Disposal problems and recycling possibilities of drilling cuttings

Karin Hofstätter

Research output: ThesisMaster's Thesis

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Abstract

The reason for this thesis work was a recent change in European law which brought new limits for landfills. One of those limiting parameters for waste is the TOC (=total organic carbon) content in solids and eluates. Due to organic polymers the TOC of the mud (and therefore also of the cuttings) is often very high. This means that most cuttings are not disposable in surface dumpsites in Austria anymore. Thus, the scope of this thesis was to find a practical, economic and environmentally friendly solution for handling drilling waste, namely cuttings. In the first part of the thesis an overview of the Austrian law concerning the deposition and recycling of drilling waste is given. It discusses the legal situation before and after November 2009 and explains in detail under which circumstances the drilled material is defined as general waste, mining waste or side-product. Then an estimate of the annual amount of problematic waste in Austria is given, introducing the term waste factor and considering different waste categories. The next part shows the documentation and interpretation of sample investigations of cuttings that were drilled with either bentonite or K2CO3-polymer muds. This analysis was done in cooperation with the Austrian operator RAG. The result was that cuttings drilled with a pure bentonite mud system can be deposited in the lowest landfill category in Austria whereas cuttings drilled with a K2CO3-polymer mud system cannot be disposed in surface dumpsites in Austria. Furthermore, experiments with retain samples were made in order to see whether dehydration or neutralization and exposure to natural or artificial sunlight would cause a reduction in TOC content and make the cuttings disposable. Dehydration did not show any downward trend but sunlight experiments showed a decrease in TOC of 40-50% in solids and 10-20% in eluate content for both light sources. However, the initial TOC values were so high that there was no change in dump category. A side observation that was made during the analysis was the inaccuracy of the TOC measurement technique. Following this, another quality check experiment was conducted and several sources of error were identified, and the question was raised whether the usual TOC measuring devices are suitable for analyzing drilled cuttings and mud. As a next step possibilities for cuttings recycling compared to cuttings deposition were discussed and a comparison of cost was conducted for three scenarios (combustion, mining backfill in a salt cavern in Germany, and recycling in the cement industry) which showed that recycling is an economically viable solution that means potential cost savings. Furthermore, the importance of recovery and reuse of mud as well as increased solids control efficiency was highlighted. The conclusions were to minimize waste volumes and increase solids control efficiency, to minimize the use of mud additives, and to realize different recycling possibilities in Austria. As a long-term approach the author recommends to invest in research for new mud systems and TOC reduction possibilities.
Translated title of the contributionProbleme der Deponierbarkeit und Verwertungsmöglichkeiten von Bohrklein
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Thonhauser, Gerhard, Supervisor (internal)
Award date8 Apr 2011
Publication statusPublished - 2011

Bibliographical note

embargoed until null

Keywords

  • TOC
  • K2CO3
  • deposition
  • recycling
  • waste
  • mining waste
  • side-product
  • polymer-mud

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