Abstract:
Geo sequestration of carbon dioxide (CO2) has been found to be one of the best solutions to reduce anthropogenic amount of greenhouse gases to the environment. Well integrity of sequestration wells should be maintained for the success of any sequestration projects. Well cement plays a vital role in well integrity for any sequestration projects, and ordinary Portland cement (OPC) based well cement has been used in underground wells. There are many problems, such as cement degradation, chemical attacks, durability issues, leakage, etc., associated with OPC based well cement. One of the best replacements for OPC based well cement would be the use of geopolymer cement, as it is economical in production, sustainable in reducing waste products, consumes less energy, doesn‟t undergo chemical attacks, durable, resistive in acidic environments and possess higher strength compared to OPC. This paper will review suitability of geopolymer as well cement under downhole conditions, and analyse the advantages of using geopolymer over OPC-based well cement. Moreover, well cement will be exposed to range of temperatures, pressures and fluid medium from the ground surface to sequestration depths of more than 1 km. Therefore, this paper aims to study the mechanical behaviour of geopolymer under different curing temperatures (from 23 ºC to 80 ºC) and curing mediums (brine, water and CO2 saturated brine). It has been found that optimum curing temperature for higher strength is 60 ºC and geopolymer exhibits high strength compared to class G cement above ambient temperature. In addition, water saturated samples showed higher strength reduction compared to brine saturated geopolymer samples.
