Now the climate change talks are in the news. This has become a routine game for the countries. Developed economies want the developing economies to cut CO2 emissions, control methane emissions (reduce agricultural activity) and promote renewable energy technology (only solar is permitted since it is money spinner). In my earlier blog I explained why solar is not economical and it is not environmentally friendly. Why all the countries are harping on coal-based power plants while a silent killer is causing more damage compared to CO2. Though methane is in the atmosphere for a shorter period its global warming potential is 34 times greater. As a result, methane emissions contributed to about one-third of today’s anthropogenic GHG warming. 24 % of methane contribution to the atmosphere comes from oil and gas wells while agriculture contributes only 3%. Let us examine how countries are wasting their energy available from abandoned oil and gas wells as well as underground coal fires.
There are greater than 27000 abandoned oil wells (also known as orphaned wells)in Gulf of Mexico alone. Similarly Texas has greater than 21000 abandoned wells. Thus in US alone there are greater than 3.2 million orphaned wells. This includes 106,687 wells in California and 2200 in New York (drilled in 1800). The cost of plugging these methane emitting wells varies from US$ $ 9.1 billion. (California wells) and 435 billion US$ (New York wells). These wells, according the US Environmental Protection Agency, are releasing much greater than 281 kilotones of methane into the atmosphere equal to consuming about 16 million barrels of crude oil. Similarly there are about 313,000 abandoned wells in California, releasing 10 kilotons of methane into the atmosphere. A few of them are capped to prevent pollution (especially from methane emissions). Imagine the number across all the oil fields of the world!!
A large number of these wells are as old as 81 years (drilled in 1940). These are on-shore wells. Abandoned Wells in the deep sea are equally large and are not capped and hence there is no control over methane emissions. All these wells were drilled to a depth of about 2.5 km. A recent systematic investigation indicates that in total in the US there are 4 million abandoned wells and in Canada the number is 370 000 (James P. Williams, Amara Regehr, Mary Kang. Methane Emissions from Abandoned Oil and Gas Wells in Canada and the United States. Environmental Science & Technology, 2020; 55 (1): 563 DOI: 10.1021/acs.est.0c04265 ). The methane emissions from these wells are about 48 g/h/well. While there are the actual scrutinized numbers, the US and Canada underestimated it by 150 % (Canada) and 20% (US). This being the case behind their backyard, the US blamed India for emitting methane from agricultural and livestock activity. What a paradox. Thus, there are millions of abandoned wells in the world but there is no data on orphaned oil wells from other countries. A recent publication reported the existence of 30 million abandoned well in the world (Gharibi, Shabnam; Mortezazadeh Emad; Hashemi Aghcheh Badi, Seyed Jalaledin; Vatani, Ali, Feasibility study of geothermal heat extraction from abandoned oil wells using a Utube heat exchanger, Energy (2018), DOI:10.1016/j.energy.2018.04.003). The question here is not the amount that has to be spent in plugging the wells and protect the environment but the damage these wells are causing to the global environment. Why are these climate change pundits harping on coal fired power plants in all the discussions that are ceremoniously minuted by the second tire economies?” and forgetting about these high methane emitting wells? Only CO2 emissions are brought to focus always. Read the recent statement by IEA’s (International Energy Agency) on CO2 emissions……..”Global energy-related CO2 emissions are heading for their second-largest annual increase ever. Demand for all fossil fuels is set to grow significantly in 2021. Coal demand alone is projected to increase by 60% more than all renewables combined, underpinning a rise in emissions of almost 5%, or 1 500 Mt. This expected increase would reverse 80% of the drop in 2020, with emissions ending up just 1.2% (or 400 Mt) below 2019 emissions levels”. On a similar tone IEA should also publish methane emissions from these wells. But they don’t data….countries mask the data. While one can see CO2 emissions from coal fired power plants, methane emissions are invisible!!!!
But these abandoned oil wells are a “blessing in disguise”. They have a huge potential to generate electricity and contribute to methane emissions reduction. The bottom-hole temperatures in these wells vary from 120 to 250 ?C. They can be utilized to generate electricity using a down the hole heat exchanger or simply circulating water if the temperatures are high. ORC technology can be brought off the shelf and can be fitted to these wells for generating electricity. Using these wells is economical because drilling new geothermal wells is expensive. A minimum of 4 MWe can be generated from each well with a cumulative economic value of 1.2 billion US$ from wells located in the US only. Not all wells’ bottom-hole temperatures are high. Many wells have lower temperatures of the order of 100 C. Such wells can be utilized to extract heat energy for space heating and cooling. For example a well with a depth of 3000 m and with the bottom-hole temperature of 125 ?C can be utilized to heat an area of 10000 m2 to 26 ?C with a water flow rate of 20 m3 /h. The cost of the system is half of the conventional heating system per year. Such wells can be utilized for district heating. The amount of CO2 saving is of the order of 457 tons /year.
This technology is also applicable to coal mines where underground coal mines are under fire. India’s current coal production is greater than 286 million tonnes. Raniganj coalfield is the largest coal mine in India. Like any other coal mines in the world, coal fire in Raniganj is very common. This is true with other coal mines in the country as well. For example, several coal seams in Jharkhand and Bihar are burning underground. Coal mine fires are due to primary combustion when oxygen and water are introduced through cracks and unsealed shafts. These coal fires continue through several years Most underground coal fires exhibit smoldering combustion and may only involve relatively small amounts of coal capable of burning in the presence of a small amount (2%) of oxygen. To give an example of the magnitude of this hazard, in the USA nearly 600 coal mine fires are burning for 80 years. Other underground coal mines that are burning are located in Russia and several east European countries. These fires are located at shallow depth and the depth in many cases does not go beyond 400-500 m. Till now this heat energy available is not put to use. Heat exchanger technology commonly used in geothermal power generation can easily be adopted in regions where underground coal mine fire is common and perennial. Continuous heat source from burning coal seams underground will provide continuous electric supply. This method controls underground coal fires, controls CO2 emission and generate electric power to million rural homes. We have the know-how and we need the “will” to implement it!!
Views expressed above are the author’s own.
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