Retention and release of scale inhibitor in clay minerals

Addition of scale inhibitor into the reservoir allowing its adsorption and or precipitation into the rock formation and subsequent release during production is one of the most common treatments used in oil field industries to avoid scale formation. Little is known however about the surface chemistry of scale inhibitor interaction with the various mineral phases present in subsea rock formations. This paper presents some recent work investigating these interactions with the spectroscopic techniques commonly employed in surface chemistry. Uptake of NTMP, a model scale inhibitor, by kaolin, halloysite and montmorillonite has been monitored by liquid phase ³¹P NMR spectroscopy. ³¹P NMR has also been used to follow the release of scale inhibitor during desorption experiments. The adsorbed inhibitor has been detected directly and quantified with X-ray photoelectron spectroscopy (XPS). XPS combined with argon ion etching has also been able to distinguish between inhibitor adsorbed onto the external surface of the clays and occluded into the interlayer spacing.