GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
GREAT SOCIALIST PEOPLE'S LIBYAN ARAB JAMAHIRIYA
GENERAL WATER AUTHORITY
TECHNICAL SPECIFICATION
FOR
DRILLING OF PRODUCTION
WATER WELLS
In
Al Jabal Al Akhdar Area
North East Libya
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM
CIRCULATION ROTARY DRILLING
GWAE
Page 1 of 6
June 2007
GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION
ROTARY DRILLING
Item
Table of Contents
Page
Item 1
Air Compressor
..
2
Item 2
Ascending Annulus Velocity
..
2
Item 3
Drill String
..
2
Item 4
Bits and Back Pressure Valve ( Check -Valve )
..
2
Item 5
Stabilization of Drill String
..
3
Item 6
Dust Deflector
..
3
Item 7
Rotating Drill Head
..
4
Item 8
Injection Pump and Injection Rate
..
4
Item 9
Mixing and Injection System
..
5
Item 10
Pressure Gauge
..
6
Item 11
Foam Detergent and Other Stabilizing Additives
..
6
Item 12
Inspection of Facilities for Air/Foam Drilling
..
6
Item 13
Water Storage
..
6
GWAE
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June 2007
GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
Requirements for Air and Air/Foam Circulation Rotary Drilling
1.
AIR COMPRESSOR
Contractor shall furnish an air compressor of required discharge and pressure
to drill the borehole at specified diameter to required depth, and to cope with
the pneumatic requirements. When selecting the air compressor's capacity,
due consideration shall be given to the water ( where applicable ) which may
be entering into the well during drilling through the water bearing formation
and which shall be lifted up, when resuming drilling after adding a pipe.
2.
ASCENDING ANNULUS VELOCITY
The minimum ascending annulus space air velocity shall be maintained at
4 500 ft/min. ( 1 371 m/min. ), when using straight air for circulation.
When applying air/foam circulation, the minimum ascending velocity shall
range from 120 - 15-0 ft/min..
3.
DRILL STRING
Contractor shall use drill pipe of outside diameter sized in relation to the
specified borehole diameter, ascending air velocity required and the
requirements of Appendix ( I ), Item 8.1.4.
For straight air circulation, Contractor shall use flush joint drill pipe.
Contractor shall use drill collars, as outlined in Appendix ( I ), Item 8.1.3. for
straight circulation rotary drilling.
4.
BITS AND BACK PRESSURE VALVE ( CHECK-VALVE )
4.1.
Tri-Cone Rock Bits:
Contractor shall use special tri-cone rock bits, equipped with air circulation
passages to the cone bearings, preferably. Diffuse air nozzle inserts ( or
similar devices ) shall be inserted into the bit shank, to distribute the air or
air/foam mixture to the bearings for cooling, and to the cones for cleaning
action.
4.2.
Downhole Percussion Bits ( Hammer Bits )
Should Contractor apply hammer-down-the hole drilling with air or air/foam
circulation, hammer-insert bits of the required diameters shall be provided.
Button insert bits ( drop center bit or equivalent ) shall be available in
sufficient quantity and type as needed to penetrate the expected formation
GWAE
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June 2007
GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
efficiently. Contractor shall have the necessary facilities, as grinding stand and
bit grinder, bit gauge, etc., to properly sharpen and bit, and to control its gauge.
4.3.
Bit-Pressure Valve ( Check Valve )
For tri-cone bits with circulation passages, a back pressure ( check valve ) with
nozzles shall be inserted into the bit shank. This check valve shall be
combined with the diffuse nozzle. Where normal tri-cone rock bits shall be
used, the back pressure valve ( check valve ) shall be placed in the bit sub
directly above the bit. ( For down hole hammers, the check valve is part of the
tool ). The back pressure valve shall close when air is shut off and it shall
prevent cuttings or muddy water with cuttings from entering the bit body
through the nozzles. This prevents the eventual plugging of the air passages
to bit bearings or the plugging of the bit nozzles. Especially where water
bearing formations are to be penetrated and strong water in-flow occurs, the
check valve shall be installed to prevent water entering into the empty drill
pipe when making connection for a new pipe.
5.
STABILIZATION OF DRILL STRING
Stabilization of the drill string shall be maintained as specified in
Appendix ( I ) , Item 8 for rotary drilling.
A modification of this hook-up may be applied, subject to borehole conditions
and approval of Owner.
6.
DUST DEFLECTOR
When drilling by straight air circulation only, a dust deflector shall be installed
below the rotary table ( or below centralizer table for top head driven rigs ), to
protect the crew from dust and drill cuttings.
The dust deflector shall surround the rotary table ( or centralizer table ) from at
least three sides and shall extend from ground level up to rotary or centralizer
table. The fourth side shall be kept open. A detachable rubber flap shall be
available, to close the fourth side, when required.
The dust deflector shall be made of strong plate rubber or canvas material, and
be fixed to the rig's frame in a detachable construction.
Drill cuttings shall be collected from inside the dust deflector.
7.
ROTATING DRILLING HEAD
When applying misted air, air/foam or still foam circulation, and when drilling
within the aquifer and applying aerated water circulation, Contractor shall use
a rotating drilling head which shall be placed on a flange on tope of the casing.
GWAE
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June 2007
GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
The rotating head shall have sufficient inside clearance to allow the specified
bit to pass.
Contractor shall supply suitable adapters and accessories to mount the rotating
drilling head on either 26" or 18" OD casing. The rotating drilling head shall
be complete with lubricating system and stripper rubber for 3½", 4½" and 5" or
greater as approved bill pipe, and for the Kelly.
8.
INJECTION PUMP AND INJECTION RATE
8.1.
Injection Pump
An injection pump shall be available and be installed either on the rig or at
another position near the rig.The injection pump shall be used for injecting
water or for injecting a mixture of water with liquid foaming agent, viscosifier,
inorganic non-biodegradable polymer, gel or other stabilizing additives, into
the airstream.
8.2.
Injection Rate
The injection pump shall have a variable discharge rate from 0-40 gpm. In
general, the injection shall not exceed 10 gpm ( 37 l/min. ). Only at excessive
water in-flow or difficult weak formation, the injection rte of the stabilizing
mixture may be increased up to 20 gpm, ( 75 l/min. ) or greater, depending
upon the actual borehole condition.
The rate of injection shall be regulated and chosen, according to borehole
requirements, formation, etc., to stabilize and to control the borehole and to
carry out the drilling program. The injection rate shall also depend upon
whether the liquid mixture is meant for misting, foaming, etc..
8.3.
Should Contractor intend to apply hammer drilling weight air circulation, the
rig shall be provided with line force oiler forcing the oil for the hammer
lubrication into the air stream. A check valve shall be installed where the oil
discharge line enters into the air discharge pipe.
9.
MIXING AND INJECTION SYSTEM
A mixing system shall be provided for the rig and connected to the injection
pump.
The mixing and injection system shall consist of:-
GWAE
Mixing and mixture storage tank, minimum volume 4m3, or more
depending upon the planned well depth and anticipated injection.
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GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
-
An injection pump, connected on one side to mixture tank by a suction
line and by return line. A pressure regulator or 3-way valve, shall be
installed in the return line; on the other side the injection pump shall
be connected to dischargeline.
-
Discharge line from injection pump to rig stand pipe and rotary hose.
The discharge line shall have included in the following order; a drain,
a check valve, a filter, a pressure compensator valve, a shut-off valve
and a T-connection to air discharge line/drilling fluid discharge line
where air compressor feeds air down to the drill string.
The pressure compensator valve shall be installed under all circumstances as it
shall maintain a constant flow of the liquid mixture into the air-stream
regardless of downstream air pressure fluctuation.
Contractor is free to propose to Owner for approval another type of
injection system, provided it can carry out the same functions.
10. PRESSURE GAUGE
A pressure gauge shall be installed in the air discharge line at an easily readable
position near the driller's stand. The pressure gauge shall have a range 30% higher
than the maximum operating pressure of the compressor and the injection pump.
11. FOAMING AGENT AND OTHER STABILIZING ADDITIVES
Contractor shall keep on the well site at all times during the drilling operations, a
sufficient stock of foaming agents, viscosifier, wetting agent, inorganic nonbiodegradable polymer, gel, or any other stabilizing additives as required for air
or air/foam circulation, under full consideration of the formations to be penetrated
according to the drilling program.
All additives used for the air/foam drilling shall be non-toxic.
Contractor shall submit to Owner for approval, a program of the mixture and
additives planned to be used for injection during air/foam drilling. The program
shall be submitted to Owner at least one week prior to spudding in. Attached to
the program shall be at a list indicating the stocks of additives.
12. INSPECTION OF FACILITIES FOR AIR/FOAM DRILLING
Contractor's air/foam drilling accessories, tools and equipment, additives, etc.
shall be inspected by Owner prior to spudding in. Spudding in shall only be
approved, if all essential requirements are provided.
GWAE
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June 2007
GENERAL WATER AUTHORITY
APPENDIX VIII- REQUIREMENTS FOR AIR AND AIR/FOAM CIRCULATION ROTARY
DRILLING
Should Contractor propose facilities other than specified to carry out air/foam
drilling, they will only be approved by Owner, if sufficient for the proper
application of the specified circulation method and for the execution of the
drilling program.
13. WATER STORAGE
Contractor shall keep on location at all times, stored in graduated tanks, sufficient
water volume to maintain continuous operation.
GWAE
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June 2007