Allegro Casing- and Liner-While-Drilling Services | Schlumberger

Allegro Casing- and Liner-While-Drilling Services

Minimize NPT and drilling risks in unstable formations

Our family of Allegro casing- and liner-while-drilling services improves well-construction efficiency and coordination to better deliver your well. This approach not only provides a way to reduce the risks associated with wellbore instability, but it also greatly increases performance through time savings—both on the drilling and flat-time portions of the time-depth curve.

Mitigate risk before you drill

Allegro service provides comprehensive application analysis to identify and mitigate drilling risks. Our suite of software simulation solutions, including the IDEAS integrated dynamic design and analysis platform, evaluates conditions such as formation strength and bit-to-rock interaction to design an ideal bit cutting structure with unique diamond cutting elements.

Allegro rendering
Calculations from simulation software are used to optimize BHA and bit design.
Allegro casing-drilling and liner-drilling services technology
Drilling with conventional drillpipe (left) creates a larger annulus, while casing while drilling (right) minimizes annulus size; rotating casing smears cuttings into the borehole wall, sealing pores in the formation to reduce fluid losses and producing a stronger borehole for improved cementing.

Increase wellbore strength

Casing while drilling smears cuttings into the borehole wall. This plastering effect strengthens wellbores for improved cementing and is proven to reduce NPT resulting from borehole-related problems, such as

  • sloughing shales
  • tight holes
  • borehole bridges
  • lost circulation
  • large-diameter surface hole resulting in hard-to-remove cuttings from the annulus
  • damaged producing zones
  • stuck pipe.

As part of the Allegro service, operations for casing drilling are further optimized to help mitigate risks before you drill. With a prejob analysis and bit and BHA customization, you can reach TD more safely and efficiently in any drilling application.

Allegro CD Service

Maximize reliability and efficiency

Allegro CD directional casing-while-drilling service is compatible with any retrievable directional-drilling BHA when the interval requires logging while drilling or directional drilling. Conveyed on drillpipe, directional casing while drilling can be used to drill sections that involve multiple bit trips or for applications using rotary steerable systems and measurement- or logging-while-drilling tools.

Key capabilities include consistent casing rotation to break static friction—enabling even WOB bit, rotation, and high annular velocity to improve borehole cleaning—and the plastering effect (or smear effect) to maximize borehole strength and stability.

Allegro CD service also includes a drill lock assembly, which connects the BHA to the bottom of the casing shoe joint and enables applying torque and weight by the casing during drilling. The rig's top drive rotates the casing, and a downhole motor provides additional rotational speed and torque to the BHA and PDC bit.

Drillstring with Allegro CD system.
Allegro CD directional casing-while-drilling service BHA.
Drillstring with Allegro CD system.
Allegro XCD Bit

Construct vertical wells while casing in one run

The Allegro XCD casing-while-drilling alloy bit is designed for drilling vertical or tangential wells to TD in one run. This PDC bit drills on standard casing that is rotated at the surface.

Eliminate dedicated drillout runs

The bit's sub is composed of durable oilfield-grade steel, and its body is a copper bronze alloy. This unique composition enables it to be drilled out by any standard PDC bit after the Allegro XCD alloy bit has been drilled to TD and the casing has been cemented. After drillout, the drillout PDC bit can continue drilling the next interval, eliminating the need for a dedicated drillout run.

The cutting structure of the Allegro XCD alloy bit can be fitted with 13-, 16-, or 19-mm PDC cutters, which are available in standard or premium grades.

XCD casing-while-drilling alloy casing bit
The Allegro XCD bit’s sub is composed of a unique alloy, enabling drillout by any standard PDC bit after drilling to TD and the casing has been cemented in place.
Allegro XCDR Reamer

Improve casing running operations

The Allegro XCDR casing running reamer aids the running of casing in difficult wellbore conditions by helping you navigate past ledges, low-side cuttings beds, and faults where casing can hang up.

Large waterways between the blades maximize the junk-slot area. Engineered ports on the blade strategically direct fluid to optimize cleaning and cool the cutting structure. The reamer’s alloy body can be easily drilled out with a standard PDC bit, eliminating a dedicated drillout run or use of a special drillout bit.

Allegro XCDR casing running reamer specifications

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