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Our most frequently asked questions about Mineral Exploration

  • How deep can you drill with Wassara in exploration?

    Basically, you can drill as deep as you want. A “deep hole” hydraulic core drilling rig can drill down to 2 500 m with H-size (96 mm) coring today. The weight of the drill string sets the limit of how deep you can drill. The rods also have a limitation of load to take.

    Similar depth limitation is valid for Wassara. Keep in mind that the number of bit changes makes the hole less easy to core drill in later. We do recommend changing the bit once per borehole. The borehole depth you can reach with two bits is very much dependent on the formation.

  • Can a standard core drilling rig take the forces from a percussion hammer like Wassara?

    Often the manufacturer of core drilling rigs (Atlas Copco, Sandvik, Boart Longyear, etc.) doesn’t allow the user to do percussive drilling with the rig during guarantee period. However, our experience is that the weight rods in the Wassara drill string take away more or less all impact from the hammer to the rotation unit on the rig. A core drilling rig is not designed for taking forces along the feed frame. It is designed mainly for high rotation speed and a smooth traveling of the rotation unit up and down on the feed frame.

    Make sure that your rig supplier is well informed before using Wassara equipment on a core drilling rig.

  • How much water is used for precollaring drilling with Wassara?

    The water needed for drilling with the W70 hammer in solid rock is
    120 - 245 l/min. This means that you will use 21 m3 for drilling 100 m in two hours.

  • What are the water requirements?

    The water used should be filtered to 100 micron or better. It can be recirculated; Wassara is developing products for this.

  • Can I use the water/mud pump on the core drilling rig for Wassara?

    Yes. For setting casing with Wassara, the standard water/mud pump is enough. The pressure needs to be 50-60 bar and the flow approx. 100 l/min. A standard water pump for core drilling gives 70 bar and 140 l/min.

    For precollaring with Wassara in solid rock you will need a high pressure water pump, with 200 bar and 400 l/min. This pump you normally don’t have on a core drilling site, so it is an extra investment.

  • Can I use standard core drilling rods for the high pressure water?

    Yes. Our experience with standard core drilling rods from the main suppliers (Sandvik, Atlas Copco and Boart Longyear) is good. 

  • How do I know when to stop drilling with Wassara and continue with a standard core drilling?

    The geologists have this information. Often the drilling contractor gets a program with exact depth of each borehole. If Wassara is used, the geologist will inform when to stop the Wassara part of the drilling.

  • In how many dimensions are Wassara hammers available for mineral exploration?

    Today we have a solution for N-size (76 mm) core drilling. N-size is by far the most common size for surface mineral exploration drilling.

    The system we have today can easily be used for B-size core drilling also. This will use the W70 hammer, same as for N-size core drilling. The exception is when the Wassara part of hole is finished, a casing string (BW or NQ) is set in the hole to get a perfect diameter (app. 60.5 mm) for the B-size core drilling.

  • Where are the drill cuttings going?

    The cuttings are coming up on the outside of the drill rods. If casing pipes are used, the cuttings will come up between the drill rods and the casing pipes.

    Different solutions can be used for leading the water and cuttings away from the drill hole to a sedimentation unit. 

  • How much faster is Wassara compared with core drilling?

    A “good” penetration rate for core drilling is 0.2 - 0.5 m/min, depending on formation. Experience with Wassara precollaring in solid rock in mineral exploration is 0.8 - 1.2 m/min, but very much depending on rock formation, bit quality and skill of the operator.

    You can probably drill approx. 5 times faster with Wassara compared with core drilling, but this cannot be guaranteed.

  • How can Wassara be a complement to RC (air) drilling?

    In RC (reverse circulation) drilling, the fuel consumption is very high because of the air compressor. By using Wassara, you can save up to 80% of the fuel cost. This is in the first part of the borehole, where you don’t need samples. As this often is the major part of the distance to be drilled, you can save a lot of money in the total project. A rig that can do RC with air hammer is very well suited also for Wassara drilling. You won’t need weight rods etc. to protect the rig.

    The RC drilling technology (with air hammer) in combination with core drilling is quite common in Australia, where multipurpose rig are used often. Instead of RC, you can use Wassara to reach the core sampling zone faster, without the heavy and expansive air compressor.