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Hollow glass microsphere grout cementing in CBM

2015-05-12 01:53:52 151

Conventional oil well cement slurry of coal seam sealing, easily lead to cementing leakage, pollution of coal reservoir, to reduce the slurry density, increase cement strength, the maximum reduction of coal reservoir damage, improve the cementing quality is very important.
At present, China's coal-bed methane drilling and completion techniques and the lack of standards for coal-bed methane reservoir properties, mostly follow the oil and gas drilling and completion technologies and standards. Conventional oil well cement slurry of coal seam sealing, easily lead to cementing leakage, pollution coal reservoirs.

Cementing the damage mechanism analysis Seam
(1) CBM main reservoir space and flow channels are pore seam and cleats, when cementing, cement slurry of solid particles transported move which caused by mechanical plugging, and then cause a substantial porosity and permeability decline, is not conducive to CBM desorption.
(2) coal seams tend to have a higher content of clay minerals, when the water mud filtrate into the coal seam, causing swelling clay minerals hydration, causing decrease in porosity and permeability. Moreover, coal itself has properties of absorbing fluid generated by the expansion, and each lead matrix swelling and absorbing fluid permeability reduction process is almost irreversible.
(3) coal reservoir has a strong heterogeneity, when cementing operation, when the cement slurry column pressure is greater than coal reservoir pressure, it can cause plastic deformation seam, lead to changes in permeability; in addition, overbalance pressure large, will affect water slurry velocity of immersion and immersion radius seams, resulting in lower coal reservoir permeability.
(4) low porosity and permeability of coal and rock, strong capillary force, when coal and rock in contact with the grout will cause the capillaries self-absorption, leading to water coal reservoir trapping damage caused by gas permeability drop, seriously affecting coal reservoir gas production.

Hollow glass beads grout
Hollow glass beads slurry mainly cement, hollow glass microspheres, reinforcing and supporting the additive composition, according to cementing needs, choose a different additive system, the design of different density slurry formulations.
In addition to the strength of the grout and cement and cement formulations label the outside, depending on the size of the water-cement ratio of cement. Select the appropriate water-cement ratio, it can be grout with good flow properties, while other properties are easy to adjust. Whether water-cement ratio is too large or too small, for slurry properties are unfavorable. Too large, floating glass beads, Strength grout; too small, poor water slurry rheological properties, not easy to pumping operations.
Hollow glass beads formulated low-density slurry, poured into the conservation atmospheric consistometer 20min at 45 ℃ condition, and then six-speed rotational viscometer rheological properties, it can be seen, hollow glass beads grout good rheological properties, rheology power-law model in line, show the grout can form a stable royal space structure, to ensure the stability of slurry.

Hollow glass beads low density, high compressive strength, good compatibility with cement additive performance, which can effectively reduce the slurry density; hollow glass slurry system performance and stability, good rheological properties meet the coalbed methane wells cementing security; hollow glass beads slurry filtration system is small, coal-bed methane wells can play a good protection.

This article from the guest baba