The Research On One Slurry System Of Coalbed Methane Well Cementing

CBM cementing facing many challenges, improving performance of low density slurry at low temperature, improving the early strength of cement stone, losing less water, shortening thickening time, increasing the cementing ability between the surface of cement stones and coal seam, reducing cement stone contraction, reducing pollution and channeling, having vital significance for CBM cementing.This paper aims at defects of the low density slurry when CBM cementing. Using the method of adding latex, taking advantage of low water loss, zero free liquid, good toughness of cement stone and cement ring not easily to be damaged when perforating, create a new kind of low density latex slurry. Through a mass of literature investigation, theoretical analysis and derivation, basing on the principle of the particle closely stacked established the gradation model of fractal continuous. Analyzed the particle size distribution of cement, hollow glass beads and micro silicon. Using the particle gradation theory to obtain the best proportion of the three. Combining the rheology and compressive strength experiment, at the last, geting the foundation formula of the low density latex slurry system. One this basis, optimization out the optimal added amount of the dispersant SWJZ is 0.8% to 1.2%. The optimal added amout of accelerator Al2(SO4)3 is 1.6% and TEA is 0.06%. The optimal added amount of fluid loss control agent TD-S is 1.8% to 2.0%. The optimal added amount of nitrogen expansion agent is 1.0%. And tested each formula performance under different conditions of density. Eventually developed the low density latex slurry system. Throughing test, the density of the slurry system can be adjusted between 1.079~1.243g/cm3. Having good rheological property, low fluid lose(<30mL), zero free water, high early compressive strength, short and adjustable thickening time, micro expansibility and strong ability of preventing channeling, etc. Effectively reduced the damage of cementing coal seam, significantly improved the cementing quality.