Recompleting the wells with an artificial lift system requires a large capital investment in addition to rig intervention, a capital which was not made available due to worsening security condition in Libya in the period between 2014 − 2017, therefore, rig-less gas lift system via Coiled Tubing was chosen as the most efficient, reliable and cost-effective technique to revive oil production from 12 dead wells. The results of this pilot project were very satisfactory.
The technique involves running coiled tubing inside the production tubing of a dead oil well, the coiled tubing is then hung over an additional special tubing hanger, made specifically for this project, fixed on the Xmas Tree. The gas is injected down continuously through a single point at the end of coiled tubing which is mixed with the oil in the production tubing annulus and helps lifting the liquid to the surface. Since compression system was not made available, due to cost cutting procedures implemented by MOG, the injection rate and injection pressure were supplied through a 2″ pipe connected to a gas well which had high wellhead pressure.
Since the wells had been dead for a couple of years, there was a high uncertainty in the design due to the lack of fresh data, therefore, N2 lifting with downhole slickline gauges and surface testing were utilized to obtain reliable and fresh data for the final design. Since, the Coiled Tubing Gas Lift System CTGL technique was implemented in Libya for the first time, two wells among 12 dead wells only were selected for the Pilot project. The results of the two wells were satisfactory. Oil production from the first two wells increased significantly from 0 BOPD to 4500 BOPD, which increased the overall total field oil production by 100% from 4500 BOPD to 11,000 BOPD. Since the reservoir communication is extremely high, nearby wells’ production was positively impacted as well, and overall field production increased from 4500 BOPD to nearly 11000 BOPD in two months.
The novelty of the technique comes from the utilization of the wellhead pressure of nearby gas wells as a source of injection pressure and injection rate which made reviving dead wells possible without investing in compression systems, seen as uneconomic for a pilot project.