INTERMITTENT GAS LIFT – THE EFFICIENT SOLUTION

This two-pen pressure recorder chart shows an intermittent gas lift (IGL) well efficiently producing 20 barrels of fluid per day (bfpd). Twelve gas injection cycles and 48 mcf of injected gas volume was consumed daily by this installation. This well is on “Time-Cycle Control”. The chart shows rapid increase in casing pressure after the time-cycle controller opens, and rapid decrease in casing pressure indicative of good gas lift valve action. The casing pressure buildup during gas injection is the same for each gas injection cycle. The tall slender tubing kicks indicate good intermittent operation with a solid liquid slug being produced rather than a gas-cut or aerated slug.

This is a 24-hour chart rotation instead of a 48-hour chart which makes these slender tubing kicks even more impressive. The casing pressure remains constant between injection cycles indicating no leaks from a gas lift valve, valves, the packer, tubing or a wellhead leak.

This shown pressure recorder chart was recovered from one of 560 active IGL wells 32 years ago operated by a major E&P Operator. An IGL well in both the Delaware and Permian Basins today, for example, producing 100 bfpd needs approximately 120 mcfd of injected gas for efficient lift. By comparison, a Gas Assisted Plunger Lift (GAPL) installation producing 100 bfpd requires 300-450 mcfd of injection. In addition, it was found that when Basin wells were converted from GAPL to IGL, fluid production increased by over 26 percent.

IGL operation is the displacement of a liquid slug to the surface by the expansion of high-pressure gas. This expansion of gas is the sole driving mechanism of this method. IGL has few moving parts and is not as mechanical a method as GAPL which requires additional field surveillance and maintenance. “Intermittent Gas Lift has advantages over other forms of artificial lift based on economics and flexibility. The lifting and equipment costs for a deep, low fluid level well are lower. Intermittent Gas Lift offers extreme flexibility over a wide range of producing rates and depths of lift with the same installation”. Dr. Herald Winkler (Texas Tech Univ.).

Significantly reducing gas injection volumes (by greater than 55% in many cases) and field compression capacity are key drivers to converting GAPL installations to IGL. This is done by replacing the orifice valve with an injection pressure operated gas lift valve on bottom, the use of a surface intermitter, and applying best gas lift industry practices. The IGL technique is used on wells producing from 10 to 300 barrels of fluid per day, and rod-pumped wells with sufficient source of natural gas can be converted to IGL.