PREPARATION METHOD OF THE MICROCAPSULES FOR LOW-TEMPERATURE WELL CEMENTATION TO BE USED TO CONTROL CEMENT HYDRATION HEAT

Abstract

A preparation method of the microcapsules for low-temperature well cementation to be used to control cement hydration heat includes: (S1) a shell material, and added into deionized water, then the resultant mixture being stirred in a thermostat water bath so as to completely dissolve it into a homogeneous and stable shell material solution; (S2) a core material and an emulsifier being put into a three-necked flask and stirred in a thermostat water bath so as to uniformly emulsify and disperse them, forming a stable oil-in-water core material emulsion, while adjusting the pH value of the emulsion with a pH adjuster; (S3) the three-necked flask containing the core material emulsion being transferred to a water bath, and then the shell material solution being dropwise added into it with stirring, after reacting, a solid-liquid mixture being poured out so as to naturally cool it to room temperature.

Claims

1. A preparation method of the microcapsules for low-temperature well cementation to be used to control cement hydration heat, comprising the following steps in proper order: S1: a shell material being weighted with 10-20 g, and added into 50-100 mL of deionized water, then the resultant mixture being stirred in a thermostat water bath at 45° C. so as to completely dissolve it into a homogeneous and stable shell material solution, said shell material being sodium silicate NaSiO.sub.3.9H.sub.2O; S2: 10-20 g of a core material and 0.02-0.1 g of an emulsifier being put into a three-necked flask and stirred in a thermostat water bath at 45° C. for 30-60 min so as to uniformly emulsify and disperse them, forming a stable oil-in-water core material emulsion, while adjusting the pH value of said emulsion to descend below 5.5 with a pH adjuster, where said core material is a binary composite phase-change material prepared by n-decanoic acid and lauryl alcohol, the preparation process of said binary composite phase-change material includes mixing n-decanoic acid with lauryl alcohol by mass ratio of 1:1, and stirring them evenly; said emulsifier is a mixture of alkylphenol polyoxyethylene ether-10 and cetyl trimethyl ammonium bromide, the mass ratio of the cetyl trimethyl ammonium bromide is 20-80%; S3: said three-necked flask containing said core material emulsion being transferred to a water bath at 50-90° C., and then said shell material solution being dropwise added into it with stirring, after reacting for 2-3 hours, a solid-liquid mixture being poured out so as to naturally cool it to room temperature, thus said cooled solid-liquid mixture being processed by suction filtration, washed with ethanol and deionized water, respectively, to remove impurities, and finally being processed by freeze-drying.

2. The preparation method according to claim 1, wherein in S2 said pH adjuster is hydrochloric acid HCl.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a Fourier transform infrared spectrum (FTIP) of the microcapsules prepared in Example 1.

[0026] FIG. 2 is a microcosmic appearance photo of the microcapsules prepared in Example 1.

[0027] FIG. 3 is a TEM photo of the microcapsules prepared in Example 3.

[0028] FIG. 4 is a differential scanning calorimetry (DSC) graph of the microcapsules prepared in Example 3.

[0029] FIG. 5 shows the test results of the hydration heat of a cement paste containing the microcapsules measured at 4° C. outside.

[0030] FIG. 6 shows the test results of the hydration heat of a cement paste containing the microcapsules measured at 8° C. outside.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0031] The present invention is further described below according to the drawings and embodiments, so as to help a person skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments, and in the view of the person skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, they are all claimed.

[0032] I. Preparation of the Microcapsules for Low-Temperature Well Cementation

EXAMPLE 1

[0033] Sodium silicate is weighted with 10 g, and added into deionized water (50 mL), then the resultant mixture is stirred magnetically at 45° C. for 10 min so as to completely dissolve. The mixed solution of lauryl alcohol (5 g) and n-decanoic acid (5 g), CTBA (0.05 g) and OP-10 (0.05 g) are put into a three-necked flask, maintaining heated at 45° C. and stirred for 30 min at a rotation speed of 2000 rpm so as to uniformly disperse the lauryl alcohol and n-decanoic acid, forming a oil-in-water (O/W) emulsion, while adjusting its pH value to be 1.5 with hydrochloric acid. The above emulsion is transferred to a thermostatic water bath at 50° C., and then the prepared sodium silicate solution is dropwise added into the three-necked flask by means of a separating funnel with stirring at a rotation speed of 300 rpm for 2 hours, subsequently, the product is transferred to a beaker and cooled to room temperature for suction filtration, then washed with absolute ethanol and deionized water and processed by freeze-drying.

EXAMPLE 2

[0034] Sodium silicate is weighted with 12 g, and added into deionized water (80 mL), then the resultant mixture is stirred magnetically at 45° C. for 10 min so as to completely dissolve. The mixed solution of lauryl alcohol (6 g) and n-decanoic acid (6 g), CTBA (0.03 g) and OP-10 (0.07 g) are put into a three-necked flask, maintaining heated at 45° C. and stirred for 30 min at a rotation speed of 2000 rpm so as to uniformly disperse the lauryl alcohol and n-decanoic acid, forming a oil-in-water (O/W) emulsion, while adjusting its pH value to be 2 with hydrochloric acid. The above emulsion is transferred to a thermostatic water bath at 60° C., and then the prepared sodium silicate solution is dropwise added into the three-necked flask by means of a separating funnel with stirring at a rotation speed of 500 rpm for 2 hours, subsequently, the product is transferred to a beaker and cooled to room temperature for suction filtration, then washed with absolute ethanol and deionized water and processed by freeze-drying.

EXAMPLE 3

[0035] Sodium silicate is weighted with 15 g, and added into deionized water (50 mL), then the resultant mixture is stirred magnetically at 45° C. for 10 min so as to completely dissolve. The mixed solution of lauryl alcohol (7 g) and n-decanoic acid (7 g), CTBA (0.02 g) and OP-10 (0.08 g) are put into a three-necked flask, maintaining heated at 45° C. and stirred for 30 min at a rotation speed of 2000 rpm so as to uniformly disperse the lauryl alcohol and n-decanoic acid, forming a oil-in-water (O/W) emulsion, while adjusting its pH value to be 2.5 with hydrochloric acid. The above emulsion is transferred to a thermostatic water bath at 70° C., and then the prepared sodium silicate solution is dropwise added into the three-necked flask by means of a separating funnel with stirring at a rotation speed of 600 rpm for 2.5 hours, subsequently, the product is transferred to a beaker and cooled to room temperature for suction filtration, then washed with absolute ethanol and deionized water and processed by freeze-drying.

EXAMPLE 4

[0036] Sodium silicate is weighted with 14 g, and added into deionized water (50 mL), then the resultant mixture is stirred magnetically at 45° C. for 10 min so as to completely dissolve. The mixed solution of lauryl alcohol (8 g) and n-decanoic acid (8 g), CTBA (0.03 g) and OP-10 (0.03 g) are put into a three-necked flask, maintaining heated at 45° C. and stirred for 30 min at a rotation speed of 2000 rpm so as to uniformly disperse the lauryl alcohol and n-decanoic acid, forming a oil-in-water (O/W) emulsion, while adjusting its pH value to be 3 with hydrochloric acid. The above emulsion is transferred to a thermostatic water bath at 80° C., and then the prepared sodium silicate solution is dropwise added into the three-necked flask by means of a separating funnel with stirring at a rotation speed of 600 rpm for 2.5 hours, subsequently, the product is transferred to a beaker and cooled to room temperature for suction filtration, then washed with absolute ethanol and deionized water and processed by freeze-drying.

EXAMPLE 5

[0037] Sodium silicate is weighted with 18 g, and added into deionized water (50 mL), then the resultant mixture is stirred magnetically at 45° C. for 10 min so as to completely dissolve. The mixed solution of lauryl alcohol (9 g) and n-decanoic acid (9 g), CTBA (0.08 g) and OP-10 (0.02 g) are put into a three-necked flask, maintaining heated at 45° C. and stirred for 30 min at a rotation speed of 2000 rpm so as to uniformly disperse the lauryl alcohol and n-decanoic acid, forming a oil-in-water (O/W) emulsion, while adjusting its pH value to be 1 with hydrochloric acid. The above emulsion is transferred to a thermostatic water bath at 90° C., and then the prepared sodium silicate solution is dropwise added into the three-necked flask by means of a separating funnel with stirring at a rotation speed of 800 rpm for 3 hours, subsequently, the product is transferred to a beaker and cooled to room temperature for suction filtration, then washed with absolute ethanol and deionized water and processed by freeze-drying.

[0038] II. Structural Representations of the Microcapsules for Low-Temperature Well Cementation

[0039] It can be seen from FIG. 1 that the strong absorption peak near 3320 cm.sup.−1 is the stretching vibration of O—H, and this peak corresponds to alcoholic hydroxyl group. The absorption peaks near 2920 cm.sup.−1 and 2850 cm.sup.−1 pertains to C—H bonds, which correspond to —CH.sub.3 and —CH.sub.2. The sharp absorption peak of the strong infrared spectrum near 1709.85 cm.sup.−1 is the stretching vibration of a carbon-oxygen double bond in —COOH. There are several weak absorption peaks of —OH in the range of 2700-2500 cm.sup.−1, and few other peaks appear in this absorption peak range, so they can be used to judge the existence of carboxylic acid. There are the antisymmetric vibrational absorption peak of Si—O—Si at 1096 cm.sup.−1 and the symmetrical vibrational absorption peak of Si—O—Si at 803.6 cm.sup.−1. There are the bending vibration absorption peak of Si—OH at 941 cm.sup.−1 and the vibration absorption peak of a Si—O group at 469 cm.sup.−1. The above analysis can prove that the core material is successfully coated with silica, and there is no chemical reaction, but a simple physical combination, between the core material and the wall material.

[0040] It can be seen from FIG. 2 that the microcapsules are spherical and fine particles, with uniform and regular distribution and good dispersion.

[0041] It can be seen from FIG. 3 that the microcapsules have an obvious core-shell structure.

[0042] III. Thermal Performance Analysis of the Microcapsules for Low-Temperature Well Cementation

[0043] It can be seen from FIG. 4 that the phase-transition point of the microcapsules is 12.5° C. at the heating stage. At the cooling stage, the phase-transition point of the microcapsules is 0.13° C. It can be seen that the microcapsules are sensitive to the change of external temperature and more suitable for a low-temperature oil well cement system.

[0044] FIGS. 5 and 6 show the test results of the hydration heat of a cement paste containing the microcapsules measured at 4° C. and 8° C. outside. It can be seen from the figures that the microcapsules can effectively reduce the hydration temperature rise of a cement paste.