Abstract
The worldwide dependence on non-renewable energy sources continues as existing energy systems have been built on these supplies. There is an established link between these conventional energy resources, greenhouse gas (GHG) emissions and climate change and its associated negative effects. As a signatory to the Paris Agreement, Trinidad and Tobago (TT) has been exploring strategies to reduce GHG emissions and the use of geothermal energy is one potential option. Through enhanced geothermal systems, TT, even without extensive volcanic heat reservoirs, can still develop this renewable source by utilizing oil reservoirs. This study evaluates the possibility of designing and evaluating geothermal systems using wells from the Forest Reserve fields in South-western Trinidad as a case study. The Forest Reserve fields have a high number of abandoned oil and gas wells which can be re-used for tapping the required heat and reducing the requirement for drilling of new injection and production geothermal wells. Key information and data from these wells and reservoirs were used as input for CMG software to model, design and evaluate the feasibility of the geothermal reservoir and wells as being possible and viable for geothermal production. A base model was constructed in the CMG software which was subjected to three essential manual sensitivity analyses (well distance, stream temperature, and injection pressure) to obtain an optimized model which was then subjected to hydraulic fracturing. The optimal model of the retrofitted geothermal systems demonstrated to be the best case scenario due to the shallow nature of the reservoir in the area of interest. Six retrofitted geothermal systems (3 injector wells and 3 producer wells) showed that capable capacity of 3.3721 MWe for a 25-year period with an Internal Rate of Return of 190% and an Net Present Value of US$1,431,263,840.00 utilizing a Minimum Acceptable Rate of Return of 10%, Capital Expenditure of US$12MM, Operating Expenditure of US$2MM and a cost of geothermal electricity at US$0.05 per kWh. These results were then used in Crystal Ball to apply Monte Carlo simulations where it confirmed that the project is 100% economically feasible. The cumulative carbon dioxide reduction after the 25-year period was 50,062,500 tons of CO2.
Highlights
The demand for energy from cleaner sources resulting from climate agreements and their associated targets has led countries to explore different energy options
The three (3) main parameters that determine the success of the production of geothermal energy are the temperature of the injected working fluid, the injection well pressure, and the distance between the injection well and producer wells (Sanyal and Butler 2005)
In a retrofitted geothermal system, the temperature of either the injected or the re-injected fluid heavily reliant on the heat transfer into the reservoir, which results in higher production performance and longer lifetime
Summary
The demand for energy from cleaner sources resulting from climate agreements and their associated targets has led countries to explore different energy options. TT is located in the Southern Caribbean and has been producing oil and gas for over 100 years; the hydrocarbon reserves have been steadily decreasing. Industrialization in TT has resulted in the country having the second-highest per capita carbon dioxide emissions in the world which is about 6 times that of the world average (Indar 2019). For more than 100 years, Trinidad and Tobago (TT) has been producing oil and gas and utilizes this as its main source of energy. As oil and gas production have steadily declined over the years, TT is currently considering removing these subsidies in an effort to make cleaner energy projects more feasible
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