Preliminary Test of Gas Wave Ejector in Coalbed Methane Well Site and Impact Analysis of Fluid Medium Characteristics on Its Pressure Port Design

Abstract

Gas wave ejector (GWE) is an efficient energy conversion device which can recover and utilize excess pressure energy of high pressure fluid. It has significant application value in the sustainable development of energy resources, including the exploitation and transportation of natural gas. The first practical application test of GWE in the natural gas industry is completed in this study. The mechanisms and regulations of the effect of actual gas properties on the pressure port design of GWE were also investigated. The primary conclusions are as follows: the composition of working medium significantly affects the propagation velocity of pressure waves. The wave propagation velocity increases as methane purity (φCH4) rises. The equipment efficiency was decreased by up to 23% of the optimal value as a result of the variation in port position brought on by the increase in φCH4 from 0.7 to 1.0. The variation of working pressure ratio has a greater impact on the device performance than the pressure value when the pressure port design kept unchanged. The intake temperature fluctuation in the range of -30°C to 50°C has no obvious influence on the ideal port design. In the coal-bed methane well site industrial test, GWE accomplishes a recovery of low-pressure well by roughly $8.83\times {10}^3\text{N}{\text{m}}^3/\text{d}$ , demonstrating its excellent ejection capacity. In addition, the variable speed test conducted under different working conditions shows that the equipment performance can be effectively enhanced by adjusting the rotation speed as the equipment structure remains unchanged with the changing working pressure/pressure ratio. In the field test range of this study, the increase of equipment ejection rate obtained by speed adjustment can rise up to 12% of the corresponding value at the designed rotation speed.