Drill cuttings are particles of crushed rock produced by the grinding action of the drill bit as it penetrates into the earth. Drill cuttings range in size from clay-sized particles (~ 2 μm) to coarse gravel (> 30 mm) and have an angular configuration. Their chemistry and mineralogy reflect that of the sedimentary strata being penetrated by the drill.
Use of traditional cuttings handling systems based on washing the cuttings. By cleaning the cuttings, the oil content in the cuttings can be brought down to approximately 100g oil content per. kg drilled cuttings, which is the average allowable discharge of oil per. well. This again means that the cleaned cuttings can be dumped to sea after cleaning is performed.
The fates of drill cuttings from offshore wells, and their effect on the marine environment, have been studied by means of side-scan sonar, scuba and underwater photography. Adverse effects are minimal and short-lived, and in some instances the accumulation of cuttings may be beneficial. Modification of normal mud and cuttings discharge procedures would be needed only in very unusual circumstances.
Oil-based drilling fluids have long been recognized as a sound technical answer to problems encountered in deep-hot holes and, more recently, to stabilize boreholes with thick intervals of reactive clay formations. However, oil-based mud product development was slowing down until the introduction of low toxicity base oils in the late seventies created a need for new investigations. This innovation sparked a resurgence of oil mud research and development which has resulted in oil-based mud (OBM) systems being used routinely in many active drilling areas worldwide.