套管式地埋管换热器节能特性的研究与应用

Research and application of energy conservation characteristics for casing buried tube heat exchanger

大庆油田进入开发后期存在着一定数量的废弃井,采用套管式地埋管换热器可以获取到废弃井的中深层的地热能。首先对废弃井转换为地热井的可行性进行分析,通过确定中深层地埋管换热方式,建立外入内出型传热计算模型并对废弃井结构改造。再具体分析大庆油田的地层土壤温度分布和确定边界条件,得出符合现实的理论计算公式。进一步分析套管式地埋管换热器取热评价指标与传热影响因素研究,得到流体流量和进口温度对传热影响因素,及循环流体进口温度对运行特性的影响对取热效率的影响规律。最后,通过对两种工况的废弃井现场试验,得到套管式地埋管换热器平均换热量为478.5 kWh。为利用大庆油田1700口废弃井的节能改造找到了一条切实可行的出路。

There are a certain number of abandoned wells in the later stage of development of Daqing oilfield,so the medium and deep geothermal energy of abandoned wells can be obtained by using the casing buried tube heat exchanger.Firstly,the feasibility of converting abandoned wells into geothermal wells has been analyzed.The heat transfer calculation model of outside-in-inside-out type is established by determining the heat exchange mode of medium-depth buried pipes,and the structure of abandoned wells is transformed.Then,the formation soil temperature distribution and boundary conditions of Daqing oilfield are analyzed in detail,and the theoretical calculation formula in line with reality is obtained.By further analyzing the research on the heat extraction evaluation index and factors influencing heat transmission of casing buried tube heat exchanger,the fluid flow rate and inlet temperature on the factors influencing heat transmission are obtained and influence of circulating fluid inlet temperature on operating characteristics and heat extraction efficiency is obtained.Finally,through the field test of abandoned wells under two working conditions,the average heat transfer of the casing buried tube heat exchanger is 478.5 kWh,which finds a practical way out for the energy conservation transformation of 1700 abandoned wells in Daqing oilfield.