Calcium Naphthenate Propagation during Flow in a Porous Medium

Injection of alkaline water can potentially yield large amounts of calcium naphthenates in the reservoir. This can cause a problem if the precipitate moves through the reservoir and accumulates in the near well bore or the production system. The objective of this work was therefore to investigate whether calcium naphthenate would propagate through a porous medium. Highly permeable (∼1 darcy) water-wet Berea sandstone was used as porous medium with toluene as the model hydrocarbon phase. A special type of naphthenic acid (ARN) was added to the toluene phase. Aqueous and toluene phases were injected at a 50/50 volume ratio with a total interstitial velocity close to 1 m/day. Three vertical core flooding experiments were performed at 85 °C. The produced fluids were analyzed for ARN. After flooding, the cores were cut in sections, crushed, and extracted with toluene under acidic conditions to yield ARN profiles.