Successful Barium Sulfate Scale Milling with Wireline Tractor 

October 2008

 

 

An oil producer in the North Sea was seeing a reduction in the production rate and believed this was caused by scale bridges above and inside the perforating zones between 12,200-12,870 feet. The operator had attempted to remove the scale with slickline, but this method was not able to break through the scale. 

 

Based on previous experience with Welltec’s wireline services, they decided to apply the Well Miller with near bit centralizer and a wide range of milling bits to remove the scale. This solution was tested extensively onshore to the customer’s satisfaction.

 

Very hard scale was experienced during the operation, which was an operational challenge. However, Welltec’s milling tools managed to mill barium sulfate scale down to the area between the 4th and 5th perforation interval. The operator continued to produce the well during the milling process so that the cuttings were brought to surface and separated but this did not allow for a measurement of the cutting volume.
 

Achievements

Cost savings were estimated to be $800,000. Logistically, the operation eliminated the need for mobilizing coiled tubing, which is a serious problem at this platform due to space restrictions. Today, Welltec is the provider of choice for this kind of service as the Well Miller proved to be the most time and cost effective solution available.

In a period of 10 days, the Well Miller milled through a 200 ft long scale restriction, thus increasing the minimum diameter through the section from 1” to 4”. This resulted in a net production increase of more than 3,000 BOPD.

 

Following the operation, the client stated:
“From the logistics center in Bergen to the support in Denmark including your customer contact in Stavanger and your offshore crews in the field they have all demonstrated that Welltec possess a group of highly motivated staff who are willing to provide that little something extra often needed to get the job done.”
 

Well Data

Maximum Deviation:	45°
Maximum Depth:	13,300 ft
Maximum temperature:	266° F