Abstract
When initially completed, many natural gas wells are capable of lifting liquids to the surface. But, with depletion of the reservoir pressure, there comes a time when liquids can no longer be lifted to the surface and they begin to accumulate in the bottom of the well, dramatically inhibiting or stopping gas production. The cause of diminished liquid-lifting ability is the decline of liquid droplet production as gas flow rates pass below the Turner-Hubbard-Dukler critical velocity. In this research, a variety of devices were tested for enhancing droplet production and liquid lifting at low gas flow rates. The devices included vibrational, rotational, and two-fluid means for droplet production. Tests in a flow loop showed that the vibrational devices are most promising for commercial application. A correlation for droplet size as a function of frequency was extended for application at any frequency of interest. Tests with a flow loop show that 3 micron drops can be transported easily at low flow rates. Heuristics in the literature on droplet transport lead to the expectation that droplets with diameters less than 30 microns can be transported from the bottom of a well to the surface without significant difficulty. An energy analysis shows that a barrel of water can be converted to 30-micron droplets for 3 to 30 cents.
