Detecting Scaling Potential in Oilfield Waters

Production of formation water during petroleum exploitation is sometimes inevitable, necessitating disposal strategies. Produced formation water can be re-injected back into the reservoir either for enhanced oil recovery schemes or for the purpose of disposal. In any case, there is a need to prevent scale formation because it leads to permeability impairment. In this work, formation water compatibility tests were conducted to detect scaling potentials using the Langelier Saturation Index (LSI). Six water samples were used; four produced water samples intended for use in water injection schemes and two water samples obtained from reservoirs needing water injection programs. The water composition of scale-forming elements such as barium, strontium and calcium were determined for all the samples. Other determined parameters included pH values, total dissolved solids (TDS) and LSI. The LSI for different ratios of produced and reservoir water mixtures were determined. Laboratory results indicated that all the water samples contained scale-forming elements and compounds, and they all had to scale potential at ambient temperature but especially at higher temperatures. The produced formation waters were incompatible with the reservoir waters in terms of their scale-forming tendency. To prevent scale formation, especially at higher temperatures, it was recommended that scale inhibitors be used with the least scale-forming produced water. It was also recommended that produced formation waters be subjected to fluid compatibility studies before use in water injection schemes to prevent scale formation.