MRC9409016-AJB

POONBOONI

LOG INTERPRETATION

494G01

Andrew BuffinSeptember 1994

CONTENTS

Page No.

Summary 2

Mud System 3

DSTIRFT Summary 3

Core Summary 3

Interpretation Method 4

Formation Water Resistivity 6

Log Permeability 7

Net Reservoir Rock Criteria 7

Conclusions 8

Figures:

1. Pickett Plot 3000-302Sm

2. Core#4 3034-3042.Sm Porosity-Permeability cross plot showing line ofbest fit

3. Porosity-Permeability cross plot for Cores #1-4

Enclosures:

1. Quick look Plot & -s~+s)

2. Ro/Rt & Raw Log Plot

3. SP Dervied Rw

MRC9409016-AJB

SUMMARY

49·1G03

2

Poonboon 1 was spudded on 29 August 1972 and is now located in T/25P, 15km north ofPelican 3 and 40km south of the Yolla gas and condensate field. The well was plugged andabandoned. Poonboon 1 was drilled on the crest of a low relief anticlinal feature. Theprimary objective of Poonboon 1 was to test the hydrocarbon potential of the Eastern ViewCoal Measures.

Only low levels of background gas were reported with an exception at 3183.3-3185.2mwhere the well kicked. The zone is badly washed out (possibly indicating a fracture zone).Testing of the zone by FITs produced low salinity water and small volumes of gas (probablysolution gas).

Poonboon 1 established the presence of good quality reservoirs, however the availability ofadditional seismic since Poonboon 1 was drilled suggests the well was drilled off structure.

A quicklook Terralog analysis was performed using the following logs:

Gamma Ray LogSpontaneous Potential LogSonic LogResistivity Logs (SFL-IND-SN-MLL)Density Log (FDC)Neutron Log (SNP (only available from 2925m-TD»

Interpretation was performed from 2700m (just below the 9% casing shoe) to TD (327Om)and displayed as an analog plot (see Enclosure 1).

The quicklook confirmed a hydrocarbon anomaly at 3180-3185m but was used primarily toestablish log derived porosity and permeability and the potential reservoir character of theEastern View Coal Measures.

MRC940901 6-AJB

MUD SYSTEM (2670-3267m)

Mud Type

Mud DensityMud ResistivityMud Filtrate ResistivityMud Cake ResistivityBottom Hole Temperature

DST/RFT SUMMARY

(Rm)(Rmt)(Rme)(BHT)

494C04

Lignosulphate

12.2 ppg0.868 !JIm @ 89°F0.482 !JIm @ nOF1.22 !JIm @ nOF218°F

3

Eight formation interval tests were performed at Poonboon 1

FIT DEPTH RECOVERY FSIP HP COMMENTS(m) (Psi) (Psi)

1 2670.1 0.1 ft3 gas 3680 4480400.0 em3 water

2 3180.3 1.4 ft3 gas 5700 62002200.0 em3 water

3 3103.2 1000.0 em3 water 6200 Lost pad seat4 2964.8 2200.0 em3 water 4500 58005 3191.3 Misrun6 3048.0 2100.0 em3 water 5000 50007 3178.2 1.1 ft3 gas 5300 53008 3255.3 2100.0 em3 water 5950 5950

CORE SUMMARY

Five eores were eut at Poonboon 1

Core Interval Reeovery(m) (%)

1 1952.9-1960.5 962 2467.6-2474.4 1003 2682.8-2690.5 1004 3034.0-3042.5 1005 3258.6-3265.9 100

494005MRC9409016-NB

INTERPRETATION METHOD

Environmentally corrected log data were evaluated using a quicklook log analysis method.

4

Parameter

*Porosity

Shale VolumeTrue ResistivityShale ResistivityWater SaturationTortuositySaturation ExponentCementation Exponent

(c/»

(Vsh)(Rt)(Rsh)(Sw)(a)(n)

, (m)

Derivation/Value

A minimum porosity value (derived from Sonic,Neutron and Density logs and a **Petra derivedporosity)Petra derived shale volumeILD-SFL-Rxo Tornado chart120/m***Indonesian Equation1.02.02.0

*Porosity:

** Petra:

An important feature of this analysis is to determine the reservoir quality ofthe Eastern View Coal Measures. Minimal core data is available to correlatelog with core porosity, therefore log derived porosities were calculated from:

1 Hunt-Raymer Sonic Equation (Shale Corrected)2 Neutron-Density Crossplot Equation (Shale Corrected)3 Petra derived porosity resolved by solving a set of linear equations

A minimum porosity was created from the existing defined porosities by takingthe minimum porosity from all the selected porosity channels.

The porosity used in this analysis represents a pessimistic value.

The Petra algorithms are simple matrix algebra procedures. Log responses arerelated to the sum of the proportions of the components each multiplied by theappropriate response coefficients in a series of simultaneous equations.

A simple Petra example for a Sandstone-Shale-Porosity system using onlydensity and sonic logs is:

Number of componentsNumber of logsThe n log equation is:

m = 3n=2

2.65 Vsst + 2.56 Vsh + 1.00 phi = density log55.5 Vsst + 81.0 Vsh + 189.0 phi = sonic log

where

Phi = vpor

MRC940901 6-AJB

*** SW:

4940065

Because of material balance the proportions of the components must sum tounity. Rewriting the above equation in matrix algebraic terms:

CV = L

C V = L

2.65 2.56 1.0 Vsst Density log55.5 81.0 189 Vsh Sonic log1.0 1.0 1.0 phi 1.0

This example is a uniquely determined system ie when the numbers of logs isless than the number of components by one, and is the most common matrix·method used for the calculation of porosity and component proportions.,

Water saturatIons are calculated using the Indonesian Equation.

where

(Rsh/Rt)05+ (Rt/Ro)05 ) ('if.)

Ro =

a =<I> =m =Rw =Vsh =Rsh =Rt =n =

a* Rw<l>m

Tortuosity (1.0)Input porosity (from minimum porosity value)Cementation factor (2.0)Formation water resistivity (temperature corrected)Shale volume (from Petra)Shale resistivity (from log data)ILD-SFL-Rxo Tornado chartSaturation exponent (2.0)

MRC94090I 6-AJB

FORMATION WATER RESISTIVITY

4940076

It was assumed that at Poonboon 1 all sands were water saturated though it appears that theFormation Water Resistivity (Rw) varies within the Eastern View Coal Measures. Anaverage Rw value has been used in the Poonboon 1 analysis to establish an Sw that honoursthe known engineering data.

The Rw was established from

Ro/Rt

Rwa

SP

Pickett Plot

Offset well data

If the calculated Ro (Rt (wet» curve and Rtcurve overlay each other a water sand ispresent, if Rt is greater than Ro then.hydrocarbons are present (see Enclosure 2).These logs were used to establish waterzones at Poonboon 1Apparent water resistivity (0.3 !lIm @Formation Temperature (see Enclosure 2)Formation water resistivity derived fromthe spontaneous potential log (seeEnclosure 3)0.208 !lIm @ Formation Temperature(Figure 1)

Pelican 5DST 5 (2855-2860.5m)4000 ppm NaCI equivalentRw = 1.39 !lIm @ 75°F

= 0.42 !lIm @ Formation Temperature

DST 5A (2869-2883m)6000 ppm NaCI equivalentRw = 0.98 !lIm @ 75°F

= 0.32 !lIm @ Formation Temperature

DST 6 (2786-2790)7500 ppm NaCI equivalentRw = 0.8 !lIm @ 75°F

= 0.27 !lIm @ Formation Temperature

Given all the data available an average Rw value used for Poonboon 1 was:

Rw = 10000 ppm NaCI equivalent= 0.58 !lIm @ 75°F= 0.2 !lIm @ Formation Temperature (218°F)

/...,,,

I_.,,.--(•,II}

1,<..

Scm

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X X

X

X:x.

':<jj'~:x~xxX x 'I<~"

x XX~ ~.X X

XXX

3000 - 3025mPICKETT PLOT

FNi '"' 0.208 ohmmX AXIS =RESISTIVITYY AXIS =POROSITY

) ) ) ) )) ) ) ) )

J I-J

PORMIN .5RT 200

•"

FIGURE 1

MRC9409016-AJB

LOG PERMEABILITY

7

Limited core data allowed a core permeability versus core porosity crossplot to beconstructed see (Figure 2). A line of best fit resulted in the following relationship betweenpermeability and porosity:

Y = 13.67 + 3.26 * (oglo X

where

Y = core porosity (</»X = core permeability (k)

10glO = Y - 13.6!

3.26

X = 1O(Y - 13.67 )3.26

After substituting core porosity for log porosity a log permeability curve was derived.

Combining the log derived porosity and permeability allows us to establish potential paysands within the Eastern View Coal Measures (see Enclosure 1).

NET RESERVOIR ROCK CRITERIA

Two cases were used to establish potential reservoir rock

A Pessimistic Case

~Log Porosity (</» > 15% 1Log Permeability (k) > 10 mdShale Volume (Vsh) < 40%

~B . Optimistic Case (using cores 1-4 porosity-permeabil" crossp10t data

(Figure 3»

! L;/Log Porosity (</» > 10%Log Permeability (k) > 5 mdShale Volume (Vsh) < 40%

Case A Case B

Gross Thickness (m) 550 550

INet/Gross (%) 7 10.5

(m) 39 58Net Sand

---->--.-........_-) )

I) ) ) ) ) ) ) )

FIGURE 2 CORE _4 3034 - 3042.5m POROSITY - PERMEABILITY CROSSPLOT SHOWING LINE OF BEST fiT

\

1000. 00

. 1

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POROSITY - PERMEABIliTY CROSSPlOT FOR CORES .1 - 4

1. 00

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. . .UNEOFBESTi=ff' ;;(coRE .4)

FIGURE 3

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5.00

40.00

20.00

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45.00

30.00

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10. 00

50.00

. 000000

I~Scm .. I

MRC9409016-AJB

CONCLUSIONS

4940128

Porosity values detennined for the Eastern View Coal Measures are the minImum(and therefore most pessimistic) values, note that the log detennined porosity valuesare generally less than the core porosities (Enclosure 1).

The log derived penneabilities being detennined from the porosities, are alsoindicative of pessimistic values although they do show a better correlation with thecore penneability (Enclosure 1).

Net pay uses two cases (Case A is flagged in the depth tracks of Enclosure 1), in bothcases the pessimistically log derived porosity and penneability is used, anyimprovement in the actual porosity and penneability will obviously improve thepotential net pay.

The reservoir characteristics of the Eastern View Coal Measures at Poonboon 1 aregood. The potential therefore exists for multiple stacked sand bodies to exist todepths of 3200m with good porosities and penneabilities.

The fonnation water resistivity (Rw) is variable throughout the Eastern View CoalMeasures as demonstrated by the various techniques used to detennine Rw inPoonboon I. Whilst this was of little consequence at Poonboon I where the well wasobviously water wet, establishing a correct Rw in the Eastern View Coal Measuresreservoirs in gas/oil wells in the Bass Basin is important to establish the correct Sw.

The hydrocarbon anomaly, originally defmed at Poonboon 1 was identified by thisquicklook. It is possible that the anomaly is due to fracturing, this fact is highlightedby the large caliper washout.

Poonboon I was effectively evaluated by the operator and plugged and abandoned,after demonstrating the existence of potentially good reservoir rocks.

T/25PPoonboon 1

Spudded 29/08/72

COMMENTS

COMMENTS

L L HALUKI

U L HALUE!

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T/25PPoonboon 1

Spudded 29/08/725cm

T/25PPoonboon 1

Spudded 29/08/72

5cm

COMMENTS

COMMENTS18lf

Po on boon 1Spudded 29/08/72T/25P

DEPTHETER

49 tlC14

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T/25PPoonboon 1

Spudded 29/08/72

COMMENTSPETRAMAJORLITHO

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O~- 0<39/

T/25PPoonboon 1

Spudded

494G15

29/08/72I~

Scm

I

T/25PPoonboon 1

Spudded 29/08/72GReOR 150 DEPTH

0 Sf .ilLO METERS

3000

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COMMENTS

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3050

3100

_ SP DERIVED RlI16000 PPII NACL BQRlI= 0.38 75DEG FRlI= 0.13 FT

_ SP DBRIVBD RlI13000 PPII NACL BQRlI= 0.42 75DBG FRlI= 0.155 FT

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SP DB RIVED RlI6500 PPII NACL EQRlI= 0.9 75DEG FRlI= 0.3 FT

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3250 _ T LONGUS

DEPTHMETERS COMMENTS

O,':?·CX391 49 f1 G16

T/25P

ScmPoonboon 1

Spudded 29/08/72 I