May/June_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 0 2 7 IMPROVED MATRIX MATERIAL FOR DIAMOND CUTTER BITS An investigation into the chemistry and type of tungsten carbide powder used for drill bits has yielded a material with improved transverse rupture strength and interesting microstructural response to thermal cycling. Jonathan W. Bitler and Samuel Lomasney, Kennametal Latrobe, Pennsylvania H ydrocarbon recovery from un- conventional plays within the petroleum and natural gas in- dustry, such as shale gas and oil sands, is challenging due to unique geologies. Drillers rely heavily onmatrix body poly- crystalline diamond cutter bits (PDCs) for these applications. However, limita- tions on the strength and erosion resis- tance of these bit bodies restrict both rotary speeds and the weight that can be placed on the bit. An investigation into the chemistry and type of tungsten carbide powder used for drill bits has yielded a material with improved ASTM B406 transverse rupture strength and interesting microstructural response to thermal cycling. Such a material en- ables design flexibility for more aggres- sive bit bodies that can support a higher rate of penetration, longer bit life, and better economic returns in these un- conventional formations. After the drop in oil prices in 2014, U.S. oil and gas companies became more innovative in their initiatives to cut costs and drive efficiencies. Pro- ductivity per well has increased from 20,000 barrels per day (bpd) in 2000 to over 150,000 bpd in 2017, despite a re- duction in the number of wells drilled per rig remaining relatively flat [1] . This increase in productivity is largely at- tributed to the techniques of horizonal drilling and fracturing, which have en- abled access to more hydrocarbon-con- taining rock formations. Despite these measured improve- ments in productivity since 2014, oil and gas companies must continue the drive toward improved drilling per- formance in unconventional plays as the recent coronavirus pandemic has caused oil prices to fall far below pro- duction costs. One recognized avenue to increasing drilling performance and achieving maximum rate of penetration (ROP) lies within the design and selec- tion of PDC bit bodies for drilling op- erations. Steel body PDC and tungsten carbide matrix PDC bits have dominat- ed oil and gas drilling in recent years and are estimated to drill more than 90% of today’s global footage with an ROP five to 10 times higher than that of conventional roller cone bits [2] . These bit bodies have been adapted to drill- ing within a variety of geological forma- tions and at different rotation speeds based on factors such as blade size and height, diamond cutter angle, cutter lo- cation, and number of cutters. Design of blade size and height has traditionally been limited by the trans- verse rupture strength (TRS) and ero- sion resistance of the base material. In general, steel-bodied bits have superior TRS but lower erosion resistance, while matrix body bits have superior erosion resistance but lower strength. These de- sign constraints have limited bit perfor- mance in relatively soft to medium hard formations such as shale gas [3] . In these formations, high rotation speeds and the high flow of cutting fluids require taller blades with an extremely high de- gree of erosion resistance typically not attainable with conventional steel bits. Alternatively, the development and ad- vancement of tungsten carbide based matrix materials for PDC bit bodies of- fers an avenue to attain the preferred mix of material properties needed to optimize ROP in unconventional formations. The manufacture of matrix PDC bit bodies is performed through an in- filtration process where a tungsten car- bide (WC) matrix powder is blended, sometimes with added metal powder, and placed into a graphite preform. The powder bed is then infiltrated with a copper-nickel-manganese-zinc alloy to form a near net shape bit body [4] . The infiltrated matrix body is then broken out from the graphite preform, cleaned, and attached to API threading. PDC cut- ters are brazed into their respective pockets and the bit is sent for final in- spection and painting. A bit body with PDC cutters is shown in Fig. 1. The type of WC matrix powder used in the infiltration process will have Fig. 1 — Infiltrated matrix PDC drill bit.