Polycrystalline diamond compact (PDC) bits by nature of their shearing action generate more torque than a roller cone bit.

Historically, PDC technology was often avoided for directional applications when used in conjunction with a positive displacement motor because of high reactive torque. The

Figure 1. D Technology directional PDC bits are designed for the ever-increasing complexity of directional applications and operators’ tougher performance objectives. (Image courtesy of Hughes Christensen)
aggressive PDC cutting action often leads to poor tool-face control or even motor stalling. This forces the operator to reduce weight on bit to control the tool-face, resulting in lower rate of penetration (ROP), more time off bottom to orientate and ultimately higher drilling costs.

D Technology directional PDC bits from Hughes Christensen combine several technologies to overcome these challenges and deliver consistent directional control, increased ROP, superior hole quality and improved tool life.

EZSteer technology
Lab tests show how the patented depth-of-cut-control technology limits the reactive torque generated by D Technology PDCs. The threshold for bearing engagement is adjusted precisely for each unique application. This provides toolface control similar to roller cone bits while preserving the ROP advantage of PDCs.

LGC technology
The gauge configuration for each D Technology PDC is determined on an application-specific basis by the company’s design application review team. Factors such as directional precision and hole quality vary by application, so each D Technology bit’s length, geometry, and cutter (LGC) technology are optimized to meet specific requirements. Log comparisons show that D Technology PDCs drill smoother, more in-gauge holes while standard PDCs drilled 1¼2 in. to 1 in. over-gauge hole sections, which correlate with high-vibration events, poor drilling efficiencies, and inadequate directional response.

System saves nearly US $900,000
In the West of Shetland area, an operator asked Hughes Christensen and Baker Hughes INTEQ to drill a challenging 3-D well profile in one run while improving the 8 1/2 in. hole quality for formation evaluation data collection.

The operator drilled from the whipstock to total depth in one run, saving 42 hours, eliminating a trip. Twenty-three stringers were encountered as the AutoTrak Xtreme motor and D Tech-nology directional PDC nearly quadrupled ROP through the stringers to 78.7 ft/hr (24 m/hr) from 20 ft/hr (6.1 m/hr).

Despite the complex trajectory, the system drilled to plan with consistent 4.75°/98.4 ft (30 m) doglegs and minimal vibration with an overall ROP of 87.6 ft/hr (26.7 m/hr). The operator drilled 4,386 ft (1,337 m) in one run, saving $894,738.

BHA runs smoothly for 123 hours
Offshore Louisiana, an operator wanted to drill a shale and sand section in one run while building to 30° and turning in synthetic mud. Low vibration and consistent directional control ensured the bottomhole assembly (BHA) worked efficiently. Abrasion-resistant cutters on this directional technology with EZSteer depth-of-cut control drilled the entire interval of 7,746 ft (2,362.5 m) in one run at an average ROP of 63 ft/hr (19 m/hr). Offset wells required four bits at an average ROP of 45 ft/hr (13.7 m/hr) to complete an interval. The D Technology PDC drilled 40% faster, saving $338,887.

Reduced vibration and better control
Offshore Nigeria, in Agbami field 7 and 8, a D Technology 17 1/2-in. PDC was used to kickoff from vertical in soft shale sequences and build to 33° on a point-the-bit rotary steerable system. Mitigating vibration through the sand stringers was crucial to delivering predictable directional control and improving drilling efficiencies. The application-specific bit drilled cumulative footage of 8,809 ft (2,686.7 m) at an average ROP of 81 ft/hr (24.7 m/hr) with low vibration. In Agbami 7, the bit built angle from 0° to 33.14°. In Agbami 8, the bit was rerun and built angle from 0° to 30°, drilling through two casing shoes. This was the first rotary-steerable field run.

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