废弃油井转地热井取热性能评价及井型对比

Heat Extraction Evaluation and Well Pattern Comparison of Abandoned Oil Wells Converted into Geothermal Wells

  • 摘要: 地热能开发具备很多优势,但建井成本占总成本一半以上,限制了其推广利用。部分油田废弃井蕴含丰富的地热资源,改造废弃油井为地热井进行取热应用可大幅降低成本,提升经济效益。达到含水经济极限的油藏也可用于热量提取,实现热−油联产。目前,大多数地热井网取热研究为定井型或/和不考虑油水两相流动。然而,不同井型下油水流动和传热特性对油田地热开发方案的设计与调整具有重要影响。为此,建立了考虑油水两相流的热流耦合模型,对比了各种井型下的生产特性,如生产温度、注采压差、产液量和产油量。研究表明:不同井型的生产温度和压差的最大差值分别可达22.56 K和1.03 MPa,注入井和生产井交叉对称分布时,取热系统具有最高的生产温度和产油量,同时具有较低的注采压差。研究揭示了不同井型热提取过程中温压场的演变特征,可为设计和调整井型提供依据,为油田热−油联产评价提供一定指导。

     

    Abstract: Geothermal energy has many advantages in utilization, but well construction account for half of the total costs, and its promotion and utilization are restricted. Some abandoned wells have abundant geothermal resources, using them to develop geothermal can significantly reduce costs. More, the high water-cut oil reservoirs that are on the verge of economic limits can also be used to extract heat and realize the co-production of heat and oil. Currently, most of the well pattern system studies are fixed well patterns or/and do not consider oil-water phases. However, the oil-water flow and heat transfer characteristics in the oil-bearing reservoir under different well patterns are of great significance for the design and adjustment of oilfield geothermal development schemes. Therefore, a new heat-flow coupling model considering oil-water two-phase flow is established. And the production characteristics of the diverse well patterns are discussed, such as production temperature, pressure difference, liquid production, and oil production. Research shows that the maximum difference of the production temperature and pressure difference of diverse well patterns can reach 22.56 K and 1.03 MPa, respectively. The injection wells and production wells are cross-symmetrically distributed, it has the highest production temperature, oil production, and lower production pressure difference. The evolution of temperature and pressure fields during heat extraction from different well patterns are revealed, providing a basis for designing and adjusting the well patterns, and it provides some guidance for the evaluation of oilfield heat-oil co-production.

     

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