NO842634L - PROCEDURE FOR AA RETARDING THE STRENGTH OF Aqueous Cement Swells. - Google Patents

Description

The invention relates to aqueous hydraulic cement slurry materials containing special setting retarders which are compounds derived from bis(methylamine)

of dicyclopentadiene.

Hydrophobically substituted phosphonic or phosphinic acids and

their alkali metal salts have been used in cements, mainly gravel/cement mixtures, to improve freeze-thaw properties and salt resistance. Alkylphosphonic acids with 6-18 carbon atoms or their alkali metal salts are thus described in US Patent 3,794,506. A sealing compound for high temperature oil and gas wells comprising portland cement and 1-hydroxyethylidene phosphonic acid trisodium or tripotassium salts as setting time - extenders are described in Derwent's abstract 71376B/39 (1979) in Soviet patent 640 019. The use of these phosphonate salts at temperatures of 75-150°C in amounts of 0.1-0.3% by weight is described in the abstract.

Other organic phosphoric acid derivatives are described to be suitable additives in cement materials as turbulence-inducing and flow property-improving additives (US Patent 3,964,921 and 4,040,854, respectively). Another turbulence inducing agent is a pyrolysis product of urea and bis(alkylene pyrophosphate) (US Patent 3,409,080).

Alkylene diphosphonic acids and their water-soluble salts are described as setting time-extending agents and water-reducing agents for gypsum plaster (US patent 4,225,361). Lignins which have been phosphonoalkylated by an ether bond or corresponding sulphonates, sulphides, hydroxyl or amine derivatives are described to be suitable mainly as dispersants or surfactants (US patent 3 8 65 8 03) and are also described to be suitable as "cement additives" without specific applications indicated.

Ultra-rapid-setting Portland cement materials have been described containing various acid salt additives (US Patent 4,066,469). It states that the use of acid phosphates as the acid salt additives is excluded since the phosphates have a characteristic strong retarding property which is special to them.

Most of the cement used in oil wells is called Portland cement. Portland cement is produced by calcining raw materials consisting of limestone, clay, shale and slag together at 1427-1538°C in a rotary cement kiln.

The resulting material is cooled and ground together

with small percentages of gypsum during the formation of portland cement. In addition to the above-mentioned raw materials, other components such as sand, bauxite, iron

oxide etc. for adjusting the chemical composition depending on the desired type of portland cement.

The main ingredients in the finished Portland cement are lime, silicon dioxide, aluminum oxide and iron. These components form the following complex compounds: tricalcium aluminate, (3CaO-Al203), tetracalcium aluminoferrite, (4CaO<*>Al203<*>Fe203), tricalcium silicate, (3CaO<*>SiO2) and dicalcium silicate, (2CaO"Si02).

When water is added to cement, setting and hardening reactions start immediately. The chemical compounds in the cement undergo the hydration and recrystallization processes that result in a hardened product. The maximum amount of water that can be used for an oil well cement is the amount that can be added before solids separation occurs. The minimum amount of water is the amount required to make the gruel pumpable. Therefore, the general proportion of water is governed by the maximum and minimum limits for a particular cement class.

The thickening time is the time the cement remains pumpable in the well. This is the most decisive property of an oil-well cement. The thickening time must be long enough so that it can be pumped into place and short enough so that operation can be resumed quickly. In general, 3 hours provides the required placement time plus a safety factor.

Other factors such as fluid loss, viscosity and density

must be taken into account, and additives that affect each of these factors as well as setting or thickening time factors as mentioned above are known to those skilled in the art.

Another parameter that has an effect on the setting time is the temperature. Cement hardens faster as the temperature increases. This must be taken into account especially when pumping cement into deeper wells, since the temperature increases after

as the depth of the well increases. The temperature also affects the strength of the cement, as the strength decreases as the temperature increases.

Because of this temperature effect, it is important to slow down the hardening of the cement used in the deeper wells.

It has now been discovered that certain new phosphonomethylated compounds are useful in aqueous cement slurries as setting retarding additives. Some of these compounds are chelating agents, while others are suitable as threshold agents for retarding the precipitation of metal ions from an aqueous solution. However, not all such compounds are suitable as cement setting retarders.

The products which are suitable as cement hardening retarders in the present invention have the following formula:

wherein the A, B, C and D substituents are each independently selected from hydrogen; -CH2PO3<H>2(methylenephosphono-);

-(CH2)nOH where n is 1-4; CH2CHOHS03H (hydroxyethyl sulfone-); CH2CHOHCH2S03H (hydroxypropyl sulfone-; -(CH2)nCOOH where n

is 1-3; and the alkali metal, alkaline earth metal, ammonia and amine salts of the aforementioned phosphonic, sulfonic or carboxylic acids, provided that at least one of the above-mentioned substituents is a methylenephosphonic acid group or a salt thereof.

It has been determined that not all dicyclopentadiene-bis(methylamine)-(DCPD-BMA) derivatives are suitable for the same purposes. Thus, only a few containing at least one methylenephosphonic acid group will be effective as setting retarders for cement. Even those containing the methylenephosphonic acid group will be ineffective if certain other groups are present. Thus, for example, the DCPD-BMA derivative containing one methylenesulfonic acid group and three methylenephosphonic acid groups does not retard the setting of cement under the conditions of the test.

While the compounds used in this way must contain at least one methylenephosphonate group as a substituent on the amine nitrogen, certain other groups may be present. Thus, the remaining amine hydrogen atoms may be unsubstituted. Substituents other than the methylenephosphone group include alkanol radicals where the alkyl group contains 1-4 carbon atoms; alkylcarboxylic acid radicals, where the alkyl group contains 2-4 carbon atoms; hydroxyethyl and hydroxypropyl sulfonic acid radicals; and the alkali metal, alkaline earth metal, ammonia or amine salts of any of the above phosphonic, sulphonic or carboxylic acid groups.

One must be aware that when mixed derivatives are obtained, it is usually not possible to direct or predict which amine hydrogen atoms are substituted. The product probably contains a mixture of isomeric compounds.

When formaldehyde and phosphoric acid are reacted with DCPD-bis(methylamine), hereafter called DCPD-BMA, the result is a new compound with the following structure:

The above compound is known to have excellent cement-retarding properties.

Other substituents for the hydrogen atoms in the amine groups of the above DCPD derivatives form suitable chelating agents, but only those compounds having at least one methylenephosphonic acid group or an alkali metal, alkaline earth metal, ammonia or amine salt derivative are effective as cement setting retarders.

Substituents other than methylene phosphonates give compounds with the following structure:

where A, B, X and Y can be hydrogen; C2-C8-hydroxyalkyl-; hydroxyethyl and hydroxypropyl sulfone, methylene, ethylene and propylene sulfone; C2-C4 alkylcarboxylic acid radicals; and alkali metal, alkaline earth metal, ammonia or amine

the salts of any of the foregoing acid derivatives;

with the additional provision that at least one of the groups must be a methylenephosphonic acid group or salt.

The following examples illustrate the preparation of the compounds suitable for the invention.

EXAMPLE 1

Deionized water (100 g) and 49^0 g (0.25 mol) of DCPD-BMA were weighed into a 500 mL round-necked reaction flask equipped with a water-cooled reflux condenser, mechanical stirrer, thermometer with temperature control, and an addition funnel. About. 120 g of concentrated HCl solution and 98.7 g (1.20 mol) of phosphoric acid were added to the aqueous amine solution and the reaction mixture was heated to reflux and kept at this for 1 hour. Aqueous 37% formaldehyde solution (85.1 g, 1.05 mol) was charged into the addition funnel and added over a period of 2 hours. The reaction mixture was heated at reflux for an additional 2 hours and then cooled. The product obtained was the DCPD-BMA derivative where each amine nitrogen atom is replaced by a methylenephosphonic acid group

EXAMPLE 2

The procedure according to Example 1 was followed, except that 0.60 mol of phosphoric acid and 0.53 mol of aqueous formaldehyde solution were used. The product obtained was the DCPD-BMA derivative where there are two methylenephosphonic acid group substituents, two hydrogen atoms remaining unsubstituted.

EXAMPLE 3

Deionized water (40 g) and 24.5 g (0.125 mol) DCPD-BMA were weighed into a 500 mL round-bottomed flask equipped with a water-cooled reflux condenser, mechanical stirrer, thermometer with temperature controller, and an addition funnel. Etch-alkali solution (10.1 g 50% strength) and 25.0 g (0.127 mol) of the sodium salt of 3-chloro-2-hydroxy-1-propanesulfonic acid were added with stirring and the reaction mixture heated at 85°C for 1 hour. Additional caustic alkali solution (21.0 g 50% strength) and 25.0 g of the sodium salt of 3-chloro-2-hydroxy-1-propanesulfonic acid were then added and the solution heated at 85°C for 1.5 hours. About. 60 g of concentrated HCl solution and 24.7 g (0.300 mol) of phosphoric acid were added and the reaction mixture heated to reflux and kept at this for 1 hour. Aqueous 37% formaldehyde solution

(21.3 g, 0.263 mol) was filled into the addition funnel and add-

set over a period of approx. 1 hour. The reaction mixture was heated at reflux for an additional 3 hours and then cooled. The product obtained was the DCPD-BMA derivative containing two methylenephosphonic acid and two 2-hydroxypropyl sulfonic acid groups -H2C-CHOH-CH2-SO3H.

EXAMPLE 4

The procedure according to Example 3 was followed, except

from the fact that 0.127 mol of the sodium salt of 3-chloro-2-hydroxy-1-propanesulfonic acid, 37.0 g (0.450 mol) of phosphoric acid and 3 2.0 g (0.394 mol) of 37% formaldehyde solution were used.

The product obtained was the DCPD-BMA derivative containing three methylenephosphonic acid groups and one 2-hydroxypropylsulfonic acid group.

EXAMPLE 5

Ethylene oxide (11.6 g, 0.263 mol) was reacted with 24.5 g (0.125 mol) of DCPD-BMA and the reaction product then phosphonomethylated according to the procedure of Example 1 using 0.300 mol of phosphoric acid and 0.263 mol of formaldehyde solution. The product obtained was the DCPD-BMA derivative containing two hydroxyethyl and two methylenephosphonic acid groups.

EXAMPLE 6

The procedure according to Example 5 was followed, except

from the amine being reacted with 0.132 mol of ethylene oxide and the reaction product phosphonomethylated using 0.4 50

mol of phosphoric acid and 0.3 94 mol of formaldehyde solution. The product obtained was the DCPD-BMA derivative containing one hydroxyethyl group and three methylenephosphonic acid groups.

EXAMPLE 7

Propylene oxide (7.6 g, 0.130 mol) was reacted with 24.5 g (0.125 mol) of DCPD-BMA and the reaction product then phosphonomethylated according to the procedure of Example 1 using 0.450 mol of phosphoric acid and 0.394 mol of formaldehyde solution . The product obtained was the same as the product of Example 6, except that it had a hydroxypropyl group instead of the hydroxyethyl group.

In a similar manner, several other compounds suitable for the invention were prepared (examples 9-11) as well as several similar compounds which are outside the scope of the invention. Their structures are listed in Table I.

The following test was used in determining whether a given compound was suitable as a setting retarder:

1. The following components were weighed:

cement - 10 0 g

water - 38 g

additive - 0.2 g active

2. Water and liquid additive were mixed; 3. Cement was added to the liquid, the bottle was tightly closed and shaken to mix; 4. The bottle was placed in a pre-heated bath at 82°C; 5. The hardening of the cement was examined after 6 and 24 hours.

A blank (without additive) was run for comparison

with each of the additives.

The following table shows the test results for

the connections indicated.

Claims (8)

1. Method for retarding the hardening of an aqueous cement slurry, which comprises adding a retarding agent to the slurry, characterized in that the retarding agent is a compound with the formula wherein the substituents A, B, C and D are independently selected from hydrogen; -CH 2 PO 3 H 2 ; -(CH2 )n OH where n is 1-4; CH2 CHOHS03 H; CH2 CHOHCH2 SO3 H; -(CH2 )n COOH where n is 1-3; and the alkali metal, alkaline earth metal, ammonia and amine salts of the aforementioned acids; provided that at least one of the above substituents is -CH 2 PO 3 H 2 or a salt thereof. 2. Method according to claim 1, where the compound used is the tetramethylenephosphonic acid derivative of dicyclopentadiene-bis(methylamine) or a salt thereof. 3. Method according to claim 1, where the compound used contains three methylenephosphonic acid groups as substituents on dicyclopentadiene-bis(methylamine) or a salt thereof. 4. Method according to claim 1, where the compound used contains two methylenephosphonic acid groups as substituents on dicyclopentadiene-bis(methylamine) or a salt thereof. 5. Method according to claim 1, where the temperature in the cement slurry is at least 82°C. 6. Method according to claim 1, where the cement slurry is injected into an oil well. 7. Method for processing a well by injecting a cement slurry into the well, characterized in that the cement slurry is the slurry produced by the method according to claim 1. 8. Well produced by the method according to claim 7.