Schlumberger

Case Study: Direct XCD Drillable Alloy Casing Bit Saves Two Colorado Wells and USD 8.6 Million

Casing while drilling substantially reduces operator’s well construction time in Denver-Julesburg basin

Challenge: Drill a 5,000-ft interval to TD through a depleted shale formation in which a BHA was lost and a second attempt stalled at approximately 2,800 ft.

Solution: Use an 8½-in Direct XCD drillable alloy casing bit on 7-in casing to drill the interval beyond 2,800 ft to TD.

Result: Drilled 2,200 ft of the interval to TD, cemented the casing, and drilled out the Direct XCD bit, allowing the operator to save the well.

Unstable shale application threatens operation

An operator working in Fremont County, Colorado, was drilling a 95⁄8-in well section through a part of the Denver-Julesburg basin’s Niobrara formation, which is characterized by unstable Pierre shale. The planned well depth was 5,000 ft, at 3,800 ft the BHA became stuck and was lost. After drilling a sidetrack to 3,410 ft, the drilling team attempted to run 95⁄8-in casing but was unable to get the casing string past 2,444 ft. The operator pulled out of the hole and made a cleanout run with drillpipe to 3,095 ft. However, after cementing the operator could only reach a depth of 2,800 ft.

Drilling alternative halts well abandonment

After 68 rig days the operator considered abandoning the well but decided to try reaching the planned TD using a Direct XCD drillable alloy casing bit.

Direct XCD bit saves first well and reduces cost of second

Reaming the casing back to bottom enabled the operator to drill the remainder of the interval to TD using an 8½-in Direct XCD bit on 7-in casing. Upon landing and cementing the casing, the bit was drilled out. The casing-while-drilling operation took approximately 10 rig days and saved the USD 5.5 million investment in the well, after which the operator continued running the production string.

Once the well was completed, the operator skidded the rig 20 ft to drill a second well. Using the same drilling design from the first well, the operator ran a 12¼-in Direct XCD bit on 95⁄8-in casing to drill from 1,600 ft to interval TD at 4,900 ft in seven days. Compared with the USD 5.5 million cost of the first well, the second well was drilled for USD 2.4 million.


Download: Direct XCD Drillable Casing Bit Saves Two Colorado Wells and USD 8.6 Million (0.63 MB PDF)

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Bronze and copper alloy body enables efficient drillout of Direct XCD bit.