With the advancement in green technology-based energy generation to achieve net-zero emissions, geothermal energy has been considered one of the options to reduce the carbon footprint from oil/gas production. In this paper, geothermal energy refers to energy generation that involves a high-pressure, high-temperature (HPHT) environment. Both geothermal energy generation and oil and gas production in such environments—which includes the use of steam-flooded wells and geothermal wells are always challenging as a result of operational issues caused by inorganic scale formation. Changes in pH, temperature, pressure, and other factors in such environments can significantly reduce the solubility limit for mineral ions, causing minerals to precipitate from the solution. Calcite (CaCO3), silica (amorphous and colloidal), and poorly crystallized metal silicates are commonly encountered mineral scales in geothermal applications when the system temperature is approximately 200 to 250 °C. Most of the commonly used scale inhibitors become inefficient in such geothermal environments as a result of structural disintegration and functional modifications. The problems are more severe in brine that contains divalent metal ions such as calcium and iron at higher concentration levels.
This paper discusses various scale inhibitor chemistries that were developed and evaluated for their tolerance and performance at geothermal conditions particularly up to 250 °C. The inhibition effect of these chemicals on calcite formation was analyzed in dynamic and static systems. The thermal stabilities of the chemistries were assessed in neat form and formulated product form using Fourier transform infrared spectroscopy (FTIR) analysis, visual inspections, and inhibition performance evaluations through both dynamic and static inhibition tests. The degradation and inhibition efficiencies of the inhibitors were evaluated before and after thermal aging.
Various energy sectors have been actively involved in projects from planning to execution to address a global objective to achieve net-zero emissions by reducing their carbon footprint by 2050. This requires extensive decarbonization and transformational changes from every aspect of the human enterprise in major interconnected systems: energy, land, industrial, and urban infrastructures.1 However, oil and natural gas remain major components of global energy production and will continue to contribute to energy consumption in the next few decades. Over time, continuous production of oil and gas from known and proven reserves has declined leading to the abandonment of marginal fields that contain several gas wells. Some of these high-pressure, high-temperature (HPHT) gas wells could be advantageously transformed into geothermal wells to generate geothermal energy.2,3 By capturing the potentiality of the natural heat reservoirs underneath the Earth's crust, geothermal energy offers a reliable and renewable alternative source to conventional heating systems, generating electricity, reducing dependence on fossil fuels, and essentially contributing to the shift toward a low-carbon future.4 On the other hand, significant capital investment will be required to achieve the complexity of the new well designs required for geothermal applications and address the technical challenges and associated risks.4 Alternatively, the energy could be extracted by circulating the produced brine from oil and gas production as thermal fluid in the system. Thermal energy from the produced hot fluid could be recovered on the surface in the form of hot fluid and steam, which could be used to operate power plants to generate electricity.3
