The Driller
  • Sign In
  • Create Account
  • Sign Out
  • My Account
  • NEWS
  • CLASSIFIEDS
  • EQUIPMENT
  • SAFETY
  • VIDEOS
  • EDUCATION
  • SOURCEBOOK
  • EVENTS
  • SUBMIT
  • ABOUT
  • SIGN UP
cart
facebook twitter linkedin youtube
  • NEWS
  • Water
  • Geothermal
  • Construction
  • Environmental
  • Mining
  • All Industry News
  • EQUIPMENT
  • Rigs & Heavy Equipment
  • Consumables
  • Pumps
  • Featured Products
  • VIDEOS
  • Newscast
  • Drill Talks
  • Ask Brock
  • Emerging Drillers
  • EDUCATION
  • Drilling Business Insights
  • Reference Desk
  • Sponsored Insights
  • EVENTS
  • Conferences & Demo Days
  • Newscast LIVE
  • SUBMIT
  • Drillers @Work
  • ABOUT
  • Contact
  • Advertise
The Driller
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
The Driller
  • NEWS
    • Water
    • Geothermal
    • Construction
    • Environmental
    • Mining
    • All Industry News
  • CLASSIFIEDS
  • EQUIPMENT
    • Rigs & Heavy Equipment
    • Consumables
    • Pumps
    • Featured Products
  • SAFETY
  • VIDEOS
    • Newscast
    • Drill Talks
    • Ask Brock
    • Emerging Drillers
  • EDUCATION
    • Drilling Business Insights
    • Reference Desk
    • Sponsored Insights
  • SOURCEBOOK
  • EVENTS
    • Conferences & Demo Days
    • Newscast LIVE
  • SUBMIT
    • Drillers @Work
  • ABOUT
    • Contact
    • Advertise
  • SIGN UP

Drilling Fluids: Funnel Viscosity Not the Whole Story

By George Dugan
George Dugan
February 1, 2012

It is ironic that of all the different types of tests that can be performed on drilling fluids, the one test most commonly performed provides us with the least amount of information. The marsh funnel viscosity test undoubtedly is the hands-down favorite among drilling contractors from any drilling industry that utilizes either mineral (bentonite) or polymer-based drilling fluids or slurry, but funnel viscosity only tells us the thickness of a drilling fluid. Determining the funnel viscosity of a drilling fluid does not accurately tell us how well the fluid will keep a hole open, convey cuttings to the surface, or perform any other function expected of a drilling fluid. It is important to understand the limitations of the funnel viscosity test, and know when to delve deeper into drilling fluids testing and rheology in order to determine whether a drilling fluid is capable of performing the functions required to complete a drilling project effectively.

Looking up the word “viscosity” in Webster’s New World Dictionary, you will find that viscosity is “the internal friction of a fluid which makes it resist flowing past a solid surface or other layers of the fluid.” This definition should get the attention of anyone using drilling fluids for rotary mud drilling, because this statement indicates that viscosity can work against us in our efforts to perform the functions expected of a drilling fluid. Higher-viscosity (thicker) drilling fluids will require more pressure at the drill bit or reamer to move the column of drilling fluid out of the hole, especially when drill cuttings are thrown into the mix, further increasing the viscosity of the returns. Additional pressure at the drilling head or reamer increases the chances of compromising the structural integrity of the hole, which can result in formation damage, loss circulation and/or frac-outs (especially in horizontal directional drilling applications). Higher-viscosity drilling fluids are more difficult to keep clean, regardless of whether one is utilizing mechanical solids-removal equipment or relying on gravity to settle drill cuttings, resulting in higher drill solids and poor-quality drilling fluids.

Bentonite drilling fluid is non-Newtonian, which means that the viscosity changes with shear. Viscosity in Newtonian fluids, such as water and oil, changes with temperature (the hotter the fluid, the thinner it gets), whereas non-Newtonian bentonite drilling fluids get thinner with shear and should pump easily, yet transform into a gel-like substance at rest and suspend drill cuttings. Bentonite drilling fluid also can be described as thyrotrophic, according to Principles of Drilling Fluid Control, because of its “ability to build up a rigid or semi-rigid gel structure if allowed to stand at rest, yet can be returned to a fluid state by mechanical agitation.” The most effective and efficient drilling fluid is one that can perform all of the functions of a drilling fluid (gel strength, suspend drill cuttings, stabilize the borehole, etc.) at the lowest possible viscosity.

The routine of checking funnel viscosity gives us a relative indication of how much bentonite or polymer is in a drilling fluid, and is a first step in matching drilling fluids to soil conditions. When recycling/re-circulating drilling fluid, it is important to test the funnel viscosity frequently in order to maintain the drilling fluid properties needed to complete a drilling project. As drilling fluid is re-circulated along with an increasing amount of retained of drill cuttings, these drill cuttings continually get ground down until they are close to the particle size of clay (0 to 2 microns). A drilling fluid contaminated with ultra-fine drill cuttings, or contaminants such as lime, can exhibit a high funnel viscosity, yet have poor fluid-loss properties that hamper the ability to maintain an open hole; low gel strength, which can lead to hole plugging and/or stuck drill pipe; and high densities that increase the chances of formation damage and loss circulation. A sand-content test will indicate the amount of drill cuttings 74 microns and larger in a drilling fluid, but a mud balance is needed in order to identify high concentrations of ultra-fine solids in a drilling fluid.

Mud weights above nine pounds per gallon indicate high levels of ultra-fine solids, and the only remedy is to discard and replace partial volumes of the solids-laden fluid with new (clean) drilling fluid to lower the solids concentration/density.

Although testing the funnel viscosity of a drilling fluid yields little information on the performance or quality of the fluid, it is a vital step in matching a drilling fluid to soil conditions, as well as maintaining a drilling fluid throughout the drilling process. It is important to understand that additional testing is needed to develop a complete picture of what is happening with a drilling fluid, and determine what is needed to make the necessary corrections to get the job done. 
ND

Share This Story

Looking for a reprint of this article?
From high-res PDFs to custom plaques, order your copy today!

George dugan 200px

George Dugan is technical sales manager for CETCO Drilling Products, a Mineral Technologies Inc. company.

Recommended Content

JOIN TODAY
to unlock your recommendations.

Already have an account? Sign In

  • geotechnical drilling rig

    6 Onsite Phrases Environmental Drillers Hate

    Here are six phrases that highlight common frustrations...
    Opinions
    By: Jeff Garby
  • Wayne Nash

    Pipe Stuck? Common Causes and Solutions for Drillers

    If you have drilled for any length of time, sooner or...
    Water Wells
    By: Wayne Nash
  • submersible pumps, water well pumps

    Selecting and Sizing Submersible Pump Cable

    This article helps pump installers and servicers decide...
    Water Wells
    By: Bob Pelikan
You must login or register in order to post a comment.

Report Abusive Comment

Subscribe For Free!
  • eNewsletters
  • Online Registration
  • Subscription Customer Service
  • Manage My Preferences

The Driller Newscast: 21st Century Drillers | Part 1 DEMAND

The Driller Newscast: 21st Century Drillers | Part 1 DEMAND

The Driller Newscast: New York Geo Talks 2025 Conference with Hands-on Driller Education

The Driller Newscast: New York Geo Talks 2025 Conference with Hands-on Driller Education

The Driller Newscast: Coiled Tubing Drilling and the Future of Geothermal

The Driller Newscast: Coiled Tubing Drilling and the Future of Geothermal

The Driller Newscast, Episode 147: Global Geothermal Collaboration at NY-GEO 2025

The Driller Newscast, Episode 147: Global Geothermal Collaboration at NY-GEO 2025

More Videos

Sponsored Content

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the The Driller audience. All Sponsored Content is supplied by the advertising company and any opinions expressed in this article are those of the author and not necessarily reflect the views of The Driller or its parent company, BNP Media. Interested in participating in our Sponsored Content section? Contact your local rep!

close
  • demo of a DM450 drilling rig during a customer factory visit
    Sponsored byGeoprobe

    Built for You: Smarter Drill Rigs, Stronger Support, Bigger Opportunities

Popular Stories

MainPhotoTwoBrothers.jpg

Two Brothers' Journey Through the Drilling Industry

AI and Drought Concerns

AI’s Growing Thirst for Water and Power

demo of a DM450 drilling rig during a customer factory visit

Built for You: Smarter Drill Rigs, Stronger Support, Bigger Opportunities

The Driller Classifieds

COMPRESSORS

EAST WEST MACHINERY & DRILLING IS BUYING AND SELLING AIR COMPRESSORS, AIR BOOSTERS, AIR ENDS & PARTS
Company: East West Machinery

DRILL RIGS

LOOKING FOR LATE MODEL TOPHEADS & DRILLTECH D25'S
Company: Spikes’s Rig Sales

DRILL RIG PARTS

MEETING DRILLERS NEEDS AROUND THE WORLD
Company: East West Machinery

ELEVATORS

SEMCO INC. PIPE ELEVATORS
Company: Semco Inc.

GROUTERS

GROUTING EQUIPMENT - GROUT PUMPS & GROUT HOSE REELS
Company: Geo-Loop Inc.

PUMP HOISTS

SEMCO INC. - BASIC PUMP HOISTS
Company: Semco Inc.

WELL PACKERS

LANSAS PRODUCTS - INFLATABLE WELL PACKERS
Company: Vanderlans Lansas Products

WELL SCREENS

WELL SCREENS & SLOTTED PIPE
Company: Alloy Screen Works

Products

Water Quality Engineering: Physical / Chemical Treatment Processes

Water Quality Engineering: Physical / Chemical Treatment Processes

By carefully explaining both the underlying theory and the underlying mathematics, this text enables readers to fully grasp the fundamentals of physical and chemical treatment processes for water and wastewater.

See More Products

Subscribe to The Driller Newscast

Related Articles

  • George Dugan

    Drilling Fluids: HDD and Vertical Drilling Fluids - Understanding the Differences

    See More
  • George Dugan

    The Differences Between Horizontal Drilling, Vertical Drilling Fluids

    See More
  • George Dugan

    Drilling Jobs Easier With the Correct Drilling Fluids

    See More

Related Products

See More Products
  • drilling.jpg

    Clay Science in Drilling and Drilling Fluids

  • M:\General Shared\__AEC Store Katie Z\AEC Store\Images\ND\new site\in-too-deep.gif

    In Too Deep: BP and the Drilling Race That Took it Down

See More Products

Related Directories

  • Jentech Drilling Supply

    Let Jentech Drilling Supply assist you in supplying and implementing a drill string to match your drilling requirements. We inventory a full range of drilling supplies, fluids, cement and grout. We also manufacture our own line of coring tooling.
  • SIMCO Drilling Equip. Inc.

    SIMCO Drilling Equipment manufactures and sells both new and used drilling rigs. All SIMCO drill rigs are fully designed, built, and sold from our location in Osceola, Iowa and has for over 50 years. We are not just an assembly plant at SIMCO. We take pride in our drill rigs and stand behind the best warranty in the industry. We specialize in water well drill rigs and geotechnical drill rigs. We also build drill rigs for pavement coring, soil sampling, geothermal heating and cooling, and many more. www.simcodrill.com
×

Dig deeper into the drilling and water supply industry!

Build your knowledge with The Driller, covering the people, equipment and technologies across drilling markets.

SIGN UP NOW
  • RESOURCES
    • Advertise
    • Contact Us
    • Directories
    • Store
    • Want More
    • Classifieds
  • SIGN UP TODAY
    • Create Account
    • eNewsletters
    • Customer Service
    • Manage Preferences
  • SERVICES
    • Marketing Services
    • Reprints
    • Market Research
    • List Rental
    • Survey/Respondent Access
  • STAY CONNECTED
    • LinkedIn
    • Facebook
    • YouTube
    • X (Twitter)
  • PRIVACY
    • PRIVACY POLICY
    • TERMS & CONDITIONS
    • DO NOT SELL MY PERSONAL INFORMATION
    • PRIVACY REQUEST
    • ACCESSIBILITY

Copyright ©2025. All Rights Reserved BNP Media.

Design, CMS, Hosting & Web Development :: ePublishing

The Driller
search
cart
facebook twitter linkedin youtube
  • Sign In
  • Create Account
  • Sign Out
  • My Account
The Driller
  • NEWS
    • Water
    • Geothermal
    • Construction
    • Environmental
    • Mining
    • All Industry News
  • CLASSIFIEDS
  • EQUIPMENT
    • Rigs & Heavy Equipment
    • Consumables
    • Pumps
    • Featured Products
  • SAFETY
  • VIDEOS
    • Newscast
    • Drill Talks
    • Ask Brock
    • Emerging Drillers
  • EDUCATION
    • Drilling Business Insights
    • Reference Desk
    • Sponsored Insights
  • SOURCEBOOK
  • EVENTS
    • Conferences & Demo Days
    • Newscast LIVE
  • SUBMIT
    • Drillers @Work
  • ABOUT
    • Contact
    • Advertise
  • SIGN UP