Sequenced polymers for monitoring the filtrate

Abstract

The present invention relates to the use of a sequenced polymer as an agent for monitoring the filtrate in a fluid injected under pressure into an oil rock, wherein the fluid comprises solid particles and/or is brought into contact with solid particles within the oil rock after being injected, the polymer comprising at least three blocks, including: at least one first block which is adsorbed, preferably irreversibly, onto at least some of the particles (p); a second block (B) having a composition other than that of the first and a mean molecular weight of more than 10,000 g/mol, and which is soluble in the fluid (F); and at least one third block of type (A) or type (B).

Claims

1. A fluid (F) for injecting under pressure into a subterranean formation, comprising a fluid loss control agent, wherein the fluid loss control agent is a block polymer (P) comprising: at least one first block (A); and at least one second block (B) with a composition distinct from that of said first block, and with a weight-average molecular weight of greater than 10 000 g/mol, and which is soluble in the fluid (F); and at least one third block of type (A) or of type (B); wherein the block polymer (P) is a polymer of comb type selected from the group consisting of: a polymer carrying several side blocks of type (A) on a linear block of type (B); a polymer carrying several side blocks of type (B) on a linear block of type (A); and a polymer carrying several side blocks of type (A) and (B) on a linear polymer chain; and wherein the blocks (A) and (B) consist of monomer units selected from the group consisting of: monomer units U1: monomer units comprising an acrylamide, monomer units U2: monomer units comprising a sulfonic acid or sulfonate functional group, monomer units U3: neutral monomer units selected from the group consisting of esters of α,β-ethylenically unsaturated mono- or dicarboxylic acids with C2-C30 alkanediols, monomer units U4: monomer units carrying ammonium groups, monomer units U5: acrylate monomer units carrying a COOH or COO— group, monomer units U6: monomer units comprising a phosphate, phosphonate or phosphinate groups, and monomer units U7: (meth)acrylate monomer units functionalized by polydimethylsiloxanes.

2. The fluid claimed in claim 1, wherein the fluid (F) is aqueous.

3. The fluid claimed in claim 1, wherein the fluid (F) does not comprise solid particles (p).

4. The fluid claimed in claim 1, wherein the fluid (F) comprises particles (p) combined with the polymer (P), the polymer being employed, in this case, as dispersing and stabilizing agent for the dispersion of the particles (p).

5. The fluid of claim 4, wherein the at least one first block (A) of the polymer (P) is adsorbed on at least a portion of the particles (p).

6. The fluid of claim 5, wherein the at least one first block (A) of the polymer (P) is adsorbed irreversibly on the particles (p).

7. The fluid claimed in claim 1, wherein the fluid (F) is an oil cement grout which comprises the polymer (P) as additive.

8. A process, comprising injecting a fluid (F) according to claim 1 under pressure into a subterranean formation, wherein said fluid (F) comprises solid particles (p) and/or is brought into contact with solid particles (p) within the subterranean formation subsequent to its injection.

Description

EXAMPLE

Poly(acrylic acid)-b-poly(N,N-dimethylacrylamide-co-AMPS)-b-poly(acrylic acid) Triblock Copolymer

(1) 1.1: Synthesis of a Poly(Acylic Acid) Block Having a Xanthate Ending

(2) The synthesis was carried out at the laboratory scale in a glass reactor equipped with a mechanical stirrer, with a system for heating/cooling and for effective regulation of temperature and with a system for reflux/condensation of the vapours.

(3) The composition of initial charges of the reactants and solvents (acrylic acid AA, xanthate, water, ethanol and V50) placed in the reactor is given in table 1.

(4) O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate (Rhodixan A1) of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(C═S)OEt was used as MADIX transfer agent. The amount shown in table 1 corresponds to the value of the expected theoretical number-average molecular weight (Mn, th=1 kg/mol), calculated by the ratio of the amount of monomer to the amount of xanthate.

(5) Sparging of the reaction mixture with nitrogen was used throughout the synthesis.

(6) The solution of the monomer in water and the solution of the initiator V-50 (2,2′-azobis(2-methylpropionamidine) dihydrochloride) in water were introduced into the reactor separately in a semicontinuous manner during predetermined periods and while retaining an unvarying temperature of 60° C.+/−2 (see table 1 with charges and reaction conditions).

(7) The general synthesis procedure is as follows: Solutions of initiator and of the monomer in water are prepared and are placed in feed vessels; subsequently, feed lines to the reactor are filled with these solutions. Sparging of the reactor with nitrogen is begun. Sparging is maintained throughout the reaction. The demineralized water, the ethanol, the acrylic acid (first part), the Rhodixan A1 and the initiator V50 (first part) are charged to the reactor. Stirring is begun at 150 rpm. The reactor is heated to 60° C. At a temperature of 60° C.). (+/−2°, cofeeding of the initiator solution semi-continuously with separate feeding of the monomer solution are begun. Appropriate amounts of the initiator solution (2) are provided at the appropriate passage of time (see table of the reaction conditions for the specific example). Starting from the same time, appropriate amounts of the monomer solution are provided in the appropriate time (see table 1 below of the reaction conditions). After the end of the two semicontinuous feeding operations, heating is maintained at 60° C. for 3 hours. The product is cooled to a temperature <40° C. and the product is discharged for analyses.

(8) According to this procedure, polyacrylic acid functionalized by the xanthate group was synthesized with a number-average molecular weight targeted at 1000 g/mol.

(9) TABLE-US-00001 TABLE 1 Conditions of the synthesis of living poly(acrylic acid) block having a xanthate ending V50 solution (2) to be AA solution to introduce introduced Theoretical semicontinuously semicontinuously Mn Initial charges of the reactants in the reactor 38.7% AA Duration of 10% V50 Duration of targeted Water Ethanol AA Xanthate V50 (1) in water introduction in water introduction Reference (g/mol) (grams) (grams) (grams) (grams) (grams) (grams) (minutes) (grams) (minutes) A1 1000 14.5 21.7 5.0 10.4 0.11 116.3 180 6.80 240

(10) The conversions of monomer and of Rhodixan A1 were determined by .sup.1H NMR.

(11) An analysis by size exclusion chromatography in a mixture of water and acetonitrile (80/20) additivated with NaNO.sub.3 (0.1N) with an 18-angle MALS detector provided the weight-average molar mass (M.sub.w) and polydispersity index (M.sub.w/M.sub.n) values given in table 2 below.

(12) TABLE-US-00002 TABLE 2 Xanthate AA Block conversion conversion M.sub.w synthesized M.sub.n, th (g) (.sup.1H NMR) (g/mol) M.sub.w/M.sub.n A1 1000 >99.5% >99.5% 1800 1.4

(13) 1.2: Synthesis of Triblock Copolymer from the Block A1

(14) 1.469 g of solution of the poly(acrylic acid) block having a xanthate ending A1 (as a 35% by weight solution), 9.83 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) (50% by weight aqueous solution), 8.50 g of dimethylacrylamide (DMAM) and 255.7 g of demineralized water are introduced into a jacketed glass reactor equipped with a stirrer blade, a bulb condenser and a nitrogen inlet. The pH is adjusted to between 2.0 and 2.5 with 37% by weight hydrochloric acid.

(15) A solution of monomers (solution A) is prepared by weighing respectively 55.68 g of AMPS (50% by weight solution), 48.16 g of DMAM and 63.934 g of demineralized water.

(16) The vessel heel is degassed for 30 minutes and heated to 40° C.

(17) When the reaction medium reaches the temperature of 40° C., 1.34 g of ammonium persulfate (APS) (5% by weight solution) and 0.21 g of sodium formaldehydesulfoxylate (NaFS) (0.25% by weight solution) are added. 167.77 g of the solution A are then introduced into the reaction medium at a flow rate of 1.40 ml/min for 2 h. At the same time, 5.15 g of 0.25% by weight NaFS solution are also added over a period of time of 2 h.

(18) In order to obtain a third PAA block with a targeted number-average molar mass of 1000 g/mol, after reacting for 2 h 30, 0.45 g of acrylic acid is added and the temperature is maintained at 40° C. for 2 h 30.

(19) The conversion of the monomers, studied by .sup.1H NMR analysis, shows a quantitative conversion.

(20) 1.3: Evaluation of the Triblock Polymer in a Cement Grout

(21) The triblock polymer was used to prepare oil cement grouts having the following formulation: Municipal water: 335 g Diblock polymer (at 20% in aqueous solution): 15 g Dykheroff black label cement (API Class G): 781.5 g

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

(23) 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).

(24) 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.

(25) 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 a 325 mesh×60 mesh metal screen (supplied by Ofite Inc., reference 170-45). The fluid loss volume collected is 27.6 ml, which corresponds to a reasonable API volume of 55 ml.