Protecting the Environment

Creating near-zero discharge in Norway: A novel environmental solution

With the Norwegian North Sea moving ever closer to banning overboard disposal of all solid and liquid drilling waste, several new technologies are being developed to meet such requirements

John E. Paulsen, Statoil ASA; Monica Norman and Jonathan Getliff, M-I l.l.c.

The holistic approach of Statoil’s Total Fluids Management and its application to the waste management cycle have resulted in a dedicated onshore environmental infrastructure and the development of worm-based bioremediation of drill cuttings generated from a specially designed drilling fluid. Such developments not only reduce waste but convert it into valuable, useful end products that help Statoil move closer to its goal of minimizing wastes and meeting its commitment to zero discharge

Increasingly, sustainable development means that operational efficiency and environmental stewardship are not mutually exclusive goals, but rather achieving the correct balance between the two is the only way to properly manage business. While the burden of meeting zero discharge requirements ultimately falls on the operator, Statoil has devised a broad strategy aimed at igniting creativity among its service-company partners to develop cost-effective solutions for meeting its stringent environmental and operational goals. This article describes the approach taken to meet these goals.

ZERO DISCHARGE BY 2005?

Statoil employs various methods to dispose of drilling wastes. These depend on the local options available, the nature of the waste and prevailing regulations. Present legislation provides North Sea operators with three choices for drill-cuttings disposal: 1) Drilled solids from water-based systems can be discharged onsite; 2) With oil-based drilling fluids, the operator can either inject the cuttings into a dedicated injection formation or ship them to shore for treatment and disposal; 3) If the oil content is <1%, it may be discharged offshore.

It now appears that, by 2005, zero-discharge could be in force throughout the Norwegian sector of the North Sea.¹ This directive would have considerable impact on drilling practices. For example, since operators may no longer be allowed to discharge cuttings from water-based drilling fluids, many will opt to employ oil-based fluid systems in applicable fields. Owing to its comparably higher performance, an invert emulsion fluid is characteristically more cost-effective, while generating less waste than its water-based counterpart. This impending transferal has fuelled operator and service-company deliberations on potential environmental impacts and sustainability.

REUSING DRILLING FLUIDS

In accordance with European Council Directive 96/61/EU for Integrated Pollution Prevention and Control (IPPC),² North Sea regulators insist upon compliance with the requirements of Best Available Techniques (BAT) in handling and treating drilling wastes. However, the exact criteria on which BATs are based are not straightforward. Drilling waste disposal issues center on both waste volume and its characteristics. To a great extent, the nature of the drilling waste and the volume generated relates directly to the specific drilling fluid(s) being used. Thus, efforts to minimize waste must take into account the drilling fluid selected, specific drilling parameters, including, among other things, hole diameter, the number of wells, and solids-handling equipment.

Complementing BAT is Best Environmental Practice (BEP), which follows the tenants of waste management hierarchy² and usually implies that waste material should be recycled to the greatest extent possible.

Historically, drilled cuttings and other types of drilling waste were regarded as unusable and treated accordingly.³ Thus, over the years, most efforts centered on simply minimizing the waste generated. Later, others identified the reuse of water-base drilling fluids as a cost-effective fluid handling method.^4,5 They suggested that reuse be performed in such a manner as to benefit both the operator and drilling fluid provider. Statoil demonstrated in a field trial the viable economic benefits of reusing drilling fluids and the associated reduction in discharges to the environment.

The reuse of drilling fluids typically means smaller volumes must be mixed and transported to the rig site. Consequently, transportation issues enter the total equation, affecting both costs and risks associated with spills and other environmental incidents. Furthermore, flexibility in treatments that allow material recycling depends highly on the nature of the waste. Thus, in computing the full environmental burden, the question of BAT becomes much more complicated. Decisions related to BAT would appear to be solved more readily through a life cycle analysis approach. It is from this backdrop that a cradle-to-grave concept emerged, Fig 1.

Fig. 1. Statoil’s TFM drilling fluid “cradle to grave” concept.

Converting drilling waste into a useful new product is regarded as a sustainable solution, as it complies with the preferred option of recycling. Some years ago, Statoil began examining drilling fluid designs that would comply with the recycling criteria. Today, it is becoming common practice for operators to request drilling fluid providers to present cradle-to-grave solutions when bidding contracts. This methodology appears to be the ideal solution to accommodate the criteria of BAT and BEP.

To prepare for zero discharge and facilitate cooperation with suppliers, Statoil has developed a Total Fluids Management (TFM) concept⁶, which is a tool for monitoring and measuring the environmental performance of its drilling operations.

TFM AND THE WASTE CYCLE

Under the auspices of a TFM contract, the drilling fluid supplier is rewarded for operational performance that complies with or exceeds the drilling plan. A key requirement for successful implementation of TFM and its “sustainable solutions” is close cooperation between the operator and service companies. Together, they must address common challenges and opportunities, and resolve the question of how to simultaneously improve environmental performance while continuing to run profitable businesses for both parties. For example, after a drilling operation, the used drilling fluid is sold back to the supplier for reconditioning. It can be re-sold to the operator for full price.

Optimum profit for the supplier is achieved by using as much reclaimed drilling fluid as possible. Since implementing TFM, Statoil has realized a significant reduction in waste, along with higher drilling rates and corresponding reductions in cost per meter drilled.^6,7,8 By applying TFM, Statoil’s reuse of oil- and water-based drilling fluids has increased 63% and 34%, respectively.⁹ Benefits are further improved due to the decrease in consumption of chemicals per meter drilled – an estimated 10%.

No decrease in oil consumption is measured with premium base oil in drilling fluids, since it has always been recycled. However, typical drilling fluid components used in the North Sea had reductions in consumption: barite, 35%; viscosifiers, 37%; glycol, 16%; and KCL brine, 20%.

Moreover, a major waste-volume reduction was achieved by treating the slop waters. Because of its high hydrocarbon content, this waste previously had been disposed of as hazardous waste. On average, the fraction of recycled slop water waste now is 78%. Since implementing TFM, and as of Jan.1 2002, a total of 10,000 m³ of slop water has been treated at dedicated EnviroCenters, which contain a number of services purposely integrated to minimize waste and recycle and reuse drilling fluids, Fig. 2. The EnviroCenters are also used to recover invert emulsion drilling fluid contaminants and settlement on rigs and supply boats; proprietary and water-soluble emulsion breakers are used to separate whole drilling fluid from water or brine contamination.

Fig. 2. The EnviroCenter concept was developed to recover and reuse slop water, oil from cuttings and another associated drilling wastes.

Recovered drilling fluid can have an oil/water ratio as high as 80/20, which is similar to the original drilling fluid. This process allows the drilling fluid to be reused as raw material in the invert emulsion manufacturing process. The oily water will be further cleaned, flocculated and filtered down to below the Norwegian requirement for coastal water discharge of less then 20 ppm. The water can be reused as is for some drilling-fluid applications, or ion-exchanged and membrane filtered to a fully reusable raw material for drilling fluids and brine applications.

MANAGING THE FLUIDS CYCLE

A holistic approach has been conceived that incorporates the total management of all fluids and waste activities and includes project planning procedures, best practices, benchmarking, specially designed software, specifically trained personnel and other fluid-related technologies. ^10,11 Additionally, the inter-linked product and service approach includes integrated data-management systems, featuring a common database to analyze the interactions between all fluid system components. This component is fundamental for continuous analysis and measuring improvement.

The natural grouping of fluid and waste management products and services at the well includes drilling, reservoir drill-in and completion fluids; solids control and filtration equipment; and waste treatment and remediation equipment and services. The process begins in the well planning stages and extends through completion, including the ultimate disposal of solid and liquid waste. The all-inclusive fluids management approach goes well beyond shared infrastructure and personnel to exploit synergies in technology and delivery inherent in this natural grouping of products and services.

Early in the well-design phase, the amount of drilling fluids and related chemicals is determined for each interval, while anticipating any risks that could require additional products, sometimes at a moment’s notice. A central element in the fluids-integration process is determining the ideal waste- remediation scheme. This complies with the cradle-to-grave approach.

WASTE REMEDIATION OPTIONS

As drilling wastes and cuttings are heterogeneous mixtures that can change from section to section depending on the formations being drilled, they are difficult to categorize. Since a uniform feedstock is one of the central tenets of most good waste-disposal technologies, it is very unlikely there will ever be a universal solution to the problem of drill-cuttings disposal. Each remediation method has advantages and disadvantages and may not always be suitable for a given situation or comply with local legislation.¹²

Today, there is a litany of onshore options (Table 1) for handling cuttings laden with oil-base fluids.¹³ Onshore treatment methods include landfill disposal; subsurface injection; bioremediation (composting and bioreacting); stabilization / solidification (briquetting, fixation with silicates or fly ash); extraction or washing (oil, detergents, and solvents); and thermal treatment (incineration and distillation, including thermal desorption and the rotary hammer mill). Generally, cuttings treatment methods can be grouped into chemical, physical or biological processes and further subdivided into methods that either clean cuttings by destroying / removing contaminants, or by stabilizing or encapsulating the waste.

An area of particular interest is converting the cuttings into a useful product or raw material. While some methods allow recovery of hydrocarbons and the energy value of the wastes by incineration in combined heat and power schemes, such energy “down cycling” still leaves an inert residue for disposal; this, in terms of the IPPC directive, is less desirable than complete reuse. Accordingly, this process might not be the best disposal option if it is possible to use the whole drill cuttings as a raw material. This is one of the drivers for studies on composting and worm-driven bioremediation of drill cuttings, as they have the potential to convert drill cuttings into compost or worm castings that could be beneficial for soils.

BIOLOGICAL TREATMENT OPTIONS

Bioremediation is a well-proven and environmentally acceptable technology that converts oil and other organic components into water and carbon dioxide, and results in the generation of metabolic energy and biomass.¹⁴ The essence of its use is the controlled, practical use of microorganisms for the breakdown of pollutants. While bioremediation is a relatively low-cost and low-emission treatment method, its cost effectiveness depends on the correct application and management of the available techniques and procedures, according to pollutant type and available infrastructure.

Current bioremediation technology focuses on ways to enhance existing natural processes that may be too slow because of environmental factors, such as temperature and oxygen availability, and technologies that improve the physical contact between the microorganisms and the chemical, which also limits degradation rates. However, because of the variable nature of drilling wastes and cuttings, there will be instances where bioremediation is not suitable or fast enough to complete the cleanup within the required time, unless the drilling fluid is engineered for biological remediation as well as optimum drilling performance.¹⁵

FLUID DEVELOPMENT

From a waste management perspective, a fluid may be easy to remediate with relatively low treatment costs, but may be more expensive up front. Conversely, a lower cost fluid system can be selected, but may require a more complicated and expensive remediation method.

In years past, fluid systems were developed for optimum drilling performance with little thought given to the eventual disposal of drilled wastes. Recently, in what is generally referred to as fluid development in a cradle-to-grave perspective, drilling fluid systems are designed not only for optimum performance, but for easy, complete and cost-effective remediation.^6,7 The emphasis here is on reducing the ultimate volume of waste generated at the source during initial design of the fluid.

ENVIRONMENTALLY COMPATIBLE FLUIDS

The motivation behind a recent R&D program run by M-I is to design a system that encompasses more than environmental benefits. The goal is to carefully select the individual fluid system components, to generate drill cuttings that actively enhance soil quality and subsequent plant growth.^16,17 Development work continues in a specially designed greenhouse – the only one of its kind in the drilling fluids industry, Fig. 3. First, the designed fluids are thoroughly tested for their drilling performance. Next, their soil ecotoxicity¹⁵ is studied, using tests such as: alfalfa seed emergence and root elongation; earthworm toxicity (eisenia fetida); springtail toxicity (folsomia candida); microbial toxicity (microtox) and aerobic biodegradability (respiration rate and hydrocarbon loss in moist soil).

Fig 3. At this specially designed greenhouse – the only one of its kind in the drilling fluids industry – scientists are researching how cuttings can be converted into material that benefits plant growth.

In addition to the environmental profile of the fluid systems, the technical performance needs to be as good as traditional invert emulsion fluids.^16,17 Varying the base oil, brine phase and weight material helps find the best cradle to grave solution, since final treatment of the drilling waste often determines which weight material is used. Selecting the right weight material may also add value to the final product. Earthworms were a unique addition to the development program; they transform the waste into a commercially beneficial by-product (worm cast) that can be used as a fertilizer.^18,19 

WORM-BASED BIOREMEDIATION

While worm farming or vermiculture is well established as a method of treating organic wastes, it has only recently been applied to the treatment of drilling wastes. In New Zealand¹⁸, more than 1,000 tons of cuttings have been “worm farmed” reducing the hydrocarbon concentration to almost background level under the correct conditions and application rates.¹⁹ Success of the project is based on cradle-to-grave planning, fluid formulation, drilling efficiency, optimum biodegradability and minimum toxicity to the earthworms. Good worm-farming techniques are also important.

Following the success of this work, a joint research project between Statoil, M-I and the Jordforsk Agricultural Research Institute is currently underway in Norway to determine if the same techniques will work under local conditions. If so, it could be applied in other parts of the world using naturally occurring earthworms, infrastructure and resources. The ultimate objective is to develop a waste management process for the Norwegian sector that will convert drill cuttings into a convert drilling wastes into a fertilizer with proven environmental benefits. A secondary objective is to better understand the worms' role in the bioremediation process, to prove its viability as a waste management option to local regulators. The first phase of the study is expected to be completed by year-end, 2002.

CONCLUSION

Operators and service companies can work closely together to create profitable, sustainable solutions to the problems of drilling wastes. In addition to the EnviroCentre concept, bioremediation – both worm-driven and in its traditional, microbial sense – appears to be an attractive example of Best Available Technique when used holistically and combined with careful fluid formulation. It allows conversion of a waste material into a useful raw material or end product, reducing costs for the operator and adding value to the end product.  

Literature Cited

¹ White Paper 58, “Environmental Politics for a Sustainable Development,” Department of Environment, Norway, 1996 – 97.

² European Council Directive 96/61/EU for Integrated Pollution Prevention and Control.

³ Nesbitt, L. E. and J. A. Sanders, “Drilling Fluid Disposal,” Journal of Petroleum Technology, December 1981, pp. 2377 – 2381.

⁴ Sørbye, E., “Reuse of Water-based Drilling Fluids – Mudbank”, OSEA paper No. 94189, presented at the 10th Offshore South East Asia Conference, Singapore, Dec. 6 – 9, 1994.

⁵ Løklingholm, G. and A. Saasen, “Minimising Discharges by Reusing Water Based Drilling Fluids,” paper presented at the Best Practice Compliance with Environmental Regulations for Offshore Drilling, Aberdeen, Scotland, 22 – 23 February, 1999.

⁶ Paulsen, J. E., A. Saasen, B. Jensen, J. T. Eia and P. Helmichsen, “Environmental Advances in Drilling Fluid Operations Applying a Total Fluid Management Concept,” AADE Paper No. 02-DFWM-HO-28, presented at 2002 AADE Technology Conference “Drilling and Completion Fluids and Waste Management,” April 23, Houston, TX.

⁷ Paulsen, J. E., A. Saasen, B. Jensen and M. Grinrød, “Key Environmental Indicators in Drilling Operations”, paper SPE 71839 presented at the Offshore Europe Conference held in Aberdeen, Sept. 4 – 7, 2001.

⁸ Getliff, J. M., A. J. Bradbury, C. A. Sawdon, J. E. Candler and G. Løklingholm, “Can Advances in Drilling Fluid Design Further Reduce the Environmental Effects of Water and Organic-phase Drilling Fluids?,” SPE paper 61040, presented at the Fifth SPE International Conference on Health, Safety and Environment, Stavanger, Norway, June 26 – 28, 2000.

⁹ Sørheim, R., C. E. Amundsen, R. Kristiansen and J. E. Paulsen, “Oily Drill Cuttings – From Waste to Resource,” SPE Paper No. 61372, presented at the Fifth SPE International Conference on Health, Safety and Environment, June 26 – 28, 2000, Stavanger, Norway.

¹⁰ Pruett, J. and C. Hudson, “Integrated Approach Optimizes Results,” The American Oil & Gas Reporter, August, 1998, pp. 86 – 91.

¹¹ Hudson, C. and S. Nicholson, “Integrated Fluids Approach Cuts Waste, Costs in Texas Wildlife Refuge,” Petroleum Engineer International, March, 1999, pp 37 – 41.

¹² Getliff, J. M, M. P. Silverstone, A. K. Sharman, M. Lenn and T. Hayes, “Waste Management and Disposal of Cuttings and Drilling Fluid Waste Resulting from the Drilling and Completion of Wells to Produce Orinoco Very Heavy Oil in Eastern Venezuela,” SPE Paper No. 46600, SPE Paper No. 46600, presented at 1998 SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production held in Caracas.

¹³ Canadian Association of Petroleum Producers, “Report on Drilling Waste Management Review,” St. John’s, Newfoundland, Canada, Aug. 29, 2000.

¹⁴ Alexander, M., “Biodegradation and Bioremediation,” Academic Press Inc., 1994, London.

¹⁵ Getliff, J., C. Flemming and J. Candler, “Biodegradation, Bioremediation And Balance – The Three B’s Of Drilling Fluids Waste Disposal,” presented at International Petroleum Environmental Conference, November 2001, Houston.

¹⁶ Curtis, G. W., F. B. Growcock, J. E. Candler, S. P. Radke and J. Getliff, “Can Synthetic-Based Muds be Designed to Enhance Soil Quality?,” AADE-01-NC-HO-11, presented at AADE National Drilling Conference, “Drilling Technology – The Next 100 Years, March 27 – 29, 2001, Houston.

¹⁷ Growcock, F. B., G. W. Curtis, B. Hoxha, S. Brooks. and J. E. Candler, “Designing Invert Drilling Fluids to Yield Environmentally Friendly Drill Cuttings,” SPE Paper No. 74474, presented at the IADC/SPE Drilling Conference, Feb. 26 – 28, 2002, Dallas.

¹⁸ Norman, M., S. Ross, G. McEwen and J. Getliff, “Minimizing Environmental Impacts and Maximizing Hole Stability: Significance of Drilling With Synthetic Fluids in NZ,” presented at the 2002 New Zealand Petroleum Conference, Feb. 24 – 27, Auckland.

¹⁹ Getliff, J., G. McEwan, S. Ross, R. Richards, “Drilling Fluid Design and the Use of Vermiculture for the Remediation of Drill Cuttings,” presented at American Association of Drilling Engineers’ Drilling and Completion Fluids and Waste Management Conference and Exhibition, April 2 – 3, Houston.

THE AUTHORS
	John E. Paulsen is project manager for the TFM group at Statoil’s Stavanger office. He joined Statoil in 1988 to work specifically with management of drilling wastes. Before joining Statoil, he worked with environmental technology and oilfield microbiology as a senior research scientist at Rogaland Research Institute for eight years; before that, two years as a consultant at Norsk Hydro Research Centre Bergen, focusing on improved oil recovery, and two years as a product developer at an offshore chemical supplier. Paulsen holds a Cand. Scient degree in microbiology from the University of Bergen.
	Monica Norman is vice president of technology for M-I l.l.c., based in Houston. She joined M-I in 1996 with the acquisition of Anchor Drilling Fluids, where she served 10 years. Then based in Stavanger, Norway, her position at Anchor was also vice president of technology. She holds a BSc in biomedical electronics, and an MSc and PhD in atomic collusion in solids from the University of Salford, England.
	Jonathan Getliff is a research scientist leading the Waste Management and Environmental Testing Group at the MI - SWACO Research and Technology Centre in Aberdeen. He has eight years’ industry experience, having previously been a research associate at the University of Bristol. He joined MI in 1994 as a microbiologist / ecotoxicologist and is charged with investigating ways to reduce the environmental impact of drilling fluids. Getliff holds a BSc in applied biology from the University of Wales Institute of Science and Technology and a PhD in microbial ecology from the University of Wales College of Cardiff.