Stabilisation/solidification of Synthetic North Sea Drill Cuttings Containing Oil and Chloride

On the UK Continental Shelf, up to 80,000 tonnes wet weight of oily drill cuttings are produced annually. These are heterogeneous wastes generated from the petroleum drilling industry, composed of significant percentages of hydrocarbons, heavy metals and chlorides. Since 1992, the discharge of drill cuttings containing more than 1% oil-on-cuttings has been prohibited. Moreover, the extensive increase in tipping fees, imposed by the Landfill Tax in October 1996, has hindered the landfilling of drill cutting as a viable option. Therefore, drill cuttings are a big problem for which the petroleum industry is keen to find solutions. This paper examines the use of stabilisation/solidification (S/S) as a technique to treat North Sea drill cuttings either as a pre-treatment prior to landfilling or for potential re-uses in construction products. Given the known difficulties with stabilising/solidifying oils and chlorides, this paper uses synthetic typical North Sea drill cutting mixes which contain typical average concentrations of hydrocarbons (4.2% w/w) and chloride (2.03% w/w) only to compare the ability of the different binder systems to treat them. A number of conventional S/S binders, namely Portland cement, hydrated lime, pulverised fuel ash and blastfurance slag, as well as novel binders, namely MgO cements, zeolites, silica fume, cement kiln dust, and compost were used. The water to dry binder ratio used was 0.4:1 and the dry binder content by weight was up to 30%. A set of physical tests (unconfined compressive strength), chemical tests (NRA leachability) and micro-structural examinations (using SEM) were conducted on the different mixes. The paper presents the behaviour of the various drill cuttings and binder mixes and compares their relative performance.