Petrolite Corporation

Balram Dhawan

Derek Redmore

John L Przybylinski

A method for inhibiting oilfield scale formation including calcite in a high brine environment comprises introducing an effective amount of a scale inhibiting composition to a high brine environment susceptible to calcite scale formation. The environment has a total dissolved solids content of at least about 150 g/l, and the scale inhibiting composition comprises an aminomethylene posphonate of the formula ##STR1## wherein x is 2 or 3, each Z is independently selected from among H and CH.sub.3, and R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently selected from among hydrogen and --CH.sub.2 PO.sub.3 M.sub.2 wherein the M's are independently selected from among the hydrogen and cations associated with Lewis bases, such that at least about 80% of the R.sup.1, R.sup.2, R.sup.3, and R.sup.4 in the composition is --CH.sub.2 PO.sub.3 M.sub.2.

Methods for inhibition of scale in high brine environments

A method for preparation of an aminomethylene phosphonate useful as a scale inhibitor in high brine environments. The method comprises phosphonomethylating an amine of the formula ##STR1## wherein x is an integer from 1 to 6 and the Z's are selected from the group consisting of hydrogen and --CH.sub.3, to produce an aminomethylene phosphonate of the formula ##STR2## wherein x and the Z's are defined as above and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are indepenedently selected from the group consisting of hydrogen and --CH.sub.2 PO.sub.3 H.sub.2, such that at least about 80% of the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 in a mixture of the aminomethylene phosphonate is --CH.sub.2 PO.sub.3 H.sub.2. Related methods and compositions are also disclosed.

A method for inhibition of scale formation using a composition comprising an N-phosphonomethylated amino-2-hydroxypropylene polymer having a molecular weight of between about 300 and about 5000 and having the structural formula ##STR1## wherein (i) R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are independently selected from the group consisting of hydrogen, phosphonomethyl radical corresponding to the formula --CH.sub.2 PO(OH).sub.2, and water treating acceptable salts of such phosphonomethyl radical, with the proviso that the percentage of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 being hydrogen does not exceed about 30; (ii) R is a divalent radical selected from the group consisting of (a) unsubstituted alkylene groups having at least about 2 and at most about 12 carbon atoms, (b) substituted alkylene groups having at least about 2 and at most about 12 carbon atoms wherein at least one hydrogen of the alkylene group is substituted with a radical selected from the group consisting of methyl, ethyl, propyl, butyl, methyl ammonium, ethyl ammonium and ammonium groups, and the other hydrogens of the substituted alkylene group are unsubstituted, (c) cycloalkylene groups having at least 3 and at most about 12 carbon atoms, and (d) --R'--N--R'-- wherein R.sub.7 is defined as R.sub.1, R.sub.2 R.sub.3, R.sub.4, R.sub.5 and R.sub.6 above, with the proviso that the percentage of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.7 being hydrogen not exceed about 30, and R' and R' are independently selected from the group consisting of such unsubstituted alkylene groups, and such cycoalkylene groups; and (iii) n is from about 1 to about 25 is disclosed.

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St. Louis, MO, United States of America

Balram Dhawan