At the end of 2019, we were challenged by an international Operator company in Argentina to provide technical support for a complex fishing operation on a recently fracked well in Vaca Muerta unconventional shale reservoir. The well intervention objective was to recover a downhole device used to isolate the annulus to the production conduit on the well, named production retrievable packer (PKR), with a confirmed fluid leak through it, that PKR was set with the objective to isolate 52 frac stages after a coil tubing plugs mill out intervention and well flow back.
Refer to figure #1 – Well diagram.
The lower completion was set on 5 1/2in Production Casing and it was composed of the following items: mechanical Packer with stinger on-off pin connection device, 2 3/8 inch pup joint × 2 ft length, 1.81 RN nipple and pump out shear out plug. The lower completion array was configured to be set on a wireline at 9,500 ft MD @30-degree deviation as per completion design.
In general, when a leak is detected on production packers, it is a fairly common industry practice to run and set a second PKR on top of the first one (bridge PKR) to get proper wellbore pressure isolation and at the same time to save time and efforts by avoiding complex maneuvers to recover the failed PKR. In this case, that general solution wasn't an option because two main reasons:
There were 7 frac stages not properly cleaned up on coiled tubing because of casing deformation issues detected during the coil tubing clean out phase, therefore the operator wanted to keep an alternative to be able to safely retrieve production TBG string & PKR to get full wellbore access without restrictions, in case an additional well cleanout job was required based on production performance evaluation.
The operator's completion engineering department decided to retrieve the first well barrier and conduct an extensive failure analysis, as this PKR model was the selected one for many other similar interventions.
Once the leak was confirmed by negative pressure leak test, a retrievable bridge plug was set to secure the well and allow the operator for wellhead change out as planned and move on with mill out interventions on the other inline wells from the pad.