SEISMIC DATA PROCESSING REPORT FOR CENTRAL …

SEISMIC DATA PROCESSING REPORT

FOR

CENTRAL PETROLEUM LIMITED

Location : Amadeus BasinPermit : EP 97Surveys : Pellinor 2D Date : September 2012

Fugro Seismic Imaging Pty Ltd69 Outram Street

West Perth WA 6005

Tel: +61 (0)8 9322 2490Fax: +61 (0)8 9481 6721

E-mail: [email protected]

FUGRO SEISMIC IMAGING PTY LTD

TABLE OF CONTENTS

1 INTRODUCTION..........................................................................................................................................................3

PERSONNEL................................................................................................................................................... 3

2ACQUISITION PARAMETERS.................................................................................................................................4

3SURVEY MAP.................................................................................................................................................................5

4LINE SUMMARY...........................................................................................................................................................6

5 PARAMETER TESTING.............................................................................................................................................7

6PROCESSING SEQUENCE DIAGRAM...................................................................................................................8

7PROCESSING SEQUENCE.........................................................................................................................................9

7.1TRANSCRIPTION...................................................................................................................................... 97.2GEOMETRY............................................................................................................................................... 97.3PHASE CONVERSION.............................................................................................................................. 97.4GAIN RECOVERY..................................................................................................................................... 97.5REFRACTION STATICS............................................................................................................................ 97.6TFDN (SHOT DOMAIN)............................................................................................................................ 97.7CDP GATHER.......................................................................................................................................... 107.8TFDN (CDP DOMAIN)............................................................................................................................ 107.9SWNA....................................................................................................................................................... 117.10DECONVOLUTION................................................................................................................................ 117.11 FIRST PASS VELOCITY ANALYSIS..................................................................................................127.12 FIRST PASS RESIDUAL STATICS......................................................................................................127.13 SECOND PASS VELOCITY ANALYSIS..............................................................................................127.14 SECOND PASS RESIDUAL STATICS.................................................................................................127.15 SCAMP...................................................................................................................................................... 137.16 PRE-STACK TIME MIGRATION 1 (PSTM)........................................................................................137.17 3RD PASS VELOCITY ANALYSIS.......................................................................................................137.18 PSTM 2.................................................................................................................................................. 137.19 NMO CORRECTION............................................................................................................................. 137.20 MUTE.................................................................................................................................................... 137.21 PRE-STACK EQUALISATION...................................................................................................................... 147.22 STATICS................................................................................................................................................ 147.23 CDP TRIM STATICS............................................................................................................................. 147.24 COMMON DEPTH POINT STACK.......................................................................................................147.25 IQFILT................................................................................................................................................... 157.26TAU-P DIP FILTER................................................................................................................................ 157.27 BAND PASS FILTER............................................................................................................................ 157.28 POST STACK SCALING....................................................................................................................... 15

8 PROCESSING SEQUENCE DISPLAYS................................................................................................................16

9 FINAL DISPLAYS.......................................................................................................................................................18

10 ARCHIVES..................................................................................................................................................................18

11 DATA DISPOSITION TO CENTRAL PETROLEUM.....................................................................................18

12 TYPICAL SEGY EBCDIC TRACE HEADERS OF PSTM GATHERS.......................................................19

13 CONCLUSION...........................................................................................................................................................20

2012 Central Petroleum Pellinor 2D Processing Report 2

1 INTRODUCTION

The 2012 Central Petroleum 2D Seismic Survey in the Amadeus Basin was processed by Fugro Seismic Imaging at its Perth office from August to September 2012.

A total of approximately 96 km of new data was acquired.

FSI received 1 x LTO2 cartridge of field data on 1st August 2012.

Field data was acquired by Terrex seismic crew 401 during July 2012.

PERSONNEL

Fugro Seismic Imaging Pty Ltd

Jennifer Allen Processing Geophysicist

Mick Curran Processing Geophysicist

Alex Tan Senior Geophysicist

Central Petroleum Limited

Nathan Palmer

Jacques Sayers


2 ACQUISITION PARAMETERS

2012 Central Petroleum 2D Seismic SurveyData recorded by: Terrex seismic crew 401

Date recorded: July 2012

Seismic source: VibroseisSource array: 3 in line over 25mVibe spacing: 12.5 m pad to pad

Vibe move up: Standing sweeps no move upSweeps per vp: 1

Sweep frequency: 570 HzSweep type: Mono, 300ms start taper, 200ms

end taperVp interval: 25 m

Recording system: Sercel 428Record length: 12 sec sweep + 6 sec listen

Sample rate: 2 millisecondsTape format: SEGD 8058Field filters: 0.8 to NQ

Data channels: 480Coverage: 240 fold

Geophone type: SM24 10 HzGeophone array: 12 in line centred on stationElement spacing: 2.08 m

Group interval: 25 mSplit spread: 5987.512.5vp12.55987.5


3 SURVEY MAP


4 LINE SUMMARY

Pellinor 2D Survey

Line Name First Stn Last Stn Length (km)PHR12-01 200 780 14.525

PHR12-02 858 200 16.475

PHR12-03 200 938 18.475

PHR12-04 646 200 11.175

PHR12-05 200 750 13.775

PHR12-06 200 1057 21.450


5 PARAMETER TESTING

The acquisition parameters were similar to the 2010 data so some processing parameters could be used here.

The processing test sequence included review of the following standard processing phases and parameter choices:

● Initial gain correction to compensate for spherical divergence and absorption losses.● Time Frequency DeNoise (TFDN) in both shot and CDP domains.● Surfave Wave Noise Attenuation (SWNA) in both shot and CDP domains.● Surface Consistent Deconvolution (SCDCN) at 2 different stages of noise attenuation processing using 4ms or 12ms gaps.● Surface Consistent Amplitude Compensation (SCAMP).● Random Noise Attenuation (RANNA)● KIRCHHOFF Pre-Stack Time Migration (PSTM)● Post stack enhancement tests● Angle Mutes-angle stacks created using 0-10 degrees, 10-25 degrees, 25-40 degrees and 0-30 degrees. These were not used in the main processing flow. Diagram below shows angles 10-50 degrees inc 10 and T-X mute.


6 PROCESSING SEQUENCE DIAGRAM

FIELD TAPE TRANSCRIPTION↓

NAVIGATION DATA MERGE WITH SEISMIC↓

GEOMETRY COMPUTATION, QC AND APPLICATION↓

PHASE CONVERSION↓

GAIN RECOVERY↓

STATICS APPLICATION TO FLOATING DATUM↓

TFDN↓

CDP SORT↓

TFDN↓

SWNA↓

DECONVOLUTION↓

1st PASS VELOCITY ANALYSIS1st PASS SURFACE CONSISTENT RESIDUAL STATICS

↓2nd PASS VELOCITY ANALYSIS

2nd PASS SURFACE CONSISTENT RESIDUAL STATICS↓

SCAMP↓

PSTM1↓

3rd PASS VELOCITY ANALYSIS↓

PSTM2↓

NMO CORRECTION↓

MUTE↓

PRE-STACK EQUALISATION↓

FLOATING DATUM TO FINAL DATUM↓

CDP TRIM STATICS↓

CDP STACK↓

IQFILT↓

TAU-P DIP FILTER↓

BANDPASS FILTER ↓

POST STACK SCALING


7 PROCESSING SEQUENCE

7.1 TRANSCRIPTION

Field data was converted from SEG-D format to Fugro’s internal format.

7.2 GEOMETRY

Geometry was assigned and survey data used to update trace positions and offsets stored in data trace header.

7.3 PHASE CONVERSION

Convert zero to minimum phase.

7.4 GAIN RECOVERY

A gain function was applied to the dataset to compensate for spherical divergence and absorption losses.Gain = Factor*(T**TPower), where factor=1, TPower=2.6

7.5 REFRACTION STATICS

Refraction first breaks were picked using Green Mountain Refraction Statics Delay Time Method which estimates the refractor velocities to model the weathering thickness. A constant weathering velocity of 1000 m/s was used for statics computation of lines where there were no upholes. Raw refraction statics were tied at intersections by averaging the two intersecting raw values and used as calibration points. An intermediate datum of 100m was used and then a final datum back to mean sea level was calculated using a velocity of 2000 m/sec.

7.6 TFDN (SHOT DOMAIN)

Time frequency de-noise was used to attenuate high amplitude noise visible on the shot gathers. For each shot all traces in a short sliding time window were transformed to the frequency domain. The frequency content of each trace was compared to the frequency content of neighbouring traces in order to identify anomalies. The comparison is working on a single frequency at a time and the phase is not altered. If any frequency component in a given trace is larger than a threshold defined as a fraction of a computed attribute (i.e. Median, Average, Lower Quartile) TFDN attenuates the anomalous amplitude to the frequency of the current trace under investigation to the level of the threshold attribute.


1st Pass TFDN ParametersStart Time (ms) 0

Frequency Range(Hz) 0-250

Horizontal Window(traces) 13

Type/Threshold LQT/4

Time Window(ms) 500

2nd Pass TFDN ParametersStart Time (ms) 500




Time Window(ms) 500

7.7 CDP GATHER

Shot records were sorted into common depth point gathers.Nominal fold = 240, CDP interval = 12.5m

7.8 TFDN (CDP DOMAIN)

Time frequency de-noise was used to attenuate high amplitude noise visible on the nmo corrected cdp gathers. For each cdp all traces in a short sliding time window were transformed to the frequency domain. The frequency content of each trace was compared to the frequency content of neighbouring traces in order to identify anomalies. The comparison is working on a single frequency at a time and the phase is not altered. If any frequency component in a given trace is larger than a threshold defined as a fraction of a computed attribute (i.e. Median, Average, Lower Quartile) TFDN attenuates the anomalous amplitude to the frequency of the current trace under investigation to the level of the threshold attribute.

1st Pass TFDN ParametersStart Time (ms) 400




Time Window(ms) 300

Ramp length(ms) 200


2nd Pass TFDN ParametersStart Time (ms) 0



Type/Threshold MED/4

Time Window(ms) 300

Ramp length(ms) 100

7.9 SWNA

Surface Wave Noise Attenuation is used to attenuate linear ground-roll visible on nmo corrected cdp gathers. The process is applied in the temporal Fourier domain, where a frequency dependent mix of adjacent traces is carried out. The number of traces to mix is governed by the surface velocity, frequency and trace spacing. Only frequencies within a specified range are attenuated.

1st SWNA ParametersFrequency Range(Hz) 0-15

Surface Wave Velocity(m/s) 600

2nd SWNA ParametersFrequency Range(Hz) 0-15


3rd SWNA ParametersFrequency Range(Hz) 0-15


7.10 DECONVOLUTION

A surface consistent deconvolution via the Weiner-Levinson algorithm was used to remove reverberation from the data and whiten the frequency spectrum.

Deconvolution ParametersOperator length(ms) 120

Gap Length(ms) 4

White Noise (%) 0.1


Design WindowsOffset(m) Start Time(ms) End Time(ms)

13 300 3000

2250 1600 3500

5987 2700 4000

7.11 FIRST PASS VELOCITY ANALYSIS

First pass velocities were interpreted using Fugro’s interactive velocity analyses program “MGIVA". Each analysis comprised a 20 CDP stacked panel, repeated 15 times with a different NMO velocity functions. The velocity function displayed at +/-3 %, +/-6%, +/-9%, +/-12%, +/-16%, +/-20% and +25% increments from a central velocity function which was based on a regional velocity function. An interactive velocity analysis routine (MGIVA) was employed displaying colour contoured spectra, a series of stacked functions, plus an interactive stack and gather of the picked function. Further QC tools include a map, isovelocity contours, and displayed surrounding functions. Analyses were performed at 1km intervals.

7.12 FIRST PASS RESIDUAL STATICS

Fugro “NEBULA” Surface-consistent Residual Statics Package computes statics based on summed cross-correlations at source and receiver locations. A pilot trace is constructed at each CDP using a weighted mix of stacked traces. Cross-correlations of the pilot trace with traces in the respective CDP gather are summed into buffers for each source and receiver station number before being resampled and picked to derive a static value.Three iterations were run with a 9-trace pilot, over a correlation window of 1200-3500 ms. The maximum static shift permitted is +/- 25 ms.

7.13 SECOND PASS VELOCITY ANALYSIS

Second pass velocity analysis was performed on gathers with first pass residuals statics applied. The first pass velocity field was used as centre function for Fugro's interactive velocity analysis package, MGIVA. Analyses were performed at 0.5km intervals.

7.14 SECOND PASS RESIDUAL STATICS

Second pass residual statics was run using the picked second pass velocity field as input to NMO corrections.A further three iterations were performed using the same parameters as the earlier residual statics run.


7.15 SCAMP

Surface consistent amplitude corrections. SCAMP is designed to analyse amplitudes in a surface consistent manner. It estimates the amplitude variations due to various components and computes weighting levels for each component, using the Gauss-Seidel iterative method.

7.16 PRE-STACK TIME MIGRATION 1 (PSTM)

Kirchhoff pre-stack time migration using smoothed 2nd pass velocities on 240 equal offset planes from 12.5m to 5987.5m with curved ray tracing option was initially output. These gathers were then input to final pass velocities analysis for final velocity picking.

7.17 3RD PASS VELOCITY ANALYSIS

Third pass velocity analysis was performed on PSTM gathers with both first and second pass residuals statics applied. The second pass velocity field was used as centre function for Fugro's interactive velocity analysis package, MGIVA. Analyses were performed at 0.5km intervals.

7.18 PSTM 2

Kirchhoff pre-stack time migration was rerun using smoothed 3rd pass velocities.

7.19 NMO CORRECTION

Dix fourth order NMO correction was performed using the final velocity functions.

7.20 MUTE

A post NMO outer trace mute was applied for two main reasons :

• to remove any coherent noise on the outer traces and • to reduce contamination from the effect of NMO stretch on the far offsets.


Outer Trace MuteOffset(m) Mute Time(ms)

100 0

300 200

700 400

900 600

1800 1000

2500 2000

6000 2500

7.21 PRE-STACK EQUALISATION

A single window, base levelling, trace by trace scale was applied to the data.

7.22 STATICS

Floating datum to final seismic reference component of the statics is applied prior to stack. This corrects the data from floating datum to a final datum. (see refraction statics 10.7). To avoid losing data above datum, data was time shifted by 500ms prior to static correction to datum and a new time origin of -500ms was established.

7.23 CDP TRIM STATICS

Fugro's “PASTA” package was used to compute cdp consistent residual statics. “PASTA” is an automatic residual statics program which applies static shifts on a CDP consistent basis, using cross-correlations of NMO-corrected CDP gather traces with a CDP pilot trace for each depth point.

7.24 COMMON DEPTH POINT STACK

The traces within each common depth point gather were summed using a Shell style weighted stack as requested and written by the programming department. 240 fold coverage and CDP interval of 12.5 m


7.25 IQFILT

Full inverse Q filtering.

7.26 TAU-P DIP FILTER

Time variant dip filter applied in the TAU-P domain.

7.27 BAND PASS FILTER

Unwanted noise that lay outside the frequency range of the desired reflection and diffraction data were removed by the application of a series of time variant filters.

Band Pass Filter Parameters

Application Time(ms)

Low cut-off(Hz) Lower corner(Hz)

Upper corner(Hz)

High cut-off(Hz)

1500 3 7 50 65

4000 3 7 40 55

7.28 POST STACK SCALING

A dual window AGC with window lengths of 1000 ms and 400 ms was used, with 50% equalisation applied.


8 PROCESSING SEQUENCE DISPLAYSPHR12-02 Brute Stack

PHR12-02 1st Pass Residuals Stack


PHR12-02 2nd Pass Residuals Stack

PHR12-02 Final Stack


9 FINAL DISPLAYSFinal displays of Final filtered stacks were produced in CGM+ format

Horizontal scale: 1 : 40,000 ( 50 traces per inch )Vertical scale: 10 cm/sec

10 ARCHIVESFor all lines on USB DriveFinal Pstm stacks in segy formatFinal filter/scale only Pstm stacks in segy formatRaw final pstm stacks in segy formatFinal velocities in western formatFinal velocities in segy formatCDP / SP coordinate listingsWeathering velocity listingsRaw NMO gathersPSTM NMO gathersFinal Processing Report

11 DATA DISPOSITION TO CENTRAL PETROLEUM

Quantity Tape # Data Media

1 947FA001USB Raw Final Stack,Final Stack,Final Stack-filter/scale only,CGM of Final Stack,CDP Coordinate Listing,Final Velocities-SEGY and Western format,Statics and Weathering Listing,Raw NMO Gathers,PSTM NMO GathersFinal Processing Report

USB


12 Typical SEGY EBCDIC Trace Headers of PSTM Gathers

C 1 CLIENT: CENTRAL PETROLEUM 2012 PELLINOR 2D SEISMIC SURVEY C 2 LINE PHR12-02 PSTM NMO GATHERS C 3 RECORDED BY TERREX SEISMIC CREW 401 JULY 2012C 4 SOURCE: 3 VIB IN LINE CENTRED ON HALF STATION 12m PAD-PADC 5 VP INT : 25m GROUP INT : 25m NO. OF SWEEPS : 1 X 5-70 HzC 6 RECORD LENGTH : 12s SWEEP + 6s LISTEN GEOPHONE TYPE: SM4 10 Hz.C 7 GEOPHONE ARRAY: 12 IN LINE OVER 25 m CENTRED ON STATION C 8 SPLIT SPREAD 480 channels INST.: SERCEL SN428 TAPE FORMAT: SEGDC 9 2ms SAMPLE RATE 240 NOMINAL FOLD COVERAGEC10 PROJECTION : GEOCENTRIC DATUM OF AUSTRALIA 1994C11 **** PROCESSING SEQUENCE ****C12 TRANSCRIPTION FROM SEGD TO FUGRO INTERNAL FORMAT.C13 TRACE EDIT AND GEOMETRY HEADER UPDATEC14 ZERO TO MINIMUM PHASE CONVERSIONC15 AMPLITUDE RECOVERY : SPHERICAL DIVERGENCE CORRECTION C16 STATICS : FLOATING DATUM CORRECTION. REFRACTION STATICS C17 INT DATUM OF 100M AND BACK TO 0M USING VR 2000M/SECC18 TIME FREQUENCY DENOISE + CDP SORTC19 TIME FREQUENCY DENOISE + SURFACE WAVE NOISE ATTENUATION C20 SURFACE CONSISTENT DECONVOLUTION-12ms GAP C21 1st PASS VELOCITY ANALYSIS : 1 KM INTERVALS + 1ST PASS RESIDUALSC22 2nd PASS VELOCITY ANALYSIS : 0.5 KM INTERVALS + 2nd PASS RESIDUALSC23 SCAMP + PSTM1 + 3rd PASS VELOCITY ANALYSIS : 0.5 KM INTERVALSC24 PSTM2C25 NMOC26 FLOATING DATUM CORRECTION : NEW TIME ORIGIN OF -500ms C27 CDP TRIM STATICC29 C30 C31 BYTE DESCRIPTION BYTE DESCRIPTIONC32 ----------------------------------------------------------------------C33 17-20 (32-bit) SP number 91-92 (16-bit) weathering velC34 21-24 (32-bit) CDP number 93-94 (16-bit) refractor velC35 41-44 (32-bit) Elevation 101-102 (16-bit) Receiver static C36 193-196 (32-bit) CDP easting 103-104 (16-bit) Datum staticC37 197-200 (32-bit) CDP northing 109-110 (16-bit) Time of first sample C38 TAPE POLARITY: NORMALC39 CDP - SP RELATIONSHIP CONV,2,201,2C40 CDPS 1 TO 1317 VPS 200 TO 858


13 CONCLUSIONThe 2012 Pellinor 2D data arrived in August 2012 and the final archives and processing report were sent at the end of September 2012.

The data was of good quality and much improvement of the gathers came through noise suppression techniques. Multiple passes of TFDN and SWNA were used prior to migration to attenuate the high amplitude inner trace noise.

Thank you to Nathan Palmer and Jacques Sayers for their feedback and timely replies.

Jennifer AllenProcessing Geophysicist


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SEISMIC DATA PROCESSING REPORT FOR CENTRAL …