Iceland Operating Procedures

JARDBORANIR HF

Standard Operating ProceduresFor

Aerated Drilling In

Iceland

Geothermal Consultants 1 Brunswick Drilling Consultants New Zealand Limited New Zealand Limited

CONTENTS

Subject Page

1. Introduction 12. Procedures 2

2.1 Initial Introduction of Aerated Fluids. 22.2 Drilling With Aerated Fluids. 32.3 Making a Connection. 42.4 Pulling Out of The Hole. 52.5 Inducing The Well to Flow. 7

3. Equipment Incorporated into BOP Stack. 104. Aerated Drilling Equipment. 115. General Notes. 12


1. Introduction:-

In the past drilling of the production section of a geothermal well was carried out using water with polymer mud sweep to assist in the clearing of cuttings. Once permeability was intersected circulation from the well was lost and drilling continued with out returns.

Using this method does have problems.• Cuttings were washed into the production zones of the well.• Nothing was known of the geology of the well unless expensive cores were cut.• Cuttings often blocked or bridge the bottom of the well. This sometimes prevented the

production liner from reaching the bottom. • The well and formation surrounding it were flooded with water from the drilling process which

resulted in the well taking a long time to recover.• The drill string often became stuck when new loss zones were encountered.• In time cuttings filled the bottom of the production liner blocking off production zones.• A long time was spent circulating large amounts of water in an attempt to wash cutting away

from the well bore into the formation.• The mud used to clean the well bore had the potential to seal off the smaller fractures in the

production zones.

Some of these problems have the potential to damage or reduce production, increase the cost of the well, and even loses the well.

In recent years the use of aerated water to drill the production section of geothermal wells has become a standard procedure in most countries. The utilisation of the aerated fluid to drill the production section of a geothermal well is beneficial to both the energy supply company and drilling contractor.

Some of the benefits for the energy supply company are:-• Production zones are not clogged because cuttings are removed from the well. • A better understanding of the geology of the geothermal fields is gained from the return of

cuttings to the surface. • A shorter recovery time for the well because it is no longer flooded with cold water.• A reduction in time spent trying to clear cuttings from the well bore.• No cuttings in the well so the production liner can be run to the bottom.• No cuttings in the well to block or fill bottom of production liner.• Smaller fractures are not sealed as no mud is used to clean the well.

Some of the benefits for the drilling contractor are:-• Less fluid volumes required from pumping system.• Less chance of drill string getting stuck.• Shorter time to drill production section of hole.• Less torque and drag when circulating with aerated fluids.


2. Procedures:-

2.1 Initial Introduction of Aerated Fluid:-

After the shoe of the production casing has been drilled out and a formation leak off test carried out.

1. Check air manifold valve alignment:-• Valve number one OPEN.• Valve number two CLOSED.• Valve number three CLOSED.• Lo torque valve CLOSED.

2. Install a string float ( non return valve ) into the drill string one single above the bottom of the hole.

3. Check Isolation Valve has been nipped open.4. Check Throttle Valve is opened 50mm only ( This valve is used to hold back pressure on

the well ).5. Check that separator valves are lined up to the shakers.6. Open Lo torque valve on air manifold.7. Start pumping at the rate of:-

• 32 litres per second for a 12.25” hole.• 18 litres per second for an 8.5” hole.

8. Introduce air into the circulating system through the air manifold by:-• Opening valve number two.• Closing valve number one.

9. Once the air has been introduced check the injection rate is:-• 0.0944 cubic metres per second for a 12.25” hole.• 0.0708 cubic metres per second for an 8.5” hole.

10. Set foam injection rate to two and a half litres per hour.11. Commence drilling ahead.12. Check fluid and cutting returns at the shakers.13. Maintain water temperature in the mud tanks between twenty five and thirty five degrees

Celsius, by mixing return water with fresh water.


Drilling With Aerated Fluid:-

Once initial circulation rates have been established and stabilised pay close attention to kill line pressure and return temperature.

Continuously monitor that there is a good fluid and cuttings return over shakers.All changes made to the circulating system should be made in small steps altering only one parameter at a time and allow that change to circulate for thirty minutes.In some wells the difference between lost circulation and good circulation could be as fine as a half a litre per second.A string float should be added to the string every one hundred and fifty metres.

Fluid returns or the kill line pressure reduces:-If this is not corrected then circulation will be lost.

1. Increase the air injection rate by 0.0236 cubic metres per minute.2. Increase foam injection rate by 2.5 litres per hour and monitor returns.3. Allow the standpipe and kill line pressures and returns to stabilise for thirty minutes.4. Monitor the returns and kill line pressure for thirty minutes

• If they have increased and stabilised continue drilling. • If they have not increased then repeat steps one through three.

Return temperature or the kill line pressure increase:-If this is not corrected the well will become more under balanced and begin to flow.

1. Increase the pump rate by five litres per second. 2. Allow the standpipe pressure, kill line pressure, and returns to stabilise for thirty minutes. 3. Monitor the kill line pressure and return temperature for thirty minutes.

• If they have stabilised then continue drilling. • If they have not stabilised:-

1. Repeat steps one through three if returns continue to increasing.2. If returns begin to drop off then reduce pump rate by two litres per second and repeat steps two

and three.

Torque or standpipe pressures increase or fill on bottom after connection:-Cuttings are not being cleared from the hole.

1. Increase foam injection by two and a half litres per hour.2. Monitor and adjust foam rates to control excessive foam returns, torque, and standpipe pressure.


Making a Connection:-

Connections should be made as quickly as possible to reduce the amount of time the pumps are off. In the production zone the return temperature will increase while the pumps are off. This may result in the well becoming more under balanced and begin to flow. Bit life will also be reduced.

1. Ream hole as required.2. Circulate hole clean of cuttings.3. Bypass air and stop pumping at the same time.

Steps to bypass air at manifold:-• OPEN valve number one. ( Bypasses air delivery from standpipe into the Blooie line.

This prevents back pressure and possible damage of the booster or compressors ).• CLOSE valve number two. ( Stops air delivery to standpipe ).• OPEN valve number three. ( Releases pressure from drill string into the Blooie line ).

4. Allow standpipe pressure to bleed back to zero.5. Break out top drive. • Make sure that floorman are well clear as there may still be trapped pressure and hot fluid in the

drill string.6. Screw top drive into next single to be drilled and add to string.7. Introduce air and start pumps at the same time.

Steps to introduce air at manifold:-• CLOSE valve number three.• OPEN valve number two.• CLOSE valve number one.

8. Set pumps back to previous parameters.9. Continue drilling.10. A short kill line pressure and return temperature increase will be noticed ten to twenty minutes

( depending on hole depth ) after the connection has been made. • This should return back to previous drilling parameters. • Monitor the increase to make sure the well does not become more under balanced and

begin to flow.


Pulling Out of The Hole:-

If the hole conditions are stable.

1. Ream hole as required.2. Circulate hole clean of cuttings.3. Bypass air.


This prevents back pressure and possible damage of the booster or compressors ).• CLOSE valve number two. ( Stops air delivery to standpipe ).• DO NOT OPEN valve number three.• Stop the foam injection once the air has been bypassed.

4. Continue pumping until return flow from the well stops. Keep the drill string moving while circulating.

5. Change pumps over to back fill and commence pumping to keep hole off pressure.6. Pull out of hole. 7. Inspect string floats once they have been removed from the drill string.

If the hole conditions are unstable.

1. Ream hole as required.2. Circulate hole clean of cuttings.3. Pull back to remove single from string.4. Set drill string in slips.5. Bypass air and stop pumping at the same time.


This prevents back pressure and damage of the booster and compressors ).• CLOSE valve number two. ( Stops air delivery to standpipe ).• OPEN valve number three. ( Releases pressure from standpipe into the Blooie line ).

6. Allow standpipe pressure to bleed back to zero.7. Break out single and remove from drill string.

• Make sure that floorman are well clear as there may still be trapped pressure and hot fluid in the drill string.

8. Screw top drive back into drill string.9. Introduce air and start pumps at the same time.


10. Set pumps back to previous parameters.11. Pull out of hole follow steps three through ten until string float is reached. 12. Before removing single from above string float.


Bypass air injection.Steps to bypass air at manifold:-

• OPEN valve number one. ( Bypasses air delivery from standpipe into the Blooie line. This prevents back pressure and possible damage of the booster and compressors ).

• CLOSE valve number two. ( Stops air delivery to standpipe ).• DO NOT OPEN valve number three.

13. Pump the drill string volume. Keep the drill string moving while circulating. Drill string volumes:-

• 5” x 19.5 pound per foot Drillpipe = 9.05 litres per metre.• 8” drill collars = 4.56 litres per metre.• 6” – 6.5” drill collars = 4.01 litres per metre.

14. Stop pumping remove single and string float from drill string.15. Introduce air and start pumps at the same time.

Steps to introduce air at manifold:-• OPEN valve number two.• CLOSE valve number one.

16. Set pumps back to previous parameters.17. Pull out of hole following steps three through seventeen.18. Once the hole conditions are stable bypass the air.


This prevents back pressure and possible damage of the booster and compressors ).• CLOSE valve number two. ( Stops air delivery to standpipe ).• DO NOT OPEN valve number three.• Stop foam injection once air has been bypassed.

19. Continue pumping until return flow from the well stops. Keep the drill string moving while circulating.

20. Change pumps over to back fill and commence pumping to keep hole off pressure.21. Pull out of hole. 22. Inspect string floats once they have been removed from the drill string.


Inducing The Well to Flow:-

When tripping into the well it will be necessary to start the well circulating off bottom.The first attempt should be made one hundred metres off bottom. If this is unsuccessful then the string should be pulled back in fifty metre steps until circulation has been regained.Once circulation has been regained the string can then be circulated to bottom.

1. Check air manifold valve alignment:-• Valve number one OPEN.• Valve number two CLOSED.• Valve number three CLOSED.

2. Install a string float ( non return valve ) into the drill string one single above the bottom of the hole.

3. Check Isolation Valve is fully open.4. Check Throttle Valve is opened 50mm only ( This valve is used to hold back pressure on the

well ).5. Check that separator valves are lined up to the shakers.6. Change mud pumps from the kill line to the standpipe.7. Start pumping at the rate that was set before the string was pulled from the hole.8. Introduce air into the circulating system through the air manifold by:-

• Opening valve number two.• Closing valve number one.

9. Once the air has been introduced check the injection rate is:-• 0.4720 cubic metres per second.• Foam injection rate set at five litres per hour.

10. When the standpipe pressure has stabilised shut down the pumps but leave the air injection running.

• The standpipe pressure will drop once the pumps have been stopped.• The standpipe pressure will then start to rise as the air begins to compress the fluid.

11. Allow the pressure and volume of the air to build up over ten minutes.12. Commence pumping at the rate that was set before the string was pulled from the hole.13. The standpipe pressure will increase, peak, and then drop.14. When the standpipe pressure has peaked and starts drop shut down the pump but leave the air

injection running.15. Repeat steps eleven and twelve.16. Continue pumping and monitor the kill line pressure and temperature for twenty minutes.


If circulation is regained:-

17. After twenty minutes there will be a rise in kill line pressure and return flow to the shakers.18. Space out the drill string so the blow out preventers can be used if required.19. If the kill line pressure is getting close to the safe operating pressure of the rotating head then

close the Annular preventer to protect the rotating head.20. The kill line pressure will reduce for a few minutes and increase again as the second air bubble

comes to surface.• This bubble will have a higher kill line pressure than the first.

21. Set the air injection and foam rates back to the rate that was set before the string was pulled from the hole.

22. Allow flow rates and pressures to stabilise for half an hour.23. Bypass air and stop pumping at the same time.


This prevents back pressure and possible damage of the booster and compressors )• CLOSE valve number two. ( Stops air delivery to standpipe )• OPEN valve number three. ( Releases pressure from standpipe into the Blooie line )

24. Allow standpipe pressure to bleed back to zero.25. Break out top drive.

• Make sure that floorman are well clear as there may still be trapped pressure in the drill string.

26. Screw top drive into next single and add to the drill string.27. Introduce air and start pumps at the same time.


28. Set pumps back to previous parameters.29. Allow pressures to stabilise before running in hole.30. Repeat steps twenty three through twenty nine until bottom is reached.31. Add string floats to the string every one hundred and fifty metres.


If circulation is not regained:-

32. Bypass air injection:-Steps to bypass air at manifold:-

• OPEN valve number one. ( Bypasses air delivery from standpipe into the Blooie line. This prevents back pressure and possible damage of the booster and compressors )

• CLOSE valve number three. ( Stops air delivery to standpipe )• DO NOT OPEN valve number three



34. Stop pumping remove single and string float from drill string35. Pull back fifty metres.36. Repeat steps one through sixteen.

• If circulation is regained repeat steps seventeen through thirty one.• If circulation is not regained repeat steps thirty two through thirty six.

If circulation has not been regained at two hundred and fifty metres off bottom :-

37. Bypass air injection:-Steps to bypass air at manifold:-

• OPEN valve number one. ( Bypasses air delivery from standpipe into the Blooie line. This prevents back pressure and possible damage of the booster and compressors ).

• CLOSE valve number two. ( Stops air delivery to standpipe ).• DO NOT OPEN valve number three.• Stop foam injection.



39. Stop pumping remove string float from drill string40. Run in the hole to bottom.41. Install string float one single off bottom.42. Start pumping at the rate that was set before the string was pulled from the hole.43. Introduce air into the circulating system through the air manifold by:-

• Opening valve number two.• Closing valve number one.

44. Start air injection at the rate that was set before the string was pulled from the hole.45. Commence drilling.

Monitor kill line and standpipe pressures as there is a possibility that circulation is regained.


3. Equipment Incorporated into BOP Stack:-

When drilling with aerated fluid extra components have to be added to the blow out prevention package. These items are known as:-

• Banjo Box – a tee installed between the rams and the annular B.O.P components.• Isolation Valve – a 10” valve used to close off the banjo box outlet from the B.O.P stack.• Throttle Valve – a 10” valve used to hold back, or choke the return flow from the well

installed down stream from the Isolation Valve.• Blooie Line – a 10” flow line from the Throttle Valve to the separator. • Rotating Head – Used to seal off the top of the B.O.P. stack.

Aerated Drilling BOP Stack Configuration:-

Because the well is in a near balanced state when drilling with aerated fluids it is important to pay close attention to the return temperatures, pressures, and volumes to maintain control of the well.


4. Aerated Drilling Equipment:-

Air compressors and a booster are used to inject the air and foam into the standpipe. This is done through a manifold.It is important to operate the valves on the manifold in the correct sequence to prevent back pressure at the booster that will damage the air equipment.

Return flow from the well travels along the Blooie line and up into the separator. The separator allows the air to be released from the fluid. The air is released through the exhaust into the atmosphere while the fluid is returned to the shaker screens. The separator can be bypassed if the return flow of fluid from the well over loads the unit and begins to exit the exhaust.

Separator:- Throttle Valve:- Air Manifold:-


5. General Notes:-

String floats are added into the drill string at one hundred and fifty metre intervals to reduce the amount of time require to bleed down the standpipe pressure. This in turn reduces the amount of time there is no cooling fluid at the drill bit.

The purpose of the throttle valve is to hold back pressure on the well bore to prevent the well from becoming under balanced and flowing. The back pressure also keeps formations stable.

The Isolation valve is a safety devise used to isolate the blooie line from the well bore. It should be in the fully open position when operating with aerated fluids. The valve will become washed out if left partly closed.

Foam is added to the circulating system to assist in the transport of cuttings from the well bore and maintaining circulation.

When changing the circulation parameters it is best to make small changes of one parameter at a time and allow the change to circulate through the well. This will prevent the well from surging. If surging takes place the operator will end up continually changing the parameters and fighting for control of the well.

Changes to the pumps will alter the well temperature quicker than changes to the air injection. If the well temperature increases rapidly, increase the pump rate to counter the increase. But again allow the change to circulate through the system.

The sprinkler on the rotating head should be kept running while drilling with aerated fluids, as this cools the rotating head and the BOP stack.

If the return temperature increases the rotating head pump maybe require to cool the rotating head and Annular. The flow from this pump should be monitored to prevent the well from being quenched.

While drilling it is important to remember that compressed air and high fluid temperatures are present. These elements require respect and drill crew should be alert and not become complacent.

When drilling with aerated fluids the bit should be run without jets ( open ).


Iceland Operating Procedures

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