Seismic indicators of gas Seismic indicators of gas hydrate and estimate hydrate and estimate

concentrations cooperate concentrations cooperate with well logwith well log

Pichamonch YataPichamonch Yata

510531092 510531092

ProposalProposal Introduce about Gas hydrate basic Introduce about Gas hydrate basic

information and seismic indicatorsinformation and seismic indicators Demonstrate some seismic indicators Demonstrate some seismic indicators

from sample fieldfrom sample field

ContentContent Introduction Introduction

What is gas hydrate?What is gas hydrate? Where is it found?Where is it found? How can find?How can find?

Seismic indicators and Seismic indicators and calculate Saturationcalculate Saturation

ConclusionConclusion

What is Gas Hydrate?What is Gas Hydrate?

• A crystalline solid ; gas molecule surrounded by a cage of water

• Mainly methane

•High concentrate

•low permeability >> gas trap

•New energy resource

•Methane is greenhouse gashttp://www.ifm-geomar.de

Tim Collette, USGS and 2006-2008 Canada-Japan Mallik Project

Where is it found?Where is it found?

can be present in marine sediments as well can be present in marine sediments as well as in permafrost soil of the polar regions. as in permafrost soil of the polar regions.

permafrost >> greensubmarine continental slopesred>> seismic methodsblue>> direct sampling

Gas Hydrate Stability in Ocean Gas Hydrate Stability in Ocean SedimentsSediments

Gas Hydrate Stability in Gas Hydrate Stability in permafrostpermafrost

How can find?How can find?

Seismic Seismic Seismic Profile Seismic Profile Well logWell log

Laboratory Laboratory StudiesStudies sediment samples sediment samples

Seismic indicatorsSeismic indicators

Bottom-simulating Bottom-simulating reflectors (BSRs) reflectors (BSRs)

Seismic ChimneySeismic Chimney Enhanced Reflection Enhanced Reflection

below BSR “Bright below BSR “Bright spots”spots”

Seismic blankingSeismic blanking

Well logs for depth interval 2000–2200 ft, showing two gas hydrate-bearing units penetrated in the Mount Elbert well, northern Alaska.

Lee, M.W., Collett, T.S., In-situ gas hydrate saturations estimated from various well logs at the Mount Elbertwell,Northern Alaska; Marine and Petroleum Geology (2009)

Bottom-simulating reflectors (BSRs)Bottom-simulating reflectors (BSRs)

Cause by negative reflection coefficient gas hydrate exists above the BSR,

whereas below the BSR there is free gas indicating the lower boundary of gas

hydrate stability

Layer1 GHBS

BSR

V1>V2 , ρ1>ρ2

Layer2 Free gas

Z=ρV

R=Z2-Z1 /Z2+Z1

R.D. Hyndman,S.R. Dallimore,2001:Natural Gas Hydrate Studies in Canada;Canadian Society of R.D. Hyndman,S.R. Dallimore,2001:Natural Gas Hydrate Studies in Canada;Canadian Society of Exploration Geophysicists26(2001),11-20Exploration Geophysicists26(2001),11-20

Example of BSR near ODP Site 889 off Vancouver Island showing the simple negative reflection waveform and simple synthetic of BSR

Seismic ChimneySeismic Chimney vertical disturbances in seismic datavertical disturbances in seismic data the upward movement of fluids or free gasthe upward movement of fluids or free gas

Enhanced Reflection below BSREnhanced Reflection below BSR

Negative-polarity reflections or “bright spots”Negative-polarity reflections or “bright spots”

Caused by strong acoustic impedance contrasts due to Caused by strong acoustic impedance contrasts due to free gas trapped beneath hydrate saturated sediment efree gas trapped beneath hydrate saturated sediment e

Acoustic frequency-filtering at the Acoustic frequency-filtering at the BHSZBHSZ

multi-frequency data setmulti-frequency data set

Higher frequencies are more attenuated when the Higher frequencies are more attenuated when the sediment is partially gas-saturatedsediment is partially gas-saturated

seismic blankingseismic blanking The presence of gas hydrate in sediment pore The presence of gas hydrate in sediment pore space that act as cement and reduce the velocity space that act as cement and reduce the velocity and density contrasts between the individual and density contrasts between the individual strata >>decrease in seismic amplitude strata >>decrease in seismic amplitude

Seismic profile from KIGAM data showing seismic chimneys, characterized by columnar amplitude reduction

Ulleung Basin East Sea(JapanSea) Ulleung Basin East Sea(JapanSea)

Seismic profile from KIGAM data showing BSR in debris-flow deposits. BSR is weak and discontinuous. Seismic chimneys are characterized by columnar zones of amplitude reduction.

Seismic profile from KIGAM data showing BSR and enhanced reflections in turbidite/hemipelagic sediments.

Show frequency drops from 47 Hz to 39 Hz across BSR, indicating attenuation of high-frequency energy by gas.

Horozal, S., et al,2009: Seismic indicators of gas hydrate and associated gas in the Horozal, S., et al,2009: Seismic indicators of gas hydrate and associated gas in the Ulleung Basin East Sea(JapanSea) and implications of heat flows...; Ulleung Basin East Sea(JapanSea) and implications of heat flows...; MarineGeology258(2009),126-138MarineGeology258(2009),126-138

seismic section at Blake Ridge, a deep sea sediment drift deposits, seismic section at Blake Ridge, a deep sea sediment drift deposits, United State United State Franco,C.,Valentina,V.,Umberta,T.,2001:Gas hydrate physical properties imaging by multi-attribute Franco,C.,Valentina,V.,Umberta,T.,2001:Gas hydrate physical properties imaging by multi-attribute analysis,Blake Ridge case history;MarineGeology,178(2001),197-210analysis,Blake Ridge case history;MarineGeology,178(2001),197-210

Blake Ridge , United StateBlake Ridge , United State

Showing BSR, enhanced reflections below the BSR and amplitude blanking above it, in Lake Baikal, SiberiaM. Vanneste, M. De Batist, A. Golmshtok, A. Kremlev, W. Versteeg,2001: Multi-frequency seismic study of gas hydrate-bearing sediments in Lake Baikal, Siberia; Marine Geology 172(2001) ,1– 27

Lake Baikal, Siberia ,Russia

M. Vanneste, M. De Batist, A. Golmshtok, A. Kremlev, W. Versteeg,2001: Multi-frequency seismic study of gas hydrate-bearing sediments in Lake Baikal, Siberia; Marine Geology 172(2001) ,1– 27

Rt measured electrical resistivityR0 formation resistivity Ø porosity Sw water saturationsA Archie-coefficientsM cementation factorN depend on lithology , varies between 1.715 (unconsolidated sediment) to 2.1661 (sandstone)

Archie’s lawArchie’s law

Effect of clay in sediments formulaClay correction

By

F is a formation factor for clean sandsac and mc are Archie parameters appropriate for clean sandCv is the volume fraction of clay in solid matrixRc is the resistivity of the clayQc is the effective clay conductivity

Calculate SaturationCalculate Saturation

Gas hydrate saturation is

In case of clean sand Qc=0

ConclusionConclusionTo interpret seismic profile there are many Gas Hydrate seismic indicator such as BSRs , Enhance reflector , Seismic chimney ,Seismic blanking

............................................................................................................

............................................................................................................

..................................

Gas hydrate saturation can calculate from various method such as use resistivity log data by Archie’s law

.....................................................................................................

.....................................................................................................

................................................

Thank you for your Thank you for your kind attentionkind attention

ReferenceM. Riede, P.E. Long, T.S. Collett.,2006:Estimates of in situ gas hydrate concentration from

resistivity monitoring of gas hydrate bearing sediments during temperature equilibration; Marine Geology 227 (2006) ,215– 225

R.D. Hyndman,S.R. Dallimore,2001:Natural Gas Hydrate Studies in Canada;Canadian Society of Exploration Geophysicists26(2001),11-20

M.W.Lee,T.S.Collett.,2008: Integrated analysis of well logs and seismic data to estimate gas hydrate concentrations at Keathley Canyon,Gulf of Mexico; Marine and Petroleum Geology25(2008), 924-931

Lee, M.W., Collett, T.S., In-situ gas hydrate saturations estimated from various well logs

at the Mount Elbertwell,Northern Alaska; Marine and Petroleum Geology (2009)

Horozal, S., Gwang H. Lee ,BoY. Yi, Dong G. Yoo ,Keun P. Park ,Ho Y. Lee ,Wonsik Kim ,,Keum suk Lee, Han J. Kim.,2009: Seismic indicators of gas hydrate and associated gas in the Ulleung Basin East Sea(JapanSea) and implications of heat flows derived from depths of the bottom-simulating reflector; MarineGeology258(2009),126-138

Franco,C.,Valentina,V.,Umberta,T.,2001:Gas hydrate physical properties imaging by multi-attribute analysis,Blake Ridge case history;MarineGeology,178(2001),197-210

Back Up

Three main methods under consideration for hydrateproduction: thermal injection, depressurization, andinhibitor injection.