多分支废弃油井层温衰减规律及注入参数对注采性能的影响

Layer temperature attenuation laws in abandoned multi-lateral oil wells and the influences of injection parameters on injection and production performance

利用废弃油井开发地热资源是降低地热开发成本、促进商业推广的有效措施,其中层温衰减规律对地热系统取热效果具有重要影响。为此,以废弃油井储层为研究对象,结合泰森多边形理论对储层裂缝进行了划分,建立了三维油水两相热流耦合数值模型,分析了不同储层条件与布井结构下的层温衰减规律,探究了注入参数等因素对地热注采性能的影响。研究结果表明:(1)低渗透储层抽采30年生产温度最大差值可达22.08 K,高渗透储层(1.0×10^(-13) m^(2))温度过度衰减,长年限采热效率低;(2)储层含油率与生产温度和发电功率呈正相关关系,生产30年后差值最大可达11.57 K与0.12 MW;(3)分支井沿垂直方向会形成低温波谷,层温衰减高于储层其余部分,数量增加对注采影响小;(4)注入速率与发电功率、生产温度分别呈正、负相关关系,但注入速率超过89 kg/s时不利于长年限开采。结论认为:(1)储层取热性能对初始渗透率最为敏感,注入速率与储层含油率次之,优先开发低渗透储层有利于长年限采热;(2)应利用油田地热降低稠油黏度,形成地热辅助采油模式,以实现经济效应最大化;(3)选取6支分支井与89 kg/s的注入速率可得到可观取热效果和较好的经济效益。

Applying abandoned oil well to geothermal development is an effective measure to reduce geothermal development cost and promote commercial promotion,and its layer temperature attenuation law has an important impact on the heat extraction effect of the geothermal system.Taking the reservoirs in an abandoned oil well as the research object,this paper classifies the reservoir fractures according to the Voronoi theory,and establishes a 3D oil-water two-phase hydro-thermal coupling numerical model.Then,the layer temperature attenuation laws under different reservoir conditions and well layout structures are analyzed.Finally,the influence of injection parameters and other factors on the geothermal injection-production performance is explored.And the following research results are obtained.First,the maximum difference of production temperature in low-permeability reservoir can reach 22.08 K after 30 years of production,and the layer temperature of high-permeability reservoir(1.0×10^(-13) m^(2)) is excessively attenuated,resulting in a low longterm heat extraction efficiency.Second,the reservoir oil content is positively correlated with production temperature and generation power,and the maximum difference after 30 years of production is 11.57 K and 0.12 MW,respectively.Third,the lateral well can form a low temperature trough along the vertical direction,where the layer temperature attenuation is higher than the rest of the reservoir,and the increase in quantity has little impact on injection and production.Fourth,the injection rate is positively correlated with generation power and negatively correlated with production temperature,respectively,but the injection rate exceeding 89 kg/s is not favorable for long-term production.In conclusion,the heat extraction performance of the reservoir is the most sensitive to initial permeability,followed by the injection rate and the reservoir oil content,and giving the priority to the development of low-permeability reservoir is conducive to long-term geothermal production.What's more,it is necessary to use oilfield geothermal to reduce the viscosity of heavy oil and form the geothermal aided oil production mode,so as to maximize the economic benefits.Furthermore,the six-lateral well with an injection rate of 89 kg/s can realize considerable heat extraction effects and better economic benefits.