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Part of the Runge Group Application of Outburst Thresholds to Non-Bulli Seam Mines Application of Outburst Thresholds to Non-Bulli Seam Mines Mark Blanch – Ray Williams 4 th August 2010 Part of the Runge Group Scope Scope Bulli seam thresholds Desorption rate fundamentals Non Bulli seam thresholds Outburst management in thick banded seams Comment and opportunities Part of the Runge Group GeoGAS – our involvement GeoGAS – our involvement Gas content and isotherm testing Quick crush method Desorption Rate Index (DRI) Outburst investigations, risk assessment, OMPs, definition of outburst thresholds Gas drainage design & gas management Part of the Runge Group Early Bulli seam gas content thresholds Early Bulli seam gas content thresholds Lama circa 1991 Desorbable gas content thresholds Structured coal 4 m 3 /t (100% CO 2 ) 8 m 3 /t (100% CH 4 ) Unstructured coal 7 m 3 /t (100% CO 2 ) 10 m 3 /t (100% CH 4 ) Part of the Runge Group Bulli seam threshold origins Bulli seam threshold origins Bulli seam experience Overseas experience (Re; Table 6 of Lamas 1995 paper) Ibbenburen (Germany) 9 m 3 /t (100% CH 4 ) Collinsville EV meter readings of (1 cc/g) translated to about 5 m 3 /t (100% CO 2 ) Part of the Runge Group Desorbable to TDGC Desorbable to TDGC Thresholdsinstructuredcoal CH4 CO2 Desorbablegascontent(m 3 /t) 8 4 Residual(x,m 3 /t) 2 2.4 TotalDesorbablegascontent(m 3 /t) 10(9.4) 6.4 Thresholdsinunstructuredcoal CH4 CO2 Desorbablegascontent(m 3 /t) 10 7 Residual(x,m 3 /t) 2 2.4 TotalDesorbablegascontent(m 3 /t) 12 9.4 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 0 10 20 30 40 50 60 70 80 90 100 % CO2 TDGC (m3/t) Lama Structured Lama Structured at 10-12 m/day Lama UnStructured (Lama1995) CH4 CO2 Dryisotherm 2.21 6.76 Moistisotherm 1.67 3.72 UGcores 2.01 1.96 UGcores(otherlab) 2 2.9 Surfacecores 2.13 1.09 Mean 2 3.27
Transcript
Page 1: Application of Outburst Thresholds to Non-Bulli Seam Mines · 2013. 7. 4. · 4th August 2010 Part of the Runge Group Scope • Bulli seam thresholds • Desorption rate fundamentals

Part of the Runge Group

Application of Outburst Thresholds

to Non-Bulli Seam Mines

Application of Outburst Thresholds

to Non-Bulli Seam Mines

Mark Blanch – Ray Williams

4th August 2010 Part of the Runge Group

ScopeScope

• Bulli seam thresholds

• Desorption rate fundamentals

• Non Bulli seam thresholds

• Outburst management in thick banded seams

• Comment and opportunities

Part of the Runge Group

GeoGAS – our involvementGeoGAS – our involvement

• Gas content and isotherm testing

• Quick crush method

• Desorption Rate Index (DRI)

• Outburst investigations, risk assessment,

OMPs, definition of outburst thresholds

• Gas drainage design & gas management

Part of the Runge Group

Early Bulli seam gas content thresholdsEarly Bulli seam gas content thresholds

• Lama circa 1991

• Desorbable gas content thresholds

• Structured coal

• 4 m3/t (100% CO2)

• 8 m3/t (100% CH4)

• Unstructured coal

• 7 m3/t (100% CO2)

• 10 m3/t (100% CH4)

Part of the Runge Group

Bulli seam threshold originsBulli seam threshold origins

• Bulli seam experience

• Overseas experience (Re; Table 6 of Lamas 1995 paper)

• Ibbenburen (Germany) 9 m3/t (100% CH4)

• Collinsville EV meter readings of (1 cc/g) translated to about 5 m3/t

(100% CO2)

Part of the Runge Group

Desorbable to TDGCDesorbable to TDGC

Thresholds!in!structured!coal! CH4! CO2!

Desorbable!gas!content!(m3/t)! 8! 4!

Residual!(x,!m3/t)! 2! 2.4!

Total!Desorbable!gas!content!(m3/t)! 10!(9.4)! 6.4!

Thresholds!in!unstructured!coal! CH4! CO2!

Desorbable!gas!content!(m3/t)! 10! 7!

Residual!(x,!m3/t)! 2! 2.4!

Total!Desorbable!gas!content!(m3/t)! 12! 9.4!

0

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0 10 20 30 40 50 60 70 80 90 100

% CO2

TD

GC

(m

3/t

)

Lama Structured

Lama Structured at 10-12 m/day

Lama UnStructured(Lama!1995) CH4! CO2!

Dry!isotherm! 2.21! 6.76!

Moist!isotherm! 1.67! 3.72!

UG!cores! 2.01! 1.96!

UG!cores!(other!lab)! 2! 2.9!

Surface!cores! 2.13! 1.09!

Mean! 2! 3.27!

Page 2: Application of Outburst Thresholds to Non-Bulli Seam Mines · 2013. 7. 4. · 4th August 2010 Part of the Runge Group Scope • Bulli seam thresholds • Desorption rate fundamentals

Part of the Runge Group

Thresholds adopted - HelensburghThresholds adopted - Helensburgh

Helensburgh

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TD

GC

(m

3/t

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Lama Structured

Helensburgh

Lama Structured at 10-12 m/day

Lama UnStructured

Part of the Runge Group

Thresholds adopted - AppinThresholds adopted - Appin

Appin

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TD

GC

(m

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Lama Structured

Appin

Lama Structured at 10-12 m/day

Lama UnStructured

Part of the Runge Group

Thresholds adopted – NRE#1Thresholds adopted – NRE#1

NRE #1

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GC

(m

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Lama Structured

NRE#1 Bulli seam

Lama Structured at 10-12 m/day

Lama UnStructured

Part of the Runge Group

Thresholds adopted – West CliffThresholds adopted – West Cliff

West Cliff

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GC

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Lama Structured

West Cliff L1

Lama Structured at 10-12 m/day

West Cliff L2

Lama UnStructured

Part of the Runge Group

Thresholds adopted – TahmoorThresholds adopted – Tahmoor

Tahmoor

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GC

(m

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Tahmoor Unrestricted

Lama Structured at 10- 12 m/day

Tahmoor Structured but limited advance rate

Lama UnStructured

Tahmoor UnStructured but limited advance rate

Part of the Runge Group

Factors of safety ???Factors of safety ???

• Difficulties in clearly defining origins

• Perceptions of absolute accuracy

• Apparent factors of safety

• “…too small to cause any major damage

or endanger life of personnel”

• “….thresholds can be increased by

multiplying by a factor of 1.2 where

development rates are reduced to be 10-

12 m/day..” based on mathematical

modelling undertaken at the time

Page 3: Application of Outburst Thresholds to Non-Bulli Seam Mines · 2013. 7. 4. · 4th August 2010 Part of the Runge Group Scope • Bulli seam thresholds • Desorption rate fundamentals

Part of the Runge Group

GeoGAS approachGeoGAS approach

• A line in the sand, combined with

OMPs and systematic drainage

programs & decision making

processes

• GeoGAS would argue

• No Gas Dynamic Incident are

acceptable

• Geological structures can’t be

defined to the required degree of

certainty

• Development rate has in some

incidents little to do with outburst

initiation

• It is pointless to debate definitions of

outburst. Uncontrolled gas events

require careful consideration

Part of the Runge Group

Desorption RateDesorption Rate

• Outburst thresholds in Australia have been based on gas

content for the past 20 years

• Desorption rate has long been regarded as significant to

outbursting:

• Hargraves EV meter, Polish Desorbometer, V30, …

• CO2 >>> CH4

• GeoGAS DRI900 transfer BU seam thresholds to non-BU seam

mines

Part of the Runge Group

Gas desorption rate isGas desorption rate is

• The rate at which gas diffuses from the coal matrix into the cleat

system, it is effected by:

• Gas content

• Gas composition

• Inherent coal properties

• Particle size

• Moisture

• Temperature

• Described by Ian Gray as “.. a combined measurement of the

crushability of coal, diffusion coefficient and gas content rolled into

one “

Part of the Runge Group

Measuring desorption rateMeasuring desorption rate

• The GeoGAS DRI is

calculated from the

quantity of gas desorbed

after 30 seconds of

crushing a 150 g sample,

normalised to the

measured gas content of

the sample

Part of the Runge Group

Outburst initiationOutburst initiation

• Normal mining is characterised by relatively low gas content

gradient ahead of the face and regular stress distribution

Part of the Runge Group

Outburst initiationOutburst initiation

• Approaching an outburst structure the coal hardens in

response to increased stress, permeability declines and the

gas content gradient steepens

Page 4: Application of Outburst Thresholds to Non-Bulli Seam Mines · 2013. 7. 4. · 4th August 2010 Part of the Runge Group Scope • Bulli seam thresholds • Desorption rate fundamentals

Part of the Runge Group

Outburst initiationOutburst initiation

• With continued mining the highly stressed barrier suddenly fails:

• The stress is suddenly reduced

• The ambient fluid pressure on the coal changes from being mostly above

desorption pressure to suddenly being well below the desorption pressure for

the gas content of the coal

• The rapid increase in gas pressure (free gas) in the fractured coal over comes

the resistance of the weakened coal mass, resulting in the sudden release of

large volumes of gas with entrained coal particles

• The initiation of the outburst is defined by the rate of gas desorption

and in turn the rapid increase in gas pressure in combination with the strength

of the confining coal barrier

Part of the Runge Group

DRI900DRI900

• In assessing gas content data from the Bulli seam using cores derived initially

from West Cliff Colliery it was found that

• The relationship between gas content and desorption rate was linear

• The desorption rate for CO2 was higher than for CH4

• A gas content of 9.5 m3/t (CH4) has essentially the same desorption rate as a gas

content of 6.2 m3/t (CO2)

• The threshold values coincide with a DRI of 900

00112233445566778899

1010

Gas c

onte

nt (m

3/t)

Ga

s c

on

ten

t (m

3/t)

00 200200 400400 600600 800 800 1000 1000 1200 1200 14001400 1600 1600 Gas volume 30 sec crushing 200 g (Gas volume 30 sec crushing 200 g (mlml))

>90% CO2 >90% CO2 <10% CO2 <10% CO2

GeoGAS Fast Desorption method GeoGAS Fast Desorption method

Part of the Runge Group

BU seam checksBU seam checks

Bulli Seam Mines

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16

0 0.2 0.4 0.6 0.8 1

CO2/CO2+CH4

Gas C

on

ten

t at

900 D

RI (m

3/t

)

Gas content threshold @

100% CH4 = 9.4 - 9.7 m3/t

Gas content threshold @

100% CO2 = 6.9 - 7.1 m3/t

DRICalcsAugust2010_MB.xls

Part of the Runge Group

Non Bulli seam thresholdsNon Bulli seam thresholds

• DRI900 has been used to establish outburst

thresholds in the Wongawilli seam, Hunter

Valley seams, Gunnedah and Bowen Basins

seams

• No GDIs regardless of the severity of other

factors

• Thresholds vary by seam and by composition

Part of the Runge Group

WW seam thresholdsWW seam thresholds

• 6.5 – 7.5 m3/t

• 0 – 65% CO2

• Little variation in

desorption rate with

gas composition

Wongawilli Seam

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Ga

sC

on

ten

t a

t 9

00

DR

I (m

3/t

)

Lama Structured (BU)

Wongawilli (T)

Wongawilli (N)

Wongawilli (D)

Part of the Runge Group

Thresholds – Newcastle MinesThresholds – Newcastle Mines

• 10 – 11 m3/t

• 95 – 100% CH4

• 8.4 m3/t

• 80% CO2

Newcastle

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CO2 (%)

Qm

at

900 D

RI

(m3/t

)

Lama Structured (BU)

West Wallarah

Fassifern

Donaldson

Greta

Wallarah / Great Northern

Page 5: Application of Outburst Thresholds to Non-Bulli Seam Mines · 2013. 7. 4. · 4th August 2010 Part of the Runge Group Scope • Bulli seam thresholds • Desorption rate fundamentals

Part of the Runge Group

Thresholds – Hunter Valley MinesThresholds – Hunter Valley Mines

Hunter Valley

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CO2 (%)

Qm

at

900 D

RI

(m3/t

)

Lama Structured (BU) Wambo

Middle Liddell Barrett

Hebden Blakefield, Glen Munro, Woodlands Hill

Kayuga/Mt Arthur Vaux

Bayswater Edinglassie

Part of the Runge Group

Thresholds – Gunnedah BasinThresholds – Gunnedah Basin

• 6.2 m3/t

• 67 - 93% CO2

Gunnedah

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at

900 D

RI

(m3/t

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Lama Structured (BU)

Hoskissons seam

Part of the Runge Group

Thresholds – Bowen Basin (MCM)Thresholds – Bowen Basin (MCM)

Bowen Basin - MCM

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RI

(m3/t

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Lama Structured (BU) Goonyella Middle (N)

German Creek ('C) Q

Harrow Creek Dysart

Goonyella Lower Goonyella Middle (B)

Goonyella Middle (G) Goonyella Middle (M)

German Creek (O)

Part of the Runge Group

Thresholds – Bowen Basin (Rangals)Thresholds – Bowen Basin (Rangals)

Bowen Basin - Rangals

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at

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RI

(m3/t

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Lama Structured (BU)

Aries, Castor, Gemini, Pollux, Orion, Pisces

Newlands Upper

B, C and D

Aries/Castor

Leichhardt ('C)

Leichhardt (E)

Part of the Runge Group

Thick banded seamsThick banded seams

• Characterized by:

• 8 – 11 m thick

• Lithological variation, banded upper

sections

• Outburst thresholds 6 – 7.5 m3/t

• Gas reservoir size 40 – 140 m3/m2

and 30 – 90 m3/m2

Ironstone band

2nd Machine band

WWSS

C Tuff

Part of the Runge Group

Thick banded seams – OB managementThick banded seams – OB management

• Challenges presented by seam

lithology:

• Testing and characterising the gas

reservoir

• Gas drainage

• Outburst barrier definition

• Gas content testing for compliance

• Authority to mine procedures

Ironstone band

2nd Machine band

WWSS

C Tuff

Page 6: Application of Outburst Thresholds to Non-Bulli Seam Mines · 2013. 7. 4. · 4th August 2010 Part of the Runge Group Scope • Bulli seam thresholds • Desorption rate fundamentals

Part of the Runge Group

Closing commentsClosing comments

• DRI900 provides a means of transferring the BU seam thresholds to other seams

utilising seam specific criteria

• The desorption rate method is arguably simplistic but does to some extent incorporate

the parameters of

• Gas content

• Gas composition

• Coal strength

• Diffusivity

• To date it has proven successful in combination with modern gas drainage programs and

rigorous risk management systems

• Hard to see a move away from the gas content / desorption rate based thresholds given

the success achieved to date and the need to validate any new form of threshold

• Ian Gray’s work on thresholds based on potential energy release offers some promise

but at this stage it is not clear that it will provide a practicable or verifiable solution

• The most certain path to raising thresholds is to clearly define unstructured coal

Part of the Runge Group

OpportunitiesOpportunities

• Opportunities that exist to improve our management of the outburst risk:

• Systematic and long term monitoring program of West Cliff & Tahmoor to prove

through quantification the safety of raised thresholds

• Critical assessment of the work done by CSIRO and Gray to determine if it can be

incorporated into mining operations

• Development of our understanding of the causes of variation in measured gas

desorption rates

• Definition of appropriate barrier sizes in non-Bulli seams

• Gas / Outburst risk management in thick banded seams presents itself as one of

the industries next big challenges and is likely to progress our outburst

management practices. It is also likely that Engineering Solutions will precede

scientific solutions

Part of the Runge Group

GeoGASGeoGAS

Part of the Runge Group

Since 1994Since 1994

• Since the last fatal outburst at West Cliff in January 1994 (ex the twin fatality at Mt Davey) and the implementation of OMP

there has been a significant reduction in the occurrence of outburst in Australia

• Ellalong (Greta seam) (1994)

• 5 outburst (up to 30t) associated with bedding plane shearing and high stress

• Measured gas content ranged from 4.9 m3/t to 7.2 m3/t (80 % CO2)

• Mt Davey NZ (Sub Morgan seam) (Nov 1997 – July 1999)

• 21 outbursts, twin fatality (30t) during drift development

• Maximum gas content measured 9.6 m3/t, predominately CH4

• West Cliff (BU seam) (April 1998)

• Outburst on face of LW23, bedding plane fault, up to 22 m3/t 100% CO2

• Tower (BU seam) (Dec 2000)

• Outburst on a dyke during remote mining, up to 13.5 m3/t 92% CH4

• Central (German Ck seam) (20 July 2001)

• Outburst on a strike slip fault, 6.9 m3/t to + 8-9 m3/t 100% CH4

• North Goonyella (GM seam) (22nd Oct 2001)

• Outburst on a strike slip fault, 6.5 m3/t 100% CH4

• Appin (BU seam) (18th March 2002)

• Outburst on a shear structure during remote mining, up to 12-14 m3/t 95% CH4

• Appin (BU seam) (2009)


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