The Development Study of a Centrifuging Technique for Oilfield Production Pit Closure

Abstract

A full-scale study was performed of a centrifuge-based process for dewatering oilfield production waste sludges in order to investigate an application of the process to an oilfield production pit closure. Full-scale experiments were performed to analyze the centrifugal sedimentation of both raw and chemically destablized production pit sludge. The two-stage process was tested: primary solids removal by centrifugal classification followed by chemical conditioning and dewatering. Also, full-scale tests were run to understand the effects of the fundamental centrifuging parameters (the bowl-scroll differential speed and the centrifugal force) on the composition and quality of the dewatering products. The concentration of metals in the production pit sludge, before and after dewatering, was analyzed in terms of the present environmental regulations. The removal of heavy metals from the centrifuge overflow was also evaluated. This study provided qualitative information on how to design an on-site, centrifuge-based system for oilfield production pits closure. The system yielded up to 60 percent volume reduction, the solids-free effluent, and the low-moisture (42 percent vol.) cake discharge. The side-product of the process was an oily, low-solids emulsion (skim layer). The study revealed a technique for minimizing the skim layer through a compromise between the centrifugal force and the differential speed.