Fracturing parameters analysis and productivity evaluation of vertical coalbed methane wells with nitrogen foam

Fracturing parameters are important parameters that affect the fracturing effect, fracture characteristics and CBM productivity. Through an in-depth understanding of the influence of fracturing parameters on productivity, it is essential to optimize the fracturing process and increase the productivity of CBM wells. Taking 45 nitrogen foam fracturing wells in Lu’an mining area as the research object, the types of fracturing operation curves and their effects on productivity were studied. The relationship between fracturing fluid dosage and productivity was discussed. The differences in productivity of nitrogen foam wells and hydraulic fracturing wells was compared and analyzed. The results show that: Nitrogen foam fracturing operation curve can be divided into four categories: stable, fluctuating, ascending and descending. The production capacity of the descending and stable fracturing curves is higher than that of the fluctuating type, the ascending curve corresponds to the worst productivity; Statistical data show that 800 m³ is suitable for total liquid volume, 450 m³ for ahead fluid and 8 m³ for displacement liquid, and about 50 000 m³ for nitrogen injection. But the higher the amount of sand-carrying liquid, the higher the productivity, which reflects that the good sand-carrying, seam-forming and sedimentation performance of nitrogen foam fracturing fluid is the key point to improve production capacity; As the whole nitrogen foam fracturing well production is significantly higher than the hydraulic fracturing of wells, the proportion of high-yield wells and medium-high-yield wells of the former is much larger than the later, 61% nitrogen foam fracturing wells had higher productivity while hydraulic fracturing wells with higher productivity was 23%. The considerable potential of nitrogen foam fracturing technology in Lu’an mining area can provide technical reference for coalbed methane development in other mining areas.