Research on adaptability of fracturing technologies for CBM horizontal wells based on the viewpoint of “unblocking and channeling”

Horizontal well fracturing stimulation is currently the most core technical means to achieve efficient development of unconventional coalbed methane resources. Although good on-site results have been achieved, there are still some problems such as unclear the goal of fracturing stimulation, unclear the adaptability of the main horizontal well fracturing technology and lack of evaluation methods for fracturing effects. In order to further improve the production and development benefits of fractured horizontal wells, this article based on the viewpoint of “unblock and channeling”that has achieved significant results in the southern part of the Qinshui Basin and has been verified by practice, combined its requirements for fracturing on high-rank coal reservoir and the characteristics of the original natural pores and fractures in the high-rank coal reservoirs in the southern part of the Qinshui Basin, referred meanwhile to the evaluation experience of previous fracturing, selected seven key indicators: Types and quantity of fracturing operation curves for each section of the horizontal well, average operating pressure, instantaneous shut-in pressure, accident type and occurrence rate, Pressure at the moment of initial gas production, Current bottomhole flowing pressure and daily gas production (Production time is more than one year), and comprehensive average stable gas production, proposed an evaluation method for the fracturing effect. Furthermore, combined with on-site comparative experiments, a study on the adaptability of the main horizontal well fracturing technology will be conducted to determine the upper limit and shortcomings of the main fracturing technology’s stimulation capacity. The results show: With the increase of burial depth and geo-stress, the difficulty of coal reservoir stimulation has shifted from easy to filter out, prone to excessive opening of natural fractures near the wellbore, making it difficult to create dominant main fracturing fractures, to difficulty in gradually opening natural fractures around the dominant main fracturing fractures, insufficient opening of secondary fractures, and difficulty in transporting fracturing sand, making it easy for desanding and sand-block.Due to the excessive pressure loss along the wellbore, the bottom sealing drag fracturing technology is unable to meet the needs of “unblocking and channeling”fracturing stimulation at depths of more than 1 000 meters.The continuous tubing fracturing technology has the problem of insufficient carrying capacity for fracturing sand after at depths exceeding 1 200 meters.The bridge shooting combined fracturing technology can not only meet the needs of the “Unblocking and Channeling” fracturing stimulation of coal reservoirs with a depth of 1 250 meters, but also has the potential to further increase the scale of fracturing stimulation, which can meet the construction and implementation of the“unblocking and channeling”fracturing stimulation of coal reservoirs under deeper conditions. The research provides important basis and support for the rational selection and upgrading of fracturing technologies in the southern part of the Qinshui Basin and other coalbed methane blocks at home and abroad.