Using gelation additive for hydraulic fracturing fluids

Abstract

A method of formulating an organo-zirconium compound is accomplished by combining in solution a dialdehyde such as glyoxal with zirconium carbonate. The reacting solution forms an organo-zirconium compound and carbon dioxide which is evolved as a gas from the solution. This eliminates the need to filter or wash the organo-zirconium compound in order to remove undesirable by-products. The organo-zirconium compound can be used as a crosslinking agent for crosslinking aqueous polymer gels used in fracturing fluids for fracturing subterranean formations of oil and gas wells.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of forming an organo-metallic compound, and particularly to an organo-zirconium compound, from a starting material of zirconium carbonate, and to a method of use of such an organo-zirconium compound in crosslinking gelled fracturing fluids used in treating subterranean formations of oil and gas wells.

2. Description of the Prior Art

Hydraulic fracturing fluids used in fracturing subterranean formations of oil and gas wells are usually formed from aqueous based fluids which are gelled by the addition of soluble polymers. These soluble polymers are often formed from solvatable polysaccharides which include such things as guar, guar derivatives and carboxylated cellulose. With very little addition of these polymers, the viscosity of the aqueous fluid can be increased dramatically. Increasing the viscosity of these aqueous based fluids for use as fracturing fluids is beneficial for various reasons. High viscosity fluids create better, larger fractures within the formation when introduced under high pressure. The higher viscosity fluids are also better able to carry proppants which are dispersed throughout the fluid and forced into the fractures so that the fractures remain open after the fluid is removed.

Typically, less than 1% by weight of the soluble polymers are added to water to form these viscous aqueous fluids. At 0.5% polymer concentration, water viscosity can be increased from about 1 cps to about 35 cps at 511 sec.sup.-1 as measured using a Fann 50 viscometer. Further enhancement of the fluid viscosity occurs by the addition of crosslinking agents. These additives are able to bind polymer strands together to form a continuous network, thus further increasing the viscosity of the fluid. With the addition of these crosslinker additives, the viscosity of the aqueous fluids can be increased and exceed 500 cps at 170 sec.sup.-1. These crosslinkers are generally formed using metal complexes of titanium, zirconium, aluminum or boron. The ligands associated with these metals are chosen so that once the complex is added to the aqueous polymer sol, the polymer must compete with the ligand for the metal. This is beneficial in that it ensures that the metal complex is homogeneously mixed in the polymer sol before crosslinking occurs. The delayed effect also results in less friction or back pressures while pumping the fluid at higher rates into the oil and gas wells.

Zirconium lactate is commonly used as a metallic crosslinker in crosslinking these aqueous polymer fluids. Zirconium lactate can provide delayed gelation and high viscosities at elevated temperatures for periods of time that are practical for hydraulic fracturing treatments in oil and gas wells. Prior art methods of formulating zirconium lactate typically involve mixing lactic acid to either zirconium hydroxychloride or zirconium oxychloride. These compounds react to form zirconium lactate as a white precipitate. To remove chloride by-products, the zirconium lactate product is filtered, washed and redissolved by neutralization with a suitable base. The base is generally sodium, potassium or ammonium hydroxide. This method of formulating zirconium crosslinkers has disadvantages, however. Washing and filtering of the zirconium lactate product usually results in less than 100% yield. As much as 10% Zr, measured as ZrO.sub.2, may be lost during washing. Wastewater from the washings must be recovered and disposed of properly. The crosslinkers formed in this manner may be polymer specific and difficult to use with other polymers, in particular guar gum. These crosslinkers are also expensive because of the extensive processing and handling of wastewater that is required.

A need exists, therefore, for a new organo-zirconium compound for use as a crosslinker for polysaccharide containing fracturing fluids which overcomes many of the difficulties associated with the prior art zirconium lactate compounds.

A need also exists for such a new organo-zirconium compound which can be simply and inexpensively manufactured from commonly available starting materials.

A need also exists for a simple method of manufacturing an organo-zirconium compound which does not generate waste or loss of product as a result of washing and separating techniques.

A need also exists for such an organo-zirconium compound which is capable of more effectively crosslinking guar based aqueous fracturing fluids.

SUMMARY OF THE INVENTION

An organo-zirconium compound is formulated by combining in solution an amount of an aldehyde or dialdehyde with an amount of a zirconium salt. Most preferably, the aldehyde is selected from the group consisting of dialdehydes having about 2-4 carbon atoms, keto aldehydes having about 3-4 carbon atoms, hydroxyl aldehydes having 2-4 carbon atoms, ortho substituted aromatic dialdehydes and ortho substituted aromatic hydroxyl aldehydes. The most preferred reactants are zirconium carbonate and glyoxal with the molar ratio of zirconium to glyoxal being in the range from about 1:0.5 to 1:20, most preferably about 1:2.5 to 1:7.

The solution of glyoxal and zirconium carbonate is allowed to react with carbon dioxide being given off as a by-product. The carbon dioxide is allowed to evolve from the solution as a gas so that the zirconium product does not need to be washed to remove undesirable by-products.

The zirconium compound produced can be used as a crosslinking agent for crosslinking viscous polymer gels, such as those used in fracturing fluids. By further neutralizing the aqueous solution, zirconium precipitate is dissolved in solution. The solution can then be added to the polymer fluid.

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A zirconium compound of the invention can be formed in a simple process by the addition of a zirconium salt to an aqueous solution of a selected aldehyde or dialdehyde. Suitable zirconium salts include carbonate, ammonium carbonate, oxychloride, acetate, tetrachloride and o-sulfate. The preferred salt is zirconium carbonate due to the nature of the by-products produced, as will be more fully described.

The aldehyde or dialdehyde (sometimes referred to collectively hereafter as "aldehyde") which is reacted with the zirconium salt is preferably selected from the group consisting of dialdehydes having 2-4 carbon atoms, keto aldehydes having about 3-4 carbon atoms, hydroxyl aldehydes having 2-4 carbon atoms, ortho substituted aromatic dialdehydes and ortho substituted aromatic hydroxyl aldehydes. Preferred aldehydes and dialdehydes include, for example, glyoxal, propane dialdehyde, 2-keto propanal, 1,4-butanedial, 2-keto butanal, 2,3-butadione, phthaldehyde, salicaldehyde, etc. The most preferred co-reactant is glyoxal, a dialdehyde, due to its ready availability from a number of commercial sources.

The zirconium carbonate is preferably reacted with the glyoxal in a molar ratio of zirconium ion to glyoxal in the range from about 1:0.5 to 1:20, most preferably in the range from about 1:2.5 to 1:7.

The process can be initiated by adding the zirconium carbonate to an aqueous solution of 40% aqueous glyoxal. Because zirconium carbonate is used, the reaction results in a by-product of carbon dioxide. Thus, during the reaction, carbon dioxide is given off as a gas which simply bubbles out of solution so that filtering and washing of the zirconium product is unnecessary. A precipitate is immediately observed. The aqueous glyoxal solution is very acidic, normally with a pH of about 2.5. At low pH, the zirconium product formed appears as a precipitate. If desired, this precipitate can be removed from solution by filtering and dried for later use.

By further neutralizing the solution with a suitable base, the zirconium precipitate can be dissolved and used as a crosslinking additive for crosslinking various viscous aqueous gels used as fracturing fluids. The solids can be slowly dissolved by neutralizing with base and heating from about 30 minutes to about 6 hours. The preferred temperature for heating can range from ambient to about 250.degree. F. The most preferred heating temperature is about 200.degree. F. for at least two hours.

The base can be added while the solution is still hot or after cooling. After the addition of base, the solution can be cooled or heating can continue. Preferred bases to use for neutralization include the alkali metal hydroxides such as potassium hydroxide or sodium hydroxide. Other bases include the alkanolamines, ammonium hydroxide and alkali metal carbonates and bicarbonates. The most preferred base is potassium hydroxide.

The preferred procedure used to make the crosslinker and its performance are described in the non-limiting examples which follow:

EXAMPLE 1

An aqueous solution of 40% (wt) glyoxal weighing 44.25 gr. was heated to 200.degree. F. Then, 20.0 gr. of zirconium carbonate (40.4% ZrO.sub.2) slurried in 20.0 gr. of DI water was slowly added to the glyoxal solution and stirred for 60 minutes. During that time, 30.0 gr of water was added to help suspend the solids. After the 60 minutes, 25.24 gr. of 46% aqueous potassium hydroxide was slowly added to the slurry. The heating continued at 200.degree. F. for another 120 minutes. During this time, the solids slowly dissolved. The dark colored solution was then cooled to ambient. The zirconium content measured as ZrO.sub.2 is 5.5% and the pH was 5.55.

EXAMPLE 2

A liter of tap water was treated with 20.0 gr. of technical grade potassium chloride to produce a 2% weight per volume (wt/vol) potassium chloride solution. Then, with agitation, 4.8 gr. of a fracturing fluid quality guar gum was added, together with 1.2 gr. of sodium bicarbonate, and hydrated for 60 minutes. Afterward, an aliquot of 250 ml of sol was taken and treated with 0.3 gr sodium thiosulfate and 0.06 ml of 50% (wt) monoethanolamine. Lastly, 0.1 ml of crosslinker prepared in Example 1 was added to the sol and stirred vigorously for 60 seconds. The pH of the sol was 8.85.

For the testing, a Fann 50 viscometer (Baroid Testing Equipment) with an R1B5 bob and cup were used. A sample of 48.0 gr was poured into the viscometer cup. The cup was screwed onto the viscometer and pressured to 200 psi with N.sub.2. The sample was then continuously sheared at 42 sec.sup.-1 while heating to 250.degree. F. At temperature, a rate sweep using 105, 84, 63 and 42 sec.sup.-1 was made and repeated every 30 minutes. The interim rate between the sweeps was 42 sec.sup.-1. The stresses corresponding to each rate of the rate sweep, together with the rates, were converted to their logarithmic value. The Power Law indices, n' and K, were then determined as described by the American Petroleum Institute's bulletin RP-39. The n' values presented in Tables 1-14 are unitless whereas the K values have the units of dyne/cm.sup.2 -sec. The Power Law indices were then used to calculate the gel's viscosity at 105, 85 and 42 sec.sup.-1. These data, over time, are shown in Table

TABLE 1______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.06 ml 50% (wt) monoethanol amine, and 0.1 ml crosslinkerpH: 8.85 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 29 246 0.740 13.791 411 434 522 60 247 0.691 15.471 367 392 487 91 248 0.664 14.889 312 335 424122 248 0.652 14.447 286 308 393152 248 0.671 12.524 271 290 366183 248 0.680 11.151 251 269 337214 248 0.714 9.103 241 255 313245 248 0.715 8.506 226 240 293______________________________________

EXAMPLE 3

The testing of the fluids described in the Examples 3-15 are conducted as stated in Example 2.

Another 250 ml aliquot of sol prepared in Example 2 was treated with 0.3 gr of sodium thiosulfate and 0.08 ml of 45% (wt) aqueous potassium carbonate. Then, 0.1 ml of crosslinker prepared in Example 1 was added with vigorous stirring for 60 sec. The pH of the sol was 8.83 and the data from the rheological evaluation are shown in Table

TABLE 2______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.08 ml 45% (wt) K.sub.2 CO.sub.3 and 0.1 ml crosslinkerpH: 8.83 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 34 248 0.676 21.613 478 512 644 65 248 0.665 18.521 390 418 530 96 248 0.641 18.057 340 366 472126 248 0.665 14.958 315 338 428157 248 0.663 13.684 285 306 388188 248 0.670 12.760 275 295 372219 248 0.742 8.532 257 271 325249 248 0.727 8.423 236 250 304277 248 0.709 8.6484 223 237 291______________________________________

EXAMPLE 4

The Example 3 was repeated except that the potassium carbonate buffer was reduced to 0.02 ml and the crosslinker increased to 0.12 ml. The sol pH was 8.55. These test data are shown in Table

TABLE 3______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.02 ml 45% (wt) K.sub.2 CO.sub.3 and 0.12 ml crosslinkerpH: 8.55 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 34 248 0.585 35.220 510 557 747 64 248 0.613 27.269 450 489 642 95 248 0.618 23.132 391 424 555126 248 0.632 19.179 346 374 485156 248 0.634 16.792 306 330 428187 248 0.623 15.897 275 298 388218 248 0.621 15.0486 258 279 365249 248 0.64 12.6557 237 256 330276 248 0.697 8.6348 211 225 278______________________________________

EXAMPLE 5

In this next example, a 250 ml aliquot was treated with 0.3 gr of sodium thiosulfate and 0.05 ml of 45% (wt) potassium carbonate. Afterwards, 0.12 ml of crosslinker prepared in Example 1 was added to the vigorously stirred sol. The sol pH was 8.81 and the rheological data obtained at 250.degree. F. are presented in Table 4.

TABLE 4______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.05 ml 45% (wt) K.sub.2 CO.sub.3 and 0.12 ml crosslinkerpH: 8.81 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 34 248 0.337 43.733 200 230 367 62 248 0.659 24.222 495 532 677 92 248 0.622 23.972 413 447 584123 249 0.586 25.954 378 412 552154 248 0.554 26.897 337 371 508185 249 0.884 5.4826 320 327 355216 249 0.699 10.1253 249 266 329247 248 0.689 9.6167 226 242 301278 249 0.728 7.5082 212 224 272309 249 0.73 6.8318 194 206 249340 249 0.760 5.643 185 194 230370 249 0.750 5.636 176 186 221401 249 0.769 5.073 173 182 214432 249 0.773 4.687 163 171 201463 249 0.779 4.290 153 161 188493 249 0.770 4.312 148 155 183524 249 0.748 4.612 143 151 180554 249 0.780 3.825 137 144 168585 249 0.744 4.837 147 155 186616 249 0.763 4.630 154 162 191647 249 0.757 4.560 147 155 184678 249 0.727 4.848 136 144 175709 249 0.725 4.453 124 131 159740 249 0.775 3.263 114 120 141771 249 0.748 3.325 103 109 130802 249 0.733 3.192 92 97 118832 249 0.793 2.231 85 89 103863 249 0.754 2.442 78 82 97894 95 0.542 18.5404 220 242 335______________________________________

EXAMPLE 6

Another 250 ml aliquot of sol described in Example 2 was treated with 0.30 gr sodium thiosulfate and 0.08 ml of 45% (wt) potassium carbonate. Then, 0.12 ml of crosslinker described in Example 1 was added to the vigorously stirred sol. The sol pH was 9.00 and the rheological data obtained at 250.degree. F. is presented in Table 5.

TABLE 5______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. guar gum, 0.30 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.08 ml 45% (wt) K.sub.2 CO.sub.3 and 0.12 ml crosslinkerpH: 9.00 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 34 248 0.542 63.259 751 827 1142 65 249 0.541 60.143 710 783 1082 96 248 0.522 60.192 651 720 1008126 248 0.500 61.778 603 670 953157 248 0.498 59.425 575 639 910188 249 0.482 60.0358 539 601 866219 248 0.469 60.4491 511 571 831250 248 0.483 54.9207 495 552 795281 248 0.479 54.3202 481 537 775312 249 0.482 51.2398 460 513 739343 249 0.475 50.945 443 494 716374 249 0.477 48.841 428 478 692404 249 0.472 48.797 418 467 678435 249 0.485 44.742 407 454 653444 249 0.480 45.127 401 448 646475 249 0.471 46.581 397 444 645506 249 0.468 45.321 381 426 620537 249 0.473 44.167 380 425 616567 249 0.483 41.667 376 419 603598 248 0.465 44.375 368 412 601629 248 0.470 42.310 359 402 584660 248 0.476 39.888 348 389 563691 248 0.476 38.688 338 377 546722 248 0.489 35.133 326 363 520753 248 0.474 36.299 314 351 508784 248 0.478 35.062 309 345 498815 248 0.480 33.105 294 329 474845 98 0.456 63.1739 502 564 827______________________________________

EXAMPLE 7

In this example, a liter of 2% (wt/vol) aqueous potassium chloride was vigorously stirred while adding 4.8 gr of fracturing fluid quality carboxymethylhydroxypropyl guar (CMHPG), a dual derivatized guar gum. Afterward, 1.2 gr of sodium bicarbonate was added as a buffer to accelerate polymer hydration. After adequate dispersing, the stirring rate was slowed and the polymer was allowed to hydrate for about an hour.

Then, as in the preceding examples, a 250 ml aliquot was withdrawn and treated with 0.45 gr of sodium thiosulfate. Next, acetic acid was added dropwise until the sol pH declined to 5.70. Afterward, 0.19 ml of crosslinker, prepared in Example 1, was added with vigorous stirring to the sol. The final pH of the fluid was 5.70 and 45.0 gr of the sol was poured into the Fann 50 cup. The rheological evaluation was conducted at 250.degree. F. and as described in Example 2. These data are presented in Table 6.

TABLE 6______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. CMHPG, 1.2 gr. NaHCO.sub.3, 0.45 gr.Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O, acetic acid added to adjust pH and0.19 ml crosslinkerpH: 5.70 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 32 248 0.579 56.054 790 864 1162 61 248 0.557 46.181 588 645 882 90 248 0.507 40.588 409 454 643119 248 0.504 29.040 289 321 455148 248 0.520 20.366 218 241 339177 249 0.551 12.402 153 169 232206 248 0.560 8.259 107 117 159235 248 0.562 7.043 92 101 137263 248 0.530 5.347 60 66 92292 248 0.529 4.430 49 55 76321 248 0.591 2.475 37 40 54350 248 0.428 4.082 28 32 48379 248 0.408 3.689 23 27 40408 248 0.456 2.686 21 24 35432 249 0.516 1.856 20 22 30461 249 0.420 2.458 17 19 28490 249 0.363 2.642 14 16 24519 248 0.364 2.339 12 14 22548 248 0.439 1.506 11 12 18577 248 0.440 1.382 10 11 17606 248 0.400 1.461 9 10 16635 248 0.265 2.462 8 9 16663 248 0.548 1.239 8 9 15693 248 0.207 2.882 7 9 15722 248 0.166 3.338 7 8 15751 248 0.239 2.416 7 8 14780 248 0.268 2.136 7 8 14809 248 0.276 2.070 7 8 14838 100 0.672 0.513 11 12 15______________________________________

EXAMPLE 8

In this example, another 250 ml aliquot was withdrawn from the stock solution prepared as described in Example 2. This sol was treated with 0.3 gr of sodium thiosulfate and 0.10 gr of fumaric acid. The sol pH, after dissolution of the acid, was 5.70. Lastly, with vigorous stirring of the sol, 0.38 ml of crosslinker prepared in Example 1 was added. The sol pH was 5.57 and the data from the rheological evaluation at 250.degree. F. is presented in Table 7.

TABLE 7______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.10 gr. fumaric acid and 0.38 ml crosslinkerpH: 5.57 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________32 248 0.708 19.068 490 521 64060 249 0.689 15.292 360 384 47889 251 0.760 6.962 228 240 284118 251 0.786 3.731 138 144 168147 251 0.724 3.238 90 95 115______________________________________

EXAMPLE 9

Another 250 ml aliquot was withdrawn from the stock solution prepared as described in Example 2. The sol was treated with 0.3 gr sodium thiosulfate and 0.5 ml of a 45% (wt) solution of potassium carbonate. The crosslinker prepared in Example 1 was diluted to 50% (wt) with tap water. Then, with vigorous stirring of the sol, 0.25 ml of the diluted crosslinker was added. The sol pH was 8.50 and the data for the rheological evaluation at 200.degree. F. is presented in Table 8.

TABLE 8______________________________________Temperature (.degree. F.): 200Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.05 ml 45% (wt) K.sub.2 CO.sub.3 and 0.25 ml of diluted crosslinkerpH: 8.50 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________34 199 0.647 25.919 501 540 69365 199 0.676 18.865 418 447 56296 199 0.621 21.635 371 402 525127 199 0.592 21.943 329 358 478155 199 0.579 21.185 299 326 439185 199 0.661 13.478 278 299 380216 199 0.648 13.356 260 280 358247 199 0.628 13.914 246 267 346278 199 0.631 12.953 233 251 326308 199 0.633 12.231 222 240 310339 199 0.656 10.562 213 229 292370 199 0.654 10.145 203 218 278401 199 0.665 9.402 198 212 269432 199 0.654 9.439 189 203 259463 199 0.685 7.614 176 188 235494 199 0.689 7.154 168 180 224525 199 0.705 6.622 168 179 220556 199 0.701 6.685 166 177 219586 199 0.680 6.899 156 166 209617 199 0.707 5.938 152 162 199627 199 0.737 5.131 151 160 192658 199 0.724 5.288 146 155 188689 199 0.682 5.982 136 146 182720 199 0.702 5.371 134 143 176751 199 0.727 4.707 132 140 170781 199 0.709 4.917 127 135 166812 199 0.686 5.280 122 131 163843 199 0.718 4.305 116 123 150874 199 0.689 4.7115 111 118 147905 199 0.732 3.831 110 116 141936 199 0.675 4.9115 108 116 146967 199 0.73 3.7031 105 112 135998 199 0.695 4.31 104 111 1381028 85 0.464 32.3876 267 299 437______________________________________

EXAMPLE 10

In this example, a liter of 2% (wt/vol) aqueous potassium chloride was vigorously stirred while adding 4.8 gr of fracturing fluid quality hydroxypropyl guar (HPG), a derivatized guar gum and 1.2 gr of sodium bicarbonate. After adequate dispersing, the stirring rate was slowed and the polymer was allowed to hydrate for about an hour.

A 250 ml aliquot was withdrawn and treated with 0.3 gr of sodium thiosulfate and 0.08 ml of 45% potassium carbonate. Then, with vigorous stirring, 0.12 ml of crosslinker prepared in Example 1 was added to the sol. The sol pH was 9.04 and the data acquired from the rheological evaluation at 250.degree. F. is presented in Table 9.

TABLE 9______________________________________Temperature (.degree. F.): 250Additives: 2% KCl, 4.8 gr. HPG, 1.2 gr. NaHCO.sub.3, 0.3 gr. Na.sub.2S.sub.2 O.sub.3.5H.sub.2 O,0.08 ml 45% (wt) K.sub.2 CO.sub.3 and 0.12 ml crosslinkerpH: 9.04 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________32 248 0.675 16.072 354 379 47761 249 0.580 20.483 290 317 42689 249 0.629 15.632 278 301 391118 249 0.577 17.076 238 261 351145 249 0.617 13.297 224 243 318173 249 0.565 15.686 207 227 309202 249 0.581 13.393 191 208 280231 249 0.571 12.945 176 192 260260 249 0.586 11.859 173 188 252289 249 0.592 11.005 165 180 239318 249 0.661 7.727 160 171 218347 249 0.599 9.329 144 157 208376 249 0.596 9.236 141 153 204405 249 0.650 6.918 136 146 187434 249 0.621 7.377 126 137 179463 249 0.611 7.373 121 131 172492 249 0.597 7.572 116 126 168521 249 0.619 6.385 108 117 154550 249 0.664 5.014 105 113 143579 249 0.689 4.331 102 109 135608 249 0.654 4.854 97 104 133616 249 0.629 5.273 94 101 132645 249 0.613 5.329 88 95 125674 249 0.663 4.124 86 92 117703 249 0.689 3.751 88 94 117732 249 0.661 4.005 83 89 113761 249 0.675 3.766 83 89 112790 249 0.698 3.294 81 86 107819 249 0.702 3.119 78 83 102848 249 0.688 3.2253 76 81 100877 249 0.686 3.1348 73 78 97906 249 0.706 2.8311 72 77 94935 249 0.691 3.0418 72 77 96964 249 0.662 3.236 67 72 91993 250 0.643 3.4503 66 71 911022 249 0.657 3.1647 64 69 881051 249 0.657 3.0802 62 67 851080 249 0.663 2.9762 62 67 841109 249 0.64 3.2035 60 65 831137 100 0.511 19.5655 201 223 315______________________________________

EXAMPLE 11

In this example, a 250 ml aliquot of CMHPG prepared as described in Example 7 was treated with 0.3 gr of sodium thiosulfate. Then, with stirring, acetic acid was added dropwise until the sol pH was 5.70. Lastly, with vigorous stirring of the sol, 0.19 ml of crosslinker prepared in Example 1 was added. The final sol pH was 5.70 and the data obtained from the rheological evaluation at 200.degree. F. are presented in Table 10.

TABLE 10______________________________________Temperature (.degree. F.): 200Additives: 2% KCl, 4.8 gr. CMHPG, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,acetic acid added to adjust pH, and 0.19 ml crosslinkerpH: 5.70 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 32 205 0.444 70.514 530 596 883 61 202 0.455 70.838 561 629 924 90 202 0.435 76.512 552 622 926118 202 0.425 78.281 539 608 913147 202 0.434 74.248 533 601 895176 202 0.446 68.372 519 583 862205 202 0.466 61.856 515 577 841234 202 0.441 65.286 484 545 808263 202 0.454 59.014 465 522 767292 202 0.444 58.220 438 492 729______________________________________

EXAMPLE 12

In this example, a 250 ml aliquot of CMHPG prepared as described in Example 7 was treated with 0.3 gr of sodium thiosulfate and 0.06 ml of 45% (wt) potassium carbonate. Then, with vigorous stirring of the sol, 0.15 ml of crosslinker prepared in Example 1 was added.

The final sol pH was 9.00 and the data acquired from the rheological evaluation at 275.degree. F. are shown in Table 11.

TABLE 11______________________________________Temperature (.degree. F.): 275Additives: 2% KCl, 4.8 gr. CMHPG, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.06 ml 45% (wt) K.sub.2 CO.sub.3 and 0.15 ml crosslinkerpH: 9.00 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 31 274 0.622 47.012 809 877 1145 60 274 0.564 48.740 641 703 955 89 274 0.533 44.902 511 564 784118 274 0.510 41.733 427 473 668147 274 0.546 31.878 385 424 584176 274 0.498 36.050 349 388 552205 275 0.522 30.511 330 365 511234 275 0.535 25.977 298 329 457263 274 0.516 26.552 279 309 435292 274 0.571 18.883 256 281 380321 274 0.558 20.908 267 293 401350 274 0.542 21.471 255 281 388379 274 0.548 19.449 237 261 359408 274 0.532 19.154 217 239 333437 273 0.569 15.422 207 227 308466 274 0.598 12.429 191 208 277495 274 0.527 15.677 173 192 268524 274 0.505 15.872 159 176 250553 274 0.544 12.159 146 160 221582 274 0.535 11.503 132 146 202610 274 0.559 9.375 120 132 180639 274 0.520 10.076 108 119 168668 274 0.566 7.544 100 110 149697 274 0.567 6.818 91 100 135726 274 0.533 7.229 82 91 126755 274 0.562 5.840 76 83 114773 274 0.581 5.025 71 78 105802 274 0.607 4.143 67 72 95831 273 0.558 4.847 62 68 93860 274 0.554 4.5336 57 63 86889 273 0.565 4.123 54 60 81918 274 0.574 3.7038 51 56 75947 273 0.528 4.1565 46 51 71976 274 0.581 3.0997 44 48 65______________________________________

EXAMPLE 13

In this example, a 250 ml aliquot of CMHPG prepared as described in Example 7 was treated with 0.3 gr of sodium thiosulfate and 0.06 ml of 45% (wt) potassium carbonate. Then, with vigorous stirring of the sol, 0.18 ml of crosslinker prepared in Example 1 was added. The final sol pH was 8.95 and the data acquired from the rheological evaluation at 300.degree. F. are shown in Table 12.

TABLE 12______________________________________Temperature (.degree. F.): 300Additives: 2% KCl, 4.8 gr. CMHPG, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.06 ml 45% (wt) K.sub.2 CO.sub.3 and 0.18 ml crosslinkerpH: 8.95 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________30 305 0.728 29.502 832 881 106759 284 0.624 31.910 555 600 78388 298 0.571 30.819 419 458 620117 299 0.539 28.911 338 373 516146 299 0.537 24.060 279 308 426175 299 0.553 18.374 229 252 346204 299 0.568 13.462 180 198 268233 299 0.581 9.721 138 151 203262 298 0.584 7.375 106 116 156291 299 0.618 4.815 81 88 115320 299 0.602 3.859 61 66 87349 298 0.619 2.809 48 52 68378 298 0.630 2.125 38 41 53407 298 0.552 2.526 31 35 47436 299 0.401 4.026 25 28 43465 299 0.314 5.343 22 25 41493 298 0.438 2.767 20 23 34522 298 0.445 2.493 19 21 31551 298 0.438 2.344 17 19 29580 298 0.518 1.456 15 17 24609 298 0.606 0.833 13 14 19638 298 0.667 0.556 12 13 16667 299 0.619 0.615 10 11 15696 298 0.446 1.168 9 10 15725 298 0.397 1.347 8 9 14754 298 0.263 2.300 7 9 15783 298 0.218 2.649 7 8 14812 298 0.207 2.680 7 8 14841 298 0.161 3.2311 7 8 14851 298 0.197 2.7087 6 8 13880 298 0.231 2.2448 6 7 13909 298 0.088 4.2004 6 7 14938 298 0.155 3.0535 6 7 13967 298 0.208 2.515 6 7 13995 298 0.167 2.9336 6 7 131024 298 0.158 2.8262 6 7 121053 298 0.194 2.4537 6 7 121082 298 0.13 3.2029 6 7 121111 297 0.174 2.6641 6 7 121140 297 0.198 2.281 5 6 111169 298 0.162 2.6941 5 7 121198 297 0.093 3.8153 6 7 131227 298 0.119 3.4276 6 7 13______________________________________

EXAMPLE 14

In this example, another 250 ml aliquot was withdrawn from the stock solution prepared as described in Example 2. This sol was treated with 0.3 gr of sodium thiosulfate. Then acetic acid was added dropwise until the sol pH achieved 5.70. Lastly, with vigorous stirring of the sol, 0.38 ml of crosslinker prepared in Example 1 was added. The sol pH was 5.70 and the data from the rheological evaluation at 200.degree. F. is presented in Table 13.

TABLE 13______________________________________Temperature (.degree. F.): 200Additives: 2% KCl, 4.8 gr. guar gum, 0.3 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,acetic acid to adjust pH and 0.38 ml crosslinkerpH: 5.70 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 32 200 0.546 25.628 310 341 470 61 202 0.552 22.357 278 306 419 89 202 0.563 20.055 262 288 392118 202 0.625 14.912 260 282 367147 202 0.529 21.147 236 261 364176 202 0.550 17.726 218 240 330205 202 0.567 15.597 208 228 309234 202 0.559 15.232 196 215 293262 202 0.589 12.378 183 199 266291 202 0.626 9.481 166 180 234______________________________________

EXAMPLE 15

Another 250 ml aliquot of sol described in Example 2 was treated with 0.30 gr sodium thiosulfate and 0.38 ml of 45% (wt) potassium carbonate. Then, 0.12 ml of crosslinker described in Example 1 was added to the vigorously stirred sol. The sol pH was 8.50 and the rheological data obtained at 275.degree. F. is presented in Table 14.

TABLE 14______________________________________Temperature (.degree. F.): 275Additives: 2% KCl, 4.8 gr. guar gum, 0.30 gr. Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O,0.38 ml 45% (wt) K.sub.2 CO.sub.3 and 0.12 ml crosslinkerpH: 8.50 Viscosity at Rates in Sec.sup.-1TIME TEMP n' K' 105s-1 85s-1 42s-1______________________________________ 32 271 0.603 21.522 339 369 488 61 272 0.575 20.274 280 307 414 90 273 0.595 14.999 228 248 330119 273 0.652 10.192 202 217 278148 273 0.659 8.537 175 188 239177 273 0.692 6.438 154 164 204206 273 0.683 5.891 135 144 180235 273 0.762 3.680 122 128 151264 273 0.720 4.060 110 117 143293 273 0.725 3.473 97 102 124322 273 0.652 4.396 87 94 120351 273 0.663 3.688 77 83 105380 272 0.724 2.731 76 80 97408 273 0.673 3.063 67 72 90______________________________________

When using the zirconium compounds of the invention as crosslinking agents for aqueous polymer gels used as fracturing fluids, a gelled polymer fracturing fluid is first prepared by adding between about 1% or less by weight of a soluble polymer such as guar, guar derivative or carboxylated cellulose to water. The zirconium crosslinking agent is then added to the gelled fluid in solution while mixing. The amount of the crosslinking agent used to carry out the method of the invention will vary over a wide range and therefore the amounts will vary according to the formation being treated. Preferably, the amount of crosslinking agent used will be in the range from about 0.005 to in excess of 1.00 weight percent, most preferably about 0.01 to 0.10 weight percent, based on the total weight of aqueous fluid. Additionally, proppants and other additives, such as gel stabilizers, buffers, crosslink delaying agents and surfactants, may be added to the fluid prior to pumping into an oil or gas well. The fluid is then pumped into the well at a sufficiently high rate or pressure to cause fractures within the hydrocarbon bearing areas of the formation. The zirconium compound is particularly useful when treating high temperature wells, i.e. those having temperatures in excess of 200.degree. F., due to the good thermal stability and retained viscosity of the crosslinked polymer gel.

An invention has been provided with several advantages. The method of the invention allows organo-zirconium compounds to be formed without producing undesirable by-products that must be removed by washing and filtering procedures. Because zirconium carbonate is used as the starting material, the reaction results in the production of carbon dioxide gas as a by-product. The carbon dioxide merely bubbles from solution as a gas so that no additional separating techniques are required. This eliminates the loss of product that would otherwise occur during the washing and filtering steps. There is also no chloride to be recovered and disposed of. The novel organo-zirconium compounds of the invention overcome many of the disadvantages of the prior art compounds, such as high cost, as well as being more applicable for guar gums utilized in aqueous based fracturing fluids.

While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.

Claims

1. A method of fracturing a subterranean formation of a well used in recovering oil or gas, comprising the steps of:

preparing an aqueous polymer fluid;

preparing a crosslinking agent by combining in solution an amount of a zirconium salt with an aldehyde or dialdehyde and allowing the solution to react;

admixing said crosslinking agent with said aqueous polymer fluid; and

injecting said polymer fluid admixed with said crosslinking agent into the well at a sufficient rate or pressure to fracture the formation.

2. The method of claim 1, wherein the aqueous polymer fluid is prepared by blending together an aqueous fluid and a hydratable polymer capable of gelling in the presence of zirconium ions.

3. The method of claim 2, wherein the hydratable polymer is selected from the group consisting of guars and derivitized guars.

4. The method of claim 3, wherein the aldehyde or dialdehyde is selected from the group consisting of dialdehydes having about 2-4 carbon atoms, keto aldehydes having about 3-4 carbon atoms, hydroxyl aldehydes having 2-4 carbon atoms, ortho substituted aromatic dialdehydes and ortho substituted aromatic hydroxyl aldehydes.

5. The method of claim 3, wherein the zirconium salt is zirconium carbonate.

6. The method of claim 3, wherein the aldehyde or dialdehyde is glyoxal.

7. A method of fracturing a subterranean formation of a well used in recovering oil or gas, comprising the steps of:

preparing an aqueous polymer fluid;

preparing a crosslinking agent by combining in solution an amount of zirconium carbonate with an aldehyde or dialdehyde and allowing the solution to react, wherein carbon dioxide gas evolves from said solution as a by-product;

admixing said crosslinking agent with said aqueous polymer fluid; and

injecting said polymer fluid admixed with said crosslinking agent into the well at a sufficient rate or pressure to fracture the formation.

8. The method of claim 7, wherein said aqueous polymer fluid is prepared by blending together an aqueous fluid and a hydratable polymer capable of gelling in the presence of zirconium ions.

9. The method of claim 7, wherein said crosslinking agent is neutralized by the addition of a suitable base before said admixing step.

10. The method of claim 9, wherein said suitable base comprises potassium hydroxide or sodium hydroxide.

11. The method of claim 7, wherein said aldehyde or dialdehyde is selected from the group consisting of dialdehydes having about 2-4 carbon atoms, keto aldehydes having about 3-4 carbon atoms, hydroxyl aldehydes having 2-4 carbon atoms, ortho substituted aromatic dialdehydes and ortho substituted aromatic hydroxyl aldehydes.

12. The method of claim 11, wherein said aldehyde or dialdehyde comprises glyoxal.

13. A method of fracturing a subterranean formation of a well used in recovering oil or gas, comprising the steps of:

preparing an aqueous polymer fluid;

preparing a crosslinking agent by combining in solution an amount of zirconium carbonate with glyoxal and allowing the solution to react, wherein carbon dioxide gas evolves from said solution as a by-product;

admixing said crosslinking agent with said aqueous polymer fluid; and

injecting said polymer fluid admixed with said crosslinking agent into the well at a sufficient rate or pressure to fracture the formation.

14. The method of claim 13, wherein said zirconium carbonate is reacted with said glyoxal in a molar ratio of zirconium ion to glyoxal in the range of about 1:0.5 to 1:20.

15. The method of claim 13, wherein said zirconium carbonate is reacted with said glyoxal in a molar ratio of zirconium ion to glyoxal in the range of about 1:2.5 to 1:7.

16. The method of claim 13, wherein said crosslinking agent is neutralized by the addition of a suitable base before said admixing step.

17. The method of claim 13, wherein said aqueous polymer fluid is prepared by blending together an aqueous fluid and a hydratable polymer capable of gelling in the presence of zirconium ions.