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    Making sense of HDD drilling fluids

    Jun/21/2018

    Why drilling fluid is essential to HDD and the mixing process

    Drilling fluids are the secret sauce on horizontal directional drilling (HDD) jobs. Drilling fluids can also be one of the most misunderstood aspects of drilling operations. Every member of your crew working around drilling operations should understand what drilling fluid is, how to mix it, the type of additives they should use for various soil conditions, how to determine pumping and pullback rates, as well as how to make adjustments on the job.

    This series of short articles will help take some of the mystery out of drilling fluids, beginning with why it is essential to HDD operations and ways to mix it.

    Why drilling fluid is important
    Here are a few of the reasons drilling fluids are used on HDD projects:

    ·  Helps extract cuttings: Failure to remove cuttings from the bore path can result in inadvertent returns (frac-out), limit distance length the drill can pilot bore, heave ground surfaces above the drill head and lead to product pullback failures.

    ·  Creates downhole stability: Drilling fluid helps the drill path keep its shape during the drilling process. Using the right type of fluid additive is also important to help a drilled hole maintain its shape when working in different soil types (drilling in sand for example).

    ·  Cools and lubricates tooling: Downhole tooling temperatures can rise quickly without the use of drilling fluids. Drill head temperatures rising above 220° Fahrenheit will permanently damage the transmitter that gives critical depth and pitch data. Drilling fluids also help keep tooling clean and reduce pullback/rotational torque pressures required to pilot out and pull product back through. 

    Drilling fluid viscosity
    You’ve now learned why using drilling fluid is essential, but it's also necessary to understand having the right viscosity (thickness) of drilling fluid.

    Drilling fluid that is too thin or light can limit the amount of cutting returns. You may still get the majority of returns, but heavier cuttings can sink to the bottom of the bore (creating a cuttings bed) and not be flushed out. After a while, this cuttings bed can create return flow issues during the rest of the drilling process (which can result in excessive product stress and inadvertent returns).

    Drilling fluid that is too thick can result in additional downhole pressure to get fluid to flow and eventually lead to inadvertent returns. Fluids follow the path of least resistance, and if the fluid is too thick — that direction is typically towards the surface.

    To check that you have the right viscosity, it’s important to measure it every time you mix up a batch of drilling fluid. You will need a Marsh funnel and cup, following these steps.

    1.  Start by filling your cup up to the fill line with drilling fluid.

    2.  Next, plug the hole in the bottom of your funnel with your finger and pour the fluid through the funnel’s screen (ensure you are wearing proper safety gloves).

    3.   There shouldn’t be any clumps of material left behind on the screen. If there is, your drilling fluid is likely not mixed correctly or fully hydrated (more on that next). Repeat until drilling fluid crests the top fill line (just under the screen) of your Marsh funnel.

    4.  Now, place the empty cup below the funnel and start a stopwatch as you remove your finger from the bottom of the funnel. You want to stop counting when the drilling fluid crests the top fill line (32 oz [.9 kg]) of your cup. This number is your drilling fluid viscosity measurement.

    You should aim for a viscosity rate of between 45 and 60 seconds for most drilling applications.

    Mixing processAlways make sure the person assigned to drilling fluid mixing is fully trained on the proper steps.

    On every new job, you should check pH levels from your water source. Drilling fluid additives (bentonite and polymers) mix better with a pH level range between 8 to 9. Municipal water will typically measure around that range. However, if you’re using water from a pond or well, the pH level will likely fall below that range. Adding soda ash will help raise the pH levels and help you use less drilling fluid products.

    When you’re ready to mix your additives with the water, powders like bentonite must be added to the hopper and liquids should be poured directly into the tank.

    Every Vermeer fluid mixing system is equipped with a bag cutter next to the hopper. Use it to split and empty the whole bag into the hopper at once. Doing it this way, instead of cutting it with a knife and slowly sifting material into the hopper, will help reduce dust levels and help prevent air from getting into the system.

    When adding bentonite, make sure it’s sent through the venturi and hopper at full throttle. You want to get the maximum implosion through the venturi to mix the product well. After enough bags of bentonite are added, keep product mixing through the venturi for approximately 10 minutes until it’s thoroughly broken up and hydrated.

    If you plan to add a polymer, you’ll need to wait until the bentonite is completely mixed (10 minutes). Adding a polymer too soon or out of sequence can cause the bentonite to ball up in the tank rendering it ineffective.

    The final step is to check the drilling fluid viscosity. If it's too thick, add additional water or thinners; if it is too thin, add more drilling fluid additives.

    A few housekeeping notes
    Mixing drilling fluid doesn’t have to be a messy job. Make sure you’re cleaning your mixing system’s hopper and venturi regularly to help prevent clogs. Also, make sure you’re washing your tank often. If there is polymer residue left in the tank when you go to mix up your next batch of drilling fluid, you could end up with small balled-up clumps of bentonite in your tank.


    Future articles of “Making sense of HDD drilling fluids” will cover the steps to calculate reamer pullback drill rates and explain the different types of drilling fluid additives available. For more information about drilling fluid mixing or the MUD hub, reach out to your local dealer, or visit Vermeer.com. 


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    Creating an HDD Fluid Management Plan

    May/02/2018

    Is your company talking a lot about mud these days? You should be.

    With increasing regulations targeting the disposal of horizontal directional drilling (HDD) fluids and rising disposal costs, mud is becoming a major concern for the industry. Failure to plan can lead to unexpected expenses, missed opportunities or be the reason why your company isn’t awarded a particular project contract in the first place.

    Creating an HDD fluid management plan will help you more accurately estimate a project before work begins and keep your crews productive on the job. This provides peace-of-mind for you and your customers that your team understands the regulations pertaining to proper drilling fluid disposal.

    How much fluid do you need
    Your estimating process should include evaluating ground conditions at the jobsite, type of drilling additives you will need and the volume of fluid required for the project.

    Ground conditions dictate the drilling additives you’ll need and the amount of fluid required. In sand or cobble, you will likely only need a mixture of bentonite. In reactive clay,you will probably have to use a polymer additive. Keep in mind that harder rock usually requires more fluid per bore distance.

    Calculating the costs and the amount of additives and water you’ll need ahead of time will not only ensure you’re tracking your expenses on the project, but will also help you determine what equipment you need on the job.

    Adding in disposal costs
    Once you know how much fluid you'll need, the next thing to determine is how you plan to dispose of the spoils afterward.

    To begin, you must research all local regulations about disposing of drilling fluids. Today, many projects require HDD fluids to be disposed of at licensed facilities, and the costs associated with dumping can vary greatly. You will want to look into where these sites are located and estimate how much you’ll pay to use them.

    But don’t forget, the disposal costs aren’t your only expense. You also have to estimate the distance between the jobsite and disposal facility, as well as the fuel and labor costs involved in making the round-trip. These expenses are easy to overlook.

    Weighing your options
    After adding up your fluid and disposal costs, it’s time to evaluate equipment options that may be able to reduce your out-of-pocket expenditures. For projects that require large volumes of fluid, bringing in a reclaimer like the Vermeer R250C can help reduce the amount of fluid and additives used by removing solids and recycling fluids.

    Solidification systems like the Vermeer MUD Hub are another option to consider for projects that have high disposal fees. Solidifying used drilling fluids can give you more disposal options. Many drilling spoils will now be able to be disposed of at a regular landfill, used for ground cover or added to composting mixes. Also, since the waste is now a solid, it can be hauled in a dumpster or dump truck, which helps keep your vacs off the road and on the job.

    On the job
    There is a lot of upfront work involved with fluid management, but your plan should not stop there. On the job, you need to make sure the crew knows how to properly mix drilling fluids, understand how to measure fluid viscosity and use the proper amount of mud during the pilot bore, reaming and pullback. Mistakes made on the job can be as costly as not planning correctly.

    Documentation
    Finally, it’s important to document your disposal process and location for your customer. Many utility companies require fluid disposal documentation, but even if your customers do not, having a paper trail can help protect your business if someone has questions in the future.

    If you have questions about creating your own HDD fluid management plan, contact your local Vermeer dealer or visit Vermeer.com.

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