Device for in-line monitoring of the quality of a water-soluble polymer solution manufactured from invert emulsion or powder of said polymer

Abstract

An apparatus for monitoring the effective dissolving of a polymer when the use region is not accessible. The apparatus includes a pipe on which are inserted, consecutively: a pump, a flowmeter, a water or brine inlet mechanism for diluting the mother solution flowing in the pipe, a mixer capable of in-line homogenization of the diluted mother solution, a first tube calibrated to simulate the distance and the conditions for moving the diluted solution in the main pipe between the point where the mother solution is diluted and the use region, a mechanism capable of reducing the pressure of the diluted solution flowing in the pipe upstream of the first tube that is calibrated from 10 to 10000 kPa (from 0.1 to 100 bar), a second calibrated tube for creating a head loss, and a device for measuring differential pressure between the inlet and the outlet of the second calibrated tube.

Claims

1. An apparatus adapted to be connected in shunt between 2 points of a main pipe, respectively: a first point whereupon a water-soluble polymer mother solution is formed, obtained by way of mixing water or brine with an invert emulsion of said polymer, or a powder of said polymer, and a second point near to where the solution is diluted; wherein the apparatus makes it possible to monitor the effective dissolving of the mother solution after dilution, between the point of introduction of the mother solution into the main pipe and the use region thereof; the apparatus containing a pipe within which is inserted, consecutively: a pump, a flowmeter, a water or brine inlet for diluting the mother solution flowing in the pipe, a mixer adapted for in-line homogenization of the diluted mother solution, a first tube that is calibrated so as to simulate a distance and conditions for moving the diluted solution in the main pipe between the point where the mother solution is diluted and a use region, a means for reducing the pressure of the diluted solution flowing in the pipe upstream of the first tube that is calibrated from 10 to 10000 kPa (from 0.1 to 100 bar), a second calibrated tube for creating a head loss, a device for measuring differential pressure between the inlet and the outlet of the second calibrated tube.

2. The apparatus according to claim 1, wherein the flowmeter is a precision flowmeter of the Coriolis effect mass flow type, or of the electromagnetic type.

3. The apparatus according to claim 1, wherein the mixer is a static mixer.

4. The apparatus according to claim 1, wherein the second tube measures between 10 and 30 meters long with an internal diameter of 5 to 20 mm, the wall having a thickness of 2 to 5 mm.

5. The apparatus according to claim 1, comprising a third calibrated tube, in the form of a calibrated coil in order to simulate the distance and the conditions for moving the mother solution in the main pipe between the point where the solution is produced and the point where it is diluted, the tube being located between the flowmeter and the water or brine inlet means.

6. The apparatus according to claim 1, wherein the tubes are in the form of a coil.

7. The apparatus according to claim 1, wherein the pump, the tubes and the flowmeter are manufactured from materials chosen from the group consisting of: Austenitic-ferritic steels and Superalloys containing mainly nickel.

8. The use of the apparatus according to claim 1 in an enhanced oil and/or off-shore gas recovery process.

9. The use of the apparatus according to claim 1 in an enhanced oil and/or on-shore gas recovery process.

10. A method for monitoring the effective dissolving of a water-soluble polymer at a use region thereof where it is not easily accessible, wherein, within a pipe: a solution is formed, obtained by way of mixing water or brine with an invert emulsion of said polymer, or a powder of said polymer, the mother solution is diluted, the diluted solution is transported to the use region thereof, between the formation of the mother solution and the dilution thereof, part of the stream flowing in the pipe is shunted in order to circulate it within in the apparatus according to claim 1, the viscosity of the diluted solution is calculated by way of the extrapolation of the pressure difference measured by the differential pressure measuring device of the apparatus according to claim 1, a viscosity is measured of a polymer solution prepared at a same concentration as that of the diluted solution, and under optimum laboratory conditions, a ratio is calculated between the value of viscosity obtained by extrapolation and the viscosity of the solution made in the laboratory, satisfactory or unsatisfactory dissolving of the polymer is deduced therefrom.

11. The method according to claim 10, wherein the shear rate in the second calibrated tube is prcfcrcntially between 1 s.sup.1 and 500 s.sup.1.

12. The method according to claim 10, wherein the water-soluble polymer mother solution has a polymer concentration of between 2,000 and 20,000 ppm and the diluted solution has a polymer concentration of between 100 and 2500 ppm.

13. The method according to claim 10, wherein the shear rate in the second calibrated tube is between 5 s.sup.1 and 200 s.sup.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an apparatus according to the present invention in particular comprising a shunt, installed on an injection pipe of a solution containing a water-soluble polymer in an enhanced oil recovery plant.

DETAILED DESCRIPTION OF THE INVENTION

(2) The apparatus according to the present invention in particular comprises on the main pipe (1) a water-soluble polymer invert emulsion inlet (2), a water or brine inlet (3), a static mixer (4) allowing for the mixing of the two fluids into a solution called mother, a second water or brine inlet (5) allowing for the dilution of this mother solution into a diluted solution, another static mixer (6) and means for transporting the mixture (7) to the use region which may be located several kilometers away from the dilution site, and bypassing the main line: A volumetric pump (8) with a flow of 0.02 m.sup.3/h (20 L/h); A precision Coriolis effect flow meter (9); A calibrated tube (10) to simulate the maturation of the polymer and the transportation of the mother solution to the point of dilution within the main pipe, said tube having a length of 50 meters, an internal diameter of 10 mm and being manufactured in super duplex steel; a water or brine inlet (11) in order to dilute the mother solution; a static mixer (12) allowing for the mixing of the mother solution and the water or brine; A calibrated tube (13) to simulate the distance between the point of dilution and the use region, said tube having a length of 400 meters, an internal diameter of 20 mm and being manufactured in super duplex steel; A valve (14) allowing for a pressure reduction of 500 kPa (5 bar); A calibrated tube (15) creating a head loss of 10 to 200 kPa (from 0.1 to 2 bar) A differential pressure measuring apparatus (16), A conduit (17) for reinjecting the solution into the main pipe.

(3) A copolymer of acrylamide and sodium acrylate (70/30 mol %) emulsion is implemented with a brine containing 3000 ppm of NaCl in an off-shore EOR process. The apparatus described above is used and positioned within the bypass of the main pipe. The pressure is 22,000 kPa (220 bar). The main pipe injection flow rate is 125 m.sup.3/h. The polymer concentration of the mother solution is 10,000 ppm. The bypass flow rate is 0.005 m.sup.3/h (5 L/s). The polymer concentration of the diluted solution is 500 ppm.

(4) In a first test, an insufficient pressure difference of 150 kPa (1.5 bar) is intentionally created within the static mixer (6) comprising only two elements. The emulsion is implemented within the apparatus described above. The deduced and calculated viscosity is 15 mPa.Math.s (15 cps). A 1000 ppm solution is made in the laboratory and the viscosity is measured at 27 mPa.Math.s (27 cps). The ratio of these two viscosities is 0.56. This ratio is low, far from 1 and it can be inferred that the emulsion has not been properly inverted. The reason is of course insufficient mixing within the static mixer (6) resulting in poor inversion of the emulsion, which the apparatus makes it possible to detect, and that cannot be compensated for, neither by dilution nor the periods of maturation.

(5) In a second test, the same emulsion is implemented in the same manner but the static mixer (6) creates a pressure differential of 1000 kPa (10 bar) by virtue of 8 elements. The emulsion is implemented within the apparatus described above. The deduced and calculated viscosity is 29 mPa.Math.s (29 cps). A 500 ppm solution is made in the laboratory and the viscosity is measured at 32 mPa.Math.s (32 cps). The ratio of these two viscosities is 0.91. This is good and makes it possible to conclude that inversion has taken place.