In field work recently conducted, it was revealed that there were no scale control measures in place
because scale prediction conducted earlier had concluded that there was no scaling risk. However, a
field survey later observed calcium carbonate deposits. In view of the inconsistency between theoretical
prediction and field observations, another scale prediction study was conducted to understand the real
field scaling potential.
Carbonate scale prediction is more challenging due to the CO2 evolution and partitioning into all three
(water/oil/gas) phases during production. This paper describes the scale prediction conducted at three
different scenarios: (1) prediction without hydrocarbon, i.e., only water production during the calculation;
(2) prediction with water and gas, i.e., gas production is considered; and (3) prediction with all three
phases, i.e., the true replication of the production. The effect of pH was studied in detail during
sensitivity runs. In addition, the effect of power oil on scaling potential is also investigated. It is well
known that pH increase has a profound effect to prompt calcium carbonate scaling potential; a local
increase in pH contributed to the solid deposition observed in field. The exclusion of the oil and gas
phases in the previous modeling underestimated the real scaling risk. The carbonate scaling potential
increases significantly when hydrocarbon was included into the calculation. The addition of power oil
has little effect on the overall scaling potential in this case.
Keywords: Carbonate Scale; Scale Prediction; Prediction Software; Modeling