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.
Besides satisfying the basic requirements of scientific drilling construction, drilling fluid should satisfy the requirements of scientific test, well logging and borehole log, etc. Detailed requirements can be found as follows:
When oil-based mud is used, the drilled formation solids (cuttings) are regarded as controlled or hazardous waste. As such, they can be disposed of in three ways: decontamination treatment followed by discharge into the sea, injection of the cuttings into the well, or transfer to a controlled hazardous-waste landfill. The lowest environmental effect for solids disposal, especially for offshore operation, is decontamination treatment followed by discharge. However, conventional decontamination technology exhibits limited efficiency in extracting oil from the drill solids.
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.