A major operator drilling an unconventional oil well in the Bakken shale ran two plug and perf completions.


(see http://www.bakerhughes.com/news-and-media/resources/case-histories/glyphaloy-79-case-history ) After drilling the deviated horizontal wellbores, the operator ran 4½ in.,11.6 lb casing to depth. Next, the operator set 43 composite frac plugs in one 9,500 ft (2896 m) horizontal wellbore and 36 in the second wellbore, and then successfully fractured each zone.


To bring the well on line, the operator needed to mill out the composite plugs. Milling out a total of 79 plugs in two wellbores could normally take a long time involving several trips downhole and pulling the bottomhole assembly (BHA) out of hole to change out worn components. Hoping for a better performance, the operator asked Baker Hughes to apply their METAL MUNCHER™ AMT milling technology. A millout BHA consisting of a 3¾-in. Glyphaloy™ composite plug mill, a 2.88 in. (73.2 mm) outside diameter (OD) Navi-Drill VIP™ motor, a 2.88 in. OD dual-back pressure valve, all from Baker Hughes, along with a 2.88 in. OD HydroPull® extended reach tool from Tempress Technologies, was compiled to run in hole on the bottom of tubing.


The first well, consisting of 43 composite plugs, was milled out in one trip without the need to pull out of hole to change the BHA components. After millout of plugs in the well was finished, the customer expressed great satisfaction with the condition of the mill and its minimal carbide wear. The customer then decided to try the same mill on the second well. The second well, consisting of 36 composite plugs, was also finished in one trip without the need to pull out of hole to change the BHA components. One mill dressed with the advanced Glyphaloy milling technology was able to mill through a total of 79 composite plugs in the two wells.


Milling this record number of frac plugs in two wells in one trip per well meant time savings that translated to significantly reduced cost for the operator. Previously, the maximum number of plugs milled with one mill was 40.

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