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A numerical investigation into the use of directionally drilled wells for the extraction of geothermal energy from abandoned oil and gas wells
Geothermics ( IF 3.9 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.geothermics.2020.101994
B.E. Harris , M.F. Lightstone , S. Reitsma

Abstract Geothermal energy is an ideal renewable resource for power production since it is not limited by the intermittency issues associated with other renewables like wind and solar. Despite its ability to provide a steady supply of electricity on demand, the adoption of geothermal is not widespread, largely due to the high cost of drilling. One way to mitigate this cost is to use abandoned oil and gas wells, which are abundant (with an estimated 2.3 million in the United States) but pose a potential hazard to the environment. Studies in the literature have proposed installing heat exchangers in vertical wells to solve this problem. Vertical designs, however, would undergo high friction and temperature losses due to the use of internal piping. Such designs also do not enable the use of the L-shaped directionally drilled wells which have greater contact with the ground at high temperatures. This paper proposes an approach for extracting geothermal energy from abandoned oil and gas wells by using directionally drilled wells, thereby improving upon the existing designs by eliminating internal piping and maximizing contact with high ground temperatures. Through additional drilling, two adjacent wells can be connected to create a continuous loop from which thermal energy can be collected for use in a power cycle. The proposed geometry was studied numerically to determine the outlet temperatures and heat extraction rates from the system for the prediction of thermal energy extraction and electrical power production. The results show that a system with 4000 m deep vertical wells and a 4800 m horizontal section could produce approximately 2 MW of thermal energy and 200 kW of power using an organic Rankine cycle. Moreover, these wells are capable of providing a heat source for electricity generation for several decades.

中文翻译:

定向井从废弃油气井中提取地热能的数值研究

摘要 地热能是一种理想的电力生产可再生资源,因为它不受与风能和太阳能等其他可再生能源相关的间歇性问题的限制。尽管地热能够按需提供稳定的电力供应,但地热的采用并不普遍,这主要是由于钻探成本高昂。降低这种成本的一种方法是使用废弃的油气井,这些井很丰富(在美国估计有 230 万口),但对环境构成潜在危害。文献研究提出在垂直井中安装换热器来解决这个问题。然而,由于使用内部管道,垂直设计会承受高摩擦和温度损失。这种设计也不能使用在高温下与地面有更大接触的L形定向钻井。本文提出了一种利用定向钻井从废弃油气井中提取地热能的方法,从而通过消除内部管道和最大限度地与高地温接触来改进现有设计。通过额外的钻孔,可以连接两个相邻的井以创建一个连续的回路,从中可以收集热能以用于动力循环。对提议的几何形状进行了数值研究,以确定系统的出口温度和热提取率,用于预测热能提取和电力生产。结果表明,具有 4000 m 深垂直井和 4800 m 水平井段的系统可以使用有机朗肯循环产生大约 2 MW 的热能和 200 kW 的功率。此外,这些井能够为发电提供几十年的热源。
更新日期:2021-02-01
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