Reduction of Fractionation of Lightweight Slurry to Geothermal Boreholes

Abstract

When designing the cement slurry for casing string cementing in geothermal boreholes, the appropriate thermal conductivity is selected. In the zone of geothermal water, where thermal energy is collected, cement slurry is used, from which the cement sheath has high thermal conductivity. On the other hand, the remaining part of the opening is sealed with slurry, from which the cement sheath will reduce thermal energy losses through appropriate thermal insulation. Cement slurry with appropriate thermal insulation includes light insulating materials. However, the use of such additives is very problematic as they are fractionated due to their low density Therefore, measures should be taken to prevent fractionation of the cement slurry for sealing geothermal boreholes. This article presents the results of research on fractionation of cement slurries for sealing geothermal boreholes. 12 slurries were used for the tests. Six of them are based on class A cement, and six based on class G cement. This action shows the differences in fractionation depending on the binder used. However, the main area of research is determining the effectiveness of counteracting fractionation by the means used for this purpose. As a result of the conducted works, a very good improvement of the cement slurry stability is obtained after the introduction of xanthan gum, as well as filtration perlite. These measures prevent fractionation, so that the cement slurry has a homogeneous structure, and the cement sheath provides the required thermal insulation in the geothermal well.

Zmiana parametrów zaczynu cementowego w obecności kopolimeru butadienowo-styrenowo-amidowego

“…Pomimo iż firmy wykonujące zabiegi cementacyjne prowadzą ciągłe badania nad doskonaleniem zaczynów cementowych, w wyniku których powinna nastąpić poprawa jakości uszczelnienia kolumn rur w otworach gazowych, nie wyeliminowano zjawiska międzystrefowych przepływów gazu. Wprawdzie literatura (Kremieniewski i Stryczek, 2019;Kremieniewski et al, 2021a) zawiera szeroki przegląd na temat mechanizmu migracji gazu i metod jej zapobiegania, jednak badania w tym zakresie nadal trwają. Symulacja warunków otworowych poprzez równoczesną rejestrację zmian ciśnienia porowego, objętości filtratu, dopływu gazu i wywieranego ciś--nienia hydrostatycznego umożliwia analizę współzależności tych czynników w czasie transformacji zaczynu cementowego.…”

Using Fumed Silica to Develop Thermal Insulation Cement for Medium–Low Temperature Geothermal Wells

“…Well cementing is usually necessary during geothermal well construction, and the cement sheath occupies a large part of the wellbore cross-section. Using thermal insulation cement (TIC) to replace conventional cement could reduce the heat loss of the geothermal fluid, thereby increasing the outlet temperature and thermal recovery efficiency [ 3 , 5 , 6 , 7 ].…”