Mechanical friction during drilling operations is a problem in long narrow, highly inclined boreholes. (Boreholes: A narrow hole drilled to establish the nature of, sample, test, or monitor soil, bedrock, or contained fluids and gases or for the abstraction of water or minerals.)
Some of the cures include the application of oil or pseudo-oil-based mud and lubricants. The use of oil and pseudo-oil-based muds are highly restricted because of environmental concerns. Even adding small amounts of oil-based lubricants to water-based muds raise questions.
Consequently, the value of finding an improved environmentally friendly friction reducer applicable in water-based mud is high.
Traditionally, friction reducers can be divided into two types: liquids and solid particles.
- Liquid’s friction reducers, form a film between the two surfaces minimizing any contact and consequently also the friction.
However, their efficiency depends heavily on mud type and may also be reduced when used together with other types of mud additives.
When used in high-solid muds the efficiency is reduced, sometimes no friction reduction is found at all.
Liquid additives include among others glycol-, oil-, ester-, and fatty acid ester-based lubricants.
- Solid friction reducers, on the other hand, do not depend as much on mud type.
One of the solid friction reducers are glass beads. Glass beads in mud act like small ball bearings downhole. Round, incompressible particles are embedded in the wall cake and provide a load-bearing surface between pipe and wall.
The beads may create a small standoff distance for pressure communication and flow as well. This standoff and point contact may reduce the overall frictional surface area.
Fine beads (44-88 µm) will pass most shaker screens but are removed by desilters. 75 µm glass beads reduce the friction by up to 68% whereas 600 µm beads crush.
GLASS BEADS are used to assist slide drilling and horizontal drilling. Pills are effective when spotted across trouble zones while tripping, logging, or running casing.
ADVANTAGES
- Reduces torque and drag
- Effective in coil-tubing drilling
- Will not float
- Temperature stable
- Provide true weight to the bit
- Aids slide drilling
- Economical
APPLICATION
Sweeps containing 10 to 20 ppb are effective when slide drilling and/or horizontal drilling. Pills containing 5 to 10 ppb spotted across trouble zones prior to logging or running casing have proved beneficial.
Typical Physical and Chemical Properties
| Physical Appearance | Round Sphere |
| Color | Clear to Colorless |
| Particle Size | 20 – 40 mesh & 170 – 325 mesh |
| Crush Strength | +/- 47,000 pounds |
| Specific Gravity | 2.5 – 2.6 |
| Hardness | 5.5 (moh’s( |
