Classifications

• • 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
  • C09K8/34—Organic liquids
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/20—Silicates
  • C01B33/36—Silicates having base-exchange properties but not having molecular sieve properties
  • C01B33/38—Layered base-exchange silicates, e.g. clays, micas or alkali metal silicates of kenyaite or magadiite type
  • C01B33/44—Products obtained from layered base-exchange silicates by ion-exchange with organic compounds such as ammonium, phosphonium or sulfonium compounds or by intercalation of organic compounds, e.g. organoclay material
• • 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
  • C09K8/14—Clay-containing compositions
  • C09K8/145—Clay-containing compositions characterised by the composition of the clay
• • 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
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S507/00—Earth boring, well treating, and oil field chemistry
  • Y10S507/905—Nontoxic composition
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S507/00—Earth boring, well treating, and oil field chemistry
  • Y10S507/91—Earth boring fluid devoid of discrete aqueous phase

Definitions

• Natural resources such as oil or gas residing in a subterranean formation can be recovered by drilling wells that penetrate the formation.
• a wellbore is typically drilled down to the formation while circulating a drilling fluid (also known as a drilling mud) through the wellbore.
• a drilling fluid also known as a drilling mud
• the drilling fluid carries the drill cuttings in a return flow stream back to the well drilling platform.
• a string of pipe e.g., casing
• the drilling fluid is then usually circulated downwardly through the interior of the pipe and upwardly through the annulus, which is located between the exterior of the pipe and the walls of the well bore.
• Primary cementing is then usually performed whereby a cement slurry is pumped down through the string of pipe and into the annulus between the string of pipe and the walls of the wellbore to allow the cement slurry to set into an impermeable cement column and thereby seal the annulus.
• Subsequent secondary cementing operations i.e., cementing operations occurring after the primary cementing operation, may also be performed.
• Organophilic clays are commonly used in oil-based drilling fluids to increase viscosity and provide for the suspension of particles, such as drill cuttings and weighting agents, therein.
• Organophilic clays are generally prepared by reacting a hydrophilic clay with an organic cation, usually a quaternary ammonium salt compound produced from a fatty nitrile.
• hydrophilic clays that may be used include bentonite and hectorite. Native clay surfaces have negatively charged sites and cationic counter-ions such as sodium and calcium cations. Thus, the clay may be treated with a cationic surfactant to displace the cations that are naturally present at the clay surfaces. The cationic surfactant is thought to become held tightly to the surfaces through electrostatic charges.
• bentonite that primarily contains sodium cations is known as sodium bentonite. Those monovalent sodium cations may be easily displaced from the clay, making a large number of anionic sites available.
• quaternary ammonium compounds are commonly used as the cationic surfactants in preparing the organophilic clays.
• Quaternary ammonium compounds contain ammonium compounds in which one or more of the hydrogen atoms attached to the nitrogen are substituted by organic radicals.
• One of the most popular quaternary ammonium compounds of the organophilic clay industry is dimethyl dihydrogenated tallow ammonium chloride (M 2 HT 2 N + Cl " ).
• M 2 HT 2 N + Cl " dimethyl dihydrogenated tallow ammonium chloride
• the oil-solubility of this compound is enhanced by its almost complete hydrocarbon structure and its two long-chain alkyl groups. Further, its two methyl groups do not sterically interfere with close packing of the ammonium cation to the clay surface.
• the dimethyl dihydrogenated tallow ammonium chloride surfactant cannot be efficiently activated at relatively low temperatures.
• Improved cationic surfactants have been developed in which the ammonium compounds have greater numbers of alkyl groups.
• One such surfactant includes a benzyl group that greatly enhances the performance of organophilic clays at cold temperatures near 45 0 F.
• the present invention provides a method of treating a well bore, comprising: providing a drilling fluid comprising a nonaqueous phase and an organophilic clay treated with a composition comprising a quaternary ammonium surfactant having at least two amide linkages; and placing at least a portion of the drilling fluid into the well bore.
• the present invention provides a method of preparing a drilling fluid, comprising: combining an organophilic clay with a quaternary ammonium surfactant having at least one amide linkage to form a mixture, and combining the mixture with a fluid comprising a nonaqueous phase to form a drilling fluid.
• the present invention provides a method of treating a well bore, comprising: providing a drilling fluid comprising a nonaqueous phase and a fluid loss control additive comprising a lignite treated with a quaternary ammonium surfactant having at least one amide linkage, and placing the drilling fluid at least partially into the well bore.
• Drilling fluids may include an organophilic clay that has been treated with a quaternary ammonium surfactant having at least one amide linkage.
• This type of cationic surfactant is substantially biodegradable, meaning that it is capable of being decomposed by natural biological processes. In particular, it undergoes aerobic biodegradation, which is the breakdown of organic chemicals by microorganisms when oxygen is present, hi this process, aerobic bacteria use oxygen as an electron acceptor and break down organic chemicals into smaller organic compounds, often producing carbon dioxide and water as the final product. Therefore, organophilic clays treated with the biodegradable cationic surfactant may be used in drilling fluids for drilling a wellbore without being concerned that the surfactant could accumulate in the environment.
• the surfactant usually never reaches toxic levels that could harm the surrounding environment and the life supported by that environment.
• a biodegradable surfactant benefit the environment, it also alleviates the need to expend energy to clean-up non-biodegradable clays and thus prevent them from contaminating the environment.
• amide linkage is defined to mean a chemical group comprising hydrocarbon chains both between the quaternary nitrogen atom and the amide group and between the amide group and the end of the functional group containing the amide group (i.e., the amide group forms a linkage between the two hydrocarbon chains).
• amide linkages is defined to mean two or more such chemical groups.
• the drilling fluids typically comprise an oil-based fluid such as diesel oil, mineral oil, invert emulsions containing water droplets dispersed in oil, synthetic olefins, esters, or combinations thereof.
• the water contained in such invert emulsions may comprise fresh water or salt water such as brine or sea water.
• An example of a suitable brine is calcium chloride brine.
• the oil-to-water volumetric ratio in the invert emulsions may be in a range of from about 95:5 to about 50:50, or alternatively from about 90:10 to about 70:30.
• organophilic clay also known as organoclay
• raw materials used in organophilic clay (also known as organoclay) manufacturing include but are not limited to bentonite such as sodium bentonite, attapulgite, hectorite, and combinations thereof.
• the amount of organophilic clay in the drilling fluid may be in a range of from about 2 pounds/barrel (lbs/bbl) to about 20 lbs/bbl.
• any quaternary ammonium surfactant having at least one amide linkage that is suitable for displacing the cations of the organophilic clay may be employed to treat the clay.
• the amount of surfactant relative to the clay may vary depending on the type of clay being used and the methods of processing.
• a weight ratio of the quaternary ammonium surfactant to organophilic clay e.g., sodium bentonite
• quaternary ammonium surfactants for treating the organophilic clays may be generally represented by the following formula:
• M " is an anion; R 1 is an alkyl group; R 2 , R 3 , and R 4 are the same or different alkyl groups, and x is greater than or equal to 1.
• M " is a chloride, methyl sulfate, bromide, acetate, or iodide ion
• R 1 is a saturated hydrocarbon having 10 or more carbon atoms
• R 2 , R 3 , and R 4 are methyl groups, ethyl groups, benzyl groups, or combinations thereof.
• R 2 , R3, or R 4 is a benzyl group, the biodegradability of the surfactant is somewhat reduced but still significant while the performance of the organophilic clay increases dramatically.
• quaternary ammonium surfactants include compounds generally represented by the following formula:
• R is an alkyl group and X " is an anion.
• R is a saturated alkyl group comprising at least 10 carbon atoms and X " is a chloride, iodide, bromide, acetate, or methyl sulfate ion.
• X " is a chloride, iodide, bromide, acetate, or methyl sulfate ion.
• such compounds contain a stearic alkyl group connected through the amide linkage and two methyl groups and a benzyl group on the ammonium ion.
• a quaternary ammonium surfactant of this type and having a C 18 saturated alkyl group substituted for R and a chloride ion substituted for X " is commercially available from the Stepan Co. under the tradename of AMMONYX SDBC surfactant. Examples of additional quaternary ammonium surfactants may be generally represented by the following formula:
• R is an alkyl group and X ' is an anion.
• R is a saturated alkyl group comprising at least 10 carbon atoms and X " is a chloride, iodide, bromide, acetate, or methyl sulfate ion.
• a quaternary ammonium surfactant of this type and having a C 18 saturated alkyl group substituted for R and a chloride ion substituted for X " is commercially available from the Stepan Co. under the tradename of AGENT X2506-13 surfactant.
• quaternary ammonium surfactants for treating the organophilic clays may comprise at least two amide linkages. Examples of such quaternary ammonium surfactants include, but are not limited to, those represented by the following general formula:
• M ' is an anion
• R 1 is an alkyl group
• R 2 , R 3 , and R 4 are the same or different alkyl groups
• x and y are greater than or equal to 1.
• M " is a chloride, methyl sulfate, bromide, acetate, or iodide ion
• R 1 is a saturated hydrocarbon having 10 or more carbon atoms
• R 2 , R 3 , and R 4 are methyl groups, ethyl groups, butyl, dodecyl, octadecyl, benzyl groups, alkoxyl, ethoxyl groups, propoxyl groups, or combinations thereof.
• R 2 , R 3 , or R 4 When one of R 2 , R 3 , or R 4 is a benzyl group, the biodegradability of the surfactant is somewhat reduced but still significant while the performance of the organophilic clay increases dramatically.
• R 2 , R 3 , and R 4 may comprise alkoxyl groups.
• An example of such a surfactant is available from Stepan Co. under the trade name ACCOSOFT 440-75, which has the following general formula:
• R 1 is an alkyl group and R 2 is the same or different alkyl group.
• the drilling fluids may further include additional additives as deemed appropriate by one skilled in the art.
• additional additives include but are not limited to an emulsifier, a filtration control agent, a weighting agent, calcium hydroxide (i.e., lime), or combinations thereof.
• all of the components in the drilling fluid may be environmentally safe to allow them to be used in environmentally sensitive regions.
• all of the surfactants contained in the drilling fluid are typically biodegradable, including the emulsifiers.
• the drillings fluids may further comprise a fluid loss control additive.
• the drilling fluids may further comprise a fluid loss control additive comprising a lignite treated with a quaternary ammonium surfactant having at least one amide linkage.
• the drilling fluids described above may be prepared by combining the organophilic clay, which has been pre-treated with a quaternary ammonium surfactant, with the other components, such as the oil-based fluid, using techniques known in the art.
• the drilling fluids may be prepared at an off-site location away from the wellbore drilling site. In this case, they are shipped to the wellbore drilling site where they may be used immediately or stored until their use is desired.
• a surfactant-treated organophilic clay may be separately stored at an on-site location near the wellbore drilling site, allowing it to be added to a drilling fluid as needed.
• the presence of the organophilic clay in a drilling fluid increases its viscosity such that it is pumpable and less likely to be lost to a subterranean formation as it is circulated through a wellbore that penetrates the formation.
• the clay also improves the ability of the drilling fluid to suspend solids such as drill cuttings and weighting agents therein.
• the performance of the clay in the drilling fluid may vary depending on the system in which it is placed, i.e., the types of the other components in the fluid, such as the surfactants.
• the clay may be treated with a quaternary ammonium surfactant having at least one amide linkage by first placing the clay in water to hydrate the clay. The resulting slurry may then be filtered through a sieve to remove impurities, followed by passing it through an ion exchange column to remove divalent cations. The slurry may then be heated and stirred while the quaternary ammonium surfactant is added thereto. It may be heated at a temperature in the range of from about 140°F to about 155 0 F for a period of time effective to react the surfactant with the organophilic clay.
• the clay treated with the surfactant may be dried by filtering it and heating the resulting filter cake at a temperature in a range of from about 140°F to about 150°F for a period of time effective to dry the filter cake.
• the dried organophilic clay may then be ground to ensure that it can be easily dispersed in fluid, followed by filtering it through a sieve to generate a consistent particle size.
• the treatment of the clay with a quaternary ammonium surfactant may be performed in a process substantially free of water.
• the phrase "without requiring a substantial amount of water” means that no step in the process of treating a clay with a quaternary ammonium surfactant comprises hydrating the clay with water, hi such a process, the clay and the quaternary ammonium surfactant may be mixed through the use of a mechanical device. Any mechanical device capable of creating such a mixture without requiring a substantial amount of water may be utilized in this process. Such mechanical devices include, but are not limited to, a blender or an extruder.
• the organophilic clay treated with the quaternary ammonium surfactant having at least one amide linkage is typically insoluble in water and not completely soluble in oil; however, it interacts more with oil than would a clay that has not been treated with the surfactant. As such, it is more compatible with oil-based drilling fluids.
• the organophilic clay also may have a Loss of Organic mass by Ignition (LOI) in a range of from about 30% to about 50% by weight, or alternatively in a range of from about 35% to about 45%.
• the LOI indicates the amount of organic matter, i.e., surfactant, present in the organophilic clay.
• Wyoming sodium bentonite was hydrated in water and then filtered twice through a 400-mesh sieve to remove impurities. The resulting slurry was passed through an ion exchange column to remove divalent cations. An aliquot of slurry was dried, and the concentration of dry bentonite was found to be 2.92% by weight of the aliquot. One kilogram of the slurry also was heated to 140-155 0 F while stirring. Then 22.6 grams of AMMONYX SDBC surfactant were added to the heated slurry over a period of approximately 5 minutes, followed by stirring the mixture an additional 30 minutes at 15O 0 F. The slurry was thereafter filtered through Whatman 50 paper placed within a Buchner funnel to remove water.
• a filter cake was removed from the filter paper and dried for 16 hours at 140-150 0 F, thereby forming a biodegradable organophilic clay in accordance with an embodiment.
• the dried organophilic clay was ground in a hammermill and then sieved through a 100-mesh screen.
• the moisture content and LOI of the organophilic clay were determined to be 1.5% and 37.0% by weight of the organophilic clay, respectively.
• sample B As shown in Table 1 below, the ground organophilic clay was then used to prepare a 350.5 niL drilling fluid sample (sample B).
• sample B contained XP-07 hydrocarbon (approximately a C 12 -C 16 linear paraffin), water, 11.6 pound (Ib) /gallon (gal) calcium chloride brine, a co-emulsifier, a BDF-364 emulsifier, calcium hydroxide (lime), BAROID weighting agent (barium sulfate) commercially available from Halliburton Energy Services, Inc.
• the components in sample B were first mixed with a MULTIMIXER mixer commercially available form Sterling Multi-Products Inc. of Prophetstown, Illinois and then with a SILVERSON mixer commercially available from Silverson Machines Limited of the United Kingdom. Sample B was further hot rolled for 16 hours at 150°F. The amounts of the components in the drilling fluid sample B are shown in Table 1.
• control sample A A 350.5 mL control sample (sample A) was also prepared that contained all of the same components except that the biodegradable organophilic clay was replaced with GELTONE II organophilic clay, which is commercially available from Halliburton Energy Services, Inc. GELTONE II clay is not sufficiently biodegradable to be used in some areas but exhibits good properties.
• the components in the control sample A were first mixed with the MULTIMIXER mixer and then with a SILVERSON mixer. The control sample A was further hot rolled for 16 hours at 150°F. Table 1 also illustrates the amounts of the components in control sample A.
• the properties of the drilling fluid containing the biodegradable organophilic clay described herein were comparable to those of the drilling fluid containing GELTONE II organophilic clay. It is noted that a larger quantity of the biodegradable clay than of the control clay was used to obtain similar properties. In particular, the yield point, which measures the carrying capacity, is very similar for both types of drilling fluids and varies little over a wide temperature range.
• Wyoming sodium bentonite was combined with either AMMONYX SDBC or AGENT X2506-13 surfactant in a bench-scale extruder and processed with small quantities of isopropyl alcohol to aid in mixing. To remove any residual alcohol, the product was dried in an oven at 15O 0 F for a short time period. The dried organophilic clays were ground in a hammermill and then sieved through a 100-mesh screen. The moisture content and LOI were determined. [0031] As shown in Table 2 below, the organophilic clays were then used to prepare drilling fluid samples. The same components as in the previous example were used, with the exception of the emulsifier additives.
• BDF-364 emulsifier and a co- emulsifier are both commercially available from Halliburton Energy Services, Inc.
• the components in samples 1-3 were mixed with a MULTIMIXER mixer and then hot rolled for 16 hours at 150°F.
• the amounts of the components in the drilling fluid samples are shown in Table 2.
• a 350.5 mL control sample (sample 1) was prepared that contained all of the same components except that the biodegradable organophilic clay was replaced with GELTONE II organophilic clay.
• the drilling fluid samples were tested to determine the plastic viscosity in centipoise (cp), the yield point, and the Fann 35 A viscometer dial readings in accordance with American Petroleum Institute Recommended Practice 13B-2, 3 r Edition, February 1998.
• Table 5 [0038] The test results shows in Table 5 show that the quarternary ammonium surfactants having at least one amide linkage can be used to produce effective fluid loss control additives comprising lignite. While the filtrate amount in sample 7 was significantly lower than for the control (sample 5), other benefits to the fluid were observed with respect to stable rheological properties and a stable electrical stability (ES) value which indicates a robust emulsion.
• ES stable electrical stability

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