Amphiphilic polymers for filtrate control

Abstract

The present invention relates to the use of amphiphilic sequenced copolymers as an agent for controlling the filtrate in a fluid (F) injected under pressure into an underground formation, comprising—at least one chain (C) soluble in the fluid (F); and—at least one block (B) that is insoluble in the fluid (F).

Claims

1. A process for controlling fluid loss in a fluid (F) injected under pressure into a subterranean formation, the process comprising forming fluid (F) with solid particles (p) in suspension and amphiphilic sequential copolymers (P) comprising: at least one chain (C) soluble in the fluid (F) comprising hydrophilic and hydrophobic units, wherein the chain (C) is obtained by micellar polymerization; and at least one block (B) insoluble in the fluid (F); and injecting the fluid (F) under pressure into the subterranean formation, thereby controlling fluid loss in the fluid (F) where the fluid (F) which comprises the copolymers (P) as additive also comprises cement particles as the solid particles (p).

2. The process according to claim 1, wherein chain (C) is obtained by a process comprising a stage (e) of micellar radical polymerization in which the following are brought into contact, within an aqueous medium (M): hydrophilic monomers, dissolved or dispersed in said aqueous medium (M); hydrophobic monomers in the form of a micellar solution, namely a solution containing, in the dispersed state within said aqueous medium (M), micelles comprising these hydrophobic monomers; and at least one radical polymerization initiator.

3. The process according to claim 1, wherein chain (C) is obtained by a process comprising a stage (E) of micellar radical polymerization in which the following are brought into contact, within an aqueous medium (M): hydrophilic monomers, dissolved or dispersed in said aqueous medium (M); hydrophobic monomers in the form of a micellar solution, namely a solution containing, in the dispersed state within said aqueous medium (M), micelles comprising these hydrophobic monomers; at least one radical polymerization initiator; and at least one radical polymerization control agent.

4. The process according to claim 3, wherein the radical polymerization control agent is a compound which comprises a thiocarbonylthio—S(C═S)—group.

5. The process according to claim 1, wherein the fluid (F) is an aqueous fluid.

6. The process according to claim 2, wherein said aqueous medium (M) is water or a water/alcohol mixture.

7. The process according to claim 2, wherein the dispersed state is obtained using at least one surfactant.

8. The process according to claim 2, wherein the at least one radical polymerization initiator is water-soluble or water-dispersible.

9. The process according to claim 3, wherein said aqueous medium (M) is water or a water/alcohol mixture.

10. The process according to claim 3, wherein the dispersed state is obtained using at least one surfactant.

11. The process according to claim 3, wherein the at least one radical polymerization initiator is water-soluble or water-dispersible.

12. The process according to claim 4, wherein the radical polymerization control agent is a xanthate.

Description

EXAMPLES

Example A Poly(Dimethylacrylamide/AMPS) 60/40 Mol % Mw=2000 kg/mol (SEC-MALS Characterization) (Comparative Example)

(1) 7.37 g of mercaptoacetic acid (1% by weight aqueous solution), 39.34 g of dimethylacrylamide (DMAm), 121.30 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) (50% by weight aqueous solution) and 820.57 g of demineralized water were weighed into a 1000 ml flask. The solution was stirred for 2 min using a magnetic bar and then the pH was adjusted to 7.6 using a 20% sodium hydroxide solution.

(2) This solution was charged to a 2 l glass reactor equipped with an anchor stirrer, with a nitrogen inlet, with a temperature probe and with a reflux condenser. Degassing by bubbling was carried out for 1 h and the solution was heated to 62° C. When the temperature was stable, 3.2 g of tetraethylenepentamine (TEPA) (10% by weight aqueous solution) were added. After 2 min, 8.21 g of sodium formaldehyde sulfoxylate (NaFS) (30% by weight aqueous solution) were added. Stirring was allowed to take place for 1 h and then the reactor was emptied.

Example B Poly(Dimethylacrylamide/AMPS/tBS) 59.55/39.7/0.75 Mol % n.SUB.H .20 Mnth 2 000 000 g/mol

(3) Stage 1. Preparation of a Micellar Solution of 4-Tert-Butylstyrene (tBS) with Sodium Dodecyl Sulfate (SDS)—SOLUTION A

(4) 27 g of SDS and 103.16 g of distilled water were introduced at ambient temperature (20° C.) into a 250 ml flask. Stirring was carried out on a water bath (35° C.) for 1 h using a magnetic bar, until a clear micellar solution was obtained. 4.84 g of tBS were then added. The mixture was stirred on the water bath (35° C.) for 1 h, until a clear micellar solution was obtained.

(5) Stage 2. Micellar Polymerization

(6) 210.8 g of dimethylacrylamide, 649.9 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) (50% by weight aqueous solution), 788 g of distilled water, 118.7 g of solution A and 5.572 g of O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(C═S)OEt (1% by weight solution in ethanol) were introduced, at ambient temperature (20° C.), into a 2500 ml flask. The pH of the mixture was subsequently adjusted to 6 using a sulfuric acid solution (10% by weight aqueous solution).

(7) The mixture was introduced into a 3 l Dewar flask equipped with a lid, with an anchor stirrer, with a temperature probe and with a nitrogen inlet. The solution was degassed by bubbling with nitrogen for 1 h. 18 g of sodium formaldehyde sulfoxylate (NaFS), in the form of a 1% by weight aqueous solution, were added to the medium all at once. After 5 minutes, 9 g of potassium sulfate (KPS), in the form of a 5% aqueous solution, were added all at once. This KPS solution was degassed beforehand by bubbling with nitrogen for 30 minutes.

(8) The polymerization reaction was then allowed to take place, with stirring, at up to 40° C., for 24 h. The mixture in the Dewar flask, returned to 25° C., was discharged.

Example C Poly(dimethylacrylamide/acrylamide/AMPS/tBS) 39.7/39.7/19.85/0.75 mol % n.SUB.H .20 Mnth 2 000 000 g/mol

(9) Stage 1. Preparation of a Micellar Solution of 4-Tert-Butylstyrene (tBS) with Sodium Dodecyl Sulfate (SDS)—SOLUTION A

(10) 40 g of SDS and 152.82 g of distilled water were introduced at ambient temperature (20° C.) into a 250 ml flask. Stirring was carried out on a water bath (35° C.) for 1 h using a magnetic bar, until a clear micellar solution was obtained. 7.18 g of tBS were then added. The mixture was stirred on the water bath (35° C.) for 1 h, until a clear micellar solution was obtained.

(11) Stage 2. Micellar Polymerization

(12) 266.7 g of acrylamide (50% by weight aqueous solution), 430.1 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) (50% by weight aqueous solution), 186 g of dimethylacrylamide, 726.5 g of distilled water, 157.1 g of solution A and 5.557 g of O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(C═S)OEt (1% by weight solution in ethanol) were introduced, at ambient temperature (20° C.), into a 2500 ml flask. The pH of the mixture was subsequently adjusted to 6 using a sulfuric acid solution (10% by weight aqueous solution).

(13) The mixture was introduced into a 3 l Dewar flask equipped with a lid, with an anchor stirrer, with a temperature probe and with a nitrogen inlet. The solution was degassed by bubbling with nitrogen for 1 h. 18 g of sodium formaldehyde sulfoxylate (NaFS), in the form of a 1% by weight aqueous solution, were added to the medium all at once. After 5 minutes, 9 g of potassium sulfate (KPS), in the form of a 5% aqueous solution, were added all at once. This KPS solution was degassed beforehand by bubbling with nitrogen for 30 minutes.

(14) The polymerization reaction was then allowed to take place, with stirring, at up to 40° C., for 24 h. The mixture in the Dewar flask, returned to 25° C., was discharged.

Example D Poly(acrylamide/AMPS/LMAm) 79.4/19.8/0.8 mol % n.SUB.H .12 Mnth 2 000 000 g/mol

(15) Stage 1. Preparation of a Micellar Solution of Laurylmethacrylamide (LMAm) with Sodium Dodecyl Sulfate (SDS)—SOLUTION A

(16) 66 g of SDS and 222.76 g of distilled water were introduced at ambient temperature (20° C.) into a 500 ml flask. Stirring was carried out on a water bath (35° C.) for 1 h using a magnetic bar, until a clear micellar solution was obtained. 11.24 g of LMAm were then added. The mixture was stirred on the water bath (35° C.) for 2 h, until a clear micellar solution was obtained.

(17) Stage 2. Micellar Polymerization

(18) 586.4 g of acrylamide (50% by weight aqueous solution), 472.7 g of 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) (50% by weight aqueous solution), 429.9 g of distilled water, 279.1 g of solution A and 5.507 g of O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(C═S)OEt (1% by weight solution in ethanol) were introduced, at ambient temperature (20° C.), into a 2500 ml flask. The pH of the mixture was subsequently adjusted to 6 using a sulfuric acid solution (10% by weight aqueous solution).

(19) The mixture was introduced into a 3 l Dewar flask equipped with a lid, with an anchor stirrer, with a temperature probe and with a nitrogen inlet. The solution was degassed by bubbling with nitrogen for 1 h. 17.5 g of sodium formaldehyde sulfoxylate (NaFS), in the form of a 1% by weight aqueous solution, were added to the medium all at once. After 5 minutes, 8.89 g of potassium sulfate (KPS), in the form of a 5% aqueous solution, were added all at once. This KPS solution was degassed beforehand by bubbling with nitrogen for 30 minutes.

(20) The polymerization reaction was then allowed to take place, with stirring, at up to 40° C., for 24 h. The mixture in the Dewar flask, returned to 25° C., was discharged.

(21) Evaluation of the Associative Polymers in Cement Grouts

(22) The non-associative control polymer described in example A and also the associative polymers resulting from examples B and C are used to prepare low-density 11.5 ppg (1 ppg=0.1205 kg/I) oil cement grouts having the following formulation: Municipal water: 477 g Polymer as gel (comprising 30% of active principle): 5.3 g Organic antifoaming agent: 1 g Dykheroff black label cement (API Class G): 321.5 g

(23) The fluid loss control agent is mixed with the liquid additives and with the municipal water before incorporation of the cement.

(24) The formulation and the filtration test were carried out according to the standard of the American Petroleum Institute (API recommended practice for testing well cements, 10B, 2nd edition, April 2013).

(25) After mixing and dispersing all the constituents of the formulation, the grout obtained was conditioned at 88° C. for 20 minutes in an atmospheric consistometer (model 1250 supplied by Chandler Engineering Inc.), prestabilized at this temperature, which makes it possible to simulate the conditions experienced by the cement grout during descent in a well.

(26) The rheology of the cement grouts is subsequently evaluated using a Chandler rotary viscometer (Chan 35 model) at the conditioning temperature of the cement slag. The viscosity is measured as a function of the shear gradient and the rheological profile of the cement slag is interpreted by regarding it as being a Bingham fluid. The characteristic quantities extracted are thus the plastic viscosity (PV, expressed in mPa.Math.s) and the yield point (yield stress, expressed in lb/100 ft.sup.2). The fluid loss control performance was determined by a static filtration at 88° C. in a double-ended cell with a capacity of 175 ml equipped with 325 mesh×60 mesh metal screens (supplied by Ofite Inc., reference 170-45). The performances of the polymers in the cement formulations are given in table 4 below:

(27) TABLE-US-00001 TABLE 4 performances FL API vol PV Reference (ml) (mPa .Math. s) A 260 6 (calculated) B 120 22 C 110 24 D  88 21

(28) The fluid loss volume is calculated when the test cannot be carried out for 30 min and when passage of the nitrogen (percolation through the filtration cell) is observed. In this instance, the comparative example A cannot provide correct control of fluid loss and the nitrogen percolates at t=20 min. In the case of the polymers B, C and D according to the invention, the nitrogen does not percolate during the 30 min of the test and the fluid loss volume remains low, at around 100 ml.

(29) Evaluation of the Associative Polymers as Fracturing Fluid or Reservoir Drilling (Drill-In) Fluid

(30) The polymer of example D is dispersed at 0.5% by weight in a 2% KCl solution. The fluid, once homogenized, is filtered against a ceramic filter with a permeability of 400 mD (supplied by Ofite, model 170-55). The filtration is carried out for 30 min under a pressure of 35 bar at a temperature of 88° C.

(31) The amount of fluid collected after 30 min is 30 ml. In the absence of filtration control, a volume of the order of 100 ml is expected in less than 1 min.