Waterway Configurations for Impregnated Core Bits

Most sizes of impregnated core bits manufactured by Dimatec are offered in several different waterway configurations. These various waterway configurations have the function of controlling the bit hydraulics. In addition, the different waterway configurations influence the total bit face contact area presented to the rock face and as a result, control the amount of bit load to be applied for effective penetration. Some of the following core bit waterway configurations may not be available in certain bit sizes due to the dimensional limitations of that particular bit crown.

When selecting a diamond impregnated core bit for use on a particular job site, waterway configuration geometry is often overlooked as a parameter that will influence and generally broaden the drilling range of a bit’s performance. For example, the ‘Turbo’ configurations (Style ‘T’ and Style ‘TT’) will provide rates of penetration that are often 15% to 35% better than ‘Regular’ full-face configurations (Style ‘W’) due to their reduced bit face contact areas. In addition, the wider canal-type waterway configurations (Style ‘TXW’ and Style ‘XXW’) allow for larger volumes of circulation fluid to be pumped through the bit. This will frequently increase the efficiency of cuttings removal in deep hole applications.

Regular Configuration (Style ‘W’)

Unless otherwise specified, this is the standard waterway configuration used on most types of impregnated core bits manufactured by Dimatec. This design uses canal type waterways that are approximately 0.12 inch (3 mm) wide. These waterways pass the circulating fluid from inside diameter of the bit crown, across the face and eject the fluid and cuttings at the outside diameter of the bit crown.

This waterway configuration is used primarily on thin-kerf core bits as well as wireline core bits that are intended for use in predominantly fractured formations.

The Dimatec code for this waterway configuration style is ‘W’. (Example: A Dimatec core bit with the descriptor ‘10W’ in its designation would indicate that the bit is supplied with 10 regular canal type waterways).

Turbo Style (Style ‘T’)

This waterway configuration is a modification of the Regular (Style ‘W’) waterway configuration. In addition to the standard canal type waterways, an equal number of intermediate partial waterways are included. The addition of these partial waterway canals reduces the bit face contact area by approximately 15% over the Regular (Style ‘W’) configuration.

The ‘Turbo’ design is best suited to formations that are hard to very hard under conditions that are solid or at most slightly broken. The Turbo (Style ‘T’) waterway configuration is not recommended for use in highly fractured formations.

Due to the reduced face contact area, core bits with the Turbo (Style ‘T’) configuration will generally cut with less bit load than a core bit of equivalent size and matrix type manufactured with the Regular (Style ‘W’) configuration and will usually do so with an equivalent or higher rate of penetration. As a result, there is less of a tendency for the drill hole to deviate due to the application of lower bit loads. The partial (turbo) waterways also assist in ejecting the fine cuttings that are created when drilling hard, consolidated, non-abrasive formations and prevent the build-up of slurry on the bit face during drilling.

The Turbo (Style ‘T’) waterway configuration is only available on thinner-walled core bits with kerf widths of up to 9 mm (0.35 inch). For core bits with thicker kerf widths, the T-Turbo (Style ‘TT’) waterway configuration is offered for conditions in which a Turbo-type configuration would be recommended.

The Dimatec code for this waterway configuration style is ‘T’. (Example: A Dimatec core bit with the descriptor ‘10W+10T’ in its designation would indicate that the bit is supplied with 10 regular canal type waterways plus 10 partial waterways).

T-Turbo Configuration (Style ‘TT’)

This design provides a reduced number of trapezoid-shaped canal type waterways that are considerably larger than those used on the Style ‘T’. This waterway geometry modification provides an 8% reduction in bit face contact area over an equivalently sized Style ‘T’ core bit without reducing the bit's flushing capacity. The reduced bit face contact area of the T-Turbo (Style ‘TT’) waterway configuration permits the diamond impregnated matrix to self-sharpen more readily. In addition, it will often provide similar or faster rates of penetration at lower bit loads than “full-face” (Regular – Style ‘W’) waterway configurations.

This waterway configuration has the same basic range of application as the Style ‘T’ but is primarily recommended where higher rotational speeds are being applied on thick-kerf wireline core bits. This waterway configuration is available for core bits in the B-Gauge (Ø 60 mm) size or larger with kerf thicknesses of 9 mm (0.35 inch) or larger.

The T-Turbo (Style ‘TT’) waterway configuration is recommended for use in shallow holes with a maximum depth of 300 metres (1,000 feet). It is not recommended for use in highly fractured formations.

The Dimatec code for this waterway configuration style is "TT". (Example: a Dimatec core bit with the descriptor '9TW+9TT' in its designation would indicate that the bit is supplied with 9 trapezoidal regular canal type waterways plus 9 trapezoidal partial waterways).

Trapezoidal Extra-Wide Configuration (Style ‘TXW’)

This waterway configuration is recommended where higher than normal flushing volumes are required. The Style ‘TXW’ waterway configuration provides a reduced number of canal type waterways when compared to the Regular (Style ‘W’) type. Not only are the waterway canals on the Style ‘TXW’ configuration wider than those found on the Style ‘W’ configuration they have a trapezoid shape that promotes the ejection of cuttings from the bit face.

Bit face contact area is typically reduced by approximately 10% when compared to an equivalently sized core bit with the Regular (Style ‘W’) waterway configuration. This reduction in contact area will often provide improved rates of penetration.

The design of the Style ‘TXW’ waterway configuration has a higher total flow area (TFA) and typically provides a 20% increase in flushing capacity over an equivalently sized core bit with the Regular (Style ‘W’) waterway configuration. It is necessary to apply higher circulation pump volumes when using Style ‘TXW’ core bits in order to achieve effective performance.

The Dimatec code for this waterway configuration style is ‘TXW’. (Example: a Dimatec core bit with the descriptor ‘8TXW’ in its designation would indicate that the bit is supplied with 8 trapezoidal extra-wide canal type waterways).

Extra-Extra-Wide Configuration (Style ‘XXW’)

This waterway configuration is recommended where very high flushing volumes are required in harder, consolidated formations. The Style ‘XXW’ waterway configuration uses a reduced number of canal type waterways when compared to the Regular (Style ‘W’) type. The waterway canals on the Style ‘XXW’ configuration are wider than those found on both the Style ‘W’ and Style ‘TXW’ configurations and typically have a width of 6.3 mm (0.25 inch). As a result, the Style ‘XXW’ configuration provides a flushing capacity increase that is approximately 40% greater than the Style ‘W’ and Style ‘T’ configurations while maintaining approximately the same bit face contact area as that of an equivalent sized core bit manufactured with the T-Turbo (Style ‘TT’) configuration.

The Style ‘XXW’ configuration develops relatively low fluid pressure at the bit face and is recommended for use in deeper holes with depths of 300 metres (1,000 feet) or greater. Other benefits of the Style ‘XXW’ waterway configuration include:

  • An equivalent or greater rate of penetration using lower bit loads than both the Style ‘W’ and Style ‘TXW’ waterway configurations due to the Style ‘XXW’ configuration’s lower bit face contact area.
  • The fluid pressure developed at the bit face is considerably lower than either the Style ‘W’, Style ‘TT’ or Style ‘TXW’ configurations and as such is less susceptible to the hydraulic lift phenomenon.

It should be noted however that the Style ‘XXW’ waterway configuration is not recommended for use in softer formations where the potential for core sample degradation exists as a result of increased circulation fluid contact. In this case, the use of either the Face Discharge (Style ‘FD’) or Slot Face Discharge (Style ‘SFD’) waterway configuration is recommended.

The Dimatec code for this waterway configuration style is ‘XXW’. (Example: A Dimatec core bit with the descriptor ‘8XXW’ in its designation would indicate that the bit is supplied with 8 extra-extra-wide canal type waterways).

Extra-Extra-Wide Free Flow Configuration (Style ‘XXWFF’)

This waterway configuration is a modification of the Style ‘XXW’. The width, shape and number of waterway canals is identical to that of the Style ‘XXW’. However, the Style ‘XXWFF’ design includes deep input fluid passages at the core bit’s inside set diameter. This feature tends to minimize the eroding action of the flow of the circulating fluid on soft, friable core samples.

This waterway configuration is commonly used on core bits in place of conventional face-discharge designs to drill soft, friable formations or harder formations that contain softer strata. Unlike conventional face-discharge type core bits, this waterway style resists the tendency for the fluid discharge ports to become blocked by silt from particles suspended in the circulating fluid. They are also less susceptible to matrix ‘glazing’ than traditional face-discharge core bits.

The availability of the Style ‘XXWFF’ waterway configuration is limited to thick-kerf wireline core bits.

The Dimatec code for this waterway configuration style is ‘XXWFF’. (Example: A Dimatec core bit with the descriptor ‘10XXWFF’ in its designation would indicate that the bit is supplied with 10 extra-extra-wide free flow type waterways).

Face-Discharge Configuration (Style ‘FD’)

This waterway configuration is recommended for use when drilling in relatively soft, unconsolidated formations and/or when using triple-tube wireline core barrel systems. Unlike core bits that are manufactured with conventional canal type waterways that eject the circulating fluid through ports on the inside diameter of the bit crown, the Face-Discharge (Style ‘FD’) configuration ejects the fluid through ports moulded into the face of the bit. The re-direction of the circulating fluid results in minimum core wash and reduces the potential for undesirable core erosion.

Each waterway element typically has a canal width of 6.3 mm (0.25 inch) with a flushing port diameter of 4.8 mm (0.19 inch). When compared to any of the internal discharge waterway configurations, the Style ‘FD’ configuration develops relatively low fluid pressures across the bit face, even when higher circulation rates are being applied.

For reference in determining the appropriate bit load, diamond impregnated core bits that are manufactured with the Style ‘FD’ waterway configuration have bit face contact areas that are similar to that of same size core bits manufactured with the Style ‘XXW’ and Style ‘TT’ waterway configurations.

The Style ‘FD’ waterway configuration is available on all wireline core bits as well as on core bits with kerf widths greater than 10 mm (0.39 inch) that are used with conventional (non-wireline) core barrel systems.

The Dimatec code for this waterway configuration style is ‘FD’. (Example: A Dimatec core bit with the descriptor ‘8FD’ in its designation would indicate that the bit is supplied with 8 face-discharge type waterways).

Slot Face-Discharge Configuration (Style ‘SFD’)

This waterway configuration is a modification of the Face-Discharge (Style ‘FD’) waterway configuration and has the same basic range of application. This style of core bit is manufactured with large trapezoidal shaped waterway canals that include slot shaped face-discharge ports. This configuration is recommended for use under conditions where standard cylindrical shaped face-discharge ports become easily blocked by silt or where high viscosity circulating fluids such as foam are in use.

The Slot Face-Discharge (Style ‘SFD’) waterway configuration is only available on core bits with outside set diameters of ‘N’-gauge (Ø 76 mm) or greater and with kerf widths of 12.7 mm (0.50 inch) or greater.

The Style ‘SFD’ waterway configuration develops fluid pressures across the bit face that are even lower than that of the similar Style ‘FD’ configuration. This results in minimal bit face fluid turbulence during operation.

The Dimatec code for this waterway configuration style is ‘SFD’. (Example: A Dimatec core bit with the descriptor ‘4SFD’ in its designation would indicate that the bit is supplied with 4 slot face-discharge type waterways).

VORTEX Configuration (Style ‘VX’)

This unique waterway configuration features an arrangement of helix-shaped fluid passage canals of variable width. The improved bit hydraulics offered by the VORTEX configuration will typically provide a 25% to 40% increase in penetration rates in soft to medium-hard formations when compared to core bits with conventional waterway configurations.

The impellor action of the VORTEX waterway configuration removes cuttings more efficiently resulting in:

  • A cleaner bit face,
  • Improved core samples,
  • Reduced time spent conditioning the hole between core runs thus providing better overall production rates,
  • Improved reaming shell life.

Unlike conventional waterway configurations that require the operator to flush the hole between drill runs in order to clean the hole of cuttings before core drilling can be resumed, the unique fluid dynamics provided by the VORTEX configuration permits the operator to continue drilling immediately after loading a new wireline inner tube (core tube).

Drill operators should be aware of the need modify their approach towards using a diamond impregnated core bit with a VORTEX waterway configuration in order to derive its full benefits:

  • Extra caution should be used when attempting to perform in-hole bit sharpening with a VORTEX bit as in-hole bit sharpening response times tend to vary when compared to conventional waterway configurations.
  • The unique cooling effect of the VORTEX waterway configuration causes these bits to “drill harder” than other configurations with identical matrix types. In some cases, this difference in matrix hardness may be as much as one full matrix type. For example, an HR9 VORTEX may drill like an HR8 TXW.

The VORTEX waterway configuration is currently offered in the following sizes of thick-kerf wireline core bits:

  • BWL
  • NWL
  • NLW2
  • HWL
  • HWL3