Geothermal energy extraction from abandoned well: a roadmap for Cambay Basin

The increased demand for energy has led to extensive production of fossil fuels, which has also increased the number of decommissioned wells. With the impetus toward the use of renewable energy and the achievement of a net zero-target, geothermal energy has become a promising renewable energy source. It serves as the base load demand but has a high capital expenditure. As drilling contributes significantly to the commissioning cost of geothermal projects, the potential of retrofitting abandoned wells with a medium geothermal gradient presents a great opportunity to boost the utilization of geothermal energy in India. In this study, recent technological advancements are outlined, along with the findings of the present researchers, to assess the potential of retrofitting abandoned wells in the Gandhar oilfield located in the Cambay Basin of Gujarat, India. Geophysical investigations in the areas where these abandoned wells exist, geochemical studies of well cores cut from prospective zones, and assessment of the geothermal gradient of the wells have all been conducted to establish the potential of the study area. The necessary parameters for low-enthalpy geothermal production from these wells, such as the temperature gradient, well depth, and casing policy/type, were evaluated. A methodology for such production was developed that includes closed-loop geothermal fluid circulation, activating the wells, isolating the hot water zones using packers, and flowing geothermal production through tubing. Energy harvesting is achieved with the aid of the organic Rankine cycle (ORC). If 50% of the abandoned wells are revived, this will significantly boost the geothermal energy market in India. The inflow-performance relationship and transient pressure testing are two specialized approaches for studying fluid flow and identifying suitable candidate wells for retrofitting. The findings from the pilot geothermal plant in the same region indicate that these retrofitted abandoned wells could generate approximately 450 kWh using the ORC. In the ORC, R1245a is used as the exchange fluid because the subsurface condition is analogous to that of Dholera, where the first ORC-based power plant was established. This study indicates that retrofitting these oilfield wells is an achievable target for harvesting geothermal energy in this region with a varying temperature of 55 to 80 °C. Using existing infrastructure to increase green energy output is a viable proposition.