Plasma heating of carbonate formations

Calcium carbonate rock samples were exposed to high temperature argon plasma to investigate the efficiency of plasma heating for fracturing carbonate formations. Plasma temperature can change the basic properties of the rock through fracture and calcination, which in turn can result in a significant increase in its porosity and permeability. Several calcium carbonate cores with a diameter of 25.4 mm and a height of 29 mm were subjected to axial plasma heating at different temperatures and for different periods of time. The experimental results indicated that the top surface temperatures of the samples ranged from 800C to 900C and the temperature reached steady state within 4 min. The scanning electron microscope (SEM) and porosity analysis of the treated samples indicated significant changes in the basic structure of the rocks and a substantial increase in both porosity and permeability. A mathematical model was developed to predict the temperature distribution along the axis of the heated sample and to estimate the time needed to achieve steady state. The model predictions were in good agreement with experimental results.