Abstract: To further meet the requirement of drainage gas recovery in low-pressure low-yield gas well, reduce operation cost and improve drainage gas recovery technique, this paper proposes a novel natural-gas-powered drainage gas recovery pump which is suitable for straight, inclined, horizontal wells. The proposed pump is designed based on pneumatic pressurization principle. The reciprocating pump is driven by pressure boost of multiple force cylinder in a closed-loop control mode, so that pumping fluids can be delivered from wellbore to ground. There are mainly three works presented. First, we introduced the structure and working principle of the novel drainage gas recovery pump, illustrated the working procedures, and made in-depth analysis of the control method and inverting logic of drive cylinder; second, the mathematical model of pump was established; Finally, the dynamic behaviors of proposed pump was simulated using MATLAB/Simulink. The influence of structure parameters (cylinder piston diameter, cylinder piston stroke, control valve switch stroke, commutator valve core diameter) on the dynamic behaviors of pump system was investigated. The pump working performance under different loads, driving forces and supercharge ratios was analyzed. Through simulation calculation, the structural parameters of drainage gas recovery pump was determined, which provides reference for model section in practical application.

Key words: drainage gas recovery, mathematic model, modeling simulation, pneumatic pressurization