Set Retarding Additives for Cement From Aminomethylenephosphonic Acid Derivatives

Hydrophobic-substituted phosphonic or phosphinic acids and their alkali metal salts have been used in cements, primarily soil/cement mixtures, to improve the freeze-thaw properties and salt-resistance. Six- to eighteen-carbon alkyl phosphonic acids or their alkali metal salts are so described in U.S. Pat. No. 3,794,506. A plugging mixture for high temperature oil and gas wells comprising Portland cement and 1-hydroxy ethylidenephosphonic acid trisodium or tripotassium salts as set time extenders is described in Derwent abstract 71376B/39 (1979) of USSR Pat. No. 640,019. The use of these phosphonate salts at temperatures of 75.degree. to 150.degree. C. in amounts of 0.1-0.3% by weight is described in the abstract.

Other organic phosphorous acid derivatives are taught to be useful additives in cement compositions as turbulence-inducing and flow-property improver additives (U.S. Pat. Nos. 3,964,921 and 4,040,854, respectively). Another turbulence-inducer is a pyrolysis product of urea and a bis(alkylenepyrophosphate) (U.S. Pat. No. 3,409,080).

Alkylene diphosphonic acids and their water soluble salts are described as set time extenders and water reducing agents for gypsum plasters (U.S. Pat. No. 4,225,361). Lignins which have been phosphonoalkylated through an ether linkage or corresponding sulfonates, sulfides, hydroxyl or amine derivatives are taught to be useful primarily as dispersants or surfactants (U.S. Pat. No. 3,865,803) and are also said to be useful as "cement additives" without indicating specific uses.

Ultra-rapid hardening Portland cement compositions are described which contain various acid salt additives (U.S. Pat. No. 4,066,469). It states that use of acid phosphates as the acid salt additives is excluded since the phosphates have a characteristically powerful retarding property peculiar to them.

Most of the cement used in oil wells is called portland cement. Portland cement is manufactured by calcining raw materials consisting of limestone, clay, shale, and slag together at 2,600.degree. to 2,800.degree. F. in a rotary kiln.

The resulting material, is cooled and interground with small percentages of gypsum to form portland cement. In addition to the above raw materials, other components such as sand, bauxite, iron oxide, etc., may be added to adjust the chemical composition depending upon the type of portland cement desired.

The principal components of the finished portland cement are lime, silica, alumina, and iron. These components form the following complex compounds: Tricalcium aluminate, (3CaO.Al.sub.2 O.sub.3), tetracalcium aluminoferrite, (4CaO.Al.sub.2 O.sub.3.Fe.sub.2 O.sub.3), tricalcium silicate, (3CaO.SiO.sub.2), and dicalcium silicate, (2CaO.SiO.sub.2).

When water is added to cement, setting and hardening reactions begin immediately. The chemical compounds in the cement undergo the processes of hydration and recrystallization which results in a set product. The maximum amount of water that can be used with an oil-well cement is the amount which can be added before solids separation occurs. The minimum amount of water is the amount required to make the slurry pumpable. Therefore, the normal water ratio is governed by the maximum and minimum limits for a particular class of cement.

Thickening time is the time that the cement remains pumpable in the well. This is the most critical property of an oil-well cement. The thickening time has to be long enough to be pumped into place and short enough to permit operations to resume quickly. Generally, 3 hours provides the necessary placement time plus a safety factor.

Other factors, such as fluid loss, viscosity and density must be taken into consideration and additives are known to the art-skilled which affect each of these factors as well as that of set, or thickening, time as mentioned above. Another parameter which has an effect on set time is temperature. Cement sets more rapidly as the temperature increases. This must be taken into consideration particularly when pumping cement into deeper wells since temperature increases as the depth of the well becomes greater. Temperature also affects the strength of the cement, the strength becoming less as the temperature increases.

Because of this temperature effect, it is important to retard the setting of the cement employed in the deeper wells.

It has now been discovered that certain new phosphonomethylated compounds containing quaternary ammonium groups are useful in aqueous cement slurries as set retarding additives. These compounds and their preparation, have been disclosed in a copending application entitled "New Compounds Containing Quaternary Ammonium and Methylenephosphonic Acid Groups", Ser. No. 489,442, filed Apr. 28, 1983.

The compounds useful as cement set retarders in aqueous cement slurries are methylene phosphonic acid derivatives having the following formula: ##STR2## wherein A, B, C and D substituents are independently selected from hydrogen, methylenephosphonic acid, or salts thereof, hydroxypropyltrialkylammonium halide, wherein the trialkylammonium moiety contains alkyl groups having from 1 to 5 carbon atoms and n is 0 to 15, and wherein said substituents include at least one methylenephosphonic acid group, or salt thereof, and at least one hydroxypropyltrialkylammonium halide group.

The compounds useful in the present invention are substituted ammonia and amines in which at least one of the amine hydrogens is substituted with a methylenephosphonic acid group or salts thereof and at least one with a quaternary ammonium radical.

It has now been discovered that such a functionality when attached to a diamine or polyamine which also contains a methylenephosphonic acid group will when added to an aqueous cement slurry retard the setting of the cement.

The following describes a typical preparation of the compounds useful in the present invention.

Ethylenediamine (EDA) (15 g, 0.25 mole) and 94 g (0.25 mole) of a 50% aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride were added to a 500 ml round-bottom reaction flask equipped with a water-cooled reflux condenser, mechanical stirrer, thermometer with a temperature controller, and an addition funnel. The reaction mixture was heated to 90.degree. C. and digested for about one hour and cooled. Approximately 60 g of concentrated hydrochloric acid solution and 67.5 g (0.82 mole) of phosphorus acid were added to the reaction flask and heated to reflux and maintained for one hour. Aqueous 37% formaldehyde solution (67.4 g, 0.83 mole) was weighed into the addition funnel and added over a two-hour period. The reaction mixture was heated at reflux for an additional three hours and then cooled. The product was the derivative of EDA in which one hydrogen had been replaced with a 2-hydroxypropyltrimethylammonium chloride group and the remaining hydrogens with methylenephosphonic acid groups. Further description can be found in the above-mentioned copending application.

The above and other related compounds were determined to be useful as cement retarders by employing the following test.

1. The following ingredients were weighed:

cement--100 g

water--38 g

additive--0.2 g active

2. Water and liquid additive were mixed;

3. Cement was added to liquid, the bottle tightly closed and shaken to mix;

4. Bottle was placed in a pre-heated 180.degree. F. bath;

5. Setting of cement was checked after 6 and 24 hours.

A blank (no additive) was run for comparison with each of the additives.

The compounds listed in Table I were prepared and tested using the above procedure. Results of these tests on retarding cement setting are given in Table II.