www.cet.edu.au

Petrophysics:

Local rock properties

Geology:

Structure & rock type

Geologically Conditioned Petrophysical

Constraints in Geophysical Joint InversionJeremie Giraud*, Mark Jessell, Mark Lindsay, Evren Pakyuz-Charrier, Roland Martin and Vitaliy Ogarko;

contact: jeremie.giraud@research.uwa.edu.au

MotivationsNeed to integrate geoscience disciplines to take advantage of complementarities to:

Reduce uncertainty and quantify

Better constrain results

Geophysics: bulk physical

properties of medium

GeologyPetrophysics

Geophysics

Common model

ObjectivesIntegrate geology and petrophysics in a single joint geophysical inversion code

Develop workflow applied in E&P settings to:

Improve geophysical imaging

Provide a formal statistical approach to uncertainty estimation

Methods Statistical description of petrophysical measurements

Use of lithology probability cube obtained from geological statistical modelling

Apply probabilities of lithologies to statistics of petrophysical measurements in joint geophysical inversion

Bayesian inversion framework

Validate workflow doing step-by-step analysis¹Inverse modelling framework²

Statistical analysis of

surface and well data to

constrain inversion⁴

Geostatistical

modelling:

probability for each

lithology³

Statistical frameworkP1

P2

PDFs

A B

A B

A B

A B

A B

A B

ResultsFisher information, Petrophysical Likelihood, model misfit, and Score show reduced

uncertainty on results¹. Each integration step improves results in terms of: Uncertainty,

Geological features of the model, Model misfit. Best results for the most integrated inversion¹

Figure 1: conceptual model for the

integration of petrophysical

measurements, geophysical data

and geological modelling in a single

workflow (circles and top part).

Elements in red tones illustrate how

petrophysics is handled, orange

tones relate to model updates in

geophysical inversion, and images

outlined in green show the

geological model and the

corresponding statistical model.

Conclusion and discussion

Multidisciplinary integration through joint inversion allows

honouring: geological modelling, geophysical data and statistics

of petrophysical measurements.

Tests were ran with real geological data with synthetic

petrophysics and geophysics: should be applied to real scenario

AcknowledgementsWe thank Peter Lelièvre, André Revil, Chris Wijns and Eun-Jung Holden for interesting discussions.

References¹ Giraud J., Pakyuz-Charrier E., Jessell M., Lindsay M., Martin R. and Ogarko V., 2017 (Submitted),Uncertainty reduction through spatially conditioned petrophysical constraints, Geophysics.

² Tarantola, A., 2005, Inverse problem theory and Methods for data fitting and model parameter estimation: Society of Industrial and Applied Mathematics Philadelphia.

³ Pakyuz-Charrier E., Lindsay M. and Jessell M., 2015, Geological models need error bars! Handling uncertainty in 3D geological modelling, Saying Goodbye to a 2D earth conference, Margaret River (Werstern Australia), 2015.

⁴ Sun J. and Li Y., 2013, Petrophysically constrained geophysical inversion using Parzen window density estimation, Extended Abstract, SEG Annual meeting 2013 Houson, doi: 10.1190/segam2013-1163.1

Increasing degree of integration in inversion

Single domain: Unconstrained

inversion

Single domain:petrophysics only

Joint inversion: Petrophysics only

Single domain:Geology and Petrophysics

Joint inversion: Geology and Petrophysics

Idealised model used for

simulations

12

34

5

6A B

2

3

4

5

6

N

A B

(a) (b) (c) (d) (e)

Future work 3D case study: Yerridabasin. Gippsland Basin

Normalized model RMS Error

10.75

0.35

Fisher info. on density contrast (m³/kg)

Fis

her

info

. on m

ag.

susc. 1

0.8

0.6

0.4

0.2

0

Pictures, top figure, from left to right:

Hatfield K. L., Evans A. J. and Harvey P. K. 2002, Defining petrophysical units of the Palmer Deep sites from let 178, Proceedings of the Ocean Drilling Program, Scientific Results. Ocean Drilling Program, pp1-17; Image geophy: http://www.earthexplorer.com/2013/images/VOXI-3Dmap.jpg from

http://explorationgeophysics.info/?cat=8; Anticline: http://facweb.bhc.edu/academics/science/harwoodr/GEOL101/Study/Images/Anticline.gif

Geological model for simulations: 6

lithologies in a cross-section extracted from

a 3D volume obtained from field data.

How to integrate quantitatively: Petrophysics, Geophysics and Geology?

True model

True model