Seismic Imaging of Seneca and Cayuga Lakes:

Christopher A. ScholzSyracuse University cascholz@syr.eduhttp://rifts.syr.edu

New York State Museum

Financial support from New York State Energy Research

Development Authority

In-kind processing support fromSterling Seismic Services, Ltd.

Collaborators:

Syracuse Univ.Chris ScholzMike McGluePeter CattaneoKiram LezzarNick PetersBob LyonsRJ HartwellPhil Arnold

Hobart-WilliamSmith CollegesJohn NicholsJohn AbbottJohn Halfman

New YorkState MuseumRich NyahayJustin DemingCourtney LugertRose SchulzeBrian Slater

Cruise participants:

Earth Satellite Corp.,1997, Remote Sensing and Fracture Analysis for Petroleum Exploration of Ordovician to Devonian Fracture Reservoirs of New York

Outline• Small Lake Seismics: Acquisition issues

and parameters: Practical experiences from the Finger Lakes

• Data processing efforts

• Preliminary interpretations and key geologic features

• The October ’02 Survey – what worked and what didn’t

Acquisition Parameters

• Approach: Simpler is better!!!

• 24-bit recording

• 12-fold data

• 12.5 m groups; ~625 m total offset

• 5 m streamer depth; 2 m gun depth

• Differential GPS acquisition (sub-meter accuracy)

• Streamer leveling: Digicourse Birds

Acquisition Equipment• OYO DAS-1 48-channel, Digital Seismic

Acquisition System

• ELICS Delph2 high-resolution seismic acquisition system (for real-time QC)

• 2 x 40 c.i. I-O Sleeve Gun airgun array

• Portable diesel-powered seismic air compressors (58 SCFM total)

• Single channel streamer (for real-time QC)• 48 Ch. 600 m (active) ITI Stealth array seismic

streamer w/ 150 m lead-in (Primary Streamer)

Acquisition Challenges

• Small vessel

• Short (but solid!) streamer

• Crooked line navigation

• Limited compressor capability….

• Streamer levelers marginal at slow shooting speeds

• Limited daylight

• Recreational boaters

• Environmentally sensitive setting

Hobart William Smith CollegesR/V William Scandling, Seneca Lake

I-O Sleeve Gun Array

(2 X 40 c.i. guns)

I-O Sleeve Gun Array

(2 X 40 c.i. guns)

I-O Sleeve Gun Array

(2 X 40 c.i. guns)

~95 km total acquisition:Cayuga, Seneca – two axial lines each

The October ‘02 Survey

Data Processing

• Initial processing by SU, subsequent intensive processing by Sterling Seismic Services, Ltd.

• Significant changes between

Brute stack

Enhanced stack

Kirckhoff Migration

Kirckhoff Migration + FK-filtering

Data Processing• Crooked line geometry• High-resolution radon demultiple routine• Kirckoff migration• FK filter

Brute stack

Enhanced stack

Kirckhoff Migration

Kirckhoff Migration + F-K Filter

Lineaments

Faults

Tracklines

InferredFault

Enhanced stack – full line

Initial Observations• Up to 200 m of Quaternary fill• Bedrock surface follows regional dip• Rugged bedrock topography – tracklines not uniformly on

top of bedrock thalweg• Considerable relief on high-amplitude events below

Quaternary fill !?!• Offsets on Paleozoic reflections – 20 ms or more

Enhanced stack – full line

Exposed bedrock

ApparentOffsets

Survey Challenges – Post-mortem• Seismic source constraints – not a limiting factor

• High velocity section – perhaps the major issue; longer streamer preferable

• Thick Quaternary fill and narrow bedrock valley – side echo effects not a major problem, but complex bedrock surface morphology had major impact

• Limited budget and cruise window – processing budget; cruise window limiting factor = amount of daylight available

• Limited number of nearby wells, with full log suites