Structural stabilizer for fiber and conventional proppant complex in efficient proppant migration and placement technology of fractured well and preparation method

Abstract

A structural stabilizer for a fiber and proppant complex to enhance proppant migration and placement in a fractured well during propping and a preparation method thereof are provided. The structural stabilizer consists of: water, inorganic salt, kaolinite, nitrogen-doped modified graphene oxide, anionic surfactant, non-ionic alkyl polyglucoside, and polyacrylamide. The structural stabilizer improves bonding between a proppant and a fiber when slick water is used in stimulated reservoir volume (SRV) fracturing, prevents separation of the fiber and the proppant during migration, thereby reducing escape rate of the fiber from the fiber and proppant complex.

Claims

1. A structural stabilizer for a fiber and proppant complex to enhance proppant migration and placement in a fractured well during propping, consisting of the following components in a mass ratio: 84.0%-95.0% of water, 0.1%-2.0% of an inorganic salt, 0.1%-5.0% of kaolinite, 0.1%-5.0% of a nitrogen-doped modified graphene oxide, 0.1%-2.0% of an anionic surfactant, 0.1%-2.0% of a non-ionic alkyl polyglucoside, and 0.05%-0.2% of polyacrylamide; wherein the non-ionic alkyl polyglucoside is selected from the group consisting of C08-C14 alkyl polyglycoside, C12-C14 alkyl polyglycoside, C12-C10 alkyl polyglycoside, and combinations thereof, and wherein addition of the structural stabilizer to the fiber and proppant complex reduces a fiber escape rate and improves a proppant placement height in the fractured well.

2. The structural stabilizer according to claim 1, wherein the inorganic salt is selected from the group consisting of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate, potassium sulfate, sodium sulfate, potassium bisulfate, and combinations thereof; and the anionic surfactant is selected from the group consisting of sodium dodecyl benzene sulfonate, dodecyl sodium sulfonate, sodium lauryl sulfate, N-acyl glutamate, and combinations thereof.

3. The structural stabilizer according to claim 2, wherein the nitrogen-doped modified graphene oxide is selected from the group consisting of amino-modified graphene oxide, skeleton nitrogen-doped graphene oxide, and combinations thereof, wherein nitrogen (N) content in the nitrogen-doped modified graphene oxide is 1-5 wt %, a number of nitrogen-doped graphene oxide layers in the nitrogen-doped modified graphene oxide is ≤10, and a layer size of each nitrogen-doped graphene oxide layer is <5 um.

4. The structural stabilizer according to claim 2, wherein the kaolinite is calcined kaolin of less than 100 mesh.

5. The structural stabilizer according to claim 2, wherein the polyacrylamide is an anionic polyacrylamide with a molecular weight of 0.1 to 1 million.

6. The structural stabilizer according to claim 1, wherein a fiber of the fiber and proppant complex is polyethylene terephthalate (PET), and a proppant of the fiber and proppant complex is quartz sand or coated sand, wherein the quartz sand is 20 to 200 mesh in particle size.

7. A method for preparing the structural stabilizer of claim 1 comprising: mixing the kaolinite, the water and the inorganic salt and stirring for 0.5-3 h to prepare a slurry; and continuously stirring the slurry while adding the nitrogen-doped modified graphene oxide, the anionic surfactant, the non-ionic alkyl polyglucoside and the polyacrylamide in turn, and stirring for 5-30 min to obtain the structural stabilizer.

8. The according to claim 7, wherein a stirring speed during preparing and stirring the slurry is 500-3,000 r/min.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a comparison of fiber and proppant morphology between Experiment 2 (left) and Experiment 12 (right);

(2) FIG. 2 is a diagram of the appearance and flowability of the structural stabilizer; FIG. 3 is a schematic diagram of Experiment 12.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment 1

(3) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 2.5 kg kaolin with 0.1 kg sodium chloride and 94.3 kg water, stir them at a rate of 2,000 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 2.5 kg nitrogen-doped modified graphene oxide, 0.2 kg sodium dodecyl benzene sulfonate, 0.2 kg APG0814, and 0.2 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 1,000 r/min for 15 min to obtain a structural stabilizer.

Embodiment 2

(4) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 1.0 kg kaolin with 0.1 kg sodium chloride, 0.1 kg potassium chloride and 93.1 kg water, stir them at a rate of 1,000 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide, 0.2 kg sodium dodecyl benzene sulfonate, kg APG0814, and 0.2 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 500 r/min for 5 min to obtain a structural stabilizer.

Embodiment 3

(5) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 1.0 kg kaolin with 0.1 kg potassium chloride and 93.2 kg water, stir them at a rate of 2,000 r/min for 1 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide, 0.2 kg sodium dodecyl benzene sulfonate, 0.2 kg APG0814, and 0.1 kg N-acyl glutamate in sequence, finally add 0.2 kg polyacrylamide, and stir them at a rate of 1000 r/min for 30 min to obtain a structural stabilizer.

Embodiment 4

(6) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 5.0 kg kaolin with 0.5 kg sodium chloride and 88.8 kg water, stir them at a rate of 1,500 r/min for 3 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide, 0.2 kg sodium dodecyl benzene sulfonate, 0.2 kg APG1214, and 0.2 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 500 r/min for 10 min to obtain a structural stabilizer.

Embodiment 5

(7) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 0.1 kg kaolin with 1 kg sodium chloride and 95.3 kg water, stir them at a rate of 500 r/min for 3 h to prepare a uniform slurry, continually stir it, then add 1.0 kg nitrogen-doped modified graphene oxide, 1 kg sodium dodecyl benzene sulfonate, 0.5 kg APG0814, 0.5 kg APG1210, and 0.5 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 2,000 r/min for 5 min to obtain a structural stabilizer.

Embodiment 6

(8) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 5.0 kg kaolin with 2.0 kg sodium chloride and 84.9 kg water, stir them at a rate of 1,500 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 2 kg nitrogen-doped modified graphene oxide, 2 kg sodium dodecyl benzene sulfonate, 2 kg APG1214, and 0.2 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 1,000 r/min for 15 min to obtain a structural stabilizer.

Embodiment 7

(9) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 5.0 kg kaolin with 0.1 kg sodium chloride and 89.5 kg water, stir them at a rate of 1,500 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide, 0.1 kg sodium dodecyl benzene sulfonate, 0.1 kg APG0814, and 0.1 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 2,000 r/min for 15 min to obtain a structural stabilizer.

Embodiment 8

(10) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 5.0 kg kaolin with 0.5 kg sodium chloride and 88.9 kg water, stir them at a rate of 2,000 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide, 0.2 kg sodium dodecyl benzene sulfonate, 0.2 kg APG0814, and 0.1 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 1,000 r/min for 15 min to obtain a structural stabilizer.

(11) The experimental results of the efficient proppant migration and placement technology in Embodiment 8 are shown in FIG. 3, with no obvious fiber escape observed.

(12) The appearance and fluidity of the structural stabilizer prepared by Embodiments 1-8 are shown in FIG. 2.

Comparative Embodiment 1

(13) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 5.0 kg kaolin with 0.1 kg sodium chloride and 89.8 kg water, stir them at a rate of 1,500 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 1,000 r/min for 15 min to obtain a structural stabilizer.

Comparative Embodiment 2

(14) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 5.0 kg kaolin with 0.1 kg sodium chloride and 94.3 kg water, stir them at a high rate for 2 h to prepare a uniform slurry, continually stir it, then add 0.2 kg sodium dodecyl benzene sulfonate, 0.2 kg APG0814, and 0.1 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 2,000 r/min for 15 min to obtain a structural stabilizer.

Comparative Embodiment 3

(15) A method to prepare a structural stabilizer for efficient proppant migration and placement technology of fractured well: mix 0.5 kg sodium chloride with 93.9 kg water, stir them at a rate of 2,000 r/min for 2 h to prepare a uniform slurry, continually stir it, then add 5.0 kg nitrogen-doped modified graphene oxide, 0.2 kg sodium dodecyl benzene sulfonate, 0.2 kg APG0814, and 0.1 kg N-acyl glutamate in sequence, finally add 0.1 kg polyacrylamide, and stir them at a rate of 1,000 r/min for 15 min to obtain a structural stabilizer.

Propping Experiment

(16) Apply the structural stabilizers prepared respectively in Embodiments 1-8 and Comparative Embodiments 1-3 to the implementation of the efficient proppant migration and placement technology, and determine the effect of the structural stabilizer on the proppant placement volume and fiber escape rate in the slick water.

(17) The experiment includes the following steps:

(18) (1) Take two dry 100 mL graduated cylinders and record them as 1# and 2# cylinders respectively; take another graduated cylinder to measure out two portions of 100 mL slick water, add them into two 250 mL beakers, and record them as 1# and 2# beakers.

(19) (2) Transfer the 1# beaker to a vertical stirrer (with a speed of 700 r/min) while weighing 15.00 g of proppant and adding it into the 1# beaker, then stir them for 2 min to make the proppant evenly distributed in the slick water; stop stirring and remove the 1# beaker quickly, stir the slick water with a glass rod while pouring it into the 1# cylinder, put the 1# cylinder on the horizontal table, and count the time; after 5 min, read the placement volume V.sub.1 of the proppant as the control group until the proppant is completely settled.

(20) (3) Weigh 0.075 g of fiber and place it in the 2# beaker, record the mass as m.sub.0, and transfer 1.0 mL of structural stabilizer with a 1.0 mL syringe (with the needle removed) into the 2# beaker at a rate of 0.5 mL/s.

(21) (4) Transfer the 2# beaker to the vertical stirrer (with a speed of 700 r/min) while weighing 15.00 g of proppant and adding it into the 2# beaker, then stir them for 2 min to make the proppant, fiber and structural stabilizer evenly distributed in the slick water; stop stirring and remove the 2# beaker quickly, stir the slick water with a glass rod while pouring it into the 2# cylinder, put the 2# cylinder on the horizontal table, and count the time; after 5 min, read the placement volume V.sub.2 of the proppant until the proppant is completely settled.

(22) (5) Pour the supernatant and floating fibers in the 2# cylinder into a 20-mesh filter, wash the fibers with clean water, and then dry and weigh them; record the mass as m.sub.2, and calculate the fiber escape rate 11 according to Equation (1): η=(m.sub.2/m.sub.0)×100%.

(23) The experimental conditions are as follows: the viscosity of the slip water is 2 to 30 mPa.Math.s, the proppant ratio is 10 to 40%, the fiber is PET polyester fiber, the fiber dosage is 0.1 to 1.0%, and the proppant is quartz sand of 20-200 meshes or precoated sand of 40-70 meshes. The determination results are shown in Table 1.

(24) Experiments 1-4 are control experiments without structural stabilizer. Structural stabilizers obtained from Embodiments 1-8 are added successively in Experiments 5-12. Structural stabilizers obtained from Comparative Embodiments 1-3 are added successively in Experiments 13-15 in turn. Experiments 16-23 are comparative experiments to adjust the parameter settings on the basis of Experiment 12.

(25) TABLE-US-00001 TABLE 1 Results of Proppant Placement Volume and Fiber Escape during the Simulated Application of Structural Stabilizer to Efficient Proppant Migration and Placement Technology Effective Slick Structure Proppant Proppant Proppant Water Fiber Stabilizer Placement Fiber Experi- Product Proppant Size ratio Viscosity Dosage Dosage Volume Escape ment No. Model Type (mesh) (%) (mPa .Math. s) Fiber Type (%) (%) (ml) (%) 1 Control Quartz sand 70 20 6 PET Polyester 0 0 20 0 Group 1 Fiber 2 Control Quartz sand 70 20 6 PET Polyester 0.5 0 24 65.3 Group 2 Fiber 3 Control Precoated 40 20 6 PET Polyester 0 0 20 0 Group 3 Sand Fiber 4 Control Precoated 40 20 6 PET Polyester 0.5 0 23 72.1 Group 4 Sand Fiber 5 Embodi- Quartz sand 30 20 6 PET Polyester 0.5 0.5 26 46.7 ment 1 Fiber 6 Embodi- Quartz sand 60 20 6 PET Polyester 0.5 0.5 27.5 33.8 ment 2 Fiber 7 Embodi- Quartz sand 90 20 6 PET Polyester 0.5 0.5 28.3 21.8 ment 3 Fiber 8 Embodi- Quartz sand 180 20 6 PET Polyester 0.5 0.5 29.2 15.6 ment 4 Fiber 9 Embodi- Quartz sand 170 20 6 PET Polyester 0.5 0.5 24.5 45.8 ment 5 Fiber 10 Embodi- Quartz sand 160 20 6 PET Polyester 0.5 0.5 24.9 35.8 ment 6 Fiber 11 Embodi- Quartz sand 100 20 6 PET Polyester 0.5 0.5 24.7 37.2 ment 7 Fiber 12 Embodi- Quartz sand 140 20 6 PET Polyester 0.5 0.5 30.5 5.8 ment 8 Fiber 13 Compara- Quartz sand 140 20 6 PET Polyester 0.5 0.5 24.4 56.7 tive Fiber Embodi- ment 1 14 Compara- Quartz sand 140 20 6 PET Polyester 0.5 0.5 24.3 66.4 tive Fiber Embodi- ment 2 15 Compara- Quartz sand 140 20 6 PET Polyester 0.5 0.5 24.6 47.4 tive Fiber Embodi- ment 3 16 Embodi- Precoated 70 20 6 PET Polyester 0.5 0.5 27 22.6 ment 8 Sand Fiber 17 Embodi- Precoated 70 20 6 PET Polyester 0.5 1.0 29.3 12.1 ment 8 Sand Fiber 18 Embodi- Quartz sand 140 20 30 PET Polyester 0.5 0.5 30.1 2.7 ment 8 Fiber 19 Embodi- Quartz sand 140 20 2 PET Polyester 0.5 0.5 16.6 33.4 ment 8 Fiber 20 Embodi- Quartz sand 140 30 6 PET Polyester 0.5 0.5 34.3 16.8 ment 8 Fiber 21 Embodi- Quartz sand 140 10 6 PET Polyester 0.5 0.2 13.0 6.8 ment 8 Fiber 22 Embodi- Quartz sand 140 20 6 Lignin Fiber 0.5 0.5 22.3 63.5 ment 8 23 Embodi- Ceramite 140 20 6 PET Polyester 0.5 0.5 26.7 26.9 ment 8 Fiber

(26) According to Table 1, it can be found that the effective placement volume of the proppant can be increased by adding fibers during placement by comparing Experiments 1 and 2 with Experiments 3 and 4, and that the addition of structural stabilizer can further enhance the effective proppant placement volume and significantly reduce the fiber escape rate by comparing Experiment 2 with Experiments 5-12, as shown in FIG. 1.

(27) Comparing Experiments 5-12 with Experiments 13-15 (the schematic diagram of Experiment 12 is shown in FIG. 3), it can be seen that the enhancement of the effective proppant placement volume by the structural stabilizer prepared in Comparative Embodiments 1-3 is equivalent to that by the structural stabilizer prepared in Embodiments 1-8 on average. In a comprehensive perspective, the structural stabilizer provided by the invention is obviously advantaged in in enhancing the effective proppant placement volume and reducing the fiber escape rate.

(28) Comparing Experiment 16 and Experiment 17, it can be learned that when the amount of structural stabilizer is increased, the effect is better on increasing the proppant placement height and reducing the fiber escape rate. Comparing Experiment 12 with Experiments 16 and 17, it can be found that when quartz sand is used as the proppant, the structural stabilizer has a better effect on increasing the effective proppant placement volume and reducing the fiber escape rate.

(29) Comparing Experiment 12 and Experiment 18, it can be seen that the structural stabilizer can further reduce the fiber escape rate when slick water with higher viscosity is used. Comparing Experiment 12 with Experiment 19, it can be learned that when slick water with low viscosity is used, the smaller the proppant ratio has a less effect on the improvement of proppant placement height and the reduction of fiber escape rate. Therefore, it follows that the solution to problem provided by the invention is highly applicable.

(30) Comparing Experiment 20 and Experiment 21, it can be seen that the smaller the amount of structural stabilizer used, the better its effect on reducing fiber escape rate, and correspondingly the weaker its effect on enhancing the effective proppant placement volume.

(31) Comparing Experiment 12 and Experiment 22, it can be seen that lignin fiber has no surface characteristics of polyester fiber, making it difficult to achieve the effect of the invention, and the efficient proppant placement effect is not significant, and the fiber escape rate is obviously higher.

(32) Comparing Experiment 12 and Experiment 23, it can be found that when ceramsite proppant has no surface functional groups of quartz sand and precoated sand, so it is difficult to achieve the effect of the invention, the efficient proppant placement effect is significantly weakened, and the fiber escape rate is obviously increased.

(33) The specific embodiment is only an explanation of the present invention, and not a limitation of the present invention. Those skilled in the art may, after reading this specification, make modifications to the embodiment as needed without creative effort, but such modifications will be protected by patent law as long as they fall within the scope of the claims of the present invention.