Most traditional polycrystalline diamond compact (PDC) cutting elements have a flat polycrystalline diamond table at the end of cylindrically shaped tungsten carbide body. During drilling, the flat diamond table engages the formation and shears the rock layer by layer. A new ridge-shaped diamond cutting element (RDE) has a similar cylindrical tungsten carbide base; however, the diamond table is shaped like a saddle with an elongated ridge running through the center of the diamond table and normal to the cutter axis. The intended cutting portion, the "ridge," engages the formation to fracture and shear the rock at the same time. The design intent was to create a unique cutting element that could combine the crush action of a traditional roller cone insert and the shearing action of a conventional PDC cutter. The new cutting elements were tested in the laboratory against standard flat PDC cutters in a rock-cutting evaluation, and later the new elements were applied to PDC bits and run under real drilling conditions. The laboratory rock-scrape tests indicated that the new cutting element not only enables the cutter to efficiently shear formation in the same way as a conventional PDC cutter, but also delivers a crushing action similar to a roller cone insert. Preliminary results indicated a reduction of roughly 40% in both cutting force and vertical force on the new ridged diamond element cutters (RDE) over a conventional PDC cutter. Similar findings were also observed during the rock-shearing test on a vertical turret lathe (VTL). Subsequent field tests in multiple areas in North America have produced faster rates of penetration (ROP) in most of the cases. The trials indicate that the new cutting element is efficient at removing rock, and a bit equipped with these elements requires less mechanical specific energy (MSE) during drilling than does a bit with a conventional PDC cutter. In addition, the reduced cutting forces reduces bit torque and thus improves the drilling tools’ life and the bit directional performance. Field data has proven this technology improves drilling performance in terms of ROP and footage over the current PDC bits fitted with traditional flat PDC cutters.
Primary cementing across the Williston basin Mission Canyon formation, a depleted zone with a low fracture gradient, can require alternative cementing techniques to achieve reduced equivalent circulating density (ECD) to minimize losses during cement placement. Achieving top of cement in this zone is challenging, and has historically required some form of remedial cementing. Some solutions have been foamed and two-stage cementing techniques; however, these techniques can be operationally complex. The solution used is a lightweight, high-performance cement slurry. This solution uses an engineered, high-crush-rated hollow sphere particle as a cement extender, thus providing the slurry with reduced density and increased solid volume fraction upon comparison to conventional slurries. This slurry is used in combination with a fiber-based loss circulation material (LCM.) The combination of the increased solids content of the cement and the fiber LCM improves the plugging efficiency across the loss circulation zone. This cementing package allows for cement to be effectively placed across the Mission Canyon loss circulation zone with single-stage cement techniques. Both case study wells sustained losses in the Mission Canyon at approximately 9,500 ft, with target true vertical depths (TVDs) approximately 10,800 ft. The average mud weight used in these wells was 10 ppg, and an aggressive LCM package was used prior to drilling into the Mission Canyon formation. Casing running rate was modified in order to reduce risk of inducing losses. Using the previously discussed design, a low-density, high-performance lead slurry was employed to cover these loss zones. A significant increase in solids content was achieved by extending this slurry with a manufactured, hollow sphere particle. This system gave an overall reduction in ECDs when compared to conventional slurries across the zone of interest. This lightweight, high-performance system was used with a fiber-based LCM package to maintain good circulation throughout cement placement. Critical job parameters were recorded throughout cementing and compared to design ones to support the observation of consistent returns to surface throughout placement. Ultrasonic cement evaluation was used to confirm top of cement post placement. The novel solution, supported by two case studies, shows the successful use of a lightweight, high -performance cement system, along with fiber-based LCM. This cementing package was used to successfully achieve required top of cement during primary cementing across depleted or naturally fractured zones in the Williston basin during a single-stage cement placement.
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