通讯员 据今日油价3月2日报道，“地热十年”这句话在媒体和能源行业的聚会上越来越常见，因为国际净零排放计划包括了从地球上提取能源的最吸引人和最清洁的方式之一：地热发电。
为了达到地球地幔辐射到地核的热量，地热公司需要钻探——而且需要钻得很深。事实上，这个新兴行业面临的最大挑战之一是钻到足够深的地方，以达到真正的高温。但是，钻这么深是有风险的，也是昂贵的。
然而有报道称，地热即使在更小的深度也能发挥相当大的作用。根据Rystad Energy最近的一项分析，要从地热井中加热的汽化水中发电，发电设施需要240至300摄氏度的温度。该分析还指出，目前多达70%的地热产出用于发电。
事实上，无论明智与否，人们都渴望让一切都电气化，这一切都与电有关，更具体地说，是无排放的电。地热非常适合这样做：虽然地热井的钻探确实涉及使用化石燃料的设备，但从寿命的角度来看，地热与风能和太阳能完全可比，考虑到它们需要的材料，风能和太阳能也并非完全无排放。
然而，由于高昂的前期成本和对钻探结果的普遍不确定性，地热能发展缓慢。行业专家总是注意到，我们脚下到处都是“热能”，但他们也强调，并不是所有的“地热”都那么容易，或者说可以以非常经济的方式达到。冰岛一直是一个很好的例子，因为它的地热资源很容易获取，还有意大利和土耳其。
难怪地热领域的大量工作都集中在使更深层钻探更经济的技术上。大型石油公司的加入对石油行业来说是件好事。毕竟，这些公司进入地热领域最有意义，因为他们最了解钻探技术。
说到石油，一些公司一直在研究和测试一些东西，可以扩大地热能的范围，使石油公司受益——将废弃的油井变成地热能井。
有一些公司正在朝着这个方向努力，要么把废弃的油井变成地热井，要么让它们成为既能产生热量又能产生石油的两用井。从理论上讲，将油井改造为地热井对促进地热的普及有很大的帮助。然而，实际上，这并不是那么简单。
德克萨斯大学奥斯丁分校地热创业组织的Jamie Beard表示，首先，这类井的流量远低于新钻的地热井。其次，在发电方面，大多数油井的温度根本不足以产生经济意义。第三，Beard表示：“现有的油井经常遭受油井完整性问题的困扰，这将使它们不适合作为一种生产地热资产使用20-40年。”
好消息是，这并不意味着把废弃井变成热能利用井是完全不可能的。记住，发电是地热钻探的主要目的，但供暖作为一个应用领域也不应被低估。
一些公司利用废弃的井注入水，加热，然后用来取暖。如果油井选择正确，发电也不是不可能的。然而，废弃的水井似乎更适合供暖。
英国律师事务所Fieldfisher油气业务主管保罗?斯托克利(Paul Stockley)表示，即便是在这个领域，也存在挑战。其中一个问题是，水需要在井中停留多长时间才能变得足够热。此外，成本也应该要注意。
废弃的井似乎最适合作为附近建筑物和设施的热源。斯托克利指出，可以用于农业作业。因为在英国，大多数陆上油井都在农田附近，所以这种匹配几乎是完美的。
因此，并不是所有的废弃油井都适合转化为地热储层。然而，一些人可能会获得二次利用机会，然后可以用来加热附近的设施。总的来说，对于发电来说，新的钻探似乎是目前更好的选择。而且，与其他任何技术一样，成本必将继续下降，特别是在大型石油投资的帮助下。甚至还出现了利用地球地热资源的新研究领域：废弃煤矿的利用。
王佳晶 摘译自 今日油价
原文如下：
Can Abandoned Oil Wells Be Used To Generate Geothermal Power?
“The decade of geothermal” is a phrase that is becoming increasingly common in media and energy industry gatherings as the international zero-emission push comes to include one of the most fascinating—and clean—ways of extracting energy from the earth: geothermal power.
To reach the heat that the mantle of the Earth radiates into the core, geothermal companies need to drill—and they need to drill deep. In fact, one of the biggest challenges for this emerging industry is drilling deep enough to get to the really high temperatures: drilling so deep is risky and costly.
Yet geothermal can do pretty well even at smaller depths. According to a recent analysis by Rystad Energy, to generate electricity from the vaporized water heated up in geothermal wells, a power generation facility needs temperatures of 240 to 300 degrees Celsius. The analysis adds that as much as 70 percent of geothermal output right now is used for electricity generation.
Indeed, with the urge to electrify everything—whether this is wise or not—it’s all about electricity and, more specifically, emission-free electricity. Geothermal is perfect for this: while the drilling of a geothermal well does involve equipment that uses fossil fuels, from a lifetime perspective, geothermal is fully comparable with wind and solar, which are also not entirely emission-free given the materials they need to operate.
Yet geothermal has been slow to take off because of the high upfront costs and the general uncertainly about the result of drilling. Industry experts invariably note that the heat is everywhere beneath us, but they also make a point of emphasizing that not all of that heat is that easy—or economical—to reach. Iceland is always a case in point with its easily reachable geothermal resources, as well as Italy and Turkey.
No wonder then that a lot of effort in geothermal has focused on the technology to make deeper drilling economical. It’s been a boon for the industry that Big Oil has joined the party. After all, these are the companies whose entry into geothermal makes the most sense, given they know drilling best.
Speaking about oil, some companies have been researching and testing something that could expand geothermal’s reach and benefit oil companies: turning abandoned oil wells into geothermal wells.
There are a few companies working in this direction, either turning abandoned wells into geothermal ones or making them double-use wells that yield both heat and oil. Theoretically, the transformation of oil wells into geothermal wells can be of great help for boosting geothermal’s popularity. Practically, however, it’s not that straightforward.
For starters, flow rates from such wells are much lower than from newly drilled geothermal wells, Jamie Beard from the Geothermal Entrepreneurship Organization at the University of Texas at Austin told Oilprice. Then there is the issue of heat: most oil wells are simply not hot enough to make economic sense if we are talking about electricity generation. Thirdly, Beard says, “existing wells often suffer from well integrity issues that will make them ill-suited for a 20-40 year lifespan as a producing geothermal asset.”
The good news is this does not mean turning abandoned wells into heat-producing reservoirs is completely off the table. Remember, electricity generation is the main purpose of geothermal drilling but heating should not be underestimated as an area of application, either.
Some companies are using abandoned wells to inject water into them, heat it, and use it for, well, heating. Power generation is also not out of the question if the well is right. Yet it seems that abandoned wells are better suited for heating purposes.
Even in that area, however, there are challenges, says Paul Stockley, head of Oil and Gas at UK-based law firm Fieldfisher. One of these is how long the water needs to stay in the well to become hot enough to be used for heating. The longer the time, the lower the viability of the system. Costs should also be borne in mind, Stockley notes. Even if drilling costs are taken out of the equation, there is injection equipment and transfer-of-heat equipment to consider.
It appears that abandoned wells are most viable as a heating source for nearby buildings and installations. For instance, Fieldfisher’s Stockley notes agricultural operations that can be heated. Since in the UK most onshore oil wells are near farmland, the match is almost perfect.
Not all abandoned oil wells, then, are suitable for converting into geothermal reservoirs. Some may, however, get a second life to heat up water that could then be used to heat a nearby facility. For electricity generation, new drilling appears to be the better option for the time being, overall. And, as with any other technology, costs are bound to continue falling, especially with the help of Big Oil investment. There are even new areas of research into harnessing the geothermal resources of the planet: flooding abandoned coal mines and using the water heated in this way to generate electricity and use it for heating and cooling.
