OIL FIELD CHEMICAL-CARRYING MATERIAL AND METHOD

Abstract

An oil field chemical-carrying material comprising granulated particles is disclosed. The granulated particles comprise alumina. An oil field chemical is integrally incorporated into the granulated particle. The particles have been aged by heating the particles in a sealed or humid environment.

Claims

1. An oil field chemical-carrying material comprising granulated particles comprising alumina and having been aged by heating the particles in a sealed or humid environment, wherein an oil field chemical is integrally incorporated into the granulated particles.

2. The oil field chemical-carrying material according to claim 1, wherein the oil field chemical is microencapsulated.

3. The oil field chemical-carrying material according to claim 1, wherein the particles are from 0.1 to 2 mm in size.

4. The oil field chemical-carrying material according to claim 1, wherein the particles are granulated using water as a binder.

5. The oil field chemical-carrying material according to claim 1, wherein the granulated particles do not comprise any polymeric binder.

6. The oil field chemical-carrying material according to claim 1, wherein the microencapsulation controls the rate of release of the tracer from the tracer-carrying material.

7. The oil field chemical-carrying material according to claim 1, wherein the granulated particles are proppant particles.

8. The oil field chemical-carrying material according to claim 1, wherein the granulated particles are uncoated.

9. The oil field chemical-carrying material according to claim 1, wherein the granulated particles are coated.

10. The oil field chemical-carrying material according to claim 1, wherein the oil field chemical is tracer.

11. A process for producing an oil field chemical-carrying material, the process comprising: mixing alumina with a microencapsulated oil field chemical to produce a mixture, granulating the mixture using water as a binder to form granulated particles, and aging the granulated particles by heating them in a sealed or humid environment.

12. The process according to claim 11, comprising drying the aged granulated particles.

13. The process according to claim 11, wherein the alumina is -alumina.

14. The process according to claim 11, wherein the heating is carried out at a constant temperature for a period of at least 4 hours.

15. The process according to claim 14, wherein the heating is carried out for a period of 4 to 48 hours.

16. The process according to claim 11, wherein the heating is carried out at a temperature of 30 to 90 C., more preferably 45 to 70 C.

17. The process according to claim 11, wherein the heating is carried out in a sealed environment created by placing the granulated particles in a container, for example a bag, and sealing the container prior to the heating.

18. The process according to claim 11, wherein the material is dried at a temperature of 40 to 80 C., more preferably 50 to 70 C.

19. The process according to claim 11 wherein the process comprises adding a rheology modifier to the mixture.

20. The process according to claim 11, wherein the oil-field carrying chemical is a tracer.

21. An oil field chemical-carrying material produced by the process of claim 11.

22. A method of delivering an oil field chemical, the method comprising injecting into a well penetrating a hydrocarbon reservoir a fluid containing an oil field chemical-carrying material comprising granulated particles wherein a microencapsulated oil field chemical is integrally incorporated into the granulated particles.

23. The method according to claim 22, wherein the oil field chemical-carrying material is an oil field chemical-carrying material according to any of claim 1 to 10 or 21.

24. The method according to claim 22, wherein the oil field chemical-carrying material comprises granulated particles in which two or more different microencapsulated oil field chemicals are integrally incorporated.

25. The method according to claim 24, wherein the microcapsule of a first microencapsulated oil field chemical provides a release at a first rate for the first microencapsulated oil field chemical, and the microcapsule of a second microencapsulated oil field chemical provides for release at a different, more rapid, rate for the second microencapsulated oil field chemical.

26. A method of monitoring a subterranean formation, the method comprising injecting, as part of a hydraulic fracturing operation, a fluid containing granulated particles comprising alumina wherein a microencapsulated tracer is integrally incorporated into the granulated particles, and detecting the tracer in fluids produced from the formation.

27. The method according to claim 26, wherein the tracer passes through the microencapsulation and is released from the particle over a period of time.

28. A method of tracing a flow of fluid from a hydrocarbon reservoir comprising the steps of placing within a well penetrating said reservoir a tracer-carrying material according to claim 10, thereafter collecting a sample of fluid flowing from the well, and analysing said sample to determine the presence or absence of the tracer.

29. A method of hydraulic fracturing a subterranean formation, the method comprising injecting into the subterranean formation a fluid containing an oil field chemical-carrying material according to claim 1.

Description

DESCRIPTION OF THE DRAWINGS

[0091] The invention will be further described by way of example only with reference to the following figures, of which:

[0092] FIGS. 1A to 1F are representations of structures of different configurations of microcapsules;

[0093] FIGS. 2A to 2C are tracer release graphs for microencapsulated and non-microencapsulated tracers; and

[0094] FIG. 3 is a graph of crush strengths.

DETAILED DESCRIPTION

[0095] FIG. 1A depicts a core shell structure (1) comprising (i) a core (2) comprising at least one tracer and (ii) a shell (3) comprising a polymeric microencapsulant.

[0096] FIG. 1B depicts a core multi shell structure (10) comprising (i) a core (2) comprising at least one tracer, (ii) a first shell (3) comprising a polymeric microencapsulant; and (iii) one or more additional shells (4) that at least partially cover the first shell.

[0097] FIG. 1C depicts a multi core shell structure (11) comprising (i) a core (2) comprising a plurality of sub cores (12) each comprising at least one tracer (12) within the sub core (12) and optionally having a shell (5) at least partially covering the sub cores (12), and (ii) a shell (3) comprising a polymeric microencapsulant around the core (2). The multi core shell structure (11) can also contain one or more additional shells that at least partially cover the first shell as shown in FIG. 1B as item (4).

[0098] FIG. 1D depicts a micro matrix (13) comprising at least one tracer entrapped within a three dimensional polymeric microencapsulant micro matrix (7).

[0099] FIG. 1E depicts a micro matrix with a shell structure (14) comprising (i) a micro matrix (7) comprising at least one tracer entrapped within the micro matrix (7), (ii) a first shell (3) comprising a polymeric microencapsulant, where the first shell at least partially covers the micro matrix (7); and (iii) one or more additional shells (4) that at least partially cover the first shell (3). The structure can have only a first shell (3) and not have one or more additional shells (4).

[0100] FIG. 1F depicts a multi core micro matrix with a shell structure (15) comprising (i) a core (2) comprising a micro matrix (7) comprising a three dimensional polymeric microencapsulant and a plurality of sub-cores (9) within the micro matrix (7), (ii) a first shell (3) comprising a different polymeric microencapsulant. The structure can also contain one or more additional shells (not shown) that at least partially cover the first shell (3), as shown as item 4 in FIG. 1E.

[0101] The microcapsules, cores and shells are shown graphically in FIGS. 1A-1F as circles for ease of illustration. The microcapsules can have any shape, including, but not limited to a sphere, a rod, an ovoid, a pseudo cuboid, a ring, etc.

[0102] In FIGS. 2A to 2C the concentration of a tracer (Tracerco, T165f) in an eluent is plotted against time. The plots are obtained by placing a tracer-carrying material into the eluent with stirring, taking samples of the eluent at various times and determining the amount of the compound of interest that is present in the eluent over time. The testing is carried out at elevated temperatures representing those found in a hydrocarbon reservoir using an eluent representative of oil. Data is plotted for a tracer-carrying material according to the invention (102-T165f MEC), in which the tracer is microencapsulated and integrally incorporated into granulated particles and another tracer-carrying material (101-T165f non-MEC) in which the tracer is not microencapsulated. FIG. 2A is a plot of the tracer concentrations in the eluent over time. FIG. 2B is a plot in which the tracer concentrations are plotted as a percentage of the tracer concentration of the tracer from the tracer-carrying material in which the tracer is microencapsulated (102). FIG. 2B is useful for comparing the relative concentrations of the tracers over time and it can be seen that the tracer from the T165f non-MEC material (101) shows a higher concentration initially, but that the T165f MEC (102) shows an improved sustained release over time. FIG. 2C is plotted on a logarithmic scale, and it can again be seen that the T165f non-MEC material (101) releases rapidly initially but then falls away, while the T165f MEC material (102) shows a more even, sustained release. The ability to alter the microencapsulation parameters also means that the release profile of the tracer-carrying material in which the tracer is microencapsulated can be tuned, while the release profile from the non-microencapsulated material cannot be adjusted so easily.

EXAMPLES

[0103] Aspects of the invention will be illustrated in the following examples.

Example 1-Preparation of Microcapsules Containing a Tracer

[0104] A tracer (Tracer A: a solid haloaromatic compound, density 2.3 g/cm3 at 25 C. and 1 atm) was ground and filtered through a 100 m sieve. 1.2 g carboxylmethylcellulose sodium salt (Sigma) was dissolved in 78.3 g water and then mixed with 15.9 g Beetle resin (BIP) and 0.35 g formic acid (96%, Sigma) to form an aqueous mixture. The aqueous mixture was stirred at 25 C. for 1 hour. 60 g of the sieved tracer and the aqueous mixture were then homogenised together for 5 minutes using a Silverson L4R laboratory homogeniser. During the homogenisation process, 300 g water was added to dilute the mixture. The homogenised mixture was stirred at 25 C. for 2 hours and then at 65 C. for 2 more hours. The resultant dispersion was filtered, dried in air for 3 days and then dried in a vacuum oven at 50 C. for 8 hours. The dried powder product containing the encapsulated tracer was filtered through a 425 m sieve. Total tracer content in the final powder product was 84%. The powders were dispersed in deionised water and tested using a Malvern Mastersizer 2000 under 85% ultrasonication for particle size. The measured volume weighted mean particle size was 23 m.

Example 2-Preparation of Microcapsules Containing a Second Oil Tracer

[0105] A second tracer (Solid tracer B: a haloaromatic compound, density 1.2 g/cm3 at 25 C. and 1 atm) was sieved through a 100 m sieve. 7.7 g carboxylmethylcellulose sodium salt (Sigma) was dissolved in 900 g water and then mixed with 101.8 g Beetle resin (BIP) and 2.24 g formic acid (96%, Sigma) to form an aqueous mixture. The aqueous mixture was stirred at 25 C. for 1 hour.

[0106] 640 g of the sieved tracer and the aqueous mixture were then homogenised together for 15 minutes using a Silverson L4R laboratory homogeniser. During the homogenisation, 300 g water was added to dilute the mixture. The homogenised mixture was stirred at 25 C. for 2 hours and then at 65 C. for 2 more hours. The resultant dispersion was filtered, dried in the air for 3 days and then dried in a vacuum oven at 50 C. for 8 hours. The dried powder product was filtered through a 425 m sieve. Total tracer content in the final powder product was 85%.

Example 3-Microencapsulation of Third Oil Tracer

[0107] A third tracer (Tracer C: a solid halogenated benzene tracer, density 3.0 g/cm3 at 25 C. and 1 atm) was ground and sieved through a 100 m sieve. 640 g of the sieved tracer was microencapsulated following the procedure outlined in Example 2. The powders were dispersed in deionised water and tested using a Malvern Mastersizer 2000 under 85% ultrasonication for particle size. The measured volume weighted mean particle size was 10.5 m. The total tracer content in the final powder product was 88%.

Example 4-Microencapsulation of a Liquid Tracer

[0108] An oil tracer (Tracer D: A liquid benzene tracer substituted with mixed halogens, density 2.0 g/cm3 at 25 C. and 1 atm) was encapsulated as described below. 1.52 g carboxylmethylcellulose sodium salt (Sigma) was dissolved in 81.8 g water and then mixed with 18.63 g Beetle resin (BIP) and 0.36 g formic acid (96%, Sigma) to form an aqueous mixture. The aqueous mixture was stirred at 25 C. for 1 hour. 0.57 g Narad Solvent Red 175 dye was dissolved in 60 g of the liquid tracer. The liquid tracer/dye mixture and the aqueous mixture were then homogenised together for 5 minutes using a Silverson L4R laboratory homogeniser. During the homogenisation process, 120 g water was added to dilute the mixture. The homogenised mixture was stirred at 25 C. for 2 hours and then at 65 C. for 2 more hours. The resultant dispersion was filtered, dried in the air for 3 days and then dried in a vacuum oven at 40 C. for 10 hours. The dried powder product containing the encapsulated tracer was filtered through a 425 m sieve.

Example 5-Microencapsulation of a Biocide

[0109] A biocide (Biocide A: an anthraquinone compound, density 1.3 g/cm3 at 25 C. and 1 atm) was encapsulated as described below. 1.2 g carboxylmethylcellulose sodium salt (Sigma) was dissolved in 78.3 g water and then mixed with 15.9 g Beetle resin (BIP) and 0.35 g formic acid (96%, Sigma) to form an aqueous mixture. The aqueous mixture was stirred at 25 C. for 1 hour. 60 g of the biocide and the aqueous mixture were then homogenised together for 5 minutes using a Silverson L4R laboratory homogeniser. During the homogenisation process, 300 g water was added to dilute the mixture. The homogenised mixture was stirred at 25 C. for 2 hours and then at 65 C. for 2 more hours. The resultant dispersion was filtered, dried in the air for 3 days and then dried in a vacuum oven at 50 C. for 8 hours. Total biocide content in the final powder product was 85%. The dried powder product containing the encapsulated biocide was filtered through a 425 m sieve.

Example 6-Granulation

[0110] Using an Eirich EL1 granulator, solid substrate, and water, a material was granulated to particles 0.1-3 mm in size. The material was sieved after manufacture and some particles were tested for moisture content using a Mettler Toledo infrared moisture balance to determine loss on drying (LOD). The preferred general method involved charging around 400 g of substrate to the EL1 and closing the lid. The EL1 was set to the granulation angle. The EL1 was then run at 4 m/s for 30 s. Around 190 ml of water was then added over 60 s with the EL1 running at 4 m/s. The EL1 was then sped up to 20 m/s for 30-60 s until seeds were seen. The speed was then reduced to 6 m/s until granules were seen. 40 g of substrate was added to dry the surface of the particles, which were then discharged and sieved. All samples were aged at 45 C. for 24 hours in a sealed bag. Preferably the bag is about 80% full by volume. The presence of moisture within the bag may be indicative of sufficient humidity during the aging process.

[0111] The following specific tests were carried out:

[0112] Test 1

[0113] 400.1 g -alumina was placed in the EL1 and mixed at 4 m/s with the mixer set to the granulation angle. 205.0 g water was added over 40 s with the EL1 running at 4 m/s. The EL1 was increased to 20 m/s for 30 s, at which point seeds were seen. The EL1 speed was reduced to 6 m/s for 45 s, at which point granules were seen. 40 g of -alumina was added to dry the surface of the particles and mixed for 30 s with the EL1 running at 4 m/s. The granules were discharged and sieved between 850 m and 2800 m. 61.53 g of granules were between 850 m and 2800 m, 376.6 g were smaller than 850 m and 8.185 g were larger than 2800 m.

[0114] Test 2a

[0115] 395 g -alumina and 5.09 g Attagel were hand mixed and then machine mixed in the EL1 for 30 s with the EL1 running at 4 m/s. 200 g water was added over 90 s with the EL1 running at 4 m/s. The EL1 was increased to 20 m/s for 20 s, at which point seeds were seen. The EL1 speed was reduced to 6 m/s for 10 s, at which point granules were seen. The LOD was 30%.

[0116] Test 2b

[0117] 395.4 g -alumina and 4.9 g Attagel were hand mixed and then machine mixed in the EL1 for 30 s with the EL1 running at 4 m/s. 194.9 g water was added over 60 s with the EL1 running at 4 m/s. The EL1 was increased to 20 m/s for 30 s, at which point seeds were seen. The EL1 speed was reduced to 6 m/s for 30 s, at which point granules were seen. The EL1 was allowed to continue running, which resulted in larger granules. Those were broken down by increasing the speed to 20 m/s, then adding 10 ml of water with the El1 at 6 m/s, then increasing the speed to 20 m/s for 15 s, then running at 6 m/s for 30 s until particles were seen. 40 g of -alumina was added to dry the surface of the particles. The LOD was 26.28%. The main fractions in the sieving were <425 m and 425-1000 m.

[0118] Test 3

[0119] 400 g -alumina was placed in the EL1 and 210 g water was added over 60 s with the EL1 running at 4 m/s. The EL1 was increased to 20 m/s for 20 s, at which point seeds were seen. The EL1 speed was reduced to 6 m/s for 30-40 s, at which point granules were seen. 40 g of -alumina was added to dry the surface of the particles and mixed for 30 s with the EL1 running at 4 m/s. The granules were discharged and sieved. The LOD was 29.46%.

[0120] Test 4

[0121] 395.0 g boehmite and 5 g Attagel were hand mixed and then machine mixed in the EL1 for 30 s with the EL1 running at 4 m/s. 195 g water was initially added, before further additions of 20 g, 26.2 g, 145.8 g, and 53.0 g of water. Further additions of 40 g and then 20 g of boehmite were then made. The particles were larger, with >70% being larger than 2 mm. The LOD was 51.4%.

[0122] Test 5

[0123] 395.0 g gibbsite and 5 g Attagel were hand mixed and then machine mixed in the EL1 for 30 s with the EL1 running at 4 m/s. 195 g water was added, which produced a wet agglomerate. A further 250 g of gibbsite was added and the EL1 speed increased to 20 m/s, which resulted in granules. 40 g of gibbsite was added to dry the granules, which were discharged and sieved.

[0124] Crush testing was carried out on a tonne testing machine. In each test a single granule was placed on the crush plate, the guard was closed, and the test button pressed. The piston was depressed until a breaking force was detected. If the particle was soft and crushed gradually rather than breaking, then the test read maximum (50 kg) and was recorded as a failure. The material from test 1 was dried in an oven at 60 C. for 24 hours. The material from tests 2b, 4a and 5 were dried in a Sherwood Tornado 501 fluid bed drier with the following settings: 60 C. air temp; 40 air speed; 5 minutes.

[0125] FIG. 3 compares the crush strength of the materials from test 4 (201), test 2b (202) and test 1 (203). Material from test 5 failed the test. The materials made from -alumina show a significant improvement in crush strength.