Trial By Fire: Under balanced Drilling for Horse Shoe ...media.cade.ca.s3.amazonaws.com/trial_by_fire.pdf · 3 Project ReviewProject Review • Four wells to drill in August, 2007

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Trial By Fire: Under balanced Drilling for Horse Shoe Canyon Coals

Trial By Fire: Under balanced Drilling for Horse Shoe Canyon Coals

CADE Conference, June, 2008Ken Holmes, Nexen Inc

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Trial By Fire: Under balanced Drilling for Horse Shoe Canyon CoalsTrial By Fire: Under balanced Drilling for Horse Shoe Canyon Coals

• Project Review• Phase I: under balanced drilling/under-reaming

– Risk management– Review of results– Learnings– Recommended Practices

• Phase II– Planning considerations– Revised risk management– UBD redesign– Implementation

• Summary/Learnings

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Project ReviewProject Review

• Four wells to drill in August, 2007• Drill lower portion of the HorseShoe Canyon under

balanced, using air as a drilling fluid• Establish the feasibility of under-reaming

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WESTASKIWIN ALBERTA LOCATION MAP

WESTASKIWIN ALBERTA LOCATION MAP

Horseshoe Canyon CBM Area

Study Area

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Risk Management Process

The Risk Management Process provides a comprehensive, iterative program to identify and manage risk.

IdentifyHazards Categorize Evaluate Manage Communicate

• Internal• External• Activities/

events

• Technical• Cost• Schedule• Regulatory• Political

• Risk Analysis• Probability of

occurrence• Impact or

severity• Risk level

• Risk Ranking

• Eliminate• Prevent• Mitigate• Effectiveness• Monitor

• Action• Compliance• Reporting

Iterate

Monitor



events





• Risk Ranking



Iterate

Monitor

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Phase I Risk ManagementPhase I Risk Management

Using air in the presence of hydrocarbons: A risk assessment is a necessity

• Hazard ID: Downhole Fire• Categorize: Technical/Cost/Schedule

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• Evaluate: – Likelihood of a fire: once in 10 years

• Methane/air mixture estimated at 1%• No public data available• One down hole fire, it involved wet gas• Identical CBM wells have been drilled with air by our

competitors in the area with no incidents– Consequence: Solely a financial loss to company

• no expected harm to people or environment

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• Evaluation Result: Risk was considered “Low”• Manage: Monitor effectiveness of our program



events





• Risk Ranking



Iterate

Monitor



events





• Risk Ranking



Iterate

Monitor

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Risk MatrixRisk MatrixRisk Matrix (Risk = Consequences x Likelihood)

Consequence Describe below what is the most likely worst possible undesired consequence that might have occurred under slightly different circumstances? For example: A 20 lb. dropped object that narrowly missed a worker on the drill floor, could have resulted in a fatality, and shall be rated as ‘High’, if the likelihood of this consequence is once every 3 years. Similarly, a head-on vehicle collision with minor injuries could have resulted in multiple fatalities, shall be rated as 'High’, if the likelihood is once every 10 years.

Likelihood How often would it be expected to have similar causes or circumstances aligned for this event to reoccur? Please make reference to site, company and industry historical data to help predict the reoccurrence frequency of such an event.

Harm to People Yes/no

Environment Effects Yes/no

Financial loss Yes/no

Impact on Reputation

Yes/no

Severity

A Remote: < once in 40 years

B Unlikely:

Once every 20 years

C Possible:

Once every 10 years

D Probable:

Once every 3 years

E Frequent:

One or more times/yr

Multiple fatalities

Outside spill response assistance required (beyond local co-op Long term impact and clean up required (>5 years)

> $10 million > 60 days business interruption

National or International media attention Shut down of operations by regulators

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Catastrophic

M

M

H

H

H

Single fatality or permanent disability

injury/illness

Outside spill response assistance required (local co-op) Long term impact and clean up required (< 5 years)

$1 to $10 million 30 to 60 days business interruption

Regional media attention Regulatory or legal action taken

4 Critical

L

M

M

H

H

Lost time injury/illness

Company spill response required Localized, short term impact and clean up required (< 2 years)

$500 k to $1 million 5 to 30 days business interruption

Local media attention Regulatory or legal action likely

3 Major

I

L

M

M

H

Modified work or medical treatment

injury/illness

Reportable event

$50 k to $500 k 1 day to 5 days business interruption

Public awareness may exist, but there is no public concern

2 Serious

I

I

L

M

M

First aid injury/illness

Non- reportable event

$5 k to $50 k 4 - 24 hours business interruption

On site communications

1 Minor

I

I

I

L

M

Estimated risk is here

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Phase 1 ResultsPhase 1 Results

• Phase I: Four well program– Planning cycle began in June 2007– Drilling commenced in August 2007– Set production casing on top of the coal– 30 m. open hole section

139.7 mm casing

120.7 mm open hole

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Phase 1 ResultsPhase 1 Results

– Drilled out with air an additional 30 metres, • Used Blackwatch Rig #10 which had it’s own air

compressor• Standard BOP stack on a full opening valve with

rotating head on top• Two float valves in place located just above the bit• Used an air circulation rate of 38 m3/min (1250

scf/min)

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Full opening valve here

Rotating Head

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Phase I ResultsPhase I Results• Drilled four wells in a row with no issues• On the fourth location, we picked up a 48” OD under-

reamer– Modified well design– Opened up the hole from 6.25” to 48”

expose more of the formation– Arms open with centrifugal force,

have carbide cutters177.8 mm casing

159 mm open hole

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Phase I ResultsPhase I Results

• Entered the 6.25” open hole and commenced under-reaming with air, at 5 metres below the casing shoe

• Circulated at 38 m3/min• Made 1.2 metres in 3 hours• Gained torque and pressure: classic signs of tight

hole• Hole packed off and the drill string became stuck

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Under reamerUnder reamer

Harvest Oil Tools,

Denver, Colo.

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• Within 8 hours, filled up the hole with water• Backed off above free point, pulled out• Ran back in with jars, made unsuccessful attempt to

dislodge the fish– history of low success on jarring fish free prior to

washing over

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• Three runs and two days later made 12 metres• Stopped wash over operations after metal shavings

appeared, along with a small amount of coal and cement

• Ran back in with a jarring assembly, and retrieved part of the fish

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Used Washover shoe:Used Washover shoe:

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Bottom of the fish:This used to be a 121 mm drill collarBottom of the fish:This used to be a 121 mm drill collar

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Top of the drill collar:We jarred on this for two hours !!Top of the drill collar:We jarred on this for two hours !!

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Casing ‘fused’ to the drill collar:Casing ‘fused’ to the drill collar:

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Phase I LearningsPhase I Learnings

• Downhole fire: Why did it happen ?– Hole cleaning during under reaming was an issue

• Circulation rate with air was 38 m3/min, annular velocity in the48” hole section was only 33 m/min.

• Circulation rate required to clean the hole was 900 m3/min, for annular velocity of 780 m/min

• Is this possible/manageable ?– Hole packed off

• Coal dust/cuttings were being recirculated• Increased temperature and pressure: compression ignition ?• Cutters on under-reamer could have caused a spark

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• Explosive envelope:– Under atmospheric conditions, methane will burn at 4 –

15 % in air• Methane/air ratio was approximately 1.0 %

– The presence of coal dust, increased temp and pressure widened the envelope.

• Analysis of coal samples showed unusually high likelihood for spontaneous combustion

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– Even though we should have been well outside the flammability envelope, a fire still occurred

– There was no visual indication on surface that a downhole fire was happening

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Phase I Recommended PracticesPhase I Recommended Practices

• If we air drilled in the HSC again, how could the probability of a downhole fire be reduced ?– Don’t under-ream !– Install downstream temperature sensors, connect to

Pason• Verify temperature frequently with Infra-red gun

– Install upstream and downstream pressure sensors, connect to Pason

• Monitor carefully, stop when an increase seen– Design for adequate annular velocity for adequate hole

cleaning

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Phase I Recommended PracticesPhase I Recommended Practices

– Circulate several bottoms up after each connection, prior to drilling ahead.

• During connections, at least half the wellbore could fill up with gas

– Drill with coil tubing– Drilling with mist injection considered, but not was not

done due to the potential for formation damage– Install a fire stop

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Phase II PlanningPhase II Planning

• What now• Planning started September 2007

– Need to drill under balanced– No HSE risk & No Fires !– Keep costs down– Minimize formation damage

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Phase II Risk Management Phase II Risk Management

• Hazard ID: Downhole Fire• Categorize: Technical/Cost• Evaluate:

– Revised risk analysis, if we drill with air– Consequence is the same as before, financial only

• Level 2/5, considered “serious”– Likelihood of a downhole fire is higher

• Considered frequent, one or more times per year– Risk elevated to a “medium” level

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Risk Matrix RevisitedRisk Matrix RevisitedRisk Matrix (Risk = Consequences x Likelihood)

Consequence Describe below what is the most likely worst possible undesired consequence that might have occurred under slightly different circumstances? For example: A 20 lb. dropped object that narrowly missed a worker on the drill floor, could have resulted in a fatality, and shall be rated as ‘High’, if the likelihood of this consequence is once every 3 years. Similarly, a head-on vehicle collision with minor injuries could have resulted in multiple fatalities, shall be rated as 'High’, if the likelihood is once every 10 years.

Likelihood How often would it be expected to have similar causes or circumstances aligned for this event to reoccur? Please make reference to site, company and industry historical data to help predict the reoccurrence frequency of such an event.

Harm to People Yes/no

Environment Effects Yes/no

Financial loss Yes/no

Impact on Reputation

Yes/no

Severity

A Remote: < once in 40 years

B Unlikely:

Once every 20 years

C Possible:

Once every 10 years

D Probable:

Once every 3 years

E Frequent:

One or more times/yr

Multiple fatalities

Outside spill response assistance required (beyond local co-op Long term impact and clean up required (>5 years)

> $10 million > 60 days business interruption

National or International media attention Shut down of operations by regulators

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Catastrophic

M

M

H

H

H

Single fatality or permanent disability

injury/illness

Outside spill response assistance required (local co-op) Long term impact and clean up required (< 5 years)

$1 to $10 million 30 to 60 days business interruption

Regional media attention Regulatory or legal action taken

4 Critical

L

M

M

H

H

Lost time injury/illness

Company spill response required Localized, short term impact and clean up required (< 2 years)

$500 k to $1 million 5 to 30 days business interruption

Local media attention Regulatory or legal action likely

3 Major

I

L

M

M

H

Modified work or medical treatment

injury/illness

Reportable event

$50 k to $500 k 1 day to 5 days business interruption

Public awareness may exist, but there is no public concern

2 Serious

I

I

L

M

M

First aid injury/illness

Non- reportable event

$5 k to $50 k 4 - 24 hours business interruption

On site communications

1 Minor

I

I

I

L

M

We’ve moved to here

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Phase II Risk ManagementPhase II Risk Management

• Manage the risk– Can we find a way to drill the HSC coals with a risk that

is As Low as Reasonably Practicable ?

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Phase II Underbalanced ProgramPhase II Underbalanced Program

• IRP 18: “The only reliable way of preventing fires and explosions is to avoid the formation of flammable mixtures.”– Can’t eliminate fuel or ignition source

• Eliminate oxygen source by using an alternative drilling fluid:– Nitrogen (possible formation damage ?)– methane (difficult to implement, expensive ?)

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Phase II Underbalanced ProgramPhase II Underbalanced Program

• Research showed that drilling with a mixture of nitrogen and max. 4% oxygen would not support combustion and minimize the likelihood of formation damage

• A good solution

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Implementation of Phase IIImplementation of Phase II

• 17 locations were drilled– Blackwatch Rig #10 set surface and production casing– Drilled open hole section with coil and nitrogen/oxygen using a

mobile membrane unit– Hole size reduced to 98 mm

• Better hole cleaning• Lower nitrogen consumption

• Project was a success.– No fires or HSE issues– Well performance was not compromised.

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Coil Tubing DrillingCoil Tubing Drilling

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Coil TubingCoil Tubing

Complete rig out in 45 minutes !

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Summary/LearningsSummary/Learnings

• Downhole fire occurred while under-reaming– The well was lost. No injuries or environmental issues– Possible cause was inadequate hole cleaning, combined with

elevated temperature, pressure and the presence of methane, coal dust

• Drilling with air: mitigative steps are available– Cost savings didn’t justify the associated risk

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Summary/LearningsSummary/Learnings

• To eliminate the risk, oxygen must be removed or lowered to less than 4%– Drill with nitrogen or methane

• Use caution when evaluating where you believe your downhole conditions are in the explosive envelope

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Documents

Trial By Fire: Under balanced Drilling for Horse Shoe ...media.cade.ca.s3.amazonaws.com/trial_by_fire.pdf · 3 Project ReviewProject Review • Four wells to drill in August, 2007