Working Towards Sustainability: Using Local Volcanic Ash as a Partial Replacement for Portland Cement in Cement Slurries to Reduce Carbon Footprint

Abstract Oilwell cement substitution reduces the amount of cement consumed during well construction by using suitable materials that act like oilfield cement through alternative production methods. Volcanic ash is a locally occurring material typically mined from igneous rocks and has cementitious properties, making it a suitable candidate for cement substitution. This paper demonstrates the value of volcanic ash as a cement substitute for well construction operations. To assess the suitability of volcanic ash as a cement substitute, detailed analytical and operational testing was conducted to evaluate its performance relative to oilfield cement. First, a series of tests was performed to determine the behavior of the volcanic ash as an independent cementitious material, followed by blending it with oilfield cement to evaluate the cement's integrity from a long-term zonal isolation perspective. In addition to routine cement performance testing, some supplementary testing, such as particle size distribution (PSD), was also performed. The testing provided the information required to successfully deploy the product in the well construction operations. All lab test results supported the effectiveness of volcanic ash as a cement substitute. The analytical and operational testing supported the value addition of local volcanic ash as a cement substitute for well construction operations. The testing focused mainly on blending ash with cement as a suitable alternative to cement substitution. The testing confirmed that the secondary gel formed fills the microscopic pores within the cement matrix, leading to a denser microstructure and increased long-term compressive strength. The operational testing made the cement designs ready for field deployment, equivalent to those of similar alternative material designs today. Using volcanic ash as a cement substitute could reduce cement consumption in well construction operations, thereby creating a positive ecological and environmental impact in the long term by reducing the need for oilfield cement production. Local volcanic ash has a strong quarry life. Therefore, it can be a suitable alternative for oilfield cement in the future. In addition, the work demonstrates the ongoing efforts to support sustainability solutions in the upstream industry.