Isatis - Geovariances

ISATIS
NEWS
The Universe
Of Geostatistics
Editorial
Isatis plus IsatOil, an Essential
Tandem in Exploration and
Production
Zonal Anisotropy : How to Model
the Variogram
Your Training Agenda
New Features of Isatis 4.0
Geovariances Newsletter N°13 – November 2001 – Oil & Gas
Editorial
ISATIS Version 4 , available now, is the
major end-of-the-year event. It was unveiled
during the 63rd EAGE Amsterdam, SPE
New Orleans and EXPOGEF 2001, Salvador
where meetings and get-togethers confirmed
once again the growing importance of
geostatistics in the petroleum sector.
We were particularly attentive to users' requests
and needs ,
especially:
new possibility of achieving data import and
export in batch mode;
directly readable Isatis datafiles in Gocad® V2;
taking into account of 2D or 3D polygons
for global estimation or volumetrics
calculations;
flattening of grids from structural
to stratigraphic system; …
(to be continued page 4)
If you intend to integrate geostatistics in your
workflow, you should think ISATIS. What other
product can claim to offer so many functionalities
and unparalleled scientific credibility, as proven by
a recent survey of our users
Not to forget that ISATIS is a toolkit that easily
links to all the major interpretation products and
reservoir characterization suites.
Isatis Users : make sure you are a registered user
before downloading version 4 from our website. CD-
ROM also available for shipping.
Where to see us next: 64th EAGE
Conference & Exhibition,
Florence 2002, Italy,
May 27-30, 2002.
Stop at our booth!
Brigitte Hogan
(hogan@geovariances.com)
Isatis plus IsatOil, an Essential Tandem in Exploration and Production
Nowadays, a key issue in the Oil Industry is the uncertainty in the calculation of the volume in place. This uncertainty results
from the combination of the spatial variability and the scarcity of the data. It is particularly important to make an optimal use of
the data of various nature ( deviated wells, seismic maps, complex faulting system, contacts).
ISATOIL has been developed precisely to tackle this problem by applying a consistent multi-layer global approach as
opposed to a sequential approach, whose weakness consists in the propagation of errors from top to bottom.
When the global reservoir system is carefully settled, ISATOIL first estimates the base case for the depths of all the layers
(making optimal use of all the relevant information including deviated wells and seismic time maps through an automated timeto-depth
conversion) and the related variance of estimation.
These layers are also constrained by the (normal) fault polygons as derived from the seismic
time maps and are finally populated with the petrophysical parameters (only considering
their lateral variations).
In a second phase, ISATOIL uses the geostatistical simulation technique in order to
produce a set of equiprobable models. Moreover each model is consistent with all the well
information (TVD of layer intercepts as well as petrophysical measurements) and the fault
system. Thus it makes sense to calculate the volume (within given polygons) for each layer
of the reservoir and each simulation outcome, which leads to a volume probability curve.
Both phases require the prior definition of a geostatistical model that can be inferred within
ISATOIL using automated procedures.
These functionalities make the integrated package ISATOIL be the geostatistical solution for the assessment of uncertainty in
the volume calculation for Oil industry.
Didier Renard (renard@cg.ensmp.fr -Centre de Géostatistique, Ecole des Mines de Paris)
49 bis avenue Franklin Roosevelt – BP91 – 77212 Avon Cedex, France – Phone : +33 (0) 60 74 90 90 – Fax : +33 (0) 1 64 22 87 28 – www.geovariances.com
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ISATIS
NEWS
The Uniiverse
Of Geostatiistiics
Consulting
consulting@geovariances.com
Zonal anisotropy: how to model the variogram
W h e n t h e e x p e r i m e n t a l v a r i o g r a m s s h o w d i f f e r e n t
b e h a v i o r s i n d i f f e r e n t d i r e c t i o n s a n a n i s o t r o p i c v a r i o g r a m
m o d e l s h o u l d b e f i t t e d t o t h e m . T h e r e a r e h o w e v e r s o m e
p r a c t i c a l d i f f i c u l t i e s i n f i t t i n g t h e m o s t a p p r o p r i a t e m o d e l .
T h e s e d i f f i c u l t i e s c a n l e a d t o a w r o n g m o d e l o f t h e t r u e
u n d e r l y i n g s t r u c t u r e . W h e n t h e d i r e c t i o n a l v a r i o g r a m s
s h o w d i f f e r e n t v a r i a b i l i t y f o r t h e d i f f e r e n t d i r e c t i o n s t h e
s i l l s a r e n o t c o m p a r a b l e . I n s u c h a c a s e g e o s t a t i s t i c s c a n
b e u s e d t o e s t a b l i s h a v a r i o g r a m m o d e l m a d e u p o f
c o m p o n e n t s h a v i n g a s o - c a l l e d " z o n a l " a n i s o t r o p y .
L e t ' s d e s c r i b e t h e p r o c e d u r e t o b e f o l l o w e d f o r c a l c u l a t i n g
a n d f i t t i n g a v a r i o g r a m m o d e l w i t h z o n a l a n i s o t r o p y b y
m a k i n g u s e o f s o m e b a t h y m e t r i c d a t a , k i n d l y p r o v i d e d b y
I F R E M E R (I n s t i t u t F r a n ç a i s d e R e c h e r c h e p o u r
l ’ E x p l o i t a t i o n d e l a M e r ) .
F i g u r e 2 s h o w s t h e v a r i o g r a m s c a l c u l a t e d a l o n g N 1 0 W
a n d N 8 0 E a n d t h e m o d e l t h a t h a s b e e n f i t t e d . A v a r i o g r a m
w i t h a z o n a l c o m p o n e n t i s r e q u i r e d h e r e . T o s i m p l i f y t h e
f i t t i n g p r o c e d u r e , t w o d i r e c t i o n s h a v e b e e n f i t t e d
i n d e p e n d e n t l y . T h a t m e a n s t h a t t h e r e s u l t i n g 2 D m o d e l
h a s t h e f o l l o w i n g f o r m ( w h e r e u a n d v r e p r e s e n t t h e t w o
m a i n d i r e c t i o n s o f a n i s o t r o p y ) :
γ ( hu
, hv
) = γ
1
( hu
) + γ
2
( hv
)
here g(2D)=Gauss(along N10W,200m)
+Spherical(along N80E,500m)
Figure 2: Experimental and modeled variogram
in the 2 main directions of anisotropy
Figure 1: Base map of the bathymetric data
T h e d a t a s h o w n o n f i g u r e 1 c o m e s f r o m a b a t h y m e t r i c
s u r v e y o r i g i n a l l y c o n d u c t e d b y t h e F r e n c h h y d r o g r a p h i c
s u r v e y ( S H O M ) c o v e r i n g a n a r e a o f a p p r o x i m a t e l y 8 k m x
5 k m a l o n g t h e S p a n i s h a n d F r e n c h m e d i t e r r a n e a n c o a s t .
D e s p i t e t h e n o n s t a t i o n a r i t y o f t h e d e p t h w h e n m o v i n g
a w a y f r o m t h e w a s t l i n e , t h e s a m p l i n g d e n s i t y a u t h o r i z e s
t o u s e v a r i o g r a m s w i t h i n a l i m i t e d n e i g h b o r h o o d . S o w e
h a v e t o c a l c u l a t e a n d m o d e l d i r e c t i o n a l v a r i o g r a m s .
T h e f i r s t t h i n g t o d o i s t o i d e n t i f y t h e 2 d i r e c t i o n s s h o w i n g
t h e m i n i m u m a n d m a x i m u m s p a t i a l c o n t i n u i t y . T h e
v a r i o g r a m m a p m a y h e l p d e t e r m i n e t h e s e d i r e c t i o n s .
T h i s m o d e l i s " a u t h o r i z e d " a n d f i t s w e l l t h e t w o m a i n
d i r e c t i o n s , b e c a u s e t h e g a u s s i a n c o m p o n e n t h a s n o e f f e c t
a l o n g N 8 0 E a n d c o n v e r s e l y t h e s p h e r i c a l c o m p o n e n t i s
n o t p r e s e n t a l o n g N 1 0 W . H o w e v e r t h i s m o d e l i s n o t
s a t i s f a c t o r y a l o n g i n t e r m e d i a t e d i r e c t i o n s , a s s h o w n i n t h e
l e f t h a n d g r a p h i c o f t h e f i g u r e 3 .
T h e m o d e l a l o n g t h e b i s e c t i n g d i r e c t i o n N 3 5 E i s g r e a t e r
t h a n t h e m o d e l i n N 8 0 E d i r e c t i o n , w h i c h i s s u p p o s e d t o b e
t h e d i r e c t i o n o f g r e a t e s t v a r i a b i l i t y ! ! !
T h e r i g h t a p p r o a c h t o m o d e l a l l d i r e c t i o n s c o n s i s t e n t l y
w i t h t h e o b s e r v a t i o n s m a d e o n t h e t w o m a i n d i r e c t i o n s o f
v a r i a b i l i t y w i l l c o n s i s t i n f i t t i n g a m o d e l w i t h t w o
c o m p o n e n t s : t h e f i r s t c o m p o n e n t i s i s o t r o p i c a n d t h e
s e c o n d z o n a l a n i s o t r o p i c .
More publications on www.geovariances.com
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ISATIS
NEWS
The Uniiverse
Of Geostatiistiics
Training
training @geovariances.com
Figure 3: Variograms in the 2 main directions of anisotropy
+ a bisecting direction
T h e s i l l o f t h e s e c o n d c o m p o n e n t i s e q u a l t o t h e d i f f e r e n c e
b e t w e e n t h e s i l l s o b s e r v e d a l o n g t h e m a i n d i r e c t i o n s o f
c o n t i n u i t y :
2
2
γ ( h
, h
) = γ
( h
)
(
)
u v
1 u + h v + γ h
2 v
I n t h e f i r s t m o d e l t h e t o t a l s i l l i s i n f a c t t h e s u m o f t h e
c o m p o n e n t s i l l s i n b o t h d i r e c t i o n s . I n t h e s e c o n d m o d e l
t h e t o t a l s i l l a l w a y s l i e s b e t w e e n t h e s i l l o f t h e i s o t r o p i c
c o m p o n e n t a n d t h e s i l l f i t t e d t o t h e v a r i o g r a m i n t h e
d i r e c t i o n o f m a x i m u m v a r i a b i l i t y ( v ) .
T o f i t s u c h a m o d e l t h a t i s c o r r e c t f o r a l l d i r e c t i o n s s o m e
c o m p r o m i s e s m u s t b e m a d e a l o n g t h e t w o m a i n d i r e c t i o n s
N 8 0 E a n d N 1 0 W . I n o u r c a s e t h e r e s u l t i n g f i t ( s e e n o n t h e
r i g h t h a n d g r a p h i c o f F i g u r e 3 ) i s m a d e u p o f :
γ (2D)= Gaussian (isotropic,170m) +
Linear(along N80E)
W h i l e t h e c o n s e q u e n c e s o f t h e f i r s t m o d e l m a y b e n o t s o
i m p o r t a n t w h e n k r i g i n g f r o m v e r y d e n s e d a t a l i k e i n o u r
b a t h y m e t r i c s t u d y , t h e y m a y b e d i s a s t r o u s w h e n
s i m u l a t i n g o r e s t i m a t i n g 3 D d a t a .
Jacques Deraisme (deraisme@geovariances.com)
Your training agenda for next year!
Geostatistical Gridding for the Oil & Gas Industry January 21-23, 2002
Oil & Gas, Isatis Essentials March 11-13, 2002
Time to Depth Conversion, the Geostatistical Approach April 24-26, 2002
Assessing Volumetrics Uncertainties: the Geostatistical Approach June 10-12, 2002
Available upon request:
Introduction to Geostatistics for Oil & Gas (5 days)
First Steps into Geostatistics (3 days)
Courses Description, Bookings: www.geovariances.com
More info: training@geovariances.com
3

ISATIS
NEWS
The Uniiverse
Of Geostatiistiics
Support
support @geovariances.com
Discover the new features of Isatis 4.0
Import or Export your data in batch mode
Run easily your import / export applications in batch:
importing or exporting tasks may now be integrated in
journal files just like for any other Isatis panel.
Even better: all the data exchange interfaces are now
available on Windows NT/2000/XP.
Exchange your wells, surfaces, 3D grids,
polygons or faults between Isatis and Gocad
Gocad V2, developed by T-SURF (Nancy), now
offers a direct read/write access to the Isatis database.
Krige data or compute Volumetrics inside 2D
or 3D Polygons
More tools and flexibility in the handling of polygons in
the new Polygon Editor: new algorithms for polygon
consistency, intersection of polygons, management of
polygons with holes, etc. have been added whilst the
Polygon Display module enables the visualization of
kriged results in combination with input data.
Global estimation is now included: you can krige
variables on complex objects that can be described
with 2D or 3D polygons.
In addition: Polygons are also taken into account in
the Volumetrics application. Statistics or risk curves
may be computed polygon by polygon or on the entire
grid.
Help Desk
support@geovariances.com
or call +33 (0)1 60 74 91 00
… “You could give some other
companies some lessons on how to
provide technical support” …
ANADARKO, UK
… “Thank you very much for your
prompt and useful answer” …
PDVSA, VENEZUELA
… “It’s a real pleasure to work
together and to use Isatis” …
ENTERPRISE OIL, UK
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Transform your geometry from structural to
stratigraphic system
A dedicated new application has been designed for
folding and unfolding of block systems: switch
between the original depositional reference system and
today's (X,Y,Z) coordinate system.
Among other handy improvements:
* Read and write ASCII files in CSV format (Comma
Separated Values): data exchanges are definitely far
much easier;
* View Labels are now attached to graphic windows:
give a title, add a note or specify parameters values in
your views;
* Measure distances and angles directly in most Isatis
graphic windows;
* Use the Calculator more efficiently: save series of
transformations in template files in order to use them
again later on. Creating selection variables has also
been added in this panel.
Complete list of Isatis V4 features
on www.geovariances.com
Press
F1 or Help
from each window
You do not know
the meaning of a
parameter
You are unsure
about the proper
method to use
Have you ever
open the
On-Line Help
49 bis avenue Franklin Roosevelt – BP91 – 77212 Avon Cedex, France – Phone : +33 (0) 60 74 90 90 – Fax : +33 (0) 1 64 22 87 28 – www.geovariances.com
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