SCOUR-RESISTANT INTERFACE ENHANCER USED FOR WELL CEMENTING OF COALBED METHANE WELLS, PREPARATION METHOD, AND APPLICATION

Abstract

A scour-resistant interface enhancer, a preparation method, and an application thereof are provided. The scour-resistant interface enhancer is a compound solution prepared by using a 0.1% surfactant CAEO-15 and a 0.3% silane coupling agent as solutes and using clear water and absolute ethanol as solvents, where the mass ratio of clear water to absolute ethanol is 9:1. The scour-resistant interface enhancer of the present invention used as pre-flush for well cementing of coalbed methane wells has good wettability modification effect, shows scour-resistant effect against cement slurry, exhibits good compatibility with cement slurry system, and can significantly improve the cementing strength and air tightness of two interfaces of coal bed and effectively enhance the cementing quality of coalbed methane wells.

Claims

1. A scour-resistant interface enhancer, wherein the scour-resistant interface enhancer is a compound solution prepared by using a surfactant CAEO-15 and a silane coupling agent as solutes and using a mixture of clear water and absolute ethanol as a solvent; a mass percentage of the surfactant CAEO-15 is 0.1%; and a mass percentage of the silane coupling agent is 0.3%.

2. The scour-resistant interface enhancer according to claim 1, wherein a mass ratio of the clear water to the absolute ethanol is 9:1.

3. A preparation method of the scour-resistant interface enhancer according to claim 1, comprising the specific steps of: (1) mixing the clear water and the absolute ethanol in proportion to obtain a solution I; (2) adding the surfactant CAEO-15 to the solution I, dropwise adding the silane coupling agent under a low-speed stirring, and continuing the low-speed stirring for 15 min to obtain the scour-resistant interface enhancer.

4. An application of the scour-resistant interface enhancer according to claim 1 in well cementing of coalbed methane wells.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiment 1

[0015] A plurality of small coal samples is taken from coal blocks on site. The upper and lower surfaces of each coal sample are polished with low-mesh sandpaper. The upper surface of each coal sample is smoothed with high-mesh sandpaper for wetting angle measurement.

Embodiment 2

[0016] (1) Emulsifiers OP-10 in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions I.

[0017] (2) Peregal O-25 in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions 2.

[0018] (3) Surfactants CAEO-15 in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions 3.

[0019] (4) Coconut diethanolamide in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions solution 4.

[0020] (5) Tween 60 in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions 5.

[0021] (6) Sodium lauryl sulfate in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions 6.

[0022] (7) Octadecyltrimethylammonium chloride in different concentrations are respectively dissolved in clear water and stirred slowly for 15 min to obtain multiple solutions 7.

[0023] The concentration is the mass ratio of surfactant to clear water.

Embodiment 3

[0024] (1) Clear water and absolute ethanol are mixed to obtain a solution 1.

[0025] (2) Surfactant CAEO-15 is added to the solution 1 and stirred at a low speed, silane coupling agent is dropwise added under the low-speed stirring, and the low-speed stirring is conducted for 15 min to yield the product.

[0026] The mass ratio of the clear water to the absolute ethanol is 9:1.

[0027] The concentration of the surfactant CAEO-15 is 0.1%.

[0028] The concentration of the silane coupling agent is 0.3%.

Comparative Example 1

[0029] The wetting angle of the surface of coal samples from different on-site blocks is tested. The experimental instrument used is an optical contact angle/interfacial tension meter, and the titration liquid used is distilled water and cement slurry filtrate. The wetting angle is an average value of three points measured. Table 1 shows that the wetting angle of the surface of the coal samples from each block is greater than 90°, exhibiting lipophilicity, and the measurement results obtained by titration with cement slurry filtrate are slightly less than those obtained by titration with distilled water. To simulate the site, the wetting angle is measured by titration with cement slurry filtrate in a subsequent process.

TABLE-US-00001 TABLE 1 Wetting angle of coal samples from different blocks Average wetting angle (°) Riverside Riverside Wangjiazhai Naluozhai Coal sample 1# 13# 7# 1# Wetting 98.0 113.2 118.6 111.8 angle measured by titration with distilled water Wetting angle 90.3 105.4 109.7 103.9 measured by titration with cement slurry filtrate

Experimental Example 1

[0030] The wettability modification effect of various surfactants on the surface of coal rocks is tested. The coal samples are soaked in seven kinds of surfactants each with different concentrations for 10 min and then taken out and air-dried to measure the surface wetting angle.

TABLE-US-00002 TABLE 2 Optimal concentration of emulsifier OP-10 Dry coal sam- Concentration/% ple 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Wetting 107.3 63.9 55.7 57.3 31.1 26.9 30.9 33.8 35.1 angle/°

TABLE-US-00003 TABLE 3 Optimal concentration of Peregal O-25 Dry coal sam- Concentration/% ple 0.02 0.04 0.06 0.08 0.1 0.2 0.3 0.4 Wetting 110.1 86.7 86.0 53.2 38.0 9.6 16.3 26.3 38.6 angle/°

TABLE-US-00004 TABLE 4 Optimal concentration of CAEO-15 Dry coal sam- Concentration/% ple 0.02 0.04 0.06 0.08 0.1 0.2 0.3 0.4 Wetting 111.3 57.9 44.8 38.6 15.6 0.0 0.0 16.2 26.7 angle/°

TABLE-US-00005 TABLE 5 Optimal concentration of coconut diethanolamide Dry coal sam- Concentration/% ple 0.1 0.2 0.22 0.24 0.26 0.3 0.4 0.5 Wetting 106.2 42.1 14.7 6.9 6.4 0.0 0.0 0.0 0.0 angle/°

TABLE-US-00006 TABLE 6 Optimal concentration of Tween 60 Dry coal sam- Concentration/% ple 0.02 0.04 0.06 0.08 0.1 0.2 0.3 0.4 Wetting 106.3 56.5 51.0 36.6 19.7 0.0 0.0 20.7 28.5 angle/°

TABLE-US-00007 TABLE 7 Optimal concentration of sodium lauryl sulfate Dry coal sam- Concentration/% ple 0.02 0.04 0.06 0.08 0.1 0.2 0.3 0.4 Wetting 108.9 40.5 24.4 9.9 15.7 24.0 29.3 30.5 31.2 angle/°

TABLE-US-00008 TABLE 8 Optimal concentration of octadecyltrimethylammonium chloride Dry coal sam- Concentration/% ple 0.05 0.07 0.1 0.13 0.15 0.2 0.3 0.4 Wetting 109.1 36.2 17.3 10.5 2.0 8.2 8.8 11.5 15.7 angle/°

[0031] It can be seen from Table 2 to Table 8 that the seven kinds of surfactants can all have a good wettability modification effect, making the surface of the coal sample change from oil-wet to water-wet. Considering the price of surfactants and the optimal concentration for wettability modification, the preferred surfactant is CAEO-15, and its optimal concentration is 0.1%.

Experimental Example 2

[0032] The scour-resistant performance after wettability modification with surfactant is tested. The coal samples from the same block are respectively soaked in a 0.1% CAEO-15 solution, a 0.3% silane coupling agent solution, and a compound solution of 0.1% CAEO-15 and 0.3% silane coupling agent for 10 min, followed by taking out, air-drying, and scouring with a cement slurry filtrate at a constant flow rate of 0.42 m/s. The wetting angle of the surface of the coal sample is measured after scouring for different durations of time.

TABLE-US-00009 TABLE 9 Scour-resistant effect after wettability modification with CAEO-15 solution Wetta- Dry bility Scouring time coal modifi- 5 30 2 5 15 30 sample cation s s min min min min Wetting 112.8 0.0 17.9 28.3 55.2 77.1 86.3 91.2 angle/°

TABLE-US-00010 TABLE 10 Scour-resistant effect after wettability modification with silane coupling agent solution Wetta- Dry bility Scouring time coal modifi- 5 30 2 5 15 30 sample cation s s min min min min Wetting 111.3 30.7 37.1 42.3 55.2 62.5 66.6 70.0 angle/°

TABLE-US-00011 TABLE 11 Scour-resistant effect after wettability modification with compound solution Wetta- Dry bility Scouring time coal modifi- 5 30 2 5 15 30 sample cation s s min min min min Wetting 112.3 0.0 10.2 15.0 19.8 24.6 26.3 27.9 angle/°

[0033] It can be seen from Table 9 to Table 11 that the CAEO-15 solution can modify the surface of the coal sample to be completely water-wet, but the wetting angle returns to 91.2° after being scoured by the cement slurry filtrate for 30 min, indicating that its wettability modification effect is good but the scour-resistant effect is poor. The silane coupling agent solution cannot modify the surface of the coal sample to be completely water-wet, but the wetting angle remains at 70.0° after being scoured by the cement slurry filtrate for 30 min, indicating that its wettability modification effect is poor but the scour-resistant effect is good. The compound solution can modify the surface of the coal sample to be completely water-wet, and the wetting angle remains at 27.9° after being scoured by the cement slurry filtrate for 30 min, indicating that its wettability modification effect and scour-resistant effect are both very good. The compound solution is a scour-resistant interface enhancer.

Experimental Example 3

[0034] The compatibility test of the scour-resistant interface enhancer and the cement slurry is carried out. The cement slurry is prepared according to the following formula: 40% G-grade oil well cement+30% slag (S140)+30% sinking bead fly ash+1.5% thixotropic agent+2.5% fluid loss reducer+4% anhydrous sodium sulfate, and the water-solid ratio is 0.6. The scour-resistant interface enhancer is mixed with the cement slurry in a certain volume ratio, and the effects of the scour-resistant interface enhancer on the rheology, filter loss, thickening of the cement slurry, and the compressive strength of set cement are measured, respectively.

TABLE-US-00012 TABLE 12 Effects of scour-resistant interface enhancer on rheological parameters of cement slurry Mixing ratio (en- hancer:ce- Φ Φ Φ Φ Φ Φ No. ment slurry) 600 300 200 100 6 3 n K 1  0:100 120 65 46 26 2 1 0.884 0.134 2  5:95 112 60 44 24 2 1 0.900 0.112 3 10:90 104 55 40 22 2 1 0.919 0.091 4 15:85 80 42 32 20 2 1 0.929 0.065 5 20:80 68 36 26 18 2 1 0.917 0.060 6 25:75 56 29 20 14 2 1 0.949 0.040

TABLE-US-00013 TABLE 13 Effects of scour-resistant interface enhancer on thickening time of cement slurry Mixing ratio (enhancer:cement slurry) 0:100 2:98 4:96 6:94 8:92 10:90 12:88 Thickening time/min 360 360 380 380 390 410 440

TABLE-US-00014 TABLE 14 Effects of scour-resistant interface enhancer on water loss of cement slurry Mixing ratio (enhancer:cement slurry) 0:100 2:98 4:96 6:94 8:92 10:90 API water loss 40 40 42 42 44 48

TABLE-US-00015 TABLE 15 Effects of scour-resistant interface enhancer on compressive strength of set cement Mixing ratio Compressive strength/MPa (enhancer:cement slurry) 24 h 48 h 72 h  0:100 13.760 14.268 14.937 5:95 12.932 13.526 14.022 10:90  10.107 10.826 11.298

[0035] It can be seen from Table 12 to Table 15 that the scour-resistant interface enhancer has little effect on the rheological parameters, API water loss, thickening time of cement slurry, and the compressive strength of set cement, indicating that the scour-resistant interface enhancer has good compatibility with cement slurry.

Experimental Example 4

[0036] The effect of the scour-resistant interface enhancer on the cementing quality of two interfaces of coal bed is tested. The cement slurry is prepared according to the following formula: 40% G-grade oil well cement+30% slag (S140)+30% sinking bead fly ash+1.5% thixotropic agent+2.5% fluid loss reducer+4% anhydrous sodium sulfate, and the water-solid ratio is 0.6. Coal cores are respectively soaked in the scour-resistant interface enhancer and clear water for a certain period of time, followed by taking out and injecting therein the cement slurry. The maintenance of the coal cores is performed at 35° C. for 48 h and 72 h under normal pressure, and the shear strength of the two interfaces is measured. The soaking is conducted for 5 min and the maintenance is performed for 48 h with the same steps. The air tightness of two interfaces is tested through the self-developed sealing performance test device for the first and second interfaces of cementing, and the average value is taken from three measurements.

TABLE-US-00016 TABLE 16 Effect of scour-resistant interface enhancer on the cementing strength of two interfaces Soaking Maintenance Maintenance Soaking medium time for 48 h for 72 h Clear water 1 min 1.148 1.604 5 min 1.142 1.554 10 min  1.156 1.629 Interface 1 min 1.263 1.826 enhancer 5 min 1.448 2.054 10 min  1.479 2.103

TABLE-US-00017 TABLE 17 Effect of scour-resistant interface enhancer on air tightness of two interfaces of coalbed cement sheath Breakthrough pressure Breakthrough pressure under clear water under interface enhancer No. soaking/MPa soaking/MPa 1 2.7 3.1 2 2.5 3.2 3 2.8 3.6 Average 2.67 3.3 value

[0037] It can be seen from Table 16 and Table 17 that the cementing strength of two interfaces of the coal core soaked in the scour-resistant interface enhancer is significantly higher than that of the coal core soaked in clear water, and the cementing strength of two interfaces is greatly increased with the prolonging of the soaking time. The cementing strength after treatment for 5 min and the cementing strength after treatment for 10 min are similar, indicating that the effect of improving the cementing strength of two interface can be achieved after treatment with the cementing quality enhancer for 5 min. The scour-resistant interface enhancer can also significantly enhance the air tightness of two interfaces of coalbed cement sheath. Therefore, the scour-resistant interface enhancer can significantly improve the cementing quality of two interfaces of coal bed.