Many mature gas /oil wells worldwide had shut-in issue due to water loading in the production string. The well killing occurs when the liquid's hydrostatic column pressure equals the reservoir pressure, stopping production. A periodical chemicals surfactant injection from surface can be a solution to solve the problem, but it is only a temporary way out. Continuos injection of a downhole foaming agent constitutes a remedy to lift the water and restore gas production definitively.
This paper describes all the equipment studied and developed for the first application of Permanent Capillary String as Deliquification System, that can be retrofitted into existing wells with rigless intervention, in order to restore production quickly. This method maintains well safety valve functionality and eliminates expensive workovers.
One of the main problems in gas wells is the so-called "liquid loading", which seriously influences the effective exploitation of hydrocarbons reserves, by restricting and eventually ending well production, especially from depleting reservoirs, as water accumulates into the wellbore.
Liquids can accumulate in a gas well through a variety of mechanisms. Usually, the gas produced from a reservoir is not dry, but it has an associated liquid phase. In some cases, liquids can come from the condensation due to pressure and temperature variations experienced by the gas along the wellbore, from interstitial water in the reservoir matrix or as the result of water coning phenomena. In all the cases, the higher density liquid phase must be transported to surface by the gas. In the event that the gas phase does not provide sufficient transport energy to lift the liquids out of the well, the liquids accumulate in the wellbore.
Liquid loading is not peculiar to low-pressure gas wells alone, but it may also exist in high-pressure gas wells with high liquid-gas ratios and large tubing diameter completions.
Capillary String technology (Fig 3:) is composed by four components:
Capillary Line (Fig 1:)
Capillary String SCSSV
Wellhead Penetrator (Fig 2:)