Production characteristics of deep coalbed methane gas reservoirs in Daning-Jixian Block and its development technology countermeasures

The Ordos Basin is rich in deep coalbed methane resources with a depth of more than 2 000 m, which is an important coalbed methane exploration and development area. A number of tests on deep coalbed methane have been carried out in Daning-Jixian Block, and preliminary results have been achieved, but the main technology of scale-efficient development needs to be studied. On the basis of the analysis of experimental data, production data and fracture monitoring data, and by the evaluation of the characteristics, production performance and fracturing effect of deep coalbed methane reservoirs in Daning-Jixian Block, the production characteristics of deep coalbed methane are analyzed and development countermeasures are proposed. The research indicates that ① Deep coal reservoirs have the characteristics of low permeability, high gas content, high gas saturation and rich free gas. ② The productivity of deep coalbed methane is mainly controlled by resource enrichment, micro-structure and effective fracturing scale. In the positive micro-structure development area, the richer the resources, the greater the fluid strength, and the greater the sand strength, the more conducive to expand the gas supply capacity and improve the single well production. ③ The production wells of deep coalbed methane are characterized by three-stage production: the high production period dominated by free gas production, the stable and decline period where free gas and adsorbed gas are produced together, and the low production period dominated by adsorbed gas production. The technology countermeasures for deep coalbed methane development are put forward based on the above, and the implementation of D6-7P1 well has achieved good production effect, which confirms that the implementation of super large-scale sand fracturing in favorable areas can effectively improve the production capacity of deep coalbed methane.