SUITABILITY ANALYSIS OF GEOTHERMAL ENERGY POTENTIAL IN THE PITTSBURGH, PENNSYLVANIA AREA

Enhanced Geothermal Systems (EGS) especially with low-grade systems are getting more recognition as a viable source for district heating and cooling. With that growing interest, the city of Pittsburgh, Pennsylvania wants to establish a sustainable residential/commercial district in which geothermal solutions will be used for direct heating/cooling. This study focuses on suitable areas in both the surface and subsurface for low grade EGS potential in and surrounding Pittsburgh in greater detail. Data from the National Geothermal Data System was used to interpolate temperature gradient and heat flow using the natural neighbor method. United States Geological Survey (USGS) and Information Handling Services (IHS) data were used to determine the thicknesses of formations. Temperature gradients in the area ranged from 13-22 °C/km with the target area being 19 – 20 °C/km. Heat flow ranged from 35-60 mW/m² with the target area being 46-60 mW/m². The temperature gradient was used to create subsea depth to 80°C and subsea depth to 150°C maps showing a range of -3809 to -3048 m and -7619 to -6858 m respectively. Preliminary suitability analysis using normalized values of the temperature gradient and heat flow shows that the area of interest has a relatively low geothermal potential compared to the rest of the Pittsburgh vicinity. Well data reveals nearby inactive wells completed before 1962 with the nearest one to the area of interest being 656 m deep and completed in 1913. A model was used to calculate years to abandonment and monthly flow rate. For a sandstone layer 61 m thick at a depth of 3810 m, the model shows 25 years (54.4 °C water in, 65.6 °C water out) and 14 years (71.1 °C water in, 82.2 °C water out) An estimated cost for a well that has a measured depth of 5000 m is around $15-17 million.