Abstract
This study proposes potential replacement for the Portland-based cement, which is a common sealant used in deep high-temperature geothermal wellbore completions. The experimental laboratory studies were focussed on alkali-activated aluminosilicates. It was proven, that the so-called, geopolymer-based sealing systems exhibit high compressive and flexural strength at elevated temperatures, good resistance towards thermal cyclic loading, high ductility, acid insensitivity, and improved water permeability. Additionally, alkali-activated aluminosilicate sealing systems are economically feasible and their CO2 emission, during the manufacturing process, is significantly lower in comparison with the conventional Portland-based cement types, making them an environmentally friendly option for deep wellbore completions in unconventional high-temperature geothermal systems.
Highlights
Recent studies have proven, that productivity of a conventional high-temperature geothermal well will be increased by a factor of ten if supercritical fluids, with temperature and pressure conditions being equal or exceeding the critical point, would have been extracted (Friðleifsson et al, 2005, 2014a, 2014b)
This study proposes potential replacement for the Portland-based cement, which is a common sealant used in deep high-temperature geothermal wellbore completions
Based on the assumption that the formation temperature is represented by a boiling point temperature-depth (BPTD) curve with boiling conditions starting at the well’s surface, which is a common assumption for well design in high-temperature hydrothermal systems, and reservoir fluids being pure water only one has to drill to a depth of approximately 3500 m (Fig. 1) to penetrate supercritical resources
Summary
That productivity of a conventional high-temperature geothermal well will be increased by a factor of ten if supercritical fluids, with temperature and pressure conditions being equal or exceeding the critical point, would have been extracted (Friðleifsson et al, 2005, 2014a, 2014b). Deep and high-temperature drilling projects in countries such as Iceland, Italy, Kenya, Japan, Greece, the USA, or Mexico have all reached cri tical temperatures and, in many cases encountered highly corrosive and hostile reservoir fluids Such extreme reservoir conditions promoted significant damages to the casing material, cement sheath, surface equipment, and eventually led to serious well failures or, in some cases, to total well abandonment. These drilling campaigns created an acute need for improvements of the currently used drilling and wellbore completion technologies exploring unconventional high-temperature geothermal resources (Kruszewski and Wittig, 2018)
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