Abstract
Well X is an oil producer in the Mississippi Canyon of the Gulf of Mexico. The well was originally designed as a smart downhole flow control (DHFC) completion that allowed split flow between two cased-hole frac-pack (CHFP) sand control completions. Unfortunately, the DHFC system failed, and the well must be produced with commingled flow from both zones. Over time the well's skin (frictional pressure loss across the completion screens) has increased to a point where the well's production rate needed to be reduced to limit erosion and maintain integrity of the completion. Well X receives pressure support from a downdip injector which has led to seawater production and introduced the risk of barium-sulfate scale. The well's previous scale prevention treatment expired at the end of 2022. The scope of the Riserless Light Well Intervention (RLWI) was to remediate skin and refresh the scale prevention treatment in both zones.
The intervention required right scoping the well control and ancillary equipment to enable successful pumping and wireline operations on a sub-ambient well under elevated subsea and surface metocean conditions. Additionally, surveillance was necessary to assess damage and allocate contributions from each zone. Individual isolation of both zones was required for acid stimulation and scale treatment. Achieving this involved either setting plugs or installing isolation sleeves across the failed flow control device.
Based on production logs, it was observed that the contributing interval of the lower zone had been reduced to about 10 ft despite having 110 ft of perforations. To address this, an acid stimulation with use of diverter pills was carried out on the lower zone which resulted in an increase in the contributing height to the full 110 ft, marking a greater than 10-fold increase. Furthermore, successful scale prevention treatments were administered to both zones to prevent barium sulfate scale deposition. Throughout the intervention, all wireline operations were carried out effectively under sub-ambient conditions without any hydrate problems, loss of well control, or seawater ingress.
Acid stimulation bullheaded from surface aided in successfully treating non-contributing intervals with the use of diverter pills. The use of the collapse rated hoses along with other well control package modifications have enabled access to other sub-ambient wellwork in this field.
