Vertical wells are drilled in the In Aminas field in Algeria with various types of drill bits, including polycrystalline diamond compact bits (PDC), tungsten carbide insert bits (TCI), and impregnated (impreg) drill bits. The operator tested a new 6-in impregnated bit with novel cutting structure concepts in an attempt to drill the section in one run. The bit was used on rotary BHA, and high speed motor BHA for two runs in the same section.
Both runs did well, and the bit maintained the sharp cutting structure till the TD of the section.
The 6-in section comprises mulitple layers of hard abrasive sandstone with unconfined compressive strength up to 35 KPSI, loose shale which is relatively soft and ends with metamorphic rock.
The new impregnated bit uses diamond segments imbedded in blades comprising diamond-grit matrix material to create a cutting structure with variable wear along the bit face. This particular combination of diamond and matrix improved overall aggressiveness and durability in the shoulder.
To drill efficiently, impregs are paired with high-speed motors or turbines. The new design successfully drilled on two different BHAs. The first was a rotary-packed BHA that drilled 406.8 ft (124 m) at 4.33 ft/hr (1.32 m/hr). The bit didn't show signs of wear and was used on a second BHA with a high-speed motor that drilled another 603.7 ft (184 m) at 6 ft/hr (1.8 m/hr). The impreg's overall performance was 1,010 ft (308 m) at 5.2 ft/hr (1.6 m/hr), and the bit pulled out of hole in a very good condition.
The solution enabled the operator to drill 200% further, more than the best offsets and saving multiple bit trips, which resulted in total savings of USD 195,000.
This article will explain the benefits of the new technology and discuss how this novel impregnated bit successfully drilled the section in one run which is the first time ever to happen.