well SAGD process.