Use of Naphthenate Flow Rigs for in situ demulsifier testing

摘要

The effect of such variables as demulsifier concentration, pH, water composition and BS&W has been investigated under low pressure separator conditions (5-10bar/50-60°C) using more novel 2-phase laboratory flow rigs originally designed for studying calcium naphthenate formation under more representative field production conditions and optimising chemical treatments. This has allowed demulsifier selection while maintaining pH and bicarbonate concentration at the required level. Use of calcium naphthenate inhibitors can lead to a reduction in the propensity for solid deposits to form, but may lead to higher BS&W levels. The balance of calcium naphthenate inhibitors/pH/demulsifier is very important and each chemical can have an impact on the performance of the others, leading to reduced quality oil and/or water, or increased naphthenate deposition. In addition to examining the appearance of the interface during tests, and monitoring the differential pressure increases in the rig, samples have been collected for analysis by Karl Fischer, to give an indication of the demulsification. More recent tests have included modifications of the test protocols to allow measurement of OIW (Karl Fischer) and WIO (Infracal) to indicate the effectiveness of oil / water separation. Further work has then utilised near infrared “Turbiscan” analysis to further elucidate the impact of various treatment chemicals on the stability of the emulsions formed in crude oil systems containing naphthenic acids both in the presence and absence of naphthenate inhibitors. In conclusion, use of a novel pressurised flow rig has enabled the testing and selection of demulsifier chemicals under more realistic separator conditions than is possible in bottle tests. This paper shows how this use of such sealed and pressurised systems has advantages when optimising demulsifier treatments.