Families of scale-inhibitors having different absorption profiles and their application in oilfield

Abstract

The current invention relates to families of scale-inhibitors having different UV/VIS absorption profiles and their application in a method for stimulating an oilfield comprising those families.

Claims

1. A method for imparting scale inhibition in an oilfield, the method comprising the steps of: a) injecting at least two inflow streams of a fluid into at least two production zones of an oil producing well that is linked to the oilfield, or into at least two different oil producing wells that are linked to the oilfield, wherein scale inhibitor having detectable moieties is introduced into the oilfield and/or into the fluid, so as to be present in the two zones or wells, wherein two different scale inhibitors are introduced, one for each of the two zones or wells, said different scale inhibitors having different detectable moieties, such that these different scale inhibitors have distinct absorption maxima that can be determined by an absorption analytical method; b) displacing oil from the oil producing well; c) recovering an outflow stream of fluid comprising the oil; wherein at least two outflow streams, one from each of the two zones or one from each of the two wells, are combined before said recovering; and d) measuring the amounts of the different scale inhibitors present in the recovered stream of fluid, or in a fluid derived from the recovered stream of fluid, by an absorption analytical method; and wherein one of the two scale inhibitors is a polymer (P1) as obtained by polymerization of: an ethylenically unsaturated carboxylic monomer; an ethylenically unsaturated sulphonic acid monomer or water soluble salts thereof; a styrene monomer, optionally substituted by one to three groups; in the presence of an hypophosphorous adduct of the formula (A1):
(X.sub.2O.sub.3P).sub.2CHYPO.sub.2X.sub.2(A1) wherein: X is H or an alkali metal, alkaline earth or ammonium, Y is an alkylene group, which may be linear or branched, having from 1 to 5 carbon atoms; and wherein the other one of the two scale inhibitors is a polymer (P2) as obtained by polymerization of: an ethylenically unsaturated carboxylic monomer; an ethylenically unsaturated sulphonic acid monomer or water soluble salts thereof; a vinyl heteroaromatic monomer comprising at least one heteroatom selected from N, P and O, which can be substituted by at least one hydrocarbon group having 1 to 6 carbon atoms, and which optionally contains functional groups; in the presence of an hypophosphorous adduct of the formula (A1):
(X.sub.2O.sub.3P).sub.2CHYPO.sub.2X.sub.2(A1) wherein: X is H or an alkali metal, alkaline earth or ammonium, Y is an alkylene group, which may be linear or branched, having from 1 to 5 carbon atoms, whereby the hypophoshorous adducts of the formula (A1) are identical or distinct.

2. The method of claim 1, wherein if in step (d) the amount of one of the two scale inhibitors is below a predetermined value, the method further comprises the step of: e) addressing a scale formation problem in the zone or well that is associated with said scale inhibitor.

3. The method of claim 1, wherein the absorption analytical method is UV/VIS spectroscopy.

4. The method of claim 1, wherein in formula (A1) Y is a methylene or an ethylene group.

5. The method of claim 1, wherein in formula (A1) X is sodium (Na).

6. The method of claim 1, wherein the vinyl heteroaromatic monomer contains sulphate, carboxylate, phosphonate and/or phosphinate functional groups.

7. A polymer having an absorption maximum between 215 and 240 nm and having an average general formula (1):
(X.sub.2O.sub.3P).sub.2CHYPO.sub.2XZ1(1) wherein X is H or an alkali metal, alkaline earth or ammonium, Y is an alkylene group, which may be linear or branched, having from 1 to 5 carbon atoms, and Z1 is a polymer chain obtained by polymerization of an ethylenically unsaturated carboxylic monomer with an ethylenically unsaturated sulphonic acid monomer or water soluble salts thereof and a styrene monomer, which can be substituted by one to three groups that may be identical or different, and which are selected to provide said absorption maximum, in the presence of an hypophosphorous adduct of the formula (A1):
(X.sub.2O.sub.3P).sub.2CHYPO.sub.2X.sub.2(A1) wherein X and Y have the same meaning as in formula (1).

8. A polymer as defined in claim 7, wherein the substituent groups of the styrene monomer are chosen from H, SO.sub.3H, SO.sub.3Na, NH.sub.2, Me.sub.2N, COOH, CH.sub.2Cl, CH.sub.2OH and OH.

9. A polymer as defined in claim 7, wherein the ethylenically unsaturated carboxylic monomer is selected from the group consisting of: acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, crotonic acid isocrotonic acid, angelic acid and tiglic acid.

10. A polymer as defined in claim 7, wherein the ethylenically unsaturated sulphonic acid monomer is selected from the group consisting of: vinyl sulphonic acid, 2-acrylamido-2-methyl propane sulphonic acid, allyl sulphonic acid, and methallyl sulphonic acid.

11. A polymer as defined in claim 7, wherein the polymer is selected from the group consisting of: copolymers of vinyl sulphonic acid with acrylic and/or maleic acid and/or vinyl phosphonic and/or vinylidene diphosphonic acid.

12. A polymer having an absorption maximum between 240 and 400 nm and having an average general formula (2):
(X.sub.2O.sub.3P).sub.2CHYPO.sub.2XZ.sub.2(2) wherein X is H or an alkali metal, alkaline earth or ammonium, Y is an alkylene group, which may be linear or branched, having from 1 to 5 carbon atoms, and Z2 is a polymer chain obtained by polymerization of an ethylenically unsaturated carboxylic monomer with an ethylenically unsaturated sulphonic acid monomer or water soluble salts thereof and a vinyl heteroaromatic monomer, which can be substituted by one to three groups that may be identical or different, and selected to provide said absorption maximum, in the presence of an hypophosphorous adduct of the formula (A2):
(X.sub.2O.sub.3P).sub.2CHYPO.sub.2X.sub.2(A2) wherein X and Y have the same meaning as in formula (2).

13. A polymer as defined in claim 12, wherein the ethylenically unsaturated carboxylic monomer is selected from the group consisting of: acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, aconitic acid, mesaconic acid, citraconic acid, crotonic acid, isocrotonic acid, angelic acid and tiglic acid.

14. A polymer as defined in claim 12, wherein the ethylenically unsaturated sulphonic acid monomer is selected from the group consisting of: vinyl sulphonic acid, 2-acrylamido-2-methyl propane sulphonic acid, allyl sulphonic acid, and methallyl sulphonic acid.

15. A polymer as defined in claim 12, wherein the polymer is selected from the group consisting of: copolymers of vinyl sulphonic acid with acrylic and/or maleic acid and/or vinyl phosphonic and/or vinylidene diphosphonic acid.

Description

EXAMPLE 1

Preparation of DPPE

(1) 480 g tetra-sodium vinylidene diphosphonate (37.4% aqueous solution, 0.47 moles) and 358 g hypophosphorus acid (16% aqueous solution, 0.47 moles) were charged to a reaction vessel and heated to 100 C.

(2) 22.3 g sodium persulphate (10% aqueous solution 0.0094 moles) were added via an addition funnel over 1 hour. The reaction mixture was left to reflux for further 2 hours and allowed to cool. The product contained no unreacted vinyl diphosphonate by .sup.31P NMR.

EXAMPLE 2

Preparation of DPPE Capped NaSS-stat-AA-stat-SVS Telomer

(3) Into a 1 L jacketed reactor equipped with a reflux condenser and mechanical agitator was added Sodium Vinyl Sulphonate (127.7 g, 25% active), a solution of DPPE (70 g, 14.7% active) and a solution of Sodium Styrene Sulphonate (146.4 g, 10%). The reaction mixture was heated to reflux temperature (115 C. jacket temperature) with stirring. Once reflux temperature was attained, three feeds were added independently to the reactor. Feed 1 comprised acrylic acid (127.4 g, 80%) and was added to the reaction mixture over 120 minutes. Feed 2 was comprised of Sodium vinyl Sulphonate (383.2 g, 25% active) and Sodium Styrene Sulphonate (146.4 g, 10%) and was added in parallel over 120 minutes. The final feed was Sodium persulphate (84.2 g, 10%) and was added over 190 minutes. Upon completion of the persulphate feed, the reaction mixture was held at reflux temperature for a further 30 minutes wherapon it was cooled to room temperature and the solution discharged. Analysis by .sup.31P NMR revealed 75% of the DPPE adduct had been reacted to form polymeric species. Aqueous GPC gave a bimodal distribution with an Mn 3198, Mw 8947 g/mol. HPLC analysis demonstrated near quantitative conversion of Acrylic acid (<10 ppm) and Sodium Styrene Sulphonate (<10 ppm).

EXAMPLE 3

Preparation of DPPE Capped 2VP-stat-AA-stat-SVS Telomer

(4) Into a 250 ml 3 necked round bottomed flask equipped with a reflux condenser and magnetic stirrer bar was added a solution of Sodium Vinyl Sulphonate (13.1 g, 25% active) and a solution of DPPE (5 g, 14.7% active). The reaction flask was heated in an oil bath set at 95 C. Once the targeted temperature was attained, three feeds were added independently to the flask. Feed 1 comprised acrylic acid (9.1 g, 80%) and 2-vinyl pyridine (1.1 g, 99.8%) and was added to the reaction mixture over 120 minutes. Feed 2 was comprised of Sodium vinyl Sulphonate (39.4, 25% active) and was added in parallel over 120 minutes. The final feed was Sodium Persulphate (6 g, 10%) and was added over 195 minutes. Upon completion of the Persulphate feed, the reaction mixture was held at temperature for a further 30 minutes whereupon it was cooled to room temperature and the solution discharged. Analysis by .sup.31P NMR revealed 60% of the DPPE adduct had been reacted to form polymeric species. Aqueous GPC (PEO calibration) gave a bimodal distribution with an Mn 3358, Mw 11580 g/mol. Multidetector GPC analysis (RI and UV @ 254 nm) confirmed homogenous incorporation of 2VP across the Molecular weight distribution. HPLC analysis demonstrated near quantitative conversion of Acrylic acid (<10 ppm) and 2-vinyl pyridine (<20 ppm).

EXAMPLE 4

Preparation of DPPE Capped 4VP-stat-AA-stat-SVS Telomer

(5) Into a 250 ml 3 necked round bottomed flask equipped with a reflux condenser and magnetic stirrer bar was added a solution of Sodium Vinyl Sulphonate (13.1 g, 25% active) and a solution of DPPE (5 g, 14.7% active). The reaction flask was heated in an oil bath set at 95 C. Once the targeted temperature was attained, three feeds were added independently to the flask. Feed 1 comprised acrylic acid (9.1 g, 80%) and 4-vinyl pyridine (1.1 g, 99.8%) and was added to the reaction mixture over 120 minutes. Feed 2 was comprised of Sodium vinyl Sulphonate (39.4, 25% active) and was added in parallel over 120 minutes. The final feed was Sodium Persulphate (6 g, 10%) and was added over 195 minutes. Upon completion of the Persulphate feed, the reaction mixture was held at temperature for a further 30 minutes whereupon it was cooled to room temperature and the solution discharged. Analysis by .sup.31P NMR revealed 49.3% of the DPPE adduct had been reacted to form polymeric species. Aqueous GPC (PEO calibration) gave a bimodal distribution with an Mn 4300, Mw 8900 g/mol. Multidetector GPC analysis (RI and UV @ 254 nm) confirmed homogenous incorporation of 4VP across the Molecular weight distribution. HPLC analysis demonstrated near quantitative conversion of Acrylic acid (<10 ppm) and 4-vinyl pyridine (<20 ppm).

EXAMPLE 5

Preparation of DPPE Capped 2-SPV-stat-AA-stat-SVS Telomer

(6) Into a 250 ml 3 necked round bottomed flask equipped with a reflux condenser and magnetic stirrer bar was added a solution of Sodium Vinyl Sulphonate (13.1 g, 25% active) and a solution of DPPE (5 g, 14.7% active). The reaction flask was heated in an oil bath set at 95 C. Once the targeted temperature was attained, three feeds were added independently to the flask. Feed 1 comprised acrylic acid (9.1 g, 80%), 1-(3-Sulfopropyl)-2-vinyl pyridinium betaine (2.32 g, 99%) and water (20.8 g) was added to the reaction mixture over 120 minutes. Feed 2 was comprised of Sodium Vinyl Sulphonate (39.4, 25% active) and was added in parallel over 120 minutes. The final feed was Sodium Persulphate (6 g, 10%) and was added over 195 minutes. Upon completion of the Persulphate feed, the reaction mixture was held at temperature for a further 30 minutes whereupon it was cooled to room temperature and the solution discharged. Analysis by .sup.31P NMR revealed 44.9% of the DPPE adduct had been reacted to form polymeric species. Aqueous GPC (PEO calibration) gave a bimodal distribution with an Mn 11556, Mw 20580 g/mol. HPLC analysis demonstrated near quantitative conversion of Acrylic acid (<10 ppm) and 1-(3-Sulfopropyl)-2-vinyl pyridinium betaine (<20 ppm).

EXAMPLE 6

Preparation of DPPE Capped 4SPV-stat-AA-stat-SVS Telomer

(7) Into a 250 ml 3 necked round bottomed flask equipped with a reflux condenser and magnetic stirrer bar was added a solution of Sodium Vinyl Sulphonate (13.1 g, 25% active) and a solution of DPPE (5 g, 14.7% active). The reaction flask was heated in an oil bath set at 95 C. Once the targeted temperature was attained, three feeds were added independently to the flask. Feed 1 comprised acrylic acid (9.1 g, 80%), 1-(3-Sulfopropyl)-4-vinyl pyridinium betaine (2.32 g, 99%) and water (20.8 g) and was added to the reaction mixture over 120 minutes. Feed 2 was comprised of Sodium vinyl Sulphonate (39.4, 25% active) and was added in parallel over 120 minutes. The final feed was Sodium Persulphate (6 g, 10%) and was added over 195 minutes. Upon completion of the Persulphate feed, the reaction mixture was held at temperature for a further 30 minutes whereupon it was cooled to room temperature and the solution discharged. Analysis by .sup.31P NMR revealed 47.2% of the DPPE adduct had been reacted to form polymeric species. Aqueous GPC (PEO calibration) gave a bimodal distribution with an Mn 5500, Mw 11300 g/mol. HPLC analysis demonstrated near quantitative conversion of Acrylic acid (<10 ppm) and 1-(3-Sulfopropyl)-4-vinyl pyridinium betaine (<20 ppm).

EXAMPLE 7

UV Absorbance Profile

(8) UV absorber monomers synthesised in examples 2-6 have been detected using UV/VIS spectroscopy. For monomers, a 10 ppm (as active polymer) solution of each sample was prepared. For polymers, a 100 ppm (as active polymer) solution of each polymer was prepared. The pH of these solutions was adjusted at 5,5. The absorbance was then measured over the wavelength range of 200 nm to 400 nm in standard 1 cm path length cells using a Perkin Elmer UV/VIS spectrophotometer.

(9) The absorbance maximum and the corresponding absorbance were determined for each sample.

(10) The results are gathered in table 3 below.

(11) TABLE-US-00003 TABLE 3 UV/VIS data Family 1 Absorbance maximum Corresponding Sample (nm) Absorbance NaSS monomer 246 1.09 Example 2 223 0.48

(12) TABLE-US-00004 TABLE 4 UV/VIS data Family 2 Absorbance maximum Corresponding Sample (nm) Absorbance 2VP monomer 278 0.92 Example 3 264 0.25 4VP monomer 246 1.05 Example 4 258 0.18 2SPV monomer 287 0.43 Example 5 269 0.24 4SPV monomer 271 0.63 Example 6 257 0.13

(13) Data from table 3 and 4 show a shift of maximum absorbance between UV-absorber monomers and polymers. This shift corresponds to a perfect incorporation of UV-absorber monomers during polymerisation.

EXAMPLE 8

Thermal Stability of UV Profiles

(14) Solutions of polymers from example 2 to 6 were made up to the desired concentration (5% active polymer) in synthetic sea water. The pH was adjusted to 5.5. 60 mls of each solution was poured into a Teflon liner (internal volume of 100 mls) of a stainless steel bomb. The individual solutions were then degassed for approximately 30 minutes. The Teflon liners were then sealed and placed into the stainless steel bombs which were placed in an oven at 212 F. for 1 week. Following this, the bombs were allowed to cool.

(15) The UV absorption profiles were determined for each aged solution after dilution at 100 ppm active polymer and compared to the one obtained on un-aged solution at the same concentration. The UV absorption profile before and after aging are exactly the same.

EXAMPLE 9

Barium Sulfate Scale Inhibition

(16) The polymers prepared in examples 2-6 were tested for their ability to inhibit barium sulphate scale formation. The test method for measuring inhibition of barium sulphate consisted of measuring the level of soluble barium after mixing of two incompatible salt solutions in a bottle, then observing the change in the mixture without agitation for a given time, and measuring the soluble barium by a spectroscopic method (ICP-AES). The experiments include a control test without inhibitor and tests in the presence of inhibitors.

(17) This evaluation was carried out at 95 C. and pH 5.5 after mixing two brines, one of which has the composition of the formation water of the Forties Field in the North Sea (contains barium) and the other has the seawater composition containing sulfate. The inhibitor was placed in the seawater. The inhibitor concentration was 15 ppm (of active ingredient) relative to the final mixture. The pH of the seawater solution containing inhibitor was brought to about 5.5 with a sodium acetate/acetic acid buffer solution.

(18) The brine compositions (Forties water and seawater) were the following:

(19) TABLE-US-00005 Ion mg/L Salt Salt (g/L) Forties Water Na.sup.+ 31275 NaCl 79.50 Ca.sup.+ 2000 CaCl.sub.2, 2H.sub.2O 7.34 Mg.sup.2+ 739 MgCl.sub.2, 6H.sub.2O 6.18 K.sup.+ 654 KCl 1.25 Ba.sup.2 269 BaCl.sub.2, 2H.sub.2O 0.48 Sr.sup.2+ 87.6 SrCl.sub.2, 6H.sub.2O 2.35 Seawater Na.sup.+ 10890 NaCl 24.40 Ca.sup.2+ 428 CaCl.sub.2, 2H.sub.2O 1.57 Mg.sup.2+ 1368 MgCl.sub.2, 6H.sub.2O 11.44 K.sup.+ 460 KCl 0.88 SO.sub.4.sup.2 2690 Na.sub.2SO.sub.4 3.97

(20) 100 ml of each of these liquids was placed in polyethylene bottles. Once the temperature of the brines has settled to 95 C. in an oven, the contents of the Forties water bottle were poured into the bottle containing the barium. The mixture was shaken manually then replaced in the oven at 95 C. for 2 hours. For each test series, two control tests were run:

(21) Min blank: this is a test without inhibitor and the barium ion content will be minimal (maximum precipitation of BaSO.sub.4);

(22) Max blank: this is a test without sulfate and without inhibitor; the seawater is replaced by purified water and the barium ion content will be maximal as there is no precipitation.

(23) After two hours of testing, the bottles were removed from the oven and a 5 ml sample is taken then diluted in 5 ml of a soaking solution whose composition is: 5000 ppm KCl/1000 ppm PVA (polyvinyl sodium sulfonate) adjusted to pH 8-8.5 (with 0.01 N NaOH). The barium from these samples is assayed (ICP-AES) and the inhibition effectiveness deduced, expressed in the formula below:

(24) $\%\mathrm{efficiency}=\frac{\left[{\mathrm{Ba}}^{2+}\right]-{\left[{\mathrm{Ba}}^{2+}\right]}_{\min }}{{\left[{\mathrm{Ba}}^{2+}\right]}_{\max }-{\left[{\mathrm{Ba}}^{2+}\right]}_{\min }}*100$
where
[Ba.sup.2+].sub.max=Ba.sup.2+ concentration in max blank
[Ba.sup.2+].sub.min=Ba.sup.2+ concentration in min blank
The results are shown in the following table 5.

(25) TABLE-US-00006 TABLE 5 % BaSO.sub.4 inhibition Inhibitor effectiveness (15 ppm) Example 2 37 Example 3 42 Example 4 45 Example 5 42 Example 6 48

(26) This test was also conducted on thermally aged polymers obtained in example 8, i.e. thermal aging Sea Water at 122 F. during 1 week. The level of performance measured on aged polymers was the same as the one measured on fresh polymers and presented in table 4.

EXAMPLE 10

Adsorption on Clay Under Static Conditions

(27) The additives according to the invention were evaluated for their ability to adsorb on clay.

(28) For this purpose, a solution of known concentration of inhibitor in synthetic brine was brought into contact for 20 hours, at 85 C., with a known quantity of solid. The solid suspension was then centrifuged and filtered, then analyzed in terms of dissolved organic carbon. The adsorbed amount was measured using the following protocol:

(29) For each solution of additive diluted in seawater at the concentration in question, the organic carbon concentration (COT.sub.SM- in ppm) and a response coefficient K (additive concentration in solution/organic carbon concentration in solution) were determined.

(30) The organic carbon concentration (COT.sub.filtrate in ppm) in the supernatant solution after adsorption was determined.

(31) The adsorbed quantity (QA) was then calculated using the following formula:

(32) $\mathrm{QA}=\frac{\left({\mathrm{COT}}_{\mathrm{SM}}-{\mathrm{COT}}_{\mathrm{Filtrate}}\right)K{V}_{\mathrm{SM}}}{1000M_{\mathrm{Solid}}{S}_{\mathrm{BET}}}$
where:
SM=volume of solution in cm.sup.3
M.sub.Solid=mass of solid in grams
S.sub.BET=specific surface of solid

(33) The clay used was ground kaolinite. Its specific surface measured by the BET method with nitrogen was 12 m.sup.2/g. For each product, solutions of 1.0 mg/l active ingredient were prepared in a brine which composition is presented in the table below.

(34) TABLE-US-00007 Salt Concentration (g/l) NaCl 2.4 MgCl.sub.2, 6H.sub.2O 5.7 CaCl.sub.2, 2H.sub.2O 1.5

(35) For each test, 15 ml of solution and 2.0 g of kaolinite were used, i.e. a liquid:solid ratio of 7.5.

(36) The results are shown in the following Table 6 below.

(37) TABLE-US-00008 TABLE 6 Quantity Adsorbed Inhibitor (mg additive/m.sup.2 clay Example 2 0.28 Example 3 0.31 Example 4 0.33 Example 5 0.39 Example 6 0.31