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Latest Advances in the Development of Ecological Drilling Fluids
 

Latest Advances in the Development of Ecological Drilling Fluids

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Paper describes the development of formate brines as green drilling fluids

Paper describes the development of formate brines as green drilling fluids

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    Latest Advances in the Development of Ecological Drilling Fluids Latest Advances in the Development of Ecological Drilling Fluids Document Transcript

    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 1/16 John Downs, Hydro Formates IBC Asia Conference Offshore/Upstream Asia-Pacific 2002 25th -26th June 2002, Sheraton Grande Sukhumvit, Bangkok Latest Advances in the Development of Ecological Drilling Fluids John D. Downs Hydro Formates Abstract The oil industry creates many millions of tonnes of drilling waste contaminated with ecotoxic drilling fluid components. A number of mechanical and fluid engineering solutions are being introduced to reduce the volume and toxicity of drilling waste discharged into the environment. This paper looks at the required specification and profile for the ideal fluid engineering solution to the drilling waste problem, and identifies the formate brines as the closest match to a truly ecological drilling fluid. A review of the use of formate brines as ecological drilling fluids over the past 8 years, including their application in the extremely sensitive environment of the Barents Sea, confirms their effectiveness under even the most demanding conditions. It is concluded that the widespread adoption of formate brines as drilling fluids will allow the oil industry to significantly reduce both the volume and toxicity of its drilling wastes. 1. INTRODUCTION The need for sustainable development of the world’s hydrocarbon resources requires the oil companies and the oilfield service companies to
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 2/16 John Downs, Hydro Formates continually look for ways of minimising the negative effects of their well construction activities on the environment. The well drilling processes alone generate many millions of tonnes of waste contaminated with toxic drilling fluid components, and much of this contaminated waste ends up being dumped somewhere or other in our ecosphere. The volume and toxicity of drilling wastes produced is to a certain extent influenced by the nature of the drilling fluids used for drilling the wells. This paper looks at what is being done by the oil industry to develop a truly ecological drilling fluid system that genuinely tries to minimise the damage caused to the environment. It starts by looking at how traditional drilling practices and conventional drilling fluid formulations tend to amplify the negative impact of well construction operations on the environment and how mainly mechanical engineering improvements are being introduced to make the operations more ecological. It then develops a specification and profile for the ideal ecological drilling fluid and argues that the formate brines are probably the only drilling fluids currently available that come close to matching the required performance criteria. The paper concludes by examining how formate brines have performed as ecological drilling and completion fluids since their first introduction to the oil industry in 1993. 2. DRILLING OPERATIONS AND THE ENVIRONMENT The dimensions of the negative impact that the oil companies’ well construction activities have on the environment is largely a function of the extent to which they continue to use traditional well bore construction techniques to access hydrocarbon deposits. Well trajectory and dimensions The traditional practice of drilling individual vertical well bores directly down to and through a hydrocarbon reservoir requires an equivalent number of surface sites, each one having a negative impact on the environment. In addition, the well bore diameters created by traditional drilling methods can be larger than necessarily required to achieve the desired hydrocarbon inflow performance. Large holes mean larger drilling installations and more waste. Formation damage Traditional drilling and well construction techniques can cause significant damage to hydrocarbon reservoirs, thereby restricting oil or gas production. This damage might require remediation by subsequent well stimulation operations, or more well bores might have to be constructed to achieve the desired reservoir drainage and production rates. The inefficient hydrocarbon recovery from wells with formation damage could
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 3/16 John Downs, Hydro Formates lead to premature well abandonment with the majority of reserves remaining in place. This in turn will almost inevitably lead to more environmental damage in the future as operators, encouraged by improved technology or higher oil prices, return to further exploit the abandoned wells/fields. Drilling fluids Traditional drilling and well construction fluids impact negatively on the environment by increasing the volume and toxicity of waste produced in the well-bore creation process. Waste volume Ideally the only significant waste that should come from the construction of a well bore is the exact hole volume of drilled rock cuttings created by the action of the drill bits, but often in practice the volume of waste produced is significantly increased by the use of traditional drilling fluids. The commonest sources of increased waste associated with the use of traditional drilling fluids are: • Dumping and dilution of drilling fluids to maintain fluid condition • Loss of fluid and weighting agent from solids-control operations • Creation of mixed fluid interfaces from displacement operations • Increased production of cuttings from well bore cavings • Use of different fluids for different well sections • Use of different drilling and completion fluids • Use of solid-weighting agents Waste toxicity The type of drilling fluid or well construction fluid used also has a major influence on the toxicity of the waste produced. Water-based well construction fluids have traditionally been based on halide salts that are toxic to freshwater and onshore environments. Non-aqueous well construction fluids have been based on mineral oils or synthetic hydrocarbons, emulsified with halide brines by using powerful surfactants. These invert emulsion fluids place a toxic burden on the environment unless extracted from the waste before disposal. Technology is available to extract the hydrocarbon phases from drilling wastes but it is rare to find the other toxic elements (halide brines, emulsifiers and barite) being removed prior to disposal. Solid weighting agents The use of barite in drilling fluids merits special mention in any review of the environmental impact of well construction operations. Despite containing 58% w/w barium, a very toxic heavy metal, large volumes of barite are traditionally added to drilling fluids to increase their density for
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 4/16 John Downs, Hydro Formates well control purposes. These finely ground particles of barite degrade the properties and performance of drilling fluids by: • Spoiling the hydraulic flow properties of the base fluid • Increasing filter cake thickness and risking differential sticking • Having the potential to sag, causing well safety/access problems • Creating difficulties in re-conditioning and re-cycling the fluid. • Causing formation damage and reducing well productivity The global barite consumption figures issued by the US government1 show that in the year 2000 some 5 million tonnes of this mineral were used in drilling fluids. A large proportion of this barite is discharged with drilling wastes into the environment. It seems that this massive pollution of the environment with a mineral containing such a highly toxic heavy metal is only tolerated by regulators because there is a common belief that the barium contained in the barite is not taken into solution by drilling fluids during use and is therefore not biologically available in drilling waste discharges as a toxicant. It is not clear on what evidence this belief is based. Barite may only have a relatively low solubility in fresh water (2 mg/l), but the majority of drilling fluids contain electrolytes such as chlorides that significantly increase the dissolution of barium from barite. Monnin 2 has shown that under atmospheric pressure a saturated sodium chloride brine will solubilise 50-100 mg/l of barium from barite at 50-100o C, and at higher temperatures and pressures the barium solubility levels can increase to 200-400 mg/l. The same paper indicates that barite is even more soluble in the calcium chloride brines that are routinely used as completion fluids and as the brine phase of oil-based drilling fluids. The barium solubilising effect of chloride brines has actually been known to the oil industry since 1960, following the publication of work carried out by Charles Templeton of Shell Development Company 3 . These moderate levels of barium taken into solution by salt-containing drilling fluids from “insoluble” barite might not sound particularly significant, but they are way in excess of the lethal concentration for bacteria, fungi, algae, aquatic plants (Lemma LC50=26 mg/l)4 and aquatic invertebrates (Daphnia LC50 = 14 mg/l) 5 . Daphnia show a 50% impairment of reproductive function at soluble barium concentrations of just 9 mg/l. The toxicity of soluble barium to the environment is recognized by the US Environmental Protection Agency which classifies any products or formulations containing >100 mg/l of soluble or extractable barium as D005 Hazardous Waste.
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 5/16 John Downs, Hydro Formates It is clearly not ideal that the oil industry discharges millions of tonnes of drilling wastes containing a toxic heavy metal that is solubilised by a common component of drilling fluids and drilling wastes to the extent that they could become classifiable as Hazardous Waste. More research is needed on this subject but, no matter what the outcome of further studies on the levels of soluble barium in drilling waste discharges, it is evident that in waste volume terms alone barite is a strong contributor to the negative impact of well construction operations on the environment. 3. ECOLOGICAL SOLUTIONS IN WELL CONSTRUCTION The word “ecological”, when used in connection with a product or practice, is defined as “tending to benefit or cause minimal damage to the environment”. The oil industry is working towards the objective of ecological well constructions through the development and implementation of new technologies that include mechanical and fluid engineering solutions (see Table 1). 4. GENERAL SPECIFICATIONS FOR DRILLING FLUIDS Drilling fluids play a vital role in the construction of the well bores that the oil companies use either to gather and channel produced fluids and gases from their subterranean sources to the surface or to convey pressure injection water/gases in the opposite direction. Some of the key properties required of conventional drilling fluids include: • Safe to use • Efficiently transmit hydraulic power with minimal pressure losses • Suspend cuttings and other solids, in static and dynamic conditions • Control well pressures • Stabilise the borehole, particularly in shale sections • Minimise formation damage and blocking of sand screens • Minimise fluid loss • Provide lubrication between metal-metal and metal-rock surfaces • Efficiently release cuttings in the solids-control equipment • Minimise waste volume and waste toxicity • Allow all forms of logging and logging interpretation • Be compatible with all elastomers and ferrous metals • Be compatible with other well construction fluids and preparations • Maintain its properties at all ambient and downhole temperatures It is remarkable that, despite almost a century of evolution, no single traditional drilling fluid can actually meet all of these requirements. For this
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 6/16 John Downs, Hydro Formates reason it has been common for operators to have to use more than one type of fluid to drill and complete individual wells. 5. SPECIFICATIONS FOR AN ECOLOGICAL DRILLING FLUID A truly ecological drilling fluid is one that is not only benign but also tends to enable the implementation of the ecological solutions (see Table 1) that have been developed for mitigating environmental problems presented by well construction operations. In essence the specification for an ecological drilling fluid is the same as the general specification for the ideal drilling fluid outlined in Section 4, but with special emphasis on: • Dual utility as a drilling and completion fluid • Minimal formation damage • Optimal fluid properties for narrow bore and extended reach drilling - maximum transmission of hydraulic power in narrow well bores - minimal hydraulic pressure losses in extended reach well bores • Minimal waste production - stabilise the borehole and cuttings - eliminate solid weighting agents - capable of simple re-cycle with minimum losses • Reduce waste toxicity and environmental burden - benign, biodegradable base fluids and solutes - low BOD and COD 6. PROFILE OF THE IDEAL ECOLOGICAL DRILLING FLUID Based on the specifications outlined above, the profile of the ideal ecological drilling fluid is a low-solids water-based solution containing the absolute minimal amounts of benign biodegradable solutes of a monovalent or non-ionic character necessary to provide the following properties over the complete range of well bore temperatures up to at least 200 deg. C.: • Fluid densities up to SG 2.4 without using solids weighting agents • Shale stabilisation • Fluid loss control • Drag reduction • Solids suspension under static and dynamic conditions • Lubrication This minimal fluid should be compatible with the common elastomers and steels used in well construction operations, and should allow the collection
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 7/16 John Downs, Hydro Formates and interpretation of all forms of mud logging and well bore logging data. The fluid should also be easy to re-condition and re-use, and should be useable in any drilling or completion operation. Perhaps surprisingly, no commercial well construction fluid appears to match this profile other than the formate brine systems that were developed by Shell in the early-1990’s as high-performance ecological drilling and completion fluids 6,7,8 . 7. FORMATE BRINES AS ECOLOGICAL DRILLING FLUIDS The formate salts of the alkali metals are very soluble in water and form benign brine systems with a broad range of beneficial properties8 that make them ideally suited for use as ecological drilling and completion fluids: • They cover a density range between SG 1.0 and SG 2.3 • They have a good Health, Safety and Environmental profile • They transmit hydraulic power with minimal pressure losses • They stabilise shales • They can be easily formulated with biodegradable biopolymers for: - fluid loss control - drag reduction - solids suspension in static and dynamic conditions • They have natural lubricating properties • They cause minimal formation damage • They can easily be recycled • They allow all forms of logging and logging interpretation • They are compatible with most elastomers and all ferrous metals • They maintain their properties at –50o C up to + 210o C The formate brines are manufactured from chemical components that are on the OSPAR List of Substances Used and Discharged Offshore which are Considered to Pose Little or No Risk to the Environment (PLONOR). Data on the toxicity of formates to a selection of aquatic and marine organisms are shown in Table 2. Benign chemicals such as formates with LC50 and EC50 figures of > 100 mg/l are generally considered to be practically non-toxic to the environment. If formate brine is discharged into the environment any potassium and caesium ions in solution will quickly become depleted by adsorption onto soil or sediments, and the formate will be removed by microbial activity. In standard OECD Biodegradability tests the formates are 90% biodegraded within 15 days, and they are therefore classified as being “readily biodegradable”8 .
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 8/16 John Downs, Hydro Formates It is interesting to consider that the universal adoption of formate brines as drilling fluids would reduce barium heavy metal discharges from drilling operations by some 3 million tonnes/year. The density range of the formate brines can be extended, if necessary, up to SG 3.0 by the addition of caesium tungstate brine – another discovery made by this author while working for Shell back in 1990. 8. ECOLOGICAL APPLICATIONS OF FORMATE BRINES Formate brines have been successfully used as ecological drilling and completion fluids in many hundreds of wells in at least 14 countries since 1993. The high-density caesium formate brines have so far been used in a total of 46 wells, including 6 reservoir drill-ins by BP and Statoil. In many cases the formate brines have enabled the implementation of the ecological solutions described in Section 3: Formation damage reduction Field results obtained over a period of 8 years have confirmed that oil and gas wells drilled and/or completed with formate brines have invariably shown higher than expected production rates. Figures published in the public domain suggest that typical production rate increases are in the 30- 40% range 9,10,11,12 , but in some instances the productivity indices (PI) and actual oil production rates have been 300-400% higher than expected 30 . The ecological benefit of these increased production rates is that fewer wells have needed to be drilled to achieve the operators’ production targets. Reduction in heavy metal discharges Formate brines have only been used in few hundred of the approximately 600,000 wells drilled in the world over the past decade, but even so in this period they have probably reduced heavy metal (barium) discharges to the environment by around 50,000 tonnes. Narrow well bore drilling and completion Formate brines were originally identified as having the ideal characteristics for use as the basis of ecological drilling fluids for deep drilling and slim hole drilling13 . The perceived advantages for formate brines in these applications were: • Maintenance of solids carrying capabilities at high temperatures • Elimination of solids sag at high down hole temperatures • Minimal circulating pressure losses
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 9/16 John Downs, Hydro Formates • Low potential for differential sticking (very thin filter cakes) • Low Equivalent Circulating Densities in long/narrow boreholes • Maximum power transmission to mud motors and bits • Non-hazardous • Compatible with reservoir minerals and liquids (i.e. non-damaging) • Compatible with drilling/completion hardware and elastomers • Environmentally responsible and readily biodegradable The first recorded field use of formate brines was by NAM in the Netherlands who formulated a sodium formate brine as a coiled-tubing drilling fluid in a well side-tracking operation in the Berkel field. This, and subsequent coiled–tubing field trials in UK and Norway by Shell and Statoil with virtually solids-free potassium formate brines 14,15 , established the true advantages of the formates for narrow-bore drilling in reservoirs. In 1995, after experiencing hole problems using conventional drilling fluids, Mobil used potassium formate brine for the first time as a high temperature drilling–in fluid in a deep slimhole horizontal gas well in Northern Germany 16 . Mobil had previously obtained favourable results with potassium formate brine as a completion and workover fluid earlier in the field development campaign. Mobil reported that the use of the formate drilling-in fluid effectively “eliminated most of the previous hole problems and significantly reduced well costs” 12 . The specific benefits realised with the formate system included: • Excellent polymer stability at 310o F • Effective hole cleaning • ROP increased by 20% • No formation damage (skin factor=0) • Thin, easily removable filter cake • Good inhibition of formation clays • No corrosion • Low differential sticking potential • Low treatment costs during drilling Mobil has drilled and completed another 15 deep slim hole wells with potassium formate brine in Germany and has concluded 17 : “ Formate-based fluids have been applied as high density, temperature stable, low solids, environmentally friendly, non-damaging, non-corrosive drilling and reservoir drilling fluids. Replacing high solids drilling fluids with low-solids formate-based fluids has resulted in a dramatic increase in drilling performance and hydraulics. Since the use of formate-based fluids has been implemented, the productivity of wells has increased compared to wells drilled with the traditional fluids ”
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 10/16 John Downs, Hydro Formates Mobil have also carried out a series of frac jobs in a deep high temperature gas well using potassium formate brine. Horizontal and multilateral well drilling and completion In 1993-94 Shell and Statoil in Norway conducted the first applications of sodium and potassium formate brines as full bore reservoir drilling-in and completion fluids, confirming their non-damaging properties in the construction of a number of extremely productive open hole horizontal wells18,19 . The later application of blended sodium/potassium formate brines as drilling-in and completion fluids for open hole multilateral horizontal wells in The Netherlands would show that “the minimal residual drilling-induced damage increased production capacity 40% over that expected, with a near-zero mechanical skin” 9 . Statoil have recently demonstrated the benefits of drilling and completing a series of 6 high angle open hole reservoir sections in the HT/HP Huldra field with SG 1.90 potassium/caesium formate brine 20 . Statoil report positive effects on well control/safety (elimination of barite sag), hole cleaning, hole stability, ECD and well performance. Extended reach drilling and completing For a number of years Shell in the UK has been drilling and completing extended reach horizontal wells in the Schooner, Ketch, Barque, Galleon, Skiff, Brigantine and Inde fields using sodium/potassium formate brine blends. Horizontal reservoir sections of up to 7,000 ft have been drilled with the formate brines and then completed in the formate brines with Expandable Sand Screens 21 . Universal fluids Formate brines have powerful shale-stabilising properties 22,23,24,25,26 and can therefore be used as universal fluids to drill entire wells from top to bottom, thus avoiding the creation of additional wastes associated with using different fluids for drilling each of the various well sections. Since 1999 potassium formate brines have been used as multi-purpose shale drilling and reservoir drilling fluids in land wells in Alberta, Canada. Over 200 wells have now been drilled and the users claim that the formate anion plays an important role in stabilising the Canadian shales 27 . The most powerful demonstration of the universal capabilities of the formates was provided in 2000 when Norsk Agip drilled the intermediate 12 ¼-in and the 8 ½-in reservoir sections of their offshore Goliath and Gamma discoveries in the environmentally-sensitive Barents Sea using SG 1.3 –1.4 sodium/potassium formate brines 28 . The use of the formate brines avoided polluting the Barents Sea fishing grounds with barium
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 11/16 John Downs, Hydro Formates heavy metal, and the brines were re-cycled and re-used in consecutive wells. Agip noted that the quality of the young and highly reactive shale cuttings brought up from downhole by the formate brines was comparable to those seen when drilling with oil-based muds. 9. NON-AQUEOUS FORMATE FORMULATIONS Until convinced otherwise a section of the drilling community will continue to have reservations about contacting shales or oil reservoirs with water- based drilling and completion fluids such as the formate brines. To satisfy the requirements of these reactionary elements a number of non-aqueous drilling fluid systems based on formates are either in development or are already in field use. While clearly not meeting the same ecological specifications of straight formate brines each of these hybrid systems represents some improvement on traditional drilling and completion fluids. Novel chloride-free invert emulsions Many thousands of wells have been drilled in Canada over the past 10 years with invert oil emulsion drilling fluids containing calcium nitrate brine as the internal phase. More recently this technology has been updated and improved by using potassium formate in place of calcium nitrate as the internal brine phase. These formulations still contain oil, emulsifiers and barite but their toxicity to the local onshore environment has been diminished somewhat by the substitution of the conventional chloride brine internal phase with firstly a nitrate brine and now a formate brine. Novel high-density invert emulsions Norsk Hydro in Norway has field tested a novel completion fluid comprising an SG 1.6 solids-free invert oil emulsion fluid containing caesium formate brine as the internal brine phase and weighting agent 29,30 . The first oil wells in the Visund field completed with conventional bromide brines had Productivity Indices (PI) of just 60-70 Sm3/d/bar. After using a caesium formate invert emulsion as the alternative perforating fluid in well A-23H a greatly improved PI of 200-300 Sm3/d/bar was achieved. Very recently a further well perforated in the caesium formate invert emulsion came in with a PI of 1000 Sm3/d/bar. The production from the two wells completed in caesium formate brine will be enough to load the Visund platform production treating facility to its maximum capacity of 100,000 bbl oil/day.
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 12/16 John Downs, Hydro Formates Development work is underway on solids-free invert emulsions containing high volume ratios of caesium formate to oil that could be taken to fluid densities of up to SG 1.8. The use of caesium tungstate brine as the internal brine phase of these formulations might allow the creation of solids-free invert emulsions with fluid densities up to SG 2.0 or higher. Novel non-aqueous formate “brines” In 1997 researchers in Norsk Hydro’s laboratories in Norway discovered that potassium formate and caesium formate are highly soluble in non- aqueous polar organic fluids such glycerol and glycols. This discovery has opened up the possibility of making benign high-density water-free and hydrocarbon-free fluids for use as novel drilling and completion fluids. These fluids will place a greater burden (e.g. oxygen demand) on the environment than aqueous formate brines, but they represent an interesting improvement over traditional brines. 10. CONCLUSIONS Although the oil industry has made many incremental improvements in the environmental acceptability of drilling fluids by modifying conventional formulation technologies it seems clear that only the formate brines break the mould and meet the criteria for classification as genuine ecological drilling fluids with universal utility throughout the various stages of the well construction process. Most importantly, the formate brines enable the implementation of various mechanical engineering solutions that have been introduced to make well construction operations more ecofriendly. Eight years of rigorous field-testing of formate brines has validated their performance under the most demanding conditions and proven their worth in sensitive environments such as the Barents Sea. The future should see formate brines being adopted as the preferred ecological drilling fluids on a global basis, allowing the oil industry to significantly reduce both the volume and toxicity of its drilling wastes. Formate brines also have a bright future in downstream segment of the oil industry as “green” substitutes for glycols and methanol in gas dehydration and hydrate inhibition processes. 11. REFERENCES 1. Searls, J.P.: “Barite”, U.S. Geological Survey, Mineral Commodity Summaries, January 2001. 2. Monnin, C.: “A thermodynamic model for the solubility of barite and celestite in electrolyte solutions and seawater to 200o C and to 1 kbar”, Chemical Geology, 155 (1999) 187-209. 3. Templeton, C.C.: “Solubility of barium sulphate in sodium chloride solutions from 25o C to 95o C “, Journal of Chemical and Engineering Data, 5 (October 1960), 514-516.
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 13/16 John Downs, Hydro Formates 4. Wang, W.: “ The effect of river water on phytotoxicity of Ba, Cd and Cr”, Environmental Pollution, 11, 193-204 (1986). 5. Beisinger, K.E. and Christensen, G.M.: “Effects of various metals on the survival, growth, reproduction and metabolism of Daphnia magna”, J. Fish Res. Board Canada, 29, 1691-1700, (1972). 6. Downs, J.D.: "Formate Brines: Novel Drilling and Completion Fluids for Demanding Environments", paper SPE 25177 presented at the 1993 SPE International Symposium on Oilfield Chemistry, New Orleans, LA, 2nd -5th March,1993. 7. Downs, J.D., Killie, S., Whale, G. and Inglesfield, C.: “Development of environmentally benign formate-based drilling and completion fluids”, paper SPE 27143 presented at the 2nd International Conference on Health, Safety & Environment, Jakarta, Indonesia, 25th -27th January, 1994. 8. Howard, S.K.: "Formate Brines for Drilling and Completion: State of the Art", paper SPE 30498 presented at the 1995 SPE Annual Technical Conference & Exhibition, Dallas, USA, 22nd -25th October, 1995. 9. Hands, N., et al.: “Drill-In Fluid Reduces Formation Damage, Increases Production Rates,” Oil & Gas Journal (13 July 1998) 65. 10. Hands, N. et al.: “Optimising Inflow Performance of a Long Multi- Lateral Offshore Well in Low Permeability, Gas Bearing Sandstone: K14-FB 102 Case Study,” SPE 50394 presented at SPE International Conference of Horizontal Well Technology, Calgary, 1-4 November 1998. 11. Hands, N., Francis, P., Whittle, A. and Rajasingam, D.: “Optimising a long multi-lateral gas well’s inflow performance”, World Oil, pp. 73-79, April 1999. 12. Sundermann,R. and Bungert, D.: “Potassium-Formate-Based Fluid Solves High Temperature Drill-In Problem,” Journal of Petroleum Technology, (November 1996),104. 13. Downs, J.D.: "Formate Brines: New Solutions to Deep Slim-Hole Drilling Fluid Design Problems", paper SPE 24973 presented at the 1992 European Petroleum Conference, Cannes, France, 16th -18th November, 1992. 14. Lord, D., Brinkhorst, J., Townsley, W. and Bogaert, P.: “Shell Expro’s first application of coiled tubing drilling”, World Oil, pp. 119-124, June 1997. 15. Svendsen, O., Saasen, A., Vassoy, B., Skogen, E, Mackin. F. and Normann, S.H. : “ Optimum fluid design for drilling and cementing a well drilled with coil tubing technology”, paper SPE 50405 presented at 1998 SPE International Conference on Horizontal Well Technology, Calgary, Alberta, Canada, 1st -4th November 1998. 16. Abou-Sayed, I.S., Chambers, M.R. and Mueller, M.W.: “Mobil completes deep, tight horizontal gas well in Germany”, Petroleum Engineer International, August 1996.
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 14/16 John Downs, Hydro Formates 17. Bungert, D., Maikranz, S., Sundermann, R., Downs, J.D., Benton, W. and Dick, M.A., “The Evolution and Application of Formate Brines in High-temperature/High-Pressure Operations”, SPE 59191 presented at 2000 IADC/SPE Drilling Conference, New Orleans, Louisiana, 23-25 February 2000. 18. Brinkhorst, J.W.: “ Optimisation of drilling fluid and clean-up operations in Rogn South, Draugen field, Norway”, presented at the Horizontal Well Technology Forum, Aberdeen, 24th -25th January 1994. 19. Svendsen, O., Toften, J.K., Marshall, D.S., and Hermansson, C.L.: “Use of a novel drill-in/completion fluid based on potassium formate brine on the first open hole completion in the Gullfaks field”, paper SPE/IADC 29409 presented at the 1995 SPE/IADC Drilling Conference, Amsterdam, 28th February-2nd March, 1995. 20. Saasen, A, Jordal, O.H., Burkhead, D., Berg, P.C., Loklingholm,G., Pedersen, E.S., Turner, J. and Harris, M.J.:”Drilling HT/HP Wells Using a Cesium Formate Based Drilling Fluid”, paper SPE 74541 presented at the 2002 SPE/IADC Drilling Conference, Dallas, Texas, 26-28th February 2002. 21. John Littlehales, Mud & Environmental Engineer, Shell UK Ltd., Personal communication, May 2001. 22. Nooner, D.W.: "Stabilising underground formations containing water- sensitive clays – by treating with hot aqueous solution of organic potassium salt”, US Patent No. 4164979-A, 21st August 1979. 23. Loftin,R.E. and Son, A.J.: "Aqueous well drilling and completion fluid composition – contains ammonium or potassium salts to prevent sloughing-off of clays from well bore, and is environmentally acceptable", US Patent No. 4536297-A, 20th August 1985. 24. Van Oort, E., Hale, A.H., Mody, F.K. and Sanjit Roy: “Critical parameters in modelling the chemical aspects of borehole stability in shales and in designing improved water-based shale drilling fluids”, paper SPE 28309 presented at the SPE 69th Annual Technical Conference and Exhibition, New Orleans, LA, USA, 25th -28th September 1994. 25. Van Oort, E., Hale, A.H., Mody, F.K. and Sanjit Roy: “Transport in shales and the design of improved water-based shale drilling fluids”, SPE Driling and Completion, pp. 137-146, September 1996. 26. Van Oort, E., “Physico-Chemical Stabilisation of Shales”, paper SPE 37263 presented at the 1997 SPE International Symposium on Oilfield Chemistry, Houston, Texas, 18th -21st February 1997. 27. Hallman, J.H., SPE, Mackey, R., Schwartz, K.:” Enhanced Shale Stabilization With Very Low Concentration Potassium Formate/Polymer Additives”, paper SPE 73731 presented at the SPE International Symposium and Exhibition on Formation Damage Control held in Lafayette, Louisiana, 20–21 February 2002.
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 15/16 John Downs, Hydro Formates 28. Zuvo, M., Asko, A.: “Sodium/potassium formate brine used as drilling fluid in sensitive Barents Sea wells”, Offshore Magazine, August 2001, 64-66 and 181. 29. Jiang, P., Taugbol, K., Mathisen, A.M., Alteras, E.: “New Low-Solids OBM Demonstrates Improved Returns as Perforating Kill Pill”, paper SPE 73709 presented at the SPE International Symposium and Exhibition on Formation Damage Control held in Lafayette, Louisiana, 20–21 February 2002. 30. Mathisen, A.M.:” Development and Application of Low Solid Oil-Based Perforation Fluids to Maximise Well Productivity”, paper presented to IQPC Drilling and Completion Fluids Conference held in Ardoe House Hotel, Aberdeen, 20-21 March 2002. Table 1 – Ecological solutions in well construction operations Objective Solution Reduction in well numbers Reduction in formation damage Horizontal wells Reduction in surface footprint Extended reach wells Multilateral wells Coiled-tubing drilling Reduction of waste volume Slim holes Improved solids control Elimination of solid weighting agents
    • IBC Asia Conference 25-26 th June 2002 Offshore/Upstream Asia-Pacific 2002 Latest Advances in the Development of Ecological Drilling Fluids 16/16 John Downs, Hydro Formates Universal drilling/completion fluid Cuttings re-injection Reduction of waste toxicity Benign drilling fluids Table 2 – Toxicity of Formates to Aquatic and Marine Organisms Species Test type Sodium formate (ppm) Potassium formate (ppm) Caesium formate (ppm) Zinc bromide (ppm) Scophthalmus maximus LC50 96 hours 6,100 1,700 260 8 Acartia tonsa EC50 48 hours 3,900 300 340 2 Skeletonema costatum EC50 72 hours 1,600 3,400 1,000 0.3 Oncorhynchus mykiss LC50 96 hours 10,000 3,500 2,100 1 Daphnia magna LC50 48 hours 1,000 540 350 6 Mysidopsis bahia LC50 96 hours 7,130 522 307 1.5