Case Study: Direct XCD Casing Bit Drills Five Wells to Access Permian Basin Reservoir Below CO2 Injection Zone

Casing-while-drilling eliminates one string from operator’s well design

Challenge: Drill five well intervals to TD below a highpressure CO2 injection zone, enabling the subsequent cementing of 5 1⁄2-in production casing while reducing NPT.

Solution: Use 7 7⁄8-in Direct XCD drillable alloy casing bit, multilobe torque (MLT) rings, and hydroformed centralizers.

Result: Cased while drilling five intervals to TD and eliminated an additional string and extensive NPT while providing a record-best cementing job.

Inefficient wellbore construction 

As part of an effort to access a reservoir in the Permian basin, an operator was using a three-string well design in which the casing point was above the field’s high pressure CO2 zone. This approach was effective, and it countered problems the operator had experienced using a two-string design. These problems included CO2 kicks, stuck pipe, wellbore collapse, poor cementing, and NPT. However, the high cost of a three-string well design made it an unsustainable option. 

Casing-while-drilling two-string well design 

To maintain the economic viability of the project, Schlumberger recommended constructing a two-string well using a Smith Bits 7 7⁄8-in Direct XCD drillable alloy casing bit and TDDirect casing-drilling and liner-drilling technology tools. They included MLT rings, which were added to the operator’s 5 1⁄2-in buttress threaded coupled casing to provide positive makeup and increase torque. Hydro-formed centralizers were also used to stabilize the casing string during drilling and help position it for cementing.

High-quality wellbore construction 

The casing-while-drilling two-string design used in five wells enabled the operator to come out of the conventionally set 8 5⁄8-in casing and drill below the high-pressure CO2 zone to TD with 5 1⁄2-in production casing. The 5 1⁄2-in production casing was cemented, and the Direct XCD casing bit was drilled out with a standard PDC bit. The operator experienced no kicks, stuck pipe, borehole collapse, or extended NPT during the operation. In addition, the TDDirect technology signature plastering effect strengthened wellbores in which production casing was successfully cemented, despite running through a high-pressure CO2 injection zone. As a result of the operation, the expense of an additional string was eliminated in five wells, and cement bond logs confirmed the cementing job was a record best for the operator below a high-pressure zone.

Download: Direct XCD Casing Bit Drills Five Wells to Access Permian Basin Reservoir Below CO2 Injection Zone  (0.72 MB PDF)

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