seismic reflection - aig.org.au · pdf fileseismic reflection deep and meaningful ... "a...

Presentation to AIG Melbourne 7 July 2015

Seismic ReflectionDeep and meaningful data for mineral exploration,

hydrogeology and geotechGreg Turner


Outline

• Role in hydrocarbon exploration• Why has the mineral industry been slow to

adopt?• Opportunities• Case histories• Derisking the application of seismic• Summary


Minerals vs hydrocarbons

Used ubiquitously in hydrocarbon industriesWHY?• Can investigate to large depths• Provides continuous maps of layer

boundaries and structures• High Resolution• Maintains resolution with depth

Used rarely in minerals industryWHY NOT?• Lack of effectiveness• Lack of need• Cost


1 Lack of Effectiveness

Hard rock seismic is hard!Complex 3D geometry and high velocity rocks requiresignificant adaptions to the technology which hasevolved in soft rock environments

Much progress has been made• More channels → higher fold• Customised processing• Interpretation experience

Slow to Adopt and Adapt - WHY?


2 Lack of Need

Drilling program to 200m:$15K/hole

Drilling program to 400m:$60K/hole

Drilling program to 1000m: $200K/hole

Typically for seismic:

Depth ► Source and Receiver ► Costspacing



3 Cost

Cost has massively reduced in last 20 years due to:• Chinese manufacturing• Increased computing powerSeismic is still expensive compared with other geophysical methods

2D ≈$10K/km 3D ≈$200K/sq kmBUT provides different information• Can investigate to large depths• Provides continuous maps of layer boundaries and structures• High Resolution• Maintains resolution with depth



The opportunity

• Faster screening around initial discovery

• Better conceptual understanding of geology andmineralisation

Optimise infrastructure capacity andplacement

More cost effective brownfields exploration

• Better mapping of structures for mine planningand mine safety


Resource growth over time


Mt Marion

GGrove

KanownaKambalda

Sunrise DamWallaby

Argyle

Ranger

Century

Cannington

Beverley

Marsden

2D Survey

3D SurveyLeinsterAgnew

CSM, IGO, LanfranchiForestania

Jundee

Telfer

Vulcan

McArthur

Tanami

Plutonic

Ballarat

Pilbara

DeGrussa

Paulsens

Tropicana

Pajingo

Cracow

CarrapateenaProminent

Hill

Hillside

Bullabulling

Rosebery

Australian minerals seismic surveys

Tennant Ck


Case history – Neves CorvoCopper–Zinc


Obrien keyslides extract_003Obrien keyslides extract_003

6 known orebodies

Are there any more?Prospective geology

700m+


Obrien keyslides extract_002


3D survey grid over mine


"A high-resolution 3D seismic survey has now beencompleted over a 21 square kilometer areasurrounding the Neves-Corvo mine. Preliminary resultshave clearly imaged the major Semblana deposit,verifying the effectiveness of this new tool in thesearch for blind massive sulphide deposits"Lundin Mining news release to theToronto stock exchange. July 21, 2011


Case Study 1: Cracow– Locating structures hosting mineralised veins

Back Creek Sedimentsoverlie western endof line


From Corbett 2002

Epithermal systems

chaotic,sub-verticalveins

alteration


AI1 AI1

AI2 AI2

AI2 > AI1 AI2 >> AI1

AlteredFragmentals

AlteredAndesiteLava

Fragmentals

Andesite Lava

SeismicProcessing

AGC Processing Partially Preserved AmplitudeProcessing

Preserved amplitude processing


Cracow – 2D seismic

8km

2km


Cracow – 2D seismic interp

8km

2km1

2

3


Cracow – recent drilling


Cracow - Vertical Section from3D Seismic Cube

Preserved Amplitude Processing

1 km

OverlyingVolcanics

InterbeddedAndesitic Lavasand Fragmentals

Increasingalteration

Reflections due to acoustic impedance (density*velocity) change across boundarybetween fragmentals and lavas


Vertical Section from 3D Seismic CubeEpithermal Gold Vein System

1 km

Location of gm-m intersections±50 m either side of section

Mineralised vein. Faultedoffset, clay alteration


Depth slice at 484m

(Adapted fromKlein2014)

Horizontal section from3D seismic cube


Horizontal section from3D seismic cube

Depth slice at 484mGrey lines represent faults, some of whichcorrespond to the location of known faultsand epithermal orebodies

(Reproduced fromKlein2014)


"Significantly the 3D seismic survey maps the location of bothknown fault/vein systems as well as a significant number of otherfaults likely to host epithermal veins. This is potentially abreakthrough technology to map complex fault and vein systemsand together with other geologic parameters directly target partsof the fault likely to host gold mineralisation.

The current and planned drill programmes are the critical test inenabling Evolution to compress the timeframes for newdiscoveries around Pajingo and Cracow through the use of 3Dseismic."

Evolution Mining Quarterly Report,30 Sep 2014


Geotech tool– pit wall stability, positioning of shafts, raise bores


Hydrogeological tool– trace acquifers, identify connectivity

From Martin et al 2013


Hydrogeological tool– map internal structure within acquifer

From Martin et al 2013


Is seismic suitable at your site?

Noise Tests,Design Optimisation

Rock PropertyMeasurements

3D Seismic Survey

Vertical SeismicProfiling,Full wave sonic,Source testing,2D seismic

Synthetic Modeling

How do we de-risk aseismic survey?


Rock property measurements

• Measure transit time through core,half core or hand specimen

• Need flat ends• Multiple samples per rock unit


Synthetic modelling

• Wide scattering

• Forward modelling of possiblegeological scenarios is crucialfor survey planning

• 3D effectsImplications for targeting

• Assess what features arepotentially resolvable


Velocity DensityAcousticImpedance

Strongreflectorsin VSPdata

Sonic anddensity logs

Reflector

Reflector

Reflector

Reflector

Reflector

Reflector


VSP

VSP’s provide the macro-scalelinkage betweengeological/petrophysicalvariations and the bulk in-situresponse measured usingsurface seismic reflectiontechniques

reflections

direct wave

dept

h

time


Strongreflectorsin VSPdata

Reflector

Reflector

Reflector

Reflector

Reflector

Reflector

VSP


Open file data sets

Opportunity to re-process based on specific objectives


Summary

TypicalSolution

(Drilling)

Sweet SpotBrownfieldExploration

> ~300m

SeismicSolution

(Seismic +Drilling)

• Data in only 1D.• Slow: 1 month to drill 1km.• Costly: $250K per km.

• Detect structures & alteration.• Directly detect some

mineralisation styles• Cost competitive @ $250K/km2

• Rapid results.• Low environmental impact• Faster 3D targeting of drilling


Steep dips?

• We did a 2D seismic line at Pegasus in the Kundanabelt, and the historic view is that in very steeply dippingstructures you don’t get a lot of information, but the earlysigns from the 2D seismic at Kundana will probably leadus to do a 3D as it very very clearly showed thestructures and enhanced the targets that they aredrilling”.

Stuart Tonkin Northern Star Resources COORIU Explorers Conference, Fremantle February 2015

seismic reflection - aig.org.au · pdf fileseismic reflection deep and meaningful ... "a...

Documents