Well construction challenges

In conventional drilling operations, wellbore instability due to the long exposure time of the formation can cause well construction challenges such as stuck pipe, which could lead to the loss of the BHA, multiple trips to reach TD, and high NPT.

Although wells in the Labaganskoe Field of the Timano-Pechora Basin experienced high ROP during conventional drilling operations, wellbore conditions caused stuck pipe, and casing was unable to reach TD. In addition, NPT from designated wiper and reaming trips often exceeded drilling time.

What Schlumberger recommended

The Allegro CD service leverages a suite of software, including the IDEAS integrated dynamic design and analysis platform, to provide a comprehensive risk analysis of drilling conditions and customize a PDC bit for specific applications. Once the bit is incorporated onto the BHA and run downhole with casing, the assembly enables more effective borehole cleaning and promotes a plastering effect: Rotating casing smears cuttings into the borehole wall and seals pores in the formation, producing a stronger borehole.

What RN-Severnaya Neft achieved

Using the Allegro CD service, Schlumberger tested 9 5/8-in casing and a six-blade, 8 11/16-in MDi613 PDC bit using 13-mm cutters and 6 3/4-in positive displacement motor (PDM) in a pilot well. In concert with the PowerDrive X6 rotary steerable system and high-ratio Rhino integrated borehole enlargement system, the Allegro CD service drilled and cased the first well to 1,056-m TD in one run—with no deviation in the planned trajectory.

For further customization in the next two wells, the Allegro CD service was used to design an 8 11/16-in X516 PDC bit with 16-mm Axe ridged diamond elements and 7 11/16-in PDM. The design improved fluid flow for better hole cleaning, generated higher torque by reducing the rpm, and created a more aggressive cutting structure for improved ROP. As compared with the first pilot well, ROP increased 110% in the second well and 135% in the third well, and both wells reached TD in a single run.

For all three wells, casing strings were set at TD without stuck pipe issues, and NPT was reduced by eliminating wiper and reaming trips, saving 3 days in well construction time.

More technical details

See SPE-196784.