Stabilizers and Reamers

Stabilizers and rolling cutter reamers are special thick walled drill collar subs that are placed in the BHA to force the drill collars to rotate at or near the center of the borehole. By keeping the drill collars at or near the center of the borehole the drill bit will drill on a nearly straight course projected by the center axis of the rigid BHA. Stabilizers and rolling cutter reamers have blades or rolling cutters that protrude from the sub wall into the annulus to near the borehole diameter. The space between the blades or rolling cutters allows the air or natural gas flow with entrained rock cuttings to return to the surface nearly unobstructed.

Figure 3-17 shows three rotating blade stabilizers. These three stabilizers are respectively, the integral blade (usually a spiral blade configuration) stabilizer, the big bear stabilizer (a larger type integral blade stabilizer), and the welded blade (spiral blade) stabilizer. The blades on these three stabilizers are machined into (integral) the stabilizer body, or are rigidly attached to the stabilizer body and, therefore, rotate with the body of the stabilizer and, thus, with the drill string itself.

Figure 3-18 shows two sleeve type of blade stabilizers. These stabilizers have replaceable sleeves (with blades). These two stabilizers are respectively, the sleeve type stabilizer, and the rubber sleeve stabilizer. The sleeve type stabilizer has a metal sleeve with the attached metal blades (sleeve rotates) and can be replaced on the stabilizer body when the blades wear. The rubber sleeve stabilizer has a sleeve that has a rubber sheath over a metal substructure (sleeve does not rotate). The rubber sleeve can be replaced on the stabilizer body when the blades wear.

In general, the rotating blade stabilizers are shop repairable. The integral blade stabilizers have gauge protection in the form of tungsten carbide inserts, or replaceable wear pads. Integral blade stabilizers can be used in abrasive, hard rock formations. When the blades are worn, the stabilizers can be returned to the machine shop and the inserts or wear pads replaced. Welded blade stabilizers are not recommended for use in abrasive, hard rock formations. When their blades become worn or damaged they can be returned to the machine shop for repairs.

Non-rotating blade stabilizers can be repaired at the drilling rig location. The worn sleeves can be removed and new ones placed on the stabilizer body. This is an important advantage over the rotating stabilizer. The non-rotating stabilizer is most effective in abrasive, hard rock formations since the sleeve is stationary and acts like a drilling bushing. This action decreases wear on the metal sleeve blades.

Stabilizers are used extensively to improve the straight hole drill capability of a BHA for both mud drilling operations and for air drilling operations. However, care must be exercised in using stabilizers in air drilling operations. The wear rate on stabilizer blades in air drilling operations will be greater than in a mud drilling operation (assuming similar geologic conditions).

Oilwell Bha

Figure 3-17: Rotating blade stabilizers (courtesy Smith International Incorporated).

Figure 3-17: Rotating blade stabilizers (courtesy Smith International Incorporated).

Figure 3-19 shows a three point rolling cutter reamer. These reamers have the roller cutters 120° apart on the circumference. The rolling cutter reamer is a special type of stabilizer tool that provides "blades" that are cylindrical roller cutter elements that can crush and remove rock from the borehole wall as the drill bit is advanced. Often the reamer is placed just above the drill bit (replacing the near bit stabilizer, see Figure 3-16). Reamers are also available in a four point rolling cutter reamer. These reamers have the rolling cutters 90° apart on the circumference.

Such rolling cutter reamers are used when drilling in abrasive, hard rock formations. The gauge of the rolling cutter reamers can be adjusted by replacing the rolling cutter elements on the stabilizer body with different outside diameter elements. Also, damaged rolling cutters can be replaced. These replacements can be accomplished at the drilling rig location. When drilling abrasive, hard rock formations, the gauge of the rolling cutter reamers are usually adjusted to be slightly under the drill bit gauge or at the drill bit gauge. The reamers provide the near-bit stabilization needed for straight drilling in abrasive formations.

Figure 3-18: Non-rotating blade stabilizers (courtesy of Smith International).

Figure 3-19: Three point rolling cutter reamer (courtesy of Smith International).

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  • tess
    What are stabilizers in oil and gas drilling?
    6 years ago
  • belladonna
    What do reamers and stabilizers do?
    5 years ago
  • AILA
    What do reamers and stablizers do?
    5 years ago
  • dorothy
    What is a rolling cutter reamers?
    1 year ago
  • angela
    What is the use of stablizeer in drilling?
    5 months ago

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