how to use stiff-foam to air-rotary drill through caving overburden

ToddGiddings, Ph.D.,P.G.ToddGiddings andAssociates,Inc.

[email protected]

How to Use Stiff-Foam to Air-Rotary DrillThrough Caving Overburden

Session DTechnical Aspects

Learning Objectives• What is profitable geo borehole drilling? • How do you drill with Stiff-Foam?• How do you make Stiff-Foam?• How does Stiff-Foam get you through the

caving overburden?• What are the advantages & disadvantages?• What is the equipment list?• What is the material list?

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Acknowledgements• Pennsylvania Ground Water Association• Baroid Corporation

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Profitable geothermal borehole drilling:• Is production drilling

• Uses a drill rig with special features

• Does NOT re-drill the same caving zone many times

• Salvages and re-uses the temporary steel casing

• Controls the water and cuttings

This is the third method in a series:

2012Case-as-you-drill

2013Convert to mud

Where was the demonstration site?

How do you drill with Stiff-Foam ?• Use a standard air-rotary drill rig

• Use a down-the-hole hammer with a button bit

• Calibrate the flow rate of the water injection pump

• Inject the polymer/water/foaming-agent mix

• Drill with a very reduced air volume and pressure

• Manage the foam-cake by using either or both:

• A de-foaming agent and a garden sprayer

• A BubbleBuster

ROCK

SOIL6-INCHSTEEL

CASING

SOIL

6-INCH

BORE

HOLE

SOIL

ROCK ROCK

ROCK

SOIL SOIL

6-INCH

BORE

HOLE

SOIL

ROCK ROCK

How do you make Stiff-Foam?• Fill a 100-gallon mixing tank with potable water

• Adjust the pH and hardness of the potable water

• Add a polymer to the water and mix by recirculating

• Measure the viscosity of the polymer-water mix

• If required, add more polymer and mix and measure

• Transfer the polymer-water mix into a storage tank

• Add the foaming agent to the polymer-water mix

• Blend in the foaming agent by stirring very gently

Laundry detergent foam while agitating

The bubbles do not persist in flowing water

One-half acre of foam-cake while trying to get through the caving overburden.

With a foam-cake mess like this, how do you even change a rod?

A Simco Model 2800 HSHT• 4,000 ft-lbs of torque• 12,000 lbs of pullback• Road weight 15,000 lbs

Ingersoll-Rand Compressorcapacity of 400 cfm @ 200 psi.During the Stiff-Foam drillingwe used only 250 cfm @ 100 psi

Driving in the temporary casing

A diverter is recommended

Filling the 100-gallon mixing tub

Wetting the pH test strip

A raw water pH of 7

Adding Soda Ash to raise the pH

An adjusted pH of 9.5

A hardness of <120 ppm

Adding the QUIK-TROL GOLD ® to the treated water

Filling the Marsh funnel

Measuring the viscosity

40 – 60 seconds per quart

Mixing the polymer by recirculating

Centrifugal Pump

Transferring the polymer/water mix into the storage tank

Adding the AQF-2® foaming agent to the polymer/water mix

Blending by gentle stirring

Discharging the cuttings and foam into a pit

The polymer/water/foaming-agent injection rate is between 3 and 5 gpm depending on the drilling rate

Connecting the BubbleBuster

Collecting the cuttings

Note the pieces of the silty-clay overburden

Note how the foam holds the cuttings together

The BubbblerBuster uses centrifugal force to burst the bubbles inside the cyclone

Spraying the BARA-DEFOAM 500® de-foaming agent

Drilling 60 feet through the caving overburden

Adding EZ-Mud® polymer to water in the grout mixer

Mixing the EZ-Mud® polymer into the water

Adding BENSEAL® granular bentonite

Pressure-tremie grouting the 60-foot borehole

The foam pit was filled in to complete the site restoration

How does Stiff-Foam get you through the caving overburden?• The air volume and pressure are low

• The low up-hole air velocity does not cause scouring

• The Stiff-Foam bubbles have a very strong skin

• The bubbles increase the viscosity of the air stream

• The bubbles carry the cuttings up the annular space

• A pseudo wall-cake is formed on the borehole wall

• You are “tip-toeing” through the caving overburden

• You are not “blasting” your way through

• This method is the least-certain of the three methods

• Can be used with any air-rotary drill rig

• Quick to set up and easy to use

• Has a low cost for equipment and materials

What are the disadvantages ?

What are the advantages of Stiff-Foam ?

• Will not work in all types of overburden

• The foam-cake in not easy to control

The equipment list for Stiff-Foam:• An air-rotary drill rig, and a diverter is recommended

• A down-the-hole hammer and bit

• A compressor

• Two 100-gallon tanks

• A 2-inch centrifugal pump with two hoses

• A mixing funnel

• A Marsh funnel

• A garden sprayer

• A BubbleBuster is optional

The material list for Stiff-Foam:• Potable water

• pH and hardness test strips

• Soda Ash (Sodium Carbonate – Na2CO3)

• QUIK-TROL GOLD® polymer

• AQF-2® foaming agent

• BARA-DEFOAM® de-foaming agent

Thank you!

how to use stiff-foam to air-rotary drill through caving overburden

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