Abstract:

The deep underground place in China is rich in coalbed methane resources, so that it is an important field of further exploration and development of coalbed methane. However, the geological conditions of deep coalbed methane resources are more complex, and it is different to deploy supporting technologies for engineering, so there is great challenge to realize efficient development. Overcoming the technical bottle-neck of efficient development of deep coalbed methane is of great significance to promote the efficient utilization of deep coalbed methane resources. Taking the development practice of deep coalbed methane in southern Yanchuan CBM Field as an example, five challenges faced in the process of early productivity construction are systematically analyzed: ① The reservoir heterogeneity is strong, and the main controlling factors for enrichment and high yield are unknown; ② The vertical resources need to be further evaluated, and the reserve utilization degree is low; ③ The deployment mode of well pattern is single, and the control area of single well in high stress and low permeability area is small; ④ The modification of the deep coalbed methane reservoir is poor, so it is difficult to achieve long-distance effective support by conventional hydraulic fracturing in the early stage; ⑤ The traditional drainage system has a long production cycle which is resulted in poor economic benefits. On this basis, through repeated exploration and practice, a new concept and key technology for efficient development of deep coalbed methane resources have been formed by “five transformations”: ① The overall productivity construction will change to accurate delineation of favorable areas; ② The development layer system changes from single layer to composite layer; ③ The well pattern deployment has converted from single vertical wells to the mixing well pattern of “vertical well + horizontal well”; ④ Reservoir reconstruction has changed from conventional fracturing to effective support fracturing; ⑤ The drainage system has changed from “slow and long-term” to “efficient increase of production”. Based on the “five transformations”, the production and construction benefits of new wells have been significantly improved, the daily output of vertical wells has increased from 1 800 m³/d to 10 000 m³/d, and that of horizontal wells increased from 10 000 m³/d to 20 000~50 000 m³/d. Good development results have been achieved, and the breakthrough of adjustment countermeasures for efficient development of southern Yanchuan CBM Field has important demonstration and driving significance for the benefit development of deep coalbed methane.

Key words: deep coalbed methane, effective support fracturing, efficient development, adjustment countermeasure, southern Yanchuan