New advances in fluid flow optimization have been incorporated into a new roller cone bit design platform developed by Security DBS Drill Bits for the QuadPack Plus line of premium bits. In a new approach to engineered hydraulics, fundamental bit design works to eliminate

Figure 1. Security DBS Drill Bits’ new QuadPack Plus bits with engineered hydraulics incorporate unique bit arm geometries that create directed flow channels, improving cuttings removal, producing higher penetration rates and significantly extending bit life. (Image courtesy of Halliburton Security DBS)
problems associated with turbulent flow by capitalizing on the way a roller cone bit functions.
Conventional roller cone bits incorporate a hydraulics design that generates turbulent fluid flow near the cutting structures. Rather than lifting cuttings, the turbulence inhibits or prevents cuttings removal from the bottom of the hole. As a result, cuttings are recirculated, hole quality suffers, penetration rate drops and bit life is shortened.

The new design platform uses engineered hydraulics to overcome the turbulent flow problems inherent in conventional roller cone designs. Testing of fluid interaction with the bit and flow impact on the hole and its entire environment demonstrated that optimized arm geometry could create directed flow channels that enhance hydraulic performance.

Engineered approach
Working with a major university in the lab, the company used computational fluid dynamics (CFD) software to determine the optimal fluid-flow regime for cuttings removal. Unlike conventional “directed hydraulics,” which simply positions bit nozzles in some given direction, the new approach optimizes cleaning and cooling of the bit by concentrating on fundamental aspects of the bit beginning with the forging design.

The total flow regime was examined using CFD software, and the entire fluid pathway was evaluated to determine how to achieve maximum efficiency. Bit nozzles were positioned to ensure unrestricted flow to the area where cuttings are generated, while flow beneath the cutting structure was analyzed to eliminate stagnant fluid zones under the cones.

With flow increased at the point of cutting action and swept from under the cones, a new forging design was developed using unique arm geometries that form channels between forging surfaces to create distinct and defined fluid paths away from the cutting area, eliminating cuttings recirculation.

In addition, lifting surfaces incorporated into the support arms generate a fluid spiral, which provides an optimum flow pattern for entraining and lifting cuttings. As a result, this engineered flow of drilling fluid removes newly generated cuttings from under the cutting structure and efficiently sweeps them up the annulus.

Initial field testing of these engineered hydraulics bits immediately resulted in dramatic improvements in rate of penetration, cost per foot and reliability. General performance of the 97¼8-in. bits currently total 11 runs in seven different applications, on both motor and rotary bottomhole assemblies (BHAs), in both vertical and high angle holes, to depths that range from 4,300 ft (1,311.5 m) to more than 13,500 ft (4,117.5 m). To date, in these onshore wells in Louisiana and Texas, the QHC1R (IADC 117W) designs have drilled a cumulative footage of 23,120 ft (7,051 m), with 4,969 total KRevs in 582 hours.

Similarly, 121¼4-in. designs of the QHC1R bit have drilled 13 runs in eight different land and offshore applications, on motor, rotary and rotary steerable BHAs. Most have been vertical runs, with one hole drilled to 50° inclination using the rotary steerable BHA. To date, these bits have drilled footage of 38,768 ft (11,824 m), with 7267 KRevs in 907.5 hours.

As these “track records” of bit performance show, the new QuadPack Plus bits with engineered hydraulics are now enabling operators to realize the benefits of more robust and reliable roller cone performance in key basins around the world.

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