design of surface seismic programs fcosfor co2 storage

Design of Surface Seismic Programs f CO Sfor CO2 Storage Monitoring

Mark S. EganMark S. EganWesternGeco North America Geophysics Manager

Houston

Objectives

Baseline seismic programStructure & stratigraphy of the storage tank & overburdenVolume of the storage tankIs the storage tank is sealed?Barriers within the tankBarriers within the tank

Repeat seismic programsRepeat seismic programsWhere is the CO2 going? Is it escaping?

Objectives of the survey designSurvey design required to meet the above objectivesy g jPermitting restrictions

Agenda

DeliverablesImage of the subsurface

Survey design parameters2D vs. 3D

Image of the subsurface

Rock properties (porosity, etc.)Shooting direction

Narrow azimuth vs. wide azimuth

A t

Geophysical issues

Aperture

Source-receiver distances

SamplingIllumination

Resolution

R t bilit

Sampling

Repeatability

Signal-to-Noise ratio

ImagingImaging

UltrasoundUltrasound3,500,000 Hz3,500,000 Hz

SeismicSeismic35 Hz35 Hz

The Seismic Method Arrival times

Amplitudes

seismic source geophone groups

ρ , Ip , Is

ρ , Ip , Is

ρ I Iρ , Ip , Is

The Seismic Method

2 km – 7 km

0 4 km 6 km0.4 km – 6 km

The Seismic Method

The Seismic Method

“2D survey”2D survey

The Seismic Method

The Seismic Method

“3D survey”3D survey

Illumination

Imaging analogy

Illumination problems from complex overburdens

Imaging analogy

Imaging analogy Shooting directionll h d dAll azimuths needed?


“Narrow azimuth” 3D survey


“Wide azimuth” 3D survey

Survey Design

Ray tracing(Requires an earth model)

Survey Design

Ray tracing(Requires an earth model)

Hit CountHighLow

Hit Count

Illumination maps from a survey design study

Dip Shooting Strike Shooting 45° Shooting

Hit CountHighLow

(A top-salt boundary)

In some surveys, a single shooting direction is not sufficient.

Illumination maps from another study

1-azimuth All azimuthsHit Count

HighLow(A base-salt boundary)

Illumination

Data courtesy of BHP Billiton, Hess Corporation and Repsol YPF

Narrow-azimuth 3D Wide-azimuth 3D

Illuminationseismic survey?seismic survey?

So we see that illumination requirements impact the width of the geophone spread and/or the the geophone spread and/or the number of source points …

what about the size of the … what about the size of the survey?

Aperture

Illuminationseismic surveyseismic survey

Aperture

Aperture

15,000-ft aperture 34,000-ft aperture

So we see that aperture decisions So we see that aperture decisions impact the size of the seismic survey …

what about the influence of aperture … what about the influence of aperture on resolution?

Lateral resolution

Lateral resolution

300 m

400 m

20 m20 m

Lateral Resolution in Imaged Section

Imaging aperture 300 m

20 m gap

Imaging aperture

20 m gap

Imaging aperture 1000 m

Faults and Fracture Networks

Acoustic Impedance Poisson’s Ratio

Faults and Fracture Networks

Acoustic impedanceAcoustic impedance Poisson’s Ratio

An example of monitoring from the North Sea

Started production in 1997Started production in 1997

Gas and water injection

Seismic surveys in 1992, 2001, 2003, …

The 1992 survey used conventional technology

Subsequent surveys used better repeatable technologySubsequent surveys used better repeatable technology

Comparison of the 2001 & 2003 seismic programs

20012003

Comparison of the 2001 & 2003 seismic programs

OWC Waterinjection movementinjection

2003 2003 velocity

“pull-down”

Difference2003

Comparison of monitoring differences

1992-2001 full DP difference 2001-2003 final DP difference

4 years production 2 years production

An additional way to improve resolution

- denser sampling

The Seismic Method


ρ , Ip , Is

ρ , Ip , Is

ρ I Iρ , Ip , Is

The Seismic Method … with denser sampling


ρ , Ip , Is

ρ , Ip , Is

ρ I Iρ , Ip , Is

Example from Texas0 Q-Land

single-sensor data

0

(Decimated)Feet

~3000

Horizontal slice

~1300 ft depth

Example from Kuwait

ProducerProducer

InjectorConventional data – interpretation shows the fluids should flow freely

ProducerProducer

Injector

Q-Land single-sensor data – interpretation shows baffles impeding flow


Amplitudes


ρ , Ip , Is

ρ , Ip , Is

ρ I Iρ , Ip , Is


Amplitudes


ρ , Ip , Is

ρ , Ip , IsReservoir Properties

Li h l

ρ I I

LithologyPorosity

Fluids ρ , Ip , IsFluidsSaturation

Reflection Amp

Log Data

Ip1

I 2 Φ

ΔI

Ip2

Poro

sity

ΔIp

2 IpAvgR =

dIIP ( )PP

P IIdI ln=∫

Reflection AmpSingle-sensor survey

Log Data

ΦPo

rosit

y

porosityIP

0% 32%

porosity

Summary

Survey design parameters2D vs 3D2D vs. 3D

Shooting direction

Narrow azimuth vs. wide azimuthNarrow azimuth vs. wide azimuth

Aperture


Sampling

SummaryN i !!!Noise !!!

Survey design parameters2D vs 3D2D vs. 3D

Shooting direction

Narrow azimuth vs. wide azimuthNarrow azimuth vs. wide azimuth

Aperture


Sampling

Modeled shot record

design of surface seismic programs fcosfor co2 storage

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