Severe deposit build-up caused an existing well to lose production within days of being brought online. Subsequent efforts to remove the scale were successful but unfortunately it returned immediately after
placing the well back online, again cutting off production. It was concluded by the operator that the scale was originating from a formation above the producing zone and channeling down.
The well was side-tracked in order to avoid the scale producing formation. Unfortunately, cementing across this zone to isolate the solutes from migrating into the production zone was seen as a challenge due to the formation properties.
The operator decided to incorporate the Welltec® Annular Barrier (WAB®) as a solution to provide integrity and remove potential cement channels. The strategy employed was to annular isolate the problematic formation from the production zone using a combination of cement and WAB’s. The WAB’s would be expanded in the green cement to ensure isolation where required. This was the first deployment of WAB’s in a highly deviated environment through a sidetrack window.
Initially, three WAB’s were mobilized with a plan to stack the barriers below the sections where the scale producing formation was thought to be encountered. After the 12 1/4″ section was drilled to total depth it was determined that only two WAB’s would be required to provide isolation.
The first WAB was successfully installed with the top at 10,273 ft (3,131.18 m) MD; the second at 10,199 ft (3,108.65 m) MD. Both WAB’s were set after the cementing operation by applying pressure to the 10 3/4” x 9 5/8″ casing string.
The WAB’s, designed to independently isolate the formation in the case of poor cement, provided a complimentary solution
with the cement in this application. This solution provided additional confidence for the required isolation and did so without any reduction to the ID of the production string.
The well has been returned to production without the previous scaling issues reoccurring, thus verifying the two-part cement / WAB solution and providing the operator more reliable production.
The WAB provided a solution that, because of its rugged construction and low upset OD, could pass through the sidetrack window. Utilized in conjunction with cement the risk of having to re-drill the well or sidetrack again due to poor cement was eliminated. Delivered within a tight timeframe, the operator was very satisfied with the execution and results.
WELL TYPE: PRODUCTION WELL
MAX. DEPTH: 10,417 FT MD
MAX. PRESSURE: 5,400 PSI @ TD
MAX. TEMPERATURE: 175°F
WAB LENGTH: 4 FT
The well has been returned to production without the previous scaling issues reoccurring, thus verifying the two-part cement / WAB® solution and providing the operator more reliable production.