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Gas Well Unloading

In the mist or bubble flow regime, the gas flow rate needed to lift water droplets can be significantly reduced by adding surfactant to reduce the surface tension. The (empirical) Turner model can be used to estimate the minimum, or critical, velocity needed to suspend and carry droplets in a flowing gas well under pressure (or more generally, in a vertically oriented pipe). The Turner velocity, Vg, is given by [59]  [Pg.357]

The lifting of water from the bottom of a gas well can also be facilitated by using surfactant to create foam using the gas flowing from the reservoir. The foam then acts to effectively lighten the water, reducing the hydrostatic back-pressure on the formation and making it easier to produce water from the well. Another benefit of down-hole foam formation can be the stabilization of flow and reduction of pressure fluctuations in a well. [Pg.357]

There are various kinds of solid, surfactant-containing sticks that can be dropped down through the casing to dissolve in bottom-hole water to release foaming surfactants, sometimes with the co-release of gas bubbles (such as CO2). [Pg.357]

These surfactant sticks (often referred to under a variety of common and trade-marked names such as soap sticks ) can be dropped manually or with automatic stick launchers. The gas-releasing capability from so-equipped sticks are not very large this feature is intended for use in stimulating completely dead wells. Alternatively, one can continuously inject foaming surfactant solution through tubing in the annulus. This consumes more surfactant but can lead to a more consistent unloading of the water with less pressure fluctuation. The surfactants that have been used are mostly anionic or anionic/non-ionic blends [53, 60]. [Pg.358]

As with other petroleum applications of foam, careful surfactant screening is needed to select surfactants capable of forming effective and economical foams for these harsh environments (see Section 11.3.2.2). Also, different surfactants are best suited to forming aqueous foams, versus aqueous foams that may encounter condensate, versus condensate foams (see Section 5.6.7). In many situations, a low-cost surfactant can be used, but difficult situations may require specialized and hence expensive surfactants which can make the foaming of bottom-hole water uneconomic. [Pg.358]


Foam fracturing and stimulation fluids Foam acidizing fluid Gas well unloading foam... [Pg.352]


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