Experimental study of the influences of water injections on CBM exploitation

ABSTRACT

In order to study the influence of water injections into a coal body on coalbed methane (CBM) recovery following hydraulic fracturing, experiments have been done in which water is injected into coal samples at adsorbate equilibrium pressures of 0.5 MPa, 0.84 MPa, 1.5 MPa and 2.5 MPa using a high-pressure adsorbate-injecting water-desorption device. The results show that the injected water can replace the adsorbed methane. The replacement ratio and quantity of adsorbed methane gradually increase with increasing quantities of injected water. Under the adsorbate equilibrium pressure of 2.5 MPa, the maximum displacement of the adsorbed methane is 11.88 mL/g when the moisture content of the coal is 10.03%. Under the adsorption equilibrium pressure of 0.84 MPa, the maximum replacement rate of the absorbed methane is 59.14% when the moisture content is 8.39%. The increase of the displacement and replacement rates shows that the adsorbed methane can be replaced by water, which further promotes improved CBM recovery.

KEYWORDS:

• Water injection
• displacement effect
• methane
• adsorbed state
• free state

Additional information

Funding

This research was supported by the National Key Research and Development Programme of China (2016YFC0801402, 2016YFC0600901), the National Natural Science Foundation of China (No. 51874122,No.51704100), the Key Research Projects of Henan Higher Education Institutions (No. 18A440004), the Program for Innovative Research Team of Henan Polytechnic University.