Abstract:
The present invention relates to an improved composition that retards setting in the cementing and recementing of oil well casings, which can be applied at depths that vary between 13123.4 and 21325.5 ft. 
     The retarding composition is constituted by the following ingredients: sodium or potassium carboxymethylcellulose; sodium tetraborate and Dextrine, it being characterized in that it also contains an inorganic acid such as boric acid.

Description:
BACKGROUND OF THE INVENTION 
     In recent years the need to exploit oil resources at very considerable depths has been observed; this phenomenon has been the cause of multiple problems in the drilling and finishing techniques for oil wells, particularly in the application of slurry for cementing and recementing oil wells, since the internal temperature of the well becomes higher as its depth increases, which causes a faster setting of the slurry and makes its handling more difficult. 
     In the drilling, finishing and repair operations of oil wells cementing of the casings is employed; this technique is conducted by introducing a cement slurry to the bottom of the oil well through the cementing pipe; the slurry is placed in the annular space between the casing and the well walls, where it sets more or less rapidly, depending on the prevailing temperature. 
     In order to overcome the disadvantages of the immediate setting of the cement slurry, the applicant has carried out research activities. 
     In U.S. Pat. No. 3,905,826, having the same assignee as the instant invention, a setting retarding composition is described which has as basic ingredients carboxymethylcellulose, dextrine, borax, and optionally organic salts, and it presents as novel feature the fact that it can be applied with good results at depths of up to 13123.4 ft. 
     OBJECT OF THE INVENTION 
     It is, therefore, a purpose of the present invention to provide an improved composition for retarding setting which can be applied with good results at operating depths between 13123.4 and 21325.5 ft. 
     Another object of the present invention is to provide an improved setting retarding composition that can be applied with stable well depth temperature of the order of 392° F. 
     An additional object of the present invention is to provide a composition that increases the setting time of cement slurries up to five hours or more. 
     These objects and others that can be accomplished within the scope of the invention, shall be better understood and observed in more detail from the following specification. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The improved setting retarding composition of the present invention is constituted by the following ingredients: 
     
         ______________________________________                weight %______________________________________Sodium carboxymethylcellulose                  14 to 17Sodium teraborate      20 to 23Dextrine               25 to 28Inorganic acid         35 to 40______________________________________ 
    
     The inorganic acid selected is boric acid. 
     In the following examples shown in Tables I through V, there appear the experimental results obtained in the evaluation of a representative composition of the present invention having the following composition: 
     
         ______________________________________                weight %______________________________________Sodium carboxymethylcellulose                  14.60Sodium tetraborate     21.86White dextrine         27.04Boric acid             36.50______________________________________ 
    
     The tests carried out to evaluate the setting retarding composition comprise: thickening time measurings for casing cementing and recementing at depths between 13780 and 20013 ft., considering a temperature gradient of 37° F./328ft.; rheological properties at 80° and 125° F.; compression resistance in a 24 hour time period; and water loss at 995.4 psi differential pressure and at temperatures of 80° and 210° F. 
     The performed tests were conducted in accordance with the procedures established by the American Petroleum Institute, as shown in report API-RP-10B &#34;recommended practice for testing oil-well cements and cement additives&#34;; for this type of tests, silica flour, cement, and water without chlorides and additives regularly used for the cementing of wells, including sodium chloride, were employed. 
     The experimental tests were carried out using silica flour in order to avoid the resistance loss which appears in cement when it is subject to high temperatures, since the retarder is applied at temperatures higher than 210° F. 
     Among the tests that were carried out to evaluate the retarder there was one to determine the compatibility of the product with Hallad -9 and D-19 water loss reducers. (High molecular weight polymers). 
     Tables I, II and II.--In these Tables are shown the results of the application tests at different well-depth static temperatures of the setting retarding composition in the cementing and recementing of wall casings, regular and short, using different concentrations of the composition. Also, it can be observed that the slurries prepared with the setting retarder are adequate for casing cementing and recementing at depths between 13780 and 20013 ft. 
     
                                           TABLE I__________________________________________________________________________Setting Retarder Dosification For Regular Casing CementingIn Deep Wells (40% Of Silica Flour Is Employed By CementWeight).Formulation: 36.5/14.6/21.86/27.04% Of Active Ingredient           Water Loss ReducersBy Cement Weight                     Hallad-9                                      D-19    Static                  NaCl                                (High mol. Weight -Depth    Temp.        Boric               Salt                                Polymers  Thickening TimeExample(ft.)    (° F)        Acid NaCMC                  Borax                       Dextrine                            (%) (%)   (%) (hrs: min)__________________________________________________________________________1    14009.1    289.4        0.1825             0.0730                  0.1093                       0.1352                            --  --    --  3:15&#34;   &#34;   0.2555             0.1022                  0.15302                        0.18928                            --  --    --  4:15&#34;   &#34;   0.2555             0.1022                  0.15302                        0.18928                            5.0 --    --  4:00&#34;   &#34;   0.1825             0.0730                  0.1093                       0.1352                            --  0.5   --  4:00&#34;   &#34;   0.1825             0.0730                  0.1093                       0.1352                            --  --    0.5 4:002    14665.3    300.2        0.3650             0.1460                  0.2186                       0.2704                            --  --    --  3:45&#34;   &#34;   0.4380             0.1752                  0.26232                        0.32448                            5.0 --    --  4:00&#34;   &#34;   0.4380             0.1752                  0.26232                        0.32448                            --  0.5   --  4:00&#34;   &#34;   0.4380             0.1752                  0.26232                        0.32448                            --  --    0.5 4:003    15321.5    309.2         0.45625             0.1825                  0.27325                       0.3380                            --  --    --  3:00&#34;   &#34;   0.5475             0.2190                  0.3279                       0.4056                            --  --    --  4:00&#34;   &#34;   0.5840             0.2336                  0.34976                        0.43264                            5.0 --    --  4:00&#34;   &#34;   0.5475             0.2190                  0.3279                       0.4056                            --  0.5   --  4:00&#34;   &#34;   0.5475             0.2190                  0.3279                       0.4056                            --  --    0.5 4:004    16010.4    320  0.63875             0.2555                  0.38255                       0.4732                            --  --    --  3:40&#34;   &#34;   0.7300             0.2920                  0.4372                       0.5408                            --  --    --  4:30&#34;   &#34;    0.63875             0.2555                  0.38255                       0.4732                            5.0 --    --  3:305    16676.5    330.8        0.8030             0.3212                  0.48092                        0.59488                            --  --    --  3:30&#34;   &#34;   0.9855             0.3942                  0.59022                        0.73008                            --  --    --  4:30&#34;   &#34;   0.9855             0.3942                  0.59022                        0.73008                            5.0 --    --  4:156    17342.5    341.6        0.9490             0.3796                  0.56836                        0.70304                            --  --    --  3:30&#34;   &#34;    1.18625              .4745                   .71045                        .8788                            --  --    --  4:30&#34;   &#34;    1.18625              .4745                   .71045                        .8788                            5.0 --    --  4:157    18011.8    350.6        1.2775             0.5110                  0.7651                       0.9464                            --  --    --  4:00&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            --  --    --  5:00&#34;   &#34;   1.2775             0.5110                  0.7651                       0.9464                            5.0 --    --  3:45&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.0 --    --  4:408    18996.0    365  1.18625              .4745                   .71045                        .8788                            --  --    --  3:30&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            --  --    --  4:30&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.0 --    --  4:159    20013.1    379.4        1.4600             0.5840                  0.8744                       1.0816                            --  --    --  4:15&#34;   &#34;   1.6425             0.6570                  0.9837                       1.2168                            --  --    --  5:00&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.0 --    --  4:05&#34;   &#34;   1.6425             0.6570                  0.9837                       1.2168                            5.0 --    --  5:00__________________________________________________________________________ Slurry density 117.3 lb/ft.sup.3 60% of water is employed by cement weigh 
    
     
                                           TABLE II__________________________________________________________________________Setting Retarder Dosification For Regular Casing CementingIn Deep Wells. (40% Of Silica Flour Is Employed By CementWeight)Formulation: 36.5/14.6/21.86/27.04% Of Active IngredientBy Cement Weight                    Water Loss Reducers    Static                     NaCl                                   Hallad-9                                           D-19Depth    Temp.        Boric                  Salt                                   (High Mol. Weight                                                 Thickening TimeExample(ft)    (° F)        Acid  NaCMC                   Borax Dextrine                               (%) (%)     (%)   (hrs :__________________________________________________________________________                                                 min)10   14009.1    289.4        0.2555              0.1022                   0.15302                         0.18928                               --  --      --    4:15&#34;   &#34;   0.2555              0.1022                   0.15302                         0.18928                               5.0 --      --    4:00&#34;   &#34;   0.1825              0.730                   0.1093                         0.1352                               --  0.5     --    3:15&#34;   &#34;   0.1825              0.730                   0.1093                         0.1352                               --  --      0.5   3:3011   14993.4    303.8        0.45625              .1825                   .27325                         .3380 --  --      --    4:00&#34;   &#34;   0.5475              0.2190                   0.3279                         0.4056                               --  --      --    5:00&#34;   &#34;   0.45625              .1825                   .27325                         .3380 5.0 --      --    3:45&#34;   &#34;   0.5475              0.2190                   0.3279                         0.4056                               5.0 --      --    4:3012   16010.4    320 0.63875              .2555                   .38255                         .4732 --  --      --    2:50&#34;   &#34;   0.7300              0.2920                   0.4372                         0.5408                               --  --      --    4:00&#34;   &#34;   0.7300              0.2920                   0.4372                         0.5408                               5.0 --      --    3:45&#34;   &#34;   0.63875              .2555                   .38255                         .4732 --  0.5     --    3:00&#34;   &#34;   0.63875              .2555                   .38255                         .4732 --  --      0.5   3:1513   17011.1    334.4        1.00375              .4015                   .60115                         .7436 --  --      --    4:00&#34;   &#34;   1.18625              .4745                   .71045                         .8788 --  --      --    5:00&#34;   &#34;   1.00375              .4015                   .60115                         .7436 --  --      --    3:45&#34;   &#34;   1.18625              .4745                   .71045                         .8788 --  --      --    4:4014   18011.8    350.6        1.2775              0.5110                   0.7651                         0.9464                               --  --      --    3:45&#34;   &#34;   1.4600              0.5840                   0.8744                         1.0816                               --  --      --    5:00&#34;   &#34;   1.2775              0.5110                   0.7651                         0.9464                               5.0 --      --    3:30&#34;   &#34;   1.4600              0.5840                   0.8744                         1.0816                               5.0 --      --    4:4015   18996.0    365 1.3870              0.5548                   0.83068                         1.02752                               --  --      --    4:00&#34;   &#34;   1.6060              0.6424                   0.96184                         1.18976                               --  --      --    5:00&#34;   &#34;   1.3870              0.5548                   0.83068                         1.02752                               --  --      --    3:45&#34;   &#34;   1.6060              0.6424                   0.96184                         1.18976                               --  --      --    4:4016   20013.1    379.4        1.4600              0.5840                   0.8744                         1.0816                               --  --      --    4:00&#34;   &#34;   1.6425              0.6570                   0.9837                         1.2168                               --  --      --    5:00&#34;   &#34;   1.4600              0.5840                   0.8744                         1.0816                               5.0 --      --    3:45&#34;   &#34;   1.6425              0.6570                   0.9837                         1.2168                               5.0 --      --    5:00__________________________________________________________________________ Slurry density 117.3 lb/ft.sup.3, 60% of water is employed by cement weight 
    
     
                                           TABLE III__________________________________________________________________________Setting Retarder Dosification For Regular Casing CementingIn Deep Wells (40% Of Silica Flour Is Employed By CementWeight).Formulation: 36.5/14.6/21.86/27.04% Of Active IngredientBy Cement Weight                 Water Loss Reducers    Static                  NaCl                                Hallad-9                                        D-19Depth    Temp.        Boric               Salt                                (High Mol. Weight Polymers)                                                Thickening TimeExample(ft)    (° F)        Acid NaCMC                  Borax                       Dextrine                            (%) (%)     (%)     (hrs :__________________________________________________________________________                                                min)17   14009.1    289.4        0.63875              .2555                   .38255                        .4732                            --  --      --      4:15&#34;   &#34;   0.63875              .2555                   .38255                        .4732                            5.0 --      --      3:40&#34;   &#34;   0.63875              .2555                   .38255                        .4732                            --  0.5     --      4:00&#34;   &#34;   0.63875              .2555                   .38255                        .4732                            --  --      0.5     4:0518   14993.4    303.8        0.8030             0.3212                  0.48092                        0.59488                            --  --      --      4:00&#34;   &#34;   0.9490             0.3796                  0.56836                        0.70304                            --  --      --      5:00&#34;   &#34;   0.82125              .3285                  0.49185                        0.60840                            5.0 --      --      4:00&#34;   &#34;   0.9855             0.3942                  0.59022                        0.73008                            5.0 --      --      5:0019   16010.4    320 0.82125              .3285                  0.49185                        0.60840                            --  --      --      3:00&#34;   &#34;   1.0950             0.4380                  0.6558                        0.81120                            --  --      --      4:30&#34;   &#34;   0.9125             0.3650                  0.5465                       0.6760                            5.0 --      --      3:15&#34;   &#34;   1.0950             0.4380                  0.6558                        0.81120                            5.0 --      --      4:3020   17011.1    334.4        1.1680             0.4672                  0.69952                        0.86528                            --  --      --      4:00&#34;   &#34;   1.36875              .5475                  0.81975                       1.0140                            --  --      --      5:00&#34;   &#34;   1.18625              .4745                  0.71045                       0.8788                            5.0 --      --      3:40&#34;   &#34;   1.36875              .5475                  0.81975                       1.0140                            5.0 --      --      4:4521   18011.8    350.6        1.2775             0.5110                  0.7651                       0.9464   --      --      3:45&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816   --      --      4:30&#34;   &#34;   1.2775             0.5110                  0.7651                       0.9464                            5.0 --      --      4:30&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.0 --      --      4:3022   18996.0    365 1.4600             0.5840                  0.8744                       1.0816                            --  --      --      4:00&#34;   &#34;   1.6425             0.6570                  0.9837                       1.2168                            --  --      --      4:50&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.0 --      --      4:00&#34;   &#34;   1.8250             0.7300                  1.0930                       1.3520                            5.0 --      --      4:4023   20013.1    379.4        1.55125              .6205                  0.92905                       1.1492                            --  --      --      4:00&#34;   &#34;   1.73373              .6935                  1.03835                       1.2844                            --  --      --      5:00&#34;   &#34;   1.55125              .6205                  0.92905                       1.1492                            5.0 --      --      4:00&#34;   &#34;   1.73375              6935                  1.03835                       1.2844                            5.0 --      --      5:00__________________________________________________________________________ Slurry density 117.36 lb/ft.sup.3, 60% of water is employed by cement weight 
    
     TABLE IV.--In this table are shown the results obtained when the setting retarder is subject to the filtering and rheological properties tests of slurries prepared with the retarder and 40% of silica flour by cement weight. 
     In these examples it is shown that the setting retarder retains cement slurry water which enables reduction and even elimination of the use of water loss reducers. The rheological properties determined at 80° F. indicate that the slurries are easy to handle during preparation; properties at 125° F. show their behaviour or performance, that is, once they are placed in the well, it is observed that viscosities and yield points decrease, which causes a reduction of friction losses during displacement of slurry to the annular space. 
     
                                           TABLE IV__________________________________________________________________________Results Of The Filtering And Rheological Properties TestsOf Slurries Prepared With Setting Retarder And 40% Of SilicaFlour By Cement Weight                    % Of Active Ingredient Water LossSetting Retarder         By Cement Weight   Rheological Properties% Of Active Ingredient                (ΔP =                                       80° F                                                (125° F)By Cement Weight         Water Loss Reducers                                 995.4 psi)                                           ζy  ζyBoric                NaCl                    Hallad-9                           D-19  80° F                                       μp*                                           lb/  μp                                                    (lb/Ex. Acid   NaCMC        Borax            Dextrine                Salt                    (High Mol. Wt. polymers)                                 ft.sup.3 /30&#39;                                       (cp)                                           100 ft.sup.2                                                (cp)                                                    100__________________________________________________________________________                                                    ft.sup.2)24  0.1825   0.0730        0.1093            0.1352                --  --     --    0.02542                                       60  28   36  50    0.1825   0.0730        0.1093            0.1352                5.0 --     --    +0.01412                                       66   4   38  29    0.1825   0.0730        0.1093            0.1352                --  0.5    --    0.00681                                       100 14   81  53    0.1825   0.0730        0.1093            0.1352                --  --     0.5   0.0088                                       42  50   41  5225  0.3650   0.1460        0.2186            0.2704                --  --     --    0.01447                                       52  20   25  25    0.3650   0.1460        0.2186            0.2704                5.0 --     --    +0.01412                                       44   5   35  24    0.3650   0.1460        0.2186            0.2704                --  0.5    --    0.01235                                       120 23   66  44    0.3650   0.1460        0.2186            0.2704                --  --     0.5   0.01197                                       93  15   50  5026  0.7300   0.2920        0.4372            0.5408                --  --     --    0.00918                                       60  16   28  20    0.7300   0.2920        0.4372            0.5408                5.0 --     --    +0.01412                                       52   6   28  1427  1.0950   0.4380        0.6558            0.8112                --  --     --    0.00423                                       83  13   33   6    1.0950   0.4380        0.6558            0.8112                5.0 --     --    0.01341                                       68   7   27   428  1.2775   0.5110        0.7651            0.9464                --  --     --    0.00247                                       90  16   38   4    1.2775   0.5110        0.7651            0.9464                5.0 --     --    0.01341                                       70   8   27   529  1.4600   0.5840        0.8744            1.0816                --  --     --    0.00211                                       100 21   42   2    1.4600   0.5840        0.8744            1.0816                5.0 --     --    0.01341                                       74  10   28   530  1.6425   0.6570        0.9837            1.2168                --  --     --    0.00141                                       110 26   46   0__________________________________________________________________________ Slurry density 117.3 lb/ft.sup.3, 60% of water is employed by cement weight* μp.-Viscosity; ζy.-yield point. 
    
     TABLE V.--In this Table are shown the results obtained when the retarding composition is subject to compression resistance tests in a 24 hour interval. The retarder is used at different concentrations according to the well depth and stable temperature, with mixtures prepared from cement and silica flour. 
     According to the results shown in the aforementioned Table, it is observed that the mixtures of cement, silica flour and retarder acquire high resistances after 24 hours of their preparation. 
     
                                           TABLE V__________________________________________________________________________Results Of The Compression Resistance Tests At 24 Hours OfSlurries Prepared With Setting Retarder And 40% Of SilicaFlour By Cement WeightSetting Retarder% Of Active Ingredient           Water Loss ReducersBy Cement Weight                              Compression    Static                  NaCl         Resistance TestsDepth    Temp.        Boric               Salt                                Hallad-9                                     D-19                                         At 24 HoursExample(ft)    (° F)        Acid NACMC                  Borax                       Dextrine                            (%) (%)  (%) psi__________________________________________________________________________31   14009.1    289.4        0.1825             0.0730                  0.1093                       0.1352                            --  --   --  3256.38&#34;   &#34;   0.1825             0.0730                  0.1093                       0.1352                            --  0.5  --  2445.84&#34;   &#34;   0.1825             0.0730                  0.1093                       0.1352                            --  --   0.5 1592.64&#34;   &#34;   0.2555             0.1022                   0.15302                        0.18928                            --  --   --  2844.0&#34;   &#34;   0.2555             0.1022                   0.15302                        0.18928                            5.0 --   --  2915.1&#34;   &#34;   0.5475             0.2190                  0.3279                       0.4056                            --  --   --   625.6832   16010.4    320  0.63875             0.2555                   0.38255                       0.4732                            --  --   --  +1791.72&#34;   &#34;    0.63875             0.2555                   0.38255                       0.4732                            5.0 --   --  +3924.72&#34;   &#34;    0.63875             0.2555                   0.38255                       0.4732                            --  0.5  --  +3441.24&#34;   &#34;    0.63875             0.2555                   0.38255                       0.4372                            --  --   0.5 +2616.48&#34;   &#34;   0.7300             0.2920                  0.4372                       0.5408                            --  --   --  1791.72&#34;   &#34;   0.7300             0.2920                  0.4372                       0.5408                            5.0 --   --  3924.72&#34;   &#34;   1.0950             0.4380                  0.6558                       0.8112                            5.0 --   --  2866.6633   18011.8    350.6        1.0950             0.4380                  0.6558                       0.8112                            --  --   --  7309.08&#34;   &#34;   1.2775             0.5110                  0.7651                       0.9464                            --  --   --  6214.14&#34;   &#34;   1.4600             0.5840                  0.8744                       0.0816                            --  --   --  5133.42&#34;   &#34;   1.2775             0.5110                  0.7651                       0.9464                            5.0 --   --&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.034   20013.1    379.4        1.4600             0.5840                  0.8744                       1.0816                            --  --   --  6541.2&#34;   &#34;   1.6425             0.6570                  0.9837                       1.2168                            --  --   --  5645.34&#34;   &#34;   1.8250             0.7300                  0.930                       1.3520                            --  --   --  4749.48&#34;   &#34;   1.4600             0.5840                  0.8744                       1.0816                            5.0 --   --  2374.74&#34;   &#34;   1.6425             0.6570                  0.9837                       1.2168                            5.0 --   --  2317.86&#34;   &#34;   1.8250             0.7300                  1.0930                       1.3520                            5.0 --   --  2275.2__________________________________________________________________________ Slurry density 117.36 lb/ft.sup.3, 60% of water is employed by cement weight 
    
     TABLE IV.--In the following Table, comparative results are shown of the efficiency of the retarder of the present invention, in comparison with other known retarders, thereby illustrating the properties presented by the new retarder are superior to those of other commercial products (A and B). 
     
                                           TABLE VI__________________________________________________________________________Setting Retarder Efficiency In Comparison With Two Com-mercial Products &#34;A&#34; And &#34;B&#34;. 40% Of Silica Flour isEmployed By Cement Weight.   Additive   Water   Concen-    Loss  Compres-   tration         Thick-              (ΔP =                    sion Re-                          Plastic   By Ce-         ening              995.4 sistance                          Visco-                              Yield   ment -         Time psi)  At 24 Hrs                          sity                              Point   Weight         C-10 T = 210° F                    C-10S 80° F                              80° FAdditive   (%)   (hr:min)              ft.sup.3 /30&#39;                    psi   (cp)                              psi__________________________________________________________________________New ret-arder   3.0    3:30               .0024                    4450.86                           83 0.0090A       3.0    3:40              0.0234                    2360.52                          106 0B       3.0    2:30              0.0191                    2630.7                           92 0.0180Efficiency(%) of newretarder incomparisonwith A         95   0.03347                    2673.36                          *   *Efficiencyof new ret-arder in com-parison withB              140 0.0273                    2403.18                          110 2.8440__________________________________________________________________________ * These were not calculated, since slurries with 3% by weight of product behave as dilatant fluids. Under these conditions, their use in cementing is disadvantageous. 
    
     According to the retarder performance in the thickening time tests, it is shown that the additive of the present invention can be successfully used at stable well depth temperatures of the order of 392° F. 
     Also, if concentrations of the retarding additive higher than 4.5% by cement weight are used, the setting of the slurry can be retarded for a period of time longer than five hours, at depths of 20013 ft. 
     The following can be cited as additional advantages of the retarder of the present invention: 
     The setting retarder is compatible with products regularly used in the cementing of oil-well casings. 
     Elimination or partial reduction of the use of water loss reducing agents. 
     Reduction of friction losses during displacement of the retarder to annular space. 
     The retarder does not produce foam during slurry preparation; consequently, the use of anti-foaming agents is eliminated. 
     Finally, it is evident that slurries prepared with silica flour and the retarder can be used safely in the cementing of casings, since they present a resistance higher than 497.7 psi, which are commendable to continue the drilling or finishing of an oil-well.