Phosphonates have been used to inhibit scale formation in oilfields for many years. The scale inhibition mechanisms and the retention and release of phosphonates have been extensively investigated. However, there is a lack of studies on the effects of phosphonates on clay mineral dissolution and secondary precipitation under relevant subsurface conditions, which are important for the oil and gas production. In this study, the interactions between diethylenetriamine penta(methylene phosphonic acid) (DTPMP, a phosphonate scale inhibitor) and biotite, an Fe-containing mica, were investigated at 95 °C and 102 atm CO2. DTPMP enhanced biotite dissolution through both aqueous complexation and surface complexation, leading to higher aqueous Si and Mg concentrations. Complexation between biotite surface sites and DTPMP molecules made cracked layers on biotite basal surfaces bend, and the cracked layers peeled off into the solution after longer reaction times. Interestingly, the aqueous concentrations of Al and Fe were lower with DTPMP than in the control, due to DTPMP-promoted secondary precipitation of Al- and Fe-containing phases. As a result of the significant precipitation with DTPMP, reacted biotite basal surfaces became much more hydrophilic than control samples. This study provides new information on the impact of phosphonate applications in oilfields, especially in shale formations, and has important implications for CO2 enhanced oil and gas recovery.

Effects of a phosphonate-based scale inhibitor on brine−biotite interactions: Implications for CO2-enhanced hydrocarbon recovery

253rd National Meeting (2017)

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