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GB2448683A - Drilling fluid including potassium sulphate and/or carbonate - Google Patents

Drilling fluid including potassium sulphate and/or carbonate Download PDF

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Publication number
GB2448683A
GB2448683A GB0706415A GB0706415A GB2448683A GB 2448683 A GB2448683 A GB 2448683A GB 0706415 A GB0706415 A GB 0706415A GB 0706415 A GB0706415 A GB 0706415A GB 2448683 A GB2448683 A GB 2448683A
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United Kingdom
Prior art keywords
ions
drilling fluid
cuttings
drilling
sulphate
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Application number
GB0706415A
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GB0706415D0 (en
Inventor
Simon Wait
Robert Preston Schlemmer
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KMC OILTOOLS BV
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KMC OILTOOLS BV
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Priority to GB0706415A priority Critical patent/GB2448683A/en
Publication of GB0706415D0 publication Critical patent/GB0706415D0/en
Publication of GB2448683A publication Critical patent/GB2448683A/en
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/04—Aqueous well-drilling compositions
    • C09K8/06—Clay-free compositions
    • C09K8/08—Clay-free compositions containing natural organic compounds, e.g. polysaccharides, or derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/03—Specific additives for general use in well-drilling compositions
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05C—NITROGENOUS FERTILISERS
    • C05C5/00—Fertilisers containing other nitrates
    • C05C5/02—Fertilisers containing other nitrates containing sodium or potassium nitrate
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05C—NITROGENOUS FERTILISERS
    • C05C5/00—Fertilisers containing other nitrates
    • C05C5/04—Fertilisers containing other nitrates containing calcium nitrate
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
    • C05F7/00—Fertilisers from waste water, sewage sludge, sea slime, ooze or similar masses
    • C—CHEMISTRY; METALLURGY
    • C05—FERTILISERS; MANUFACTURE THEREOF
    • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
    • C05F7/00—Fertilisers from waste water, sewage sludge, sea slime, ooze or similar masses
    • C05F7/005—Waste water from industrial processing material neither of agricultural nor of animal origin
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/03—Specific additives for general use in well-drilling compositions
    • C09K8/032—Inorganic additives
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/04—Aqueous well-drilling compositions
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/04—Aqueous well-drilling compositions
    • C09K8/05—Aqueous well-drilling compositions containing inorganic compounds only, e.g. mixtures of clay and salt
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/04—Aqueous well-drilling compositions
    • C09K8/06—Clay-free compositions
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/04—Aqueous well-drilling compositions
    • C09K8/06—Clay-free compositions
    • C09K8/08—Clay-free compositions containing natural organic compounds, e.g. polysaccharides, or derivatives thereof
    • C09K8/10—Cellulose or derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/04—Aqueous well-drilling compositions
    • C09K8/06—Clay-free compositions
    • C09K8/12—Clay-free compositions containing synthetic organic macromolecular compounds or their precursors
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/32—Non-aqueous well-drilling compositions, e.g. oil-based
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/32—Non-aqueous well-drilling compositions, e.g. oil-based
    • C09K8/36—Water-in-oil emulsions
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E21B21/06—Arrangements for treating drilling fluids outside the borehole
    • E21B21/063—Arrangements for treating drilling fluids outside the borehole by separating components
    • E21B21/065—Separating solids from drilling fluids
    • E21B21/066—Separating solids from drilling fluids with further treatment of the solids, e.g. for disposal
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E21B21/06—Arrangements for treating drilling fluids outside the borehole
    • E21B21/068—Arrangements for treating drilling fluids outside the borehole using chemical treatment
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/34—Arrangements for separating materials produced by the well
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
    • Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
    • Y02A40/20—Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Processing Of Solid Wastes (AREA)

Abstract

The present invention relates to the drilling of well bores and the disposal of cuttings and spoils from the drilling operation. There is provided a method of modifying water-based and oil-based well bore drilling fluids comprising sodium ions and corresponding halide ions, e.g. chloride ions, the method comprising replacing the sodium ions with potassium ions and replacing the halide ions with sulphate and/or carbonate ions. A method of treating drill cuttings is also provided which typically involves adding to the cuttings calcium nitrate or ammonium nitrate so as to precipitate calcium sulphate and/or calcium carbonate from solution, leaving cuttings that are rich in nitrate and potassium and which may be used as a fertilizer or otherwise disposed of without environmental damage.

Description

1 2448683 Modified drilling fluid and method of treating drilling
cuttings The present invention relates to the field of well bore drilling for access to subterranean stores of resources such as petroleum oil and natural gas. In particular, the present invention concerns a well bore drilling fluid, a method of drilling using the fluid and drill cuttings obtained by the method. The present invention involves the use of a water-based and oil based drilling fluid.
Oil based (oleaginous) drilling fluids are well known in the art and are used, essentially, to lubricate well bores during drilling, and to provide a carrier for the removal of drilling spoil or drill cuttings back to the surface during drilling. The drill fluid contaminates and makes up a significant portion of the drill cuttings carried to the surface. Such cuttings are considered to be an environmentally harmful waste product, which may be contaminated with oil and chemicals added to the drilling fluid so as to optimize drilling performance in the particular location.
The treatment and disposal of drilling wastes produced both onshore and offshore presents many challenges. In particular, the treatment of wastes onshore raises issues (i) relating to the current lack of recycling options, and (ii) the potential long term liability associated with disposal.
Where possible, the preference is to provide a system whereby the drilling fluid is tailor made to minimise the onshore disposal issues relating to the drilling waste generated. Drill cuttings in particular present large volumes of wastes which are typically treated and disposed of onshore into licensed disposal sites.
Contaminants on drill cuttings normally arise from the drilling fluid associated with them, rather than the rock itself. A number of contaminants and properties associated with drilling fluids are of particular concern including: * Hydrocarbons -which have hazardous properties * Organic surfactants * Chlorides and sodium cations -which may leach into the environment * Alkalinity -potentially corrosive * Heavy metals -environmental poisons In recent years work has been conducted to make drill cuttings more environmentally friendly in response to regulatory conditions. On the one hand efforts have been made to provide treatments of oil-containing based drill cuttings which render them less toxic and suitable for disposal or use as topsoil. On the other hand attempts have been made to use less toxic drilling fluids such as water-based silicate fluids. Specific examples of relevant disclosures are discussed below.
US-A-6,838,082 (Growcock) discloses a biodegradable oil-based well bore fluid.
The oil part includes a C(1 1-18) paraffin which is emulsified. The waste may be mixed with a filler such as sawdust to provide a vermiculture composition. In preferred embodiments the use of halide salts is said to be avoided. US 2005/0090405 (Growcock) is a related document and has claims directed to a drilling fluid rather than the compost. This document also has method claims directed to a method of treating drill cuttings to provide a remediated soil. The fluid is free of halogen ions and has instead salts of biodegradable anions.
WO 2005/0082553 (Adams) discloses a chemical -biological stabilization process for repairing soils and cuttings contaminated with oils and petroleum derivatives.
Calcium oxides and organic conditioners are applied to dilute the total petroleum hydrocarbon concentration to a non toxic level.
US 6711830 (Gary Hensley et al) discloses a drill cuttings treatment system. This provides a method for treating cuttings containing oil-based drilling fluid. A non-toxic additive is used to reduce oil content to less than 1%. The mixture additive and cuttings mixture is disposed of in the immediate vicinity of the well.
US 7059805 (Addison) discloses a method for the environmental pacification of drill cuttings. Oil or water based drill cuttings are treated by adding limestone coke ash. This entraps the wet drilling fluid by binding to the ash. The resulting material may be used as a road base.
WO 2006/032931 (Strong et al) discloses a method for remediating drill cuttings which involves heat treating the cuttings to produce solids and a by-product oilIwater liquid stream. A weir tank is used to separate remaining solids from the liquid stream.
WO 03/072903 (Cordova) discloses a drill cutting treatment method for safe disposal of oil-contaminated clay cuttings obtained from an oil-based drilling fluid. Oil is removed by sulphuric acid treatment and alkaline (lime) treatment to leave a soil which may be safely disposed of.
WO 2004/013455 (Killham et al) discloses a method for the decontamination of drill cuttings and other waste material. A steam generator is used to drive off oil from the cuttings. The ratio of C:N:P is monitored to ensure that the cuttings are compatible with micro-organisms added to the cuttings. Activated carbon and desalination stages may also be included.
US 2001/0039887 (Reddoch) discloses a drilling fluid recovery and cuttings processing system. This system uses a cuttings press to remove drilling fluid for re-use and a dryer to dry the pressed cuttings. Lime and fly ash may be added to the solids before disposal of the spoil in the environment.
US-A-5,725,771 (Aliphat et al) discloses a process for enzyme pre-treatment of drill cuttings. A lipase is used to hydrolyse synthetic (ester based) drilling mud.
This pre-treatment helps render the cuttings suitable for disposal into the sea (or elsewhere).
Both water-based mud (WBM) and invert emulsion oil-based (OBM) drilling fluids can be used for the drilling of a well. The primary function of any drilling fluid is to control formation pressure, transport cuttings and maintain a stable well bore.
WBMs typically contain components such as sodium and chloride ions depending on the specific type of drilling fluid and its formulation. Both sodium and chloride ions can be detrimental to soils, plant growth and aquifers in the high concentration often found in these drilling fluids, and therefore cause environmental problems for the disposal of drilling fluids by, for example, landfill, dumping or use as topsoil.
Conmion inhibitive water based muds such as KCI polymer, KCJ polymer glycol, and silicate mud systems contain elevated concentrations of chlorides. In the case of the silicate mud systems, pH is commonly controlled using sodium hydroxide and so high levels of sodium, as well as chloride from KCI are encountered.
According to one aspect of the present invention there is provided a method of modifying a well bore drilling fluid composition comprising sodium ions and corresponding halide ions, the method comprising replacing the sodium ions with potassium ions and replacing the halide ions with sulphate and/or carbonate ions.
The halide ions may be chloride ions. The drilling fluid may be a water-based drilling fluid or an oil-based drilling fluid.
According to another aspect of the invention, there is provided a drilling fluid obtainable by the method hereinbefore described.
According to yet another aspect of the invention there is provided a well bore drilling fluid comprising a water activity controlling agent comprising potassium ions and sulphate and/or carbonate ions. Preferably the drilling fluid is free of sodium and chloride ions.
According to a further aspect of the invention, there is provided a method of well bore drilling comprising: (i) providing a drilling fluid as hereinbefore described, (ii) using the drilling fluid in the drilling of a well bore, (iii) collecting the drill cuttings (iv) treating the drill cutting by adding at least one agent which reacts with the carbonate and/or sulphate ions to form a solid precipitate thereof, thereby to remove the carbonate and/or sulphate ions from solution.
The treating agent preferably comprises a nitrate. The agent is preferably may be selected from calcium nitrate or calcium ammonium nitrate, or agents which provide free nitrate and calcium ions when added.
In one embodiment, the drilling fluid is an oil-based fluid and before the treatment step (iv) the cuttings are thermally treated to form solids having a hydrocarbon content of less that 1%. In this case the solids are may be treated at step (iv) by mixing in a liquid comprising calcium nitrate or ammonium nitrate. The treated cuttings may be used as a top-soil or top soil fertilizer. Thus according to another aspect of the invention there is provided a fertilizer comprising treated drill cuttings obtainable by a method according to the foregoing treatment method.
The present inventor has realised that an environmentally friendly disposal of drilling fluids maybe achieved by modifying the drilling fluid composition.
Specifically, that for all WBM systems, the sources of sodium and chloride can be replaced with potassium and sulphate or carbonate respectively. The removal of the sodium and chloride sources in the WBMs reduces the risk of contamination the soil and aquifers. Furthermore it facilitates the remediation of the drill cuttings produced during drilling. The cuttings are a mixture of the rock dnlled through, covered in the drilling fluid.
In one preferred aspect of the invention calcium nitrate and/or calcium ammonium nitrate are added to the drilling fluid. The addition of calcium nitrate precipitates out the sulphate as the low solubility calcium sulphate, or the carbonates as the very low solubility calcium carbonate. Thus leachable elements remaining in the fluid cuttings are potassium and nitrate, common constituents of a fertiliser. Thus WBMs may be modified so as to provide drilling cuttings which may be used as fertilizers in agriculture, and which may readily be disposed of as top soils without fear of environmental damage from sodium or potassium ions.
Oil based drilling fluid (OBM) is typically an emulsion of oil and saline water, where the oil is the Continuous phase. The saline phase is present (i) as part of the overall system to provide the rheological properties as an emulsion and (ii) to provide activity control.
The saline phase is commonly a solution of calcium chloride in water. The concentration of the calcium chloride is from very low levels up to 30 %. In some cases a sodium salt can be used in the saline phase, for example sodium bromide.
According to a particular aspect of the invention, there is provided a method of modifying OBMs in which any sodium and/or chloride ion are replaced with potassium, typically in the form of potassium sulphate or potassium carbonate.
In the case of OBM cuttings, further treatment is often completed prior to final disposal to reduce the impact to the environment of the oil on the cuttings, which typically varies between 4 to 25% by weight. Details of the treatment are set out below.
Following is a description by way of example only of methods of putting the present invention into effect.
Drilling fluid composition The table below shows a typical range of prior art formulations for a KCI polymer drilling fluid. The actual concentrations of products vary depending on the particular drill requirements, which may depend upon the underlying geology at the bore site.
KCIJ Polymer Product Purpose Concentration _____________ Range in lb/bbl KCI (lblbbl) Water Activity 1 -98 ___________________ Control Alkalinity Caustic Soda o.i -0.75 ____________________ control Xanthan Gum Viscosity 0.5 -20 Filtration Pregelatinised starch 2 -8 ___________________ Control Filtration Polyanionic Cellulose Control and I -4 ________________________ Viscosifjer _________________ Partially Hydrolysed Shale 1 -3 Polyacrylamide Encapsulator ________________ Weighting Barite 0-110 ______________________ Agent ________________ In this invention example, the KCI is replaced by K2S04 to give a new formulation in accordance with the present invention: K2SOd Polymer Product Purpose Concentration ______________ Range in lb/bbl K2S04 (lbfbbl) Water Activity 1 -37.8 Control Alkalinity Caustic Soda o.i -0.75 ______________________ control Xanthan Gum Viscosity 0.5 -20 Filtration Pregelatinised starch 2 -8 ____________________ Control Filtration Polyanionic Cellulose Control and 1 -4 _____________________ Viscosi tier Partially Hydrolysed Shale 1 -3 Polyacrylamide Encapsulator _______________ Barite Weighting 0-110 ____________________ Agent _______________ Thus, in the new formulation is that the potassium chloride has been replaced by potassium sulphate. This then allows for ease of treatment of the drill cuttings by calcium nitrate to provide an environmentally friendly material which may serve as a fertilizer. The treatment of drill cuttings is described in the following section
of this description.
Treatment of water based muds Drill cuttings from a well bore are processed using conventional separation apparatus such as shale shakers and centrifuges. The cuttings are collected and processed either at the rig site, or moved to a centrally located site for processing.
At the rig site the cuttings are typically collected in suitable reservoirs such as, waste pits (either lined or unlined), corrals (steel or concrete pits), or simply laid to rest on the ground (not preferable) for processing later.
In some cases the drill cuttings are processed continuously (online) so that as they are produced from the centrifuge and shale shaker, they are transported either directly (by auger, vacuum or pneumatic handling system), or via a temporary coral (steel or concrete and moved by excavator / bob cat, shovel etc) into the processing plant as they are produced.
The processing plant is typically a mixer where the drill cuttings are mixed with calcium nitrate solution and other chemical additives as deemed fit to provide the desired properties. The other chemical additives might be acid or alkali agents to change the pH, or nutrients required by plants, for example phosphorus and magnesium. The additives will generally be in aqueous form and stored in liquid storage tanks.
The mixer can be of various types including a cement mixer (truck or small unit), a pug mill, ploughshare mixer, or auger. The essential action is to mix the cuttings and additives together to allow the reaction to take place between the sulphate / carbonate in the cuttings derived fluid and the added calcium.
The addition of the calcium nitrate precipitates out sulphate as the low solubility calcium sulphate, or carbonates as the very low solubility calcium carbonate, leaving behind the leachable elements potassium and nitrate, common constituents of a fertiliser.
The reaction between the constituents is very fast but requires mixing to bring the two components together. A typical mixing system can process between 2 and 30 MT of drilling cuttings and centrifuge waste per hour. The temperature of mixing is not especially limited, provided the liquid components do not cool to a point where the salts precipitate out or freeze.
The processed cuttings are then suitable for reuse as a fertiliser soil amendment material to improve the quality of some types of soils.
In the drilling fluid described above, the actual concentration of potassium sulphate might be 15 lbs / barrel. The reaction between potassium sulphate and calcium nitrate can be described as: K2S04 + Ca(N03) -2KN03 + CaSO4 (precipitate) Therefore one mole of potassium nitrate can be reacted with one mole of calcium nitrate to produce potassium nitrate and a precipitate of calcium sulphate (a fairly insoluble compound). Thus, for a pile of drill cuttings containing a total quantity of 1000 kg of potassium sulphate to stoichiometrically react the potassium sulphate would require the addition of 942 kg of calcium nitrate.
Treatment of oil based muds The above process can also apply to the treatment of oil based mud and cuttings in a similar way. However, when treating the cuttings off the shaker and centrifuge, the mixing with calcium nitrate and other additives produces a waste which is rich in potassium and nitrate, but which also contains oil (hydrocarbon) at levels between 3% and 25% by weight.
In this case the presence of potassium nitrate in the treated spoil makes the final treatment by bioremediation more easily achievable. The lack of sodium and chloride in OBM cutting and the presence of potassium and nitrate have a positive impact on the speed of bioremediation. Typical bioremediation might be composting, land farming, land spreading or other methods where bacteria and fungi are grown to metabolise the hydrocarbon and turn them into carbon dioxide and water.
In an alternative method of the invention, the untreated OBM drill cuttings may first be transported to a thermal plant, either direct or indirect fired. Here the solids exiting the thermal plant typically now contain less than 1% hydrocarbon and sometimes less than 0.1% hydrocarbon. These pre-treated low hydrocarbon solids can now be treated in a mixing plant by the addition of calcium nitrate and other amendments, as described above, for possible recycling as a potassium and nitrate rich soil amendment.

Claims (14)

  1. Claims 1. A method of modifying a well bore drilling fluid composition
    comprising sodium ions and corresponding halide ions, the method comprising replacing the sodium ions with potassium ions and replacing the halide ions with sulphate and/or carbonate ions.
  2. 2. A method as claimed in claim 1 wherein the halide ions are chloride ions.
  3. 3. A method as claimed in claim 1 or claim 2 wherein the drilling fluid is a water-based drilling fluid.
  4. 4. A method as claimed in claim 1 or claim 2 wherein the drilling fluid is an oil-based drilling fluid.
  5. 5. A drilling fluid obtainable by the method of any of claims 1 to 4.
  6. 6. A well bore drilling fluid comprising a water activity controlling agent comprising potassium and sulphate and/or carbonate ions.
  7. 7. A well bore drilling fluid as claimed in claim 6 which is free of sodium and chloride ions.
  8. 8. A method of well bore drilling comprising: (i) providing a drilling fluid according to any of claims 5 to 7, (ii) using the drilling fluid in the drilling of a well bore, (iii) collecting the drill cuttings (iv) treating the drill cutting by adding at least one agent which reacts with the carbonate and/or sulphate ions to form a solid precipitate thereof, thereby to remove the carbonate and/or sulphate ions from solution.
  9. 9. A method as claimed in claim 8 wherein the agent comprises a nitrate.
  10. 10. A method as claimed in claim 8 or claim 9 wherein the agent is selected from calcium nitrate or calcium ammonium nitrate.
  11. 11. A method as claimed in any of claims 8 to 10 wherein the drilling fluid is an oil-based fluid and before the treatment step (iv) the cuttings are thermally treated to form solids having a hydrocarbon content of less that 1%.
  12. 12. A method as claimed in claim 11 wherein the solids are treated at step (iv) by mixing in a liquid comprising calcium nitrate or ammonium nitrate.
  13. 13. A method as claimed in any of claims 8 to 12, further comprising using the treated cuttings as a top-soil or top soil fertilizer.
  14. 14. A fertilizer comprising treated drill cuttings obtainable by a method according to any of claims 8 to 13.
GB0706415A 2007-04-02 2007-04-02 Drilling fluid including potassium sulphate and/or carbonate Withdrawn GB2448683A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010151729A1 (en) * 2009-06-25 2010-12-29 Ditommaso Frank A Method of making pure salt from frac-water/wastewater
US20130067762A1 (en) * 2006-10-04 2013-03-21 Varco I/P, Inc. Reclamation of components of wellbore cuttings material
CN104497996A (en) * 2014-11-27 2015-04-08 中国石油集团川庆钻探工程有限公司工程技术研究院 Calcium nitrate environment-friendly drilling fluid and preparation method
US9073104B2 (en) 2008-08-14 2015-07-07 National Oilwell Varco, L.P. Drill cuttings treatment systems
US10556196B2 (en) 2013-03-08 2020-02-11 National Oilwell Varco, L.P. Vector maximizing screen

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113079732A (en) * 2021-04-08 2021-07-09 安徽师范大学皖江学院 Method for improving greenish saline soil by using shale gas field water-based drilling cuttings and application of method

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GB2153411A (en) * 1984-01-25 1985-08-21 Agip Spa Aqueous drilling fluid
US4895665A (en) * 1989-04-26 1990-01-23 George D. Smith Method for treating and reclaiming oil and gas well working fluids and drilling pits
EP0668339A1 (en) * 1994-02-18 1995-08-23 Baker Hughes Incorporated Drilling fluid additive for watersensitive shales and clays, and method of drilling using the same
US5814230A (en) * 1996-08-30 1998-09-29 Willis; H. Craig Apparatus and method for separation of solids from liquid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2153411A (en) * 1984-01-25 1985-08-21 Agip Spa Aqueous drilling fluid
US4895665A (en) * 1989-04-26 1990-01-23 George D. Smith Method for treating and reclaiming oil and gas well working fluids and drilling pits
EP0668339A1 (en) * 1994-02-18 1995-08-23 Baker Hughes Incorporated Drilling fluid additive for watersensitive shales and clays, and method of drilling using the same
US5814230A (en) * 1996-08-30 1998-09-29 Willis; H. Craig Apparatus and method for separation of solids from liquid

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130067762A1 (en) * 2006-10-04 2013-03-21 Varco I/P, Inc. Reclamation of components of wellbore cuttings material
US8533974B2 (en) * 2006-10-04 2013-09-17 Varco I/P, Inc. Reclamation of components of wellbore cuttings material
US9073104B2 (en) 2008-08-14 2015-07-07 National Oilwell Varco, L.P. Drill cuttings treatment systems
WO2010151729A1 (en) * 2009-06-25 2010-12-29 Ditommaso Frank A Method of making pure salt from frac-water/wastewater
US8158097B2 (en) 2009-06-25 2012-04-17 Fracpure Holdings Llc Method of making pure salt from FRAC-water/wastewater
US8273320B2 (en) 2009-06-25 2012-09-25 Fracpure Holdings Llc Method of making pure salt from frac-water/wastewater
US8529155B2 (en) 2009-06-25 2013-09-10 Fracpure Holdings Llc Method of making pure salt from frac-water/wastewater
US10556196B2 (en) 2013-03-08 2020-02-11 National Oilwell Varco, L.P. Vector maximizing screen
CN104497996A (en) * 2014-11-27 2015-04-08 中国石油集团川庆钻探工程有限公司工程技术研究院 Calcium nitrate environment-friendly drilling fluid and preparation method
CN104497996B (en) * 2014-11-27 2017-04-19 中国石油集团川庆钻探工程有限公司工程技术研究院 Calcium nitrate environment-friendly drilling fluid and preparation method

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