Improving the sustainability of oil well cementing operations: blending Portland cement with pozzolana

Abstract

Cementing is one of the most critical drilling operations in the oil and gas industry. However, the production and utilization of cement is a major emitter of CO₂ into the atmosphere. Processes and technologies that can reduce the overall carbon footprint of the oil and gas industry while meeting the increasing global demand for energy are of key interest to stakeholders. Furthermore, local cement when compared with imported class G cement is unable to meet the compressive strength requirement of an oil well cement. Therefore, the objective of the present study is to investigate for the first time the capability of natural pozzolana clay from Ghana as a sustainable alternative to improve the physical and rheological properties of local Portland cement for well cementing operations. Pozzolana is a naturally occurring clay that is mainly composed of silica and alumina. To achieve this, well cementing blends of varying percentages with up to 30 % of pozzolana and 70 % of local Portland cement by mass were formulated and examined to determine their rheological properties, free fluid, and compressive strength. The experimental results indicated that blending natural pozzolana material and local Portland cement effectively reduced the free fluid of local Portland by up to 85 % and the plastic viscosity by up to 62.5 %. Furthermore, the addition of pozzolana significantly increased the compressive strength of local Portland cement by up to 188.5 %. Based on the results, it can be concluded that pozzolana can improve the performance of local Portland oil well cement and further reduce the carbon footprint of the oil and gas extraction process by minimizing the quantity of Portland cement used for well cementing operation.