Summary
This paper details a new technology for the continuous treatment of
contaminated drill cuttings at a throughput of 500 kg/hr, and can be scaled-up
for use in offshore locations.
The change in legislation for oily cuttings discharges in the North Sea at
the beginning of the century resulted in the introduction of a 1% residual oil
limit for discharged cuttings. At the time, because nothing was capable of
achieving a 1% level offshore, only two options existed to deal with oily
cuttings: containment for onshore processing (skip and ship), and injection
(CRI). With time, a thermomechanical cuttings cleaning process has produced
cuttings with oil <1%, although with a significant deck space impact and
restricted throughput.
Previous studies have shown that microwave treatment is able to reduce oil
levels to well below 1% in a laboratory environment, and this work has studied
the scale-up of the system to a 500 kg/hr continuous process. The manufacture
of a pilot-scale cuttings treatment system involved the collaboration between
microwave and electromagnetic engineering specialists, bulk solids handling,
and process engineering disciplines. The feed cuttings are conditioned in a
solids mixer, before being fed by way of a conveyor to a specifically designed
microwave cavity. The oil is removed and recovered using an extraction and
condensation system, with the product oil being very similar in composition to
the base oil in the drilling mud. Residual oil levels of <0.1% are
obtainable, and cuttings throughputs of 500 kg/hr are possible using a 30-kW
microwave source. The microwave process typically consumes 60 kWh of electrical
energy per tonne of cuttings, and the trade-off between microwave power,
residual oil content, cuttings throughput, and overall energy requirements are
discussed in this paper.
This is the first step in the development of a modular system, with low-deck
impact, flexible processing rates, and reduced environmental signature.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
19 November 2007
- Meeting paper published:
15 April 2008
- Revised manuscript received:
12 August 2008
- Manuscript approved:
21 August 2008
- Published online:
20 August 2009
- Version of record:
28 September 2009
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