Agua del Cajón Field produces from conventional and unconventional formations since 1970. As a mature gas field, the average gas rate per well is 7.000 m3/d with a GLR of 10.000. Reservoir pressure is 25% of its original and 70% of the wells produce from several formations, with perforated intervals longer than 500 meters.
As flow rate decreases, gas doesn't have enough turbulence to remove liquid, leading to an increase in dynamic bottomhole pressure due to liquid loading. This effect deepens the decline resulting in gas resources unproduced.
There are different solutions for these kind of problems: reducing wellhead pressure using compression, capillary strings for foamer injection, velocity string or gas lift.
Gas lift is an attractive solution to reach gas speeds higher than critical by injecting a supplementary gas flow. This technique has achieved good results during several years in Agua del Cajon field. Despite working properly in the tubing (being efficient to remove liquid from injection mandrels to surface), it didn't solve liquid accumulation in the perforated interval.
Capex developed a customized bottom-hole equipment that optimizes well performance, by injecting gas lift below the packer.
A cross-over packer with a concentric pipe design is used, allowing injected gas to be conducted through the annular space between them and to extract liquid and gas from the bottom of the well by the central tube of reduced diameter. The production gas can be produced with the liquid at the end of the pipe, or rise through the annular space (casing-outer tubing) and join the liquid production and injected gas through a crossover located below the packer. The advantage of this system is that it ensures the removal of liquids from the lower part of the well with an optimized flow of injection gas.
In the last 5 years, 25 devices were installed with operative success in all cases. Gas flow rate increased an average of 80% after the intervention. Liquid production increment is also observed in most cases. Reserves were gained as it was able to reduce the abandonment gas flow rate.