PREPARING FOR A

DRILLING PROJECT

A CONTRACTOR’S PERSPECTIVE

BY:

PAUL BALEMI

CONTRACTORS LTD

PLANNING A DIRECTIONAL DRILL SHOT

IN AN URBAN ENVIRONMENT

INSTALLATION BY INTELLIGENT

DIRECTIONAL DRILLING METHODS

PLANNING A DIRECTIONAL DRILL

SHOT IN AN URBAN ENVIRONMENT

FIRST CONSIDERATION:

• THE SIZE OF DRILL RIG REQUIRED

• SITE CONSTRAINTS

• WHICH METHODOLOGY SHOULD BE USED

• TYPE OF PIPE TO BE INSTALLED

• OPTIONAL MACHINES WITH DIRECTIONAL

STEERING OPTIONS

• GROUND CONDITONS

A GUIDE FOR THE SIZE OF DRILL RIG

REQUIRED

• The diameter and length of pipe to be installed.

Diameter (mm) 50 100 150 200 250 300

110 3000 4000 - - - -

125 3300 4500 5000 - - -

160 4000 5000 6000 7000 - -

180 4250 5500 7000 8000 - -

225 450 6000 7500 9000 11000 -

250 4750 6500 8250 10000 12000 15000

280 5000 7000 9000 12000 14000 19000

315 5500 8000 10000 12500 15000 20000

355 6000 9000 12000 15000 20000 25000

400 10000 15000 20000 25000 30000 40000

450 17000 20000 25000 35000 48000 65000

500 20000 28000 35000 50000 65000 90000

630 25000 35000 50000 68000 88000 100000

The above figures are based on a backcut diameter recommended as 1.5 x pipe diameter

Directional Drilling - Installation & Pullback Pressure (lbs Force)

Length (m)

SITE CONSTRAINTS

• SPACE AVAILABLE FOR SET UP

For the size of the machine required plus any

mud handling equipment

To weld pipe string and install the pipe.

Lead in length required for pilot bore to

obtain correct grade and correct alignment.

Is a blind shot an option.

Maxi Rig Set Up

Transportation of Pipe String

RESTRICTED

SITES

Lead in length required for pilot bore to

obtain correct grade and correct alignment.

OBSTRUCTIONS TO BE TAKEN INTO

ACCOUNT FOR SET UP

– Traffic control and

pedestrian access.

– Other utilities

overhead and

underground.

3. THE TYPE OF MACHINE REQUIRED

• Surface launch.

• Pit launch

• Tolerances for installation

• Straight line or includes change of

direction and or change in grade.

• Depth of cover to pipe

• SURFACE LAUNCH

Laser Guided Pit Bore Machine

Pit Launch Machine

Machine Assembled in Pit

4. TYPE OF PIPE TO BE INSTALLED

P.E.

PVC

CERAMIC

CONCRETE

STEEL

P.E.

Advantages:

• Long lengths welded into a single strings to

allow continuous pulling operation, flexible to

allow to accommodate lead in and stringing.

• Can be made in short lengths with mechanical

joints (push lock fit) for straight bores.

• Lightweight

Disadvantages:

• Area required to weld long string. May have to

be transported to rig at time of pull back.

PE pipe

PVC

Advantages:

• Straight rigid lengths for more accurate grade to finished pipe.

• Short lengths available in restrained joint up to 150 diameter.

• Lightweight

• Butt Welded – Fusible PVC

Disadvantages:

• Less flexible than PE pipe for lead in more suitable for straight shots.

• Not available in sizes above 400mm.

Fusible PVC

CERAMIC

Advantages:

• Good Strength with higher load specifications for shallow depths requirements.

• Ideal for straight shots.

Disadvantages:

• Only suitable for straight shots.

• More installation time.

• More expensive

CONCRETE

• Advantages:

• Good range of diameters including larger sizes.

• Good Strength

• Price

• Disadvantages:

• Straight shots required.

• Shorter lengths, more joints.

• More installation time required.

STEEL

Advantages:

• Good strength

• Can also be rammed through unstable or loose

rock and cobbles.

• Variable lengths available.

Disadvantages

• Less flexibility, more suited to straight bores.

• Cost and time to weld.

5. OPTIONAL MACHINES WITH

DIRECTIONAL DRILLING STEERING

OPTIONS

1. STRAIGHT BORE LASER GUIDED PIT

MACHINE.

2. PIT MACHINE WITH WALKOVER

STEERING SYSTEM.

STRAIGHT BORE LASER GUIDED PIT

MACHINE

Advantages

• Very accurate bores.

• Minimum backream size 20-25mm larger than pipe.

• Big thrust capacity for size of rig.

• Suited to confined space sites.

• Short lengths of pipe can be installed.

• Blind Shots.

Disadvantages

• 120m maximum bore length.

• Requires up to 3m diameter pit.

• Longer set up time.

• Slower drill and pull back speeds.

• Only straight bores.

Advantages

• Can accommodate changes in grade and alignment.

• Small set up area required.

• Light weight.

• Can be man handled onto site.

Disadvantages

• Normally smaller sizes of pipe installed.

• Shorter bore lengths generally up to 75metres.

PIT MACHINE WITH WALKOVER

STEERING SYSTEM

INSTALLATION BY

INTELLIGENT DIRECTIONAL

DRILLING METHODS

METHODS CONSIST OF THE

FOLLOWING:

Locate All of Other Underground Services In or

Near the Bore Path

Pre Plan the Bore Shot

Determine the Best Location System that will

suit the job.

Check ground conditions to be encountered.

The logs sheets results from piloting and or

backreaming

The drillers log sheet records

Correct pullback speed

Locate All of Other Underground

Services In or Near the Bore Path

• Surface Detection

Locating by Cable Detectors

Underground Radar.

Marking out from maps.

Pilot for Services

CCTV Laterals

Determine Accuracy of Mapping Records

• Vacuum excavation with sucker truck and jetting.

• Excavation of pilot holes – by hand around

service or by photographs.

• Location of sewer or storm water laterals using

CCTV with sonde to detect depth and position.

Pre Plan The Bore Shot

• Accurately plot the bore path, and confirm required clearance between services.

• Some walk over steering systems have provision for planning the bore path in the software, which is then used to guide the locater to carry out more accurate piloting. Otherwise a manual asbuilt should be carried out in preparation for the intended plan.

• Check bore path for interference to Steering Locater System and make allowances.

• For road crossings and drilling under building or structures other location methods needs to determined.

Determine the Best Location System

that will suit the job.

• The Walkover in Ground Positioning

System

• The Magnetic Wired Steering System

• Gyroscope Navigation Guidance System.

• Laser Guided System

Bore plan must include the ground

conditions to be encountered

• Field inspection of the ground conditions.

• Ground conditions must be monitored whilst

pilot boring. i.e. Rotation and thrust pressure

will confirm the designed mud plan is correct or

needs adjusting to achieve desired results.

• Pre reaming before pipe installation will also

confirm mud design is correct for pipe

installation.

The log sheet results from piloting

and or backreaming

• The log sheet results from piloting and or

backreaming must be used to pre- plan the

drillers mud design – pressure and speed of

pullback for pipe installation.

The drillers log sheet records

1. The drillers log sheet records are the most important Quality Assurance Control for correct installation. The pullback speed must be controlled to match the mudflow. Bore hole diameter less the pipe volume over the flow rate of the drill rig mud pump equals the speed of pullback.

Borehole Volume (Ltr) – Pipe Volume(Ltr)

Mud Pump Capacity (Ltr/min.)

Drillers Log SheetsJB CONTRACTORS LTD

DIRECTIONAL DRILLING QUALITY ASSURANCE

PILOT BORE/ BACK REAM / PIPE INSTALLATION

CLIENT DATE

SITE ADDRESS JB JOB NO.

DRILL ENGINEER PIPE DESCRIPTION

OPERATOR LENGTH OF BORE

LOCATOR MACHINE

PULL BACK SPEED - TIME PER ROD BACK REAM SIZES

PLANNED WATER POLYMER BENTONITE ROD TIME

Rod No. Start Log

Stop

Operation

Rotation

Pressure

Pull Back

Pressure

Water

Quantity

Water

Pressure Ground condition, comments

Correct pullback speed

• Too Fast

– Possible Hydrolock

– Mud frackout due to extra downhole pressure

– Lack of mudflow to pipe lead end resulting in voids around the pipe.

• Too Slow

– Mud washout from around the pipe leading to future voids.