Managing drilling waste

Sept. 4, 2006
I would like to offer a different perspective on managing offshore drilling wastes from that presented in the article “Canadians evaluate technologies to manage offshore drilling cuttings”.

I would like to offer a different perspective on managing offshore drilling wastes from that presented in the article “Canadians evaluate technologies to manage offshore drilling cuttings” (OGJ, Aug. 7, 2006, p. 43). In that article, the authors used a complicated numerical weighting and ranking system to evaluate eight technology options. Their results suggest that three drilling waste management methods (vertical centrifuge, horizontal centrifuge, and reinjection) are the optimum ones.

The two types of centrifuges suggested by the authors would be used to remove sufficient synthetic-based fluids from cuttings so they can meet regulatory standards. The authors refer to the US standards of 6.9% retention of base fluids. Other countries follow different standards that may not be successfully met by centrifuge technology, so the ranking scheme is only valid for the US regulatory standards. If drilling fluids other than synthetic-based fluids are used, these comparisons are not relevant either.

Three of the selected technologies (bioreactor, incineration, and thermal desorption) are rarely used at offshore platforms because of space or safety limitations. Grinding is not an end-point treatment technology for drilling wastes. It may be a preliminary step before reinjection, however. I was surprised that the authors did not include as one of their waste management options collection of drilling wastes with transport back to shore for disposal. This is commonly used in the US Gulf of Mexico and in other selected parts of the world that have well-established onshore waste management infrastructure. Exclusion of this option from the authors’ model reduces its applicability to an international perspective.

Although their multicriteria decision statistics are scientifically sound and elegant, I fear that they could lead readers to a conclusion that the three “optimum technologies” are the best choices for all offshore platforms. In my work over the past decade evaluating onshore and offshore management of oil field wastes, I find overwhelmingly that one size does not fit all situations.

The key features that oil company managers must consider when selecting a waste management option include:

  • What do the applicable regulations and current and anticipated government policies allow you to do?
  • What is technically feasible (i.e., do you have the physical facilities and environmental conditions at your location to allow a particular option; this also includes the presence or absence of an established onshore infrastructure)?
  • Do your company’s policies rule out certain management options, or have you had a bad experience with a technology at another location?
  • Is a particular management option cost-effective (includes capital costs, O&M costs, and the potential of long-term liability costs)?

These factors are embedded into the decision-tree logic that I developed as part of the Technology Identification Module of Argonne’s Drilling Waste Management Information System (DWMIS - http://web.ead.anl.gov/dwm/; see OGJ, Aug. 2, 2004, p. 31). That online module asks users to answer a series of yes/no questions and then generates a short list of waste management options that are applicable to the user’s site. The technologies on the short list vary depending on the user’s answers to the questions.

To emphasize the point that the choice of offshore drilling waste management options is best done on a site-by-site basis, I reference a 2003 report that I coauthored that describes many aspects of slurry injection technology for disposal of drilling wastes (this technology is also known as reinjection).1 In the economic considerations chapter of that report, we described a series of published papers that compared the costs of various combinations of: a) injecting cuttings at the platform, b) using lower-cost oil-based muds and hauling the cuttings to shore for disposal, and c) using synthetic-based muds and discharging the cuttings to the ocean following treatment. The results showed that no option was always the least costly, nor was any option always the most costly. Each of the three options was preferred in at least one location.

I commend the authors for their efforts. However, I believe that waste management is better evaluated through careful study of each site’s conditions and regulatory climate rather than attempting to characterize certain waste management options as “optimal” across-the-board.

If you have any questions, please call me at (202) 488-2450.

John A. Veil
Argonne National Laboratory
Washington, DC

  1. Veil, J.A., Desseault, M.B., “Evaluation of Slurry Injection Technology for Management of Drilling Wastes,” prepared by Argonne National Laboratory for the US Department of Energy, Office of Fossil Energy, National Petroleum Technology Office, May 2003, available at http://www.ead.anl.gov/pub/dsp_detail.cfm?PubID=1584.