Alternative Method of Injection of Nanoemulsion for Intensifying Coalbed Methane Recovery

The disadvantages of high usage and adsorption loss of surfactants are adverse to the extraction of coalbed methane (CBM) in coal seam fracturing. Here, a nanoemulsion (TW80–AES NE) consisting of Tween 80 (TW80) and sodium fatty alcohol polyoxyethylene ether sulfate (AES) was fabricated as a carrier of the surfactant. The experimental results show that TW80–AES NE, as a carrier of the surfactant, possesses lower surface tension than surfactant solution; therefore, TW80–AES NE is subjected to smaller capillary resistance in the pores of the coal seam and can enter smaller pores, such as micropores, of the coal seam, which can reduce injection pressure and improve the injection effect. TW80–AES NE has higher stability in coal rock pores, which makes the adsorption rate of TW80–AES NE on coal rock smaller and the effective intrusion depth deeper. TW80–AES NE promotes methane desorption through competitive adsorption, achieving a higher desorption volume and faster desorption rate with less surfactant content.