The Role of Calcite in CO2 Increase 25% During Cyclic Steam Injection in Sandstone Heavy Oil Reservoir: Case Study

Cyclic steam EOR pilot project has been deployed in sandstone reservoir type, heavy oil field of Petroleum Development Oman, South Operation, and recently within August to October 2011 showing an interesting CO₂ increase from 1% to the level of 25% mol in gas phase as phenomena. This paper discuss the implementation of Root Cause Analysis, developing steam core flood techniques to understand the increasing mechanism of CO₂, and the proactive well surveillance will help to monitor accurately the increasing level and the impact. The impact of high CO₂ to well and operation integrity also have been studied. The Low GOR (<25 scf/bbl) found to be a limitation of reservoir, while the heavy oil characteristics 14 API will limit a level increase from the well. The only possible CO₂ increased are coming from a thermal evaporation mechanism of formation water and rock mineralogy. The basis simplified chemistry model have been developed as steam energy reaction, one mole of CO₂ was produced for each mole of H₂O injected at steam temperatures. From the detail mineralogy study found that the sandstone reservoir from the field containing Dolomite and Calcite. The surface CO₂ found to be the total amount of evaporation from rock mineralogy, Calcite from formation water and from origin associate reservoir gas. And finally, the CO₂ percentage increase in the surface will be less than 3 scf/bbl.