engleski

Revitalization of abandoned oil and gas wells for a geothermal heat exploitation by means of closed circulation – case study of deep dry well “Pčelić-1“

Aim of our research is to present evaluation of using abandoned deep hydrocarbon reservoirs and dry wells in Croatian part of Pannonian Basin as geothermal energy source. Croatia has been exploring and exploiting hydrocarbon reserves in Pannonian Basin from mid 20th century. Therefore, many oil and gas wells are reaching the end of their production phase and many are already abandoned. These wells could be considered for geothermal energy production through the coaxial heat exchanger principle, which is usually used in shallow geothermal energy extraction. Using the abandoned deep well Pčelić located in Drava sub-basin as case study, we derived available energy and fluid temperature change during 20 years of operation for two cases ; one with the constant base heat load throughout the year and second as variable heat load depending on outside air temperature. We determined that the maximum potential heat extraction in variable system is 1750 MWh per year, with 1.5 MW of peak heating power in winter, depending on sink temperature, climate and consumer input data. Maximum theoretical constant heat extraction for possible industrial direct heating could be 400kW during the entire period of 20 years, with fluid temperature reaching steady-state at favorable 50°C. To define ratio between extracted heat and consumed energy at the circulating pump, we presented Seasonal Performance Factor (SPF) analysis similar to heat pump systems. Lower values of SPF linked to higher flow rate implies higher energy extraction. Results showed that when using lower flow, SPF ratio is high as 280, and for higher flow SPF ratio drops to only 25.

Geothermal energy, revitalization of oil wells

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