Non-toxic high-density fluid for completion applications

Abstract

A modified high density brine for use in subterranean drilling and completion operations. The modified high density brine includes the addition of high density particle addition that can optionally be surface-modified. The resultant modified high density brine eliminates the need for toxic, corrosive, and costly ZrBr.sub.2 additions or other ionic additives to boost the density of the modified high density brine to 15-17 lbs./gallon or greater.

Claims

1. A fluid having a density of at least 14.5 lbs./gallon at room temperature comprising: a base brine having a density of at least 8.9 lbs./gallon at room temperature, said base brine includes one or more of ZrBr.sub.2, ZrI.sub.2, NH.sub.4Cl, KCl, NaCl, KBr, CaCl.sub.2, CeBr.sub.2, NaBr, potassium formate, cesium formate, and CaBr.sub.2; and, a plurality of high density particles having a density greater than 2.5 g/cc, said high density particles have a mean particle size of less than 500 nm, said high density particles surface modified for dispersion in said base brine and/or to inhibit or prevent settling of said high density particles in said base brine, said high density particles formed of or includes one or more materials selected from iron, tungsten, chromium, cobalt, nickel, copper, zinc, manganese, molybdenum, bismuth, lead, tin; CeO.sub.2, WO.sub.3, WC, WCl.sub.3, Fe.sub.3O.sub.4, Fe.sub.2O.sub.3, TiO.sub.2, Cr.sub.2O.sub.3, ZrO.sub.2, BaO, PbO, Bi.sub.2O.sub.3, WSi.sub.2, silicides, TaN, WO.sub.2, FeO, ferrites, tungstates, ZnO, zirconates, BaTiO.sub.3, Al.sub.2O.sub.3, and SiO.sub.2, said surface modification of said high density particles includes a coating, said coating includes a compound selected from the group consisting of siloxane compound, silazane compound, polyacrylamide compound, and hydrogel compound.

2. The fluid as defined in claim 1, wherein said high density particles are added to said base brine at a concentration of about 1-5 lbs./gallon.

3. The fluid as defined in claim 1, wherein said fluid has a viscosity of less than 500 cP.

4. The fluid as defined in claim 1, wherein said high density particles are added at a concentration so as to increase the fluid density by at least 0.5 lbs./gallon.

5. The fluid as defined in claim 1, wherein said surface modification has a coating thickness of 0.5-50 nm.

6. The fluid as defined in claim 1, further including a dispersant.

7. The fluid as defined in claim 6, wherein said dispersant is selected from a) a polymer dispersant having an ammonium acrylate salt as a constituent unit of the copolymer component including ammonium polyacrylate salt, and copolymer ammonium salt of alkyl polyacrylate and acrylate, and/or b) two or more types of dispersant including at least one type of polymer dispersant having ammonium acrylate salt as constituent unit as copolymer component, and at least one type selected from other dispersants.

8. The fluid as defined in claim 6, wherein said dispersant includes a water-soluble anionic dispersant selected from triethanolamine lauryl sulfate, ammonium lauryl sulfate, triethanolamine polyoxy ethylene alkyl ether sulfate, poly styrene sulfonic acid, poly acrylamido methylpropanesulfonate, 2-acrylamido-2-methylpropanesulfonate, 3-(methacryloylamino)propyl}dimethyl(3-sulfopropyl) ammonium hydroxide, Poly(2-acrylamido-3-methylpropnaesulfonate), and/or poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic acid) with various ratios of comonomers.

9. The fluid as defined in claim 6, wherein said dispersant includes a polymer dispersant of polycarboxylate type include polymer of carboxylic monomer having unsaturated double bond.

10. The fluid as defined in claim 6, wherein said dispersant includes a water-soluble nonionic dispersant selected from polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyalkylene alkylether, polyoxyethylene derivative, polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethyelene sorbitan mono-oleate, polyoxy ethylene sorbitan trioleate, tetraoleic polyoxyethylene sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol mono-oleate, polyoxyethylene alkylamine, polyoxyethylene cured castor oil, 2-hydroxyethyl methacrylate, and/or alkyl alkanolamide.

11. The fluid as defined in claim 6, wherein said dispersant includes a water-soluble cationic dispersant include polyvinyl pyrrolidone, coconut amine acetate, and/or stearyl amine acetate.

12. The fluid as defined in claim 6, wherein said dispersant includes water-soluble biphoteric dispersant such as lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, poly(sulfobetaine methacrylamide), block copolymers of (sulfobetaine methacrylamide)/(methacrylic acid), 3-([dimethyl(3-trimethoxysilyl)propyl]ammonio) propane-1-sulfonate, and/or 2-alkyl-N-carboxymethyl-N-hydroxy ethyl imidazolinium betaine.

13. The fluid as defined in claim 6, wherein a weight ratio of said high density particles to said dispersant is 20-80:1.

14. A method for forming said fluid as defined in claim 1 comprising: a. providing said base brine having a density of 8.9-16 lbs./gallon at room temperature; and, b. adding a plurality of said high density particles to said base brine to form a fluid having a density of at least 14.5 lbs./gallon at room temperature.

15. A method for using said fluid as defined in claim 1 in a subterranean drilling or subterranean completion operation comprising: inserting said fluid in a subterranean formation.

Description

DESCRIPTION OF THE INVENTION

(1) The present invention relates to drilling and completion fluids for use in hydrocarbon-bearing and geothermal subterranean formations and to methods of drilling and completing subterranean zones using those fluids. The present invention is directed to a high-density brine. The high density brine includes the addition of modified high density nanoparticles that have been surface-modified. The resultant brine eliminates the need for toxic, corrosive, and costly ZrBr.sub.2 or Cesium formate additions or other ionic additives to boost the brine density to 15-17 lbs./gallon or greater.

(2) The properties of a calcium bromide heavy brine are set forth in the below table.

(3) TABLE-US-00002 TABLE 1 Calcium Bromide Density and Composition Information Spec Density Gravity Water CaBr.sub.2 CaBr.sub.2 Br TCT lbs./gal. SG bbl lbs. 95% wt. % wt. % ° F. 11.6 1.393 0.860 186 36.3 29.0 −32 11.7 1.405 0.856 192 37.1 29.7 −36 11.8 1.417 0.852 198 37.9 30.3 −40 11.9 1.429 0.848 203 38.6 30.9 −45 12.0 1.441 0.844 209 39.3 31.4 −50 12.1 1.453 0.840 214 40.1 32.1 −55 12.2 1.465 0.836 220 40.8 32.6 −61 12.3 1.477 0.832 226 41.5 33.2 −67 12.4 1.489 0.828 231 42.2 33.7 −73 12.5 1.501 0.824 237 42.8 34.2 −80 12.6 1.513 0.820 242 43.5 34.8 −88 12.7 1.525 0.816 248 44.2 35.3 −92 12.8 1.537 0.811 254 44.8 35.8 −96 12.9 1.549 0.807 259 45.5 36.4 −87 13.0 1.561 0.803 265 46.1 36.9 −78 13.1 1.573 0.799 271 46.8 37.4 −70 13.2 1.585 0.794 277 47.4 37.9 −63 13.3 1.597 0.790 282 48.0 38.4 −53 13.4 1.609 0.786 288 48.6 38.9 −43 13.5 1.621 0.781 294 49.2 39.3 −39 13.6 1.633 0.777 299 49.8 39.8 −34 13.7 1.645 0.772 305 50.4 40.3 −27 13.8 1.657 0.768 311 51.0 40.8 −20 13.9 1.669 0.763 317 51.6 41.3 −13 14.0 1.681 0.758 323 52.1 41.7 −7 14.1 1.693 0.754 328 52.7 42.1 1 14.2 1.705 0.751 333 53.1 42.5 10 14.3 1.717 0.744 340 53.8 43.0 17 14.4 1.729 0.739 346 54.3 43.4 23 14.5 1.741 0.734 352 54.9 43.9 30 14.6 1.753 0.730 358 55.4 44.3 36 14.7 1.765 0.724 364 56.0 44.8 43 14.8 1.777 0.719 370 56.5 45.2 50 14.9 1.789 0.714 376 57.0 45.6 56 15.0 1.801 0.709 382 57.6 46.1 61 15.1 1.813 0.704 388 58.1 46.5 66 TCT - crystallization temperature. BBL - barrel (approx. 42 gallons per barrel) Specific gravity measured at 77° F.

(4) From Table 1, the maximum obtainable density for CaBr.sub.2 brine is 15.1 lbs./gal. at 66° F. (the maximum temperature of most well completion operations). However, a density of 15.1 lbs./gal. CaBr.sub.2 brine cannot be used for deep water operations since the crystallization of the CaBr.sub.2 brine at such density is too high due to the cold deep water effects on the riser. Typically, the maximum density for CaBr.sub.2 brine that can be used in deep water operation is 14.5 lbs./gal., which CaBr.sub.2 brine has a crystallization temperature of 30° F. In some deep water operations, the CaBr.sub.2 brine needs to have an even lower density.

(5) In accordance with the present invention, the usable density of CaBr.sub.2 brine in deep water operations has been increased to 16 lbs./gal. or greater by the addition of the high density particle addition to the CaBr.sub.2 brine. In one non-limiting embodiment of the invention, high density particle addition in the form of cerium oxide particles having a particle size of about 60-80 nm, and a density of about 7.22 g/cm.sup.3 where added to the CaBr.sub.2 brine to achieve a density of the modified CaBr.sub.2 brine of about 17 lbs./gal. without creating solids in the modified CaBr.sub.2 brine that would plug the well formation or the filter press and filter cartridge. As such, modified CaBr.sub.2 brine can be classified as a solids-free completion fluid.

(6) Non-limiting benefits related to the high density particle addition to a heavy brine in accordance with the present invention include: lower crystallization temperature of the modified brine at higher densities; no special equipment required to use the modified brine; the modified brine is stable at high density and temperatures; the modified brine has a low viscosity; the modified brine can be readily available in bulk; the modified brine does not contain pollutants; the modified brine meets current U.S. environmental requirements; the modified brine can be re-used like regular completion fluids; and the modified brine is not a safety or health hazard to personnel or marine life.

(7) Non-limiting applications of the modified heavy brine that includes the high density particle addition include: reservoir drill-in fluid; completion fluid; workover fluid; packer fluid; gravel pack fluid; and potential for frac fluid.

(8) The surface modified particle as envisioned in this invention can be transformed into a liquid-free form, as an easily transported densifier for multiple brine systems.

Example 1

(9) 35 nm SiO.sub.2 particles were surface functionalized with the silane diol ether ([3-(2,3-dihydroxypropoxy) propyl]-trimethoxysilane to form a functionalized particle with a single coating. The coated particle was added to a CaBr.sub.2 brine and formed a stable dispersion of 5 wt. % silica particulate, 51.5 wt. % CaBr.sub.2 with a density of 14.9 lbs./gal and a viscosity <20 cP at room temperature (e.g., 77° F.).

Example 2

(10) A short chain silane coupling agent with a diol functionality was grafted to 80 nm SiO.sub.2 particles. The coated silica particles were then isolated to a powder form via a drying process. This dry, treated silica was then added to a 52 wt. % CaBr.sub.2 brine at a rate of 1 part powder to 12 parts brine by weight. The mixture was then sonicated and resulted in a stable dispersion that was filterable with a 2 micron filter and had a density of 14.6 lbs./gal at room temperature.

Example 3

(11) 150 nm CeO.sub.2 particles were surface modified by reacting with polydiethylsiloxane. The modified CeO.sub.2 particles were dispersed in CaBr.sub.2 clear brine using a high shear mixer at a rate of 1 kg of particles to 1 gallon of 15.4 lbs./gallon CaBr.sub.2 brine. The resultant heavy brine had a density of 17.2 lbs./gallon at room temperature (i.e., 77° F.). The high density brine was passed through a 2 micron filter without changing density. The viscosity of the CaBr.sub.2 brine was increased less than 20%, and the change in crystallization temperature is less than 5° C.

Example 4

(12) 150 nm ZrO.sub.2 particles were surface modified by reacting with poydiethylsiloxane. 1 kg of surface functionalized ZrO.sub.2 particles was added to 1 gallon of 15.4 lbs./gallon CaBr.sub.2 clear brine. The resultant fluid had a density of 17.0 lbs./gallon at room temperature (i.e., 77° F.).

Example 5

(13) 100 nm CeO.sub.2 powder was surface treated by grafting on polyacrylamide ligands. The PAA grafted CeO.sub.2 particles were mixed in a standard sand mixer with 14.8 lbs./gallon CaBr.sub.2 clear brine at a rate of 1.1 kg/gallon. After stabilizing for 4 hours, the resultant fluid had a density of 17 lbs./gallon at room temperature (i.e., 77° F.).

Example 6

(14) 85 nm CeO.sub.2 was surface activated with a nitric acid and peroxide treatment to facilitate coating the particle with and amine functionalized silane coupling agent. The amine functionality enabled the addition of an additional polysulfonic acid ligand to the particle/shell structure. When the treated particles are added to a 14.2 lbs./gal CaBr.sub.2 brine, no precipitant or settling was observed. The final density of the mixture was 14.7 lbs./gal.

Example 7

(15) Using an application rate of 1 gm of tetraethyl orthosilicate per gm of BaTiO.sub.3, 120 nm BaTiO.sub.3; particles were coated with a 12 nm layer of silica to enhance its ability to accept an alternate coating or functionalization. This material was then treated/coated with an amine functionalized silane coupling agent, KH-550 at a loading of 5 umol/m.sup.2 of BaTiO.sub.3. A dispersant layer of polyacrylamide methylpropanesulfonic acid was added to the functionalized tail of the silane at a loading of 7 wt. % dispersant/BaTiO3, thus creating particles with multiple coatings. When 12 wt. % of this particulate was added to a 9.5 lbs./gal NaCl brine, the resulting solution was readily filterable through a 2 micron filter, had a viscosity <15 cP at room temperature (e.g., 77° F.), and a density of 10.4 lbs./gal.

(16) In Examples 1-7, the silica coating is applied to the particles using tetraethyl orthosilicate (TEOS) in a base catalyzed setting. The application rate is typically in the range of 0.4 to 1.5 gm (and all values and ranges therebetween) of TEOS per gram of particulate and more typically in the range of 0.75 to 1.2 gm/gm (and all values and ranges therebetween). The coupling agent (when used) is generally added to the densifying particulate at a loading of 3.0 to 11 umol/m.sup.2 of particle surface area (and all values and ranges therebetween), and typically at a loading of 4.0 to 8.0 umol/m.sup.2. Dispersant use is dependent on the dispersant type as well as the particulate. Loadings are in the range of 5-15 wt. % dispersant/mass of particulate (and all values and ranges therebetween).

(17) It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention has been described with reference to preferred and alternate embodiments. Modifications and alterations will become apparent to those skilled in the art upon reading and understanding the detailed discussion of the invention provided herein. This invention is intended to include all such modifications and alterations insofar as they come within the scope of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall there between. The invention has been described with reference to the preferred embodiments. These and other modifications of the preferred embodiments as well as other embodiments of the invention will be obvious from the disclosure herein, whereby the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.