Authors: Charles Kubacak, Lead Production Engineer, Ovintiv (Encana Services Co) – Permian South; Eric Hale, Technical Sales-Gas Lift, Flowco Production Solutions; Matt Young, Sales Director, Flowco Production Solutions
Flowco engineers partnered with Ovintiv to analyze past production profiles to create a more efficient design for future wells in the same landing zone. This new concept in gas lift design, was engineered to accommodate higher liquid rate initial production, as well as lower rate later life production without the need for a work-over to make the production change. Reservoir data and predicted rates from similar rock were reviewed prior to the solution selection. Deployment of permanent downhole gauges in these systems was critical for accurate measurement of flowing and static bottom hole pressure (BHP) and provided verification of the optimal and efficient point to switch production from annular to tubing flow.
A hybrid gas-lift system was installed on a well in the Wolfcamp basin with 2.875” 6.5# L-80 production tubing inside 5.5” 20# P-110 production casing. Injection was established down the tubing through a series of annular flow gas lift mandrels to produce high fluid volumes initially with the larger cross-sectional flow area up the tubing and casing annulus, with the ability to transition from annular flow to tubing flow without direct well intervention.
By taking these wells down to a much lower fluid rate and then switching to tubing flow, we did not increase flowing bottom hole pressure, which would result in a loss in production. Further, well economics are enhanced by the immediate reduction in required lift gas.
The Nodal Analysis program allows for a gas lift performance curve to be created. This curve accounts for the directional changes within the wellbore and tubing string. Modeling showed the tubing performance curves from the 3.816” equivalent flow ID and 2.441” ID converge with one another around the 500-800 BLPD range. This gave us a baseline to help get an efficient design installed for the operator. Readings from the downhole pressure gauge confirm the adjustment KPI’s for the performance curve.
Another advantage to the reduction in gas injection volumes needed for the test well was gas diverted to help feed another annular flow well. The hybrid system has also been effective to help de-water frac-impacted wells that may have watered out due to offset frac activity that had direct hydraulic communication from an offset well.
The tubing will have full-drift ID with the type of annular flow mandrels provided. We took a high fluid-rate well down to a mid to low rate with the ability to run a plunger, if required.
This approach in transitioning from annular flow to tubing flow has been beneficial in optimizing production in a hybrid gas well in the Permian. In addition to mitigating a well work-over and reducing the required lift-gas volume, there have been additional long-term production gains. The benefits of this gas lift system are applicable to many basins around the world.