For

From

© Ikon Science Ltd

A seismic inversion method for fluvial

reservoirs in Southeast Asia

Mark Sams Ikon Science

David Carter Kris Energy

28th April 2017

SEC 2017

2

Motivation

Frequency (Hz)

Am

plit

ud

e

Geology

Seismic

3

Motivation

Aco

ustic im

ped

ance (g

/cm3 x m

/s)

Full-band

AI Inversion

Low spatial

frequency

variations may

arise from poor

spatial sampling

of the well data Yellow / reds =

low impedance After Li & Zhao (2014),

4

Modern day Fluvial Sand Bodies – Analogues of the Sub-surface

Deposits vary from narrow (often

sinuous) ‘shoe-string’ sands to wider

sands with complex internal

architecture

Fluvial deposits often contain abrupt

lateral facies changes due to climatic

variations and the lateral limits of channel

migration prior to avulsion

In the subsurface these often control the

sweep pattern during production

Motivation

5

Productive Fluvial Hydrocarbon Reservoirs from 3-D Seismic

Narrow reservoirs with

internal architecture

that controls sweep

pattern and local

compartmentalization,

Wide, locally composite

reservoirs containing

abandoned channels that

influence the drainage

areas of wells

Reservoir A Depletion Drive

Reservoir B Water Drive

A

B

Well 1 Well 2 Well 3 Well 4 Well 5 Well 6

~3300’ ss, ~3500’ ss,

reds = sands

after Carter (2003),

Motivation

6

Locally adapting LF model

Sand Shale

Porosity Saturation

Acoustic Impedance

Relative Impedance

Absolute Impedance

Impedance Trends

Low Frequency

7

Thailand case

100

ms

Acoustic Impedance gm/cc.m/s

2000 - 12000 2000 - 12000 2000 - 12000 -4000 - 4000 2000 - 12000

8

Thailand case

2000 - 12000

Acoustic Impedance gm/cc.m/s

1.5 - 3.0

100

ms

Vp/Vs

2000 - 12000 1.95 - 2.95

Density gm/cc

1.95 - 2.95 1.5 - 3.0

9

Thailand case gm

/cc.m/s

10

Metrics

1-2-6-12 Hz

LF model from interpolation of first well drilled

Cross correlation 0.75

RMS error 288 g/cc.m/s

LF model from interpretation

Cross correlation 0.94

RMS error 60 g/cc.m/s

Accuracy

11

Issues

12

Issues

13

Issues

14

Limitations

Profiles with no useful seismic response

Issues

15

Seismic velocities m

/s

gm/cc.m

/s

1-2Hz

16

Well locations

CONFIDENTIAL

17

Vietnam

CONFIDENTIAL

18

Thailand

CONFIDENTIAL

19

Vietnam

CONFIDENTIAL

20

Vietnam

CONFIDENTIAL

21

Facies based inversion

CONFIDENTIAL

22

LF models are a very important part of quantitative seismic reservoir characterisation

Standard approach to LF model construction is not suitable for fluvial reservoirs

A locally adapting approach has significant advantages

This approach can be automated through a facies based inversion

Any method requires

Understanding the geology

Understanding the rock physics

Conclusions

Thank you. Any questions?