Upload
angel-saldana
View
254
Download
0
Embed Size (px)
Citation preview
8/9/2019 Dynamic Reservoir Characterization
1/14
Colorado Scho
ol
of Mines
Fundamentals in Well Log
Interpretation
GPGN 532 -A
Final
project
ba
sed
on the
paper:
Dynamic Reservoir Characterization
of a C02 Huff'n'Puff.
Central Vacuum Unit, Lea County New Mexico
Davis T.L., Ben
so
n R.D ., Roche
S.
L. and Sc
uta
M.S.; 1
7, Expanded
bst
racts S
PE
Inter
na
t ional Meeting)
Efrai n Mendez
Golden,
December 3, 1998
8/9/2019 Dynamic Reservoir Characterization
2/14
EXECUTI VE SUMMARV
Oyoamic Rcserv
oir
Characlerizalioo can be notably enhanced by the use
of 40,
3C
sc ismology. Afier a feasibility analysis, thi s technology can be applied to monitor fluid
front movements during
field
production and lO determine the variability, with
in rock/fluid properties of the reservoir. rhe improved reservoir characterization will
increase the hydrocarbon recovery, reducing operaling costS with a resulting better
reservoir management. The end resull is ncreased reserves produced al a lower COSI
OBJE IVE
OF
THI S TECHNICAL REI)ORT
/ ro describe the methodology known
as
40, 3C seismology, ils basic principies,
applications and economic j ustificalion 10
be
applied in reservoir characlerization
CONTENTS
40,
3C Seismology.
What
does it mean ?
11. Physical principies and imp1ementation
III. Application
IV. Economic justification
V. Conclusions and Recommendations
40, 3C SEISMOLOGV. WHAT DOES IT MEAN?
11
is
well known that Ihreedimensional
30)
seismology has been
{he
most impacting
e..
technology over Exploration and Production industry during last years. Today, 3D
ttd; seismic shows high costlbenetit ratios by reducing the dry-hole
ris
k as well as
by
m improving the fie ld development and production strategies. Conventional 3D seismic
= : : 1 1 : 0 ~ : c : ~ ~ ~ o : : ~ : m : d s o : ; ~ ~ i ; h : p ; : : : h r e : : i : : : ~ U 1 P ~ : a i : : n ~ ~ : r ~ : :
: :::
framework and some stratigraphic features ofthe reservoirs . Nowadays, new altcmalives
in the knowledge of reservoir rack and fluid properties come out by the combined use of
- three component (3C) seismic data, tha is, by using compressional and shear waves,
acquired during 3D, 3C seismic surveys.
Oynamic: Reservoir Charoc:te";zGtioo
Efrojn
e n
u
bec: 3. 1
99
8
8/9/2019 Dynamic Reservoir Characterization
3/14
Recently, the time as the fourth dimension, has been added to this technology oblaining
whal we know as 40 (time lapse), 3C sei smology . This powerfullool consists in the
repeated acquisition
of
30, 3C seismic surveys. over producing fields, with the
pUrpse
of monitoring fluid movemcnts and changes
in
reservoir properties by comparing Ihe
seismic response from each other survey.
Ahhough this is nOI
yet
a matute technology, Ihe increascd hydrocarbon recovery and
reduction in operating costs
are
doing Iha140, 3C seismology hegins to be recognized as
an integral part of dynamic reservoir characterizalion. As Rbonda Duey (1998) said,
Someday 4D seismic lechnology may be used as routinely as 3D seismic is toclay.
11. BA81C PRJNCIPLES AND IMPLEMENTATION
In
exploration seismology. two body waves are generated artificial1y propagating through
the
subsurface with different mode of propagalion related to the nature of rock
defonnation (Figure 1
.
According to Hook 's Law, eaeh wave stresses the rock inducing
a strain proportional 10 the stress. Ouring thc passage ofthe primary or eompressional (P)
wave, Ihe rock changes volume but nol shape in response to altemaling compressive and
tensional stresses whereas, with
the
trave1-path of Ihe slower secondary or shear (8)
wave, the rock changes shape but not volume (Danbom, 1986).
The magnitudes
ofthe
velocides
Vp
and
V r
are influenced by the elastieily
oflhe
A ~
w
d
they are travelling. With isotropic media p provides a measure of the bulk rock
compressibility, rigidily and dcnsity, whereas
Vs
is
sensitive to rigidity
and
density.
As
wc know, 8 waves can not propagate in a
fl
uid (rigidity equals to zero). ~ hand,
Ihe
ratio p s appears strongly correlated with the reservoir produclion charaeteristies,
showing a strong dependence on porosily and playing an important
rol
e
in
seismic
interpretadon nol only as lithology identifier but also for anisotropic inlensity estimation.
Al]
rock systerns are anisotropie
lO
sorne degree. rneaning thal one o' more physical
properties ehange as they are mcasured in differenl directions. The effect of
r o p y on
P wave trave1tirnes is usually small, however S waves exhibit splitting
b i r e f ~ n c e
thut
is,
depcndenec of velocity on the dircclion ofpolarization. n a fractured medium, the
incident S wavc splits into two components, a fasl 81 and a slow
S2
(Figu re 2 . Thc
[)ynamie Reservoir Ch(U '(lcteri:zation
efra
l MemH:Z
t ec 3, 1998
8/9/2019 Dynamic Reservoir Characterization
4/14
degree of splitting gives a rough measure oflhe fracture intensity (Figure 3), whereas the
polarization
of
the [aster SI wave
is
generally parallel
to
the str
ike of
the fractures.
Fractures are probably he mosl importan anisolropic property in fluid flow because they
cause/ several rock properties, such as penneability,
10
have difIerenl values parallelto
the fracture planes Ihan Ihey do perpendicular ~ ~ ~
~ / U
This clcar dependence 00 fluids and fracturing i o m p o n n t seismology valuablc
for the reservoir engineer (Figures 3
10
5). Now, by cxtending Ihis knowledge,
he
differences between successivc seismic surveys will indicatc changes
in
producing
rescrvoirs, such as fluid m o v e m
J
~ the change of reservoir properties., mainly
pcnneability, with
tlIt.
time. Davis ft (1997), refers "The penneability of a fonnation, or
the corme
8/9/2019 Dynamic Reservoir Characterization
5/14
program in Vacuum field , New Mexico (Figure 6). The main objective
is
to demonstrate
the capability of repeated (time-Iapse) 3D, 3C seismology to detect
and
monitor changcs
in
rock/fluid properties assoeiated with the CO
2
injection, soak, and wilhdrawal ("puff"
or produclion phase) processes.
Vacuum Field is located on a arge E-NE anticJina Slructure. The San Andres and
Grayburg fonnalions eorrespond
10
the rim of a broad carbonate shelf province to the
north and northwesl, and the rim of a deeper intraeralonic basin, on Ihe southeast and
easl. San Andres carbonates at depths from 4200ft to 4800ft are Ihe main produclion
zones. The producing interva shows average porosity of 11.6% and average penneability
of22.3md, wilh an initial reservoir pressure of 1628 psia at 4500ft. Reservoir pressure
Is
maintained aboye Ihe bubble point pressure (764 psia) by waterflooding. The production
data suggest an effective penneabilily pathway extending northwesl from CVU-97 where
the reservo r tends 10 higher produclions than in the soulheasl portion
of
he mapped area.
In
Ihis sense Ihcre is a SW to NE trend thal separales a higher production rone in the NW
portion from a ower perfonnance
in
the SE portion.
The
C h
"huff-n-pufl" occurred in well CVV-
97.
A base 3D, 3C SUlvey (Oclober 28 10
Novembcr 13, 1995) was shot prior
10
injection, which occurred from November 13
10
Oecember
8.
The "soak" period extended from Deccmber 8 to December 28, afier which
Ihe wetl was relumed lo produclion. A second 3D, 3C survey was acquired from
December
21 10
Oecember 28 during the "soak" periodo
Ouring th e injection process and "soak" periad the reservoir pore pressure and fluid are
altered. lllercfore, severa dynamic changes 10 the reservoir propenies between the base
and repeated surveys are expected. Examples of P and S migraled seclions before and
after the inj ection program revel seismic di fferences
in
the signal (Figure
7)
. Time-Iapse
interpretation consisted in manipulating th ese differences to reveal characteristics of the
dynamic response of the bulk rock/fluid properties lo the changing reservoir conditions
The P and S waves show a CO
2
bank fonned to the sou
th of
injection well. In this sense,
a P wave amplitude anomaly (Figure 8) an d a shear wave anisotropy anomaly (Figure 9)
coincide with the Ol bank. The polarization angle of SI also confinns the regional
maximum horizontal stress direction. The velocity anisotropy anomaly can e explained
Dyl lOmic: I
l:I:.serYOir CMr
8/9/2019 Dynamic Reservoir Characterization
6/14
by variations
in
pore pressure which could affee
the
percentage of open fractures
affecting the degree of shear wave splitting. Also changes in fluid viscosity may affect
the wettability ofthe rock frame and rigidity
of
this type
of
media.
Pore pressure changes and variations in fluid properties have produced a multicomponent
40 signature detectable using the seismic data. t can be considered a significant advance
in
geophysical applications toward reservoir monitoring.
IV. ECONOMIC JUSTIFICATION
After he feasibility analysis has dictated a "good candidate reservoir for 40 3C
seismology", the economic justification can
e
supported considering that the data
obtained may e used to enhance hydrocarbon reeovery, revitalize old fields, reduce
operation wsts, prolong well life andlor change production slrategies. Even more, new
well localions can be pro)Xlsed by identifying bypassed accumulations in the interwell
regions where only seismic data can provide infonnation.
Ideal1y enhanced acquisilion repeatability should consider the sume acquisition method
for each survey and accurate source and receiver positioning (perhaps even using a
pennanent receiver installation). These aspccts should also tend lo deerease the eosts for
each new repeated survey. The end result is inereased reserves produced at a lower cost ,
V. CONCLUSIONS ANO RECOMMENOATlONS
40 3C seismology can help to make better decisions and simulate scenarios
to
optimize production, improve oil rewvery and reduce costs. Better reservoir
management can e achieved
by
updating and improving the static and dynamic
reservoir model periodically.
Project success in a 40 3C seismology campaign requires
tha!
a change
in
petrophysica[ fluid propenies will change the seismic response
of
the reservoir. A
feasibility analysis will hclp
lo
make decisions about the implementation of this
teehnique under particular cond itions.
Oynamic Reservoir Characterization is a multidisciplinary teehnology that needs not
onJy
the se ismic interpretation but also the integrated analysis ofborehole and
production data, reservoir simulation and modeling.
Dynornic
Rescrvoir Chorocterizotion
Efrain Mendez
cc 3. 1998
8/9/2019 Dynamic Reservoir Characterization
7/14
REFERENCES
l. Arestad J.F., Davis T.L. and Benson R.O.; 1996, "Utilizing 3-D, 3-C Seisrnology for
RescIVoir Property Characterizalion al Joffre Field, Alberta, Canada". Applications
of
3-D
Seisrnic Data
to
Exploralion
and
Production. Edited
by
Weirner P. and Davis T.L. AAPG
Studies
in
Geology,
No.
42-5EG Geophysical Developrnents Scries, No . 5, p. l7 l-1
78
2. Danborn S.H. and Dornenico S.N .; 1986, "Shear Wave Exploraton". Geophysical
Developrnenl Scrics, V.l Sodety
of
Exploration Geophysicists.
3 Davis T.L., Denson R. D., Roche S.L., and Scuta M
.S.; 1997,
"Dynamic
ReseIVoir
Characterizalon of a COl Huff' n' Puff, Central Vacuurn Unit, Lea County, New e x i c o ~
Expandcd Abstracts, 1997 Annual Technical Conference and Exhibition, Sociely of
PetroleumEngineers, l
nc.
4. Duey R., 1997; "4D Seismic on Cuning Edge of ReseIVoir Monitoring Technology". Hart's
Show Special Edition, AAPG Annual Convcntion
5. Ehrorn D., Shcriff R. E., 1992; "Anisotropy and ReseIVoir Development". Reservoir
Geophysics, Invesligations
in
Gcophysics
No.
7. 50ciety ofExploralion Geophysicists
6. King G.; 1996, "4-D seisrnic improves reseIVoir rnanagement decisions. Parts I and 2",
World Oil, MaTCh and April1996
7. Hardage B.A.; 1996, "Combining P-Wave and S-Wave Seismic Dala to lmprove Prospect
Evalualion". Report oflnvesligations No. 237, Bureau ofEconornic Gcology, T
he
University
ofTexas atAustin
8. Lurnley D.E., Behrens R.A. and Wang
l ;
1997, "Assessing
Ihe
technical risk of a 4-D
seismic project". The Leading Edge,
16,
p.1287- 1
291
9. Mueller M.C.; 1992, "Using shear waves to predict laleral variability
in
vertical fracture
intensily". The Leading Edge, II,p.29-35
\O. Nestvold E.O.; 1996, "T
he
impact of 3-D Se ismic Data on Exploration, Field Development,
and Production". Applicatio ns
of
3-D Seismic Data
10
Exploration and Production. Edited by
Weimer
P.
and Davis T .L. AAPG Studies in Geology,
No.
42-5EG Gcophysical
Developments Series,
No.
5 p.I -7
. Peeters M.; 1998, "From Pictures 1 Properties". Paper
presente
on the inauguration of the
Baker Hughes Distinguished Chair of Petrophysics Borehole Geophysics". Colorado
SchoolofMines
12.
Wang Z
.;
1997, "Feasibility oftirne-Iapse scisrnic reseIVoir monitoring: The physical bas is".
The LeadingEdge, 16,p.1327-1 329
13. 1997, 1998, "Reservoir Characterization Project, Phases VI and VII". Final
Reports. Colorado School ofMines
[)yno.lTl
ie
R u ~ t V ( I i r Charaetari:ZOotion
frain
Mende.:z
[ ae 3,1
99
8/9/2019 Dynamic Reservoir Characterization
8/14
C
P
WAVE
----, :
I I I
I I
i 1
, ,
L _
J
L
.J
Comp r
eulon
Teosion
S-WAVE
~ :
,
=
__J
Clockwl,.
Fig.
1.
Distortion
of
an elementary cube
of
a medium caused
by
passage
of
a
P
wave (above) and an S wave (below). (Danbom, 1987)
Fig. 2. Principies
of
S wave splitting in a fractured rack medi
um.
The
incident S wave spl its into two compone
nt
s, the fast SI polarized in
th
e
direction
of
the maximum horizontal stress
a ,)
whereas S2 is polarized
in the direction
of
minimum horizontal stress
cr
min)
(Hardage, 1996)
8/9/2019 Dynamic Reservoir Characterization
9/14
Fig. 3. Spa
ti
a
ll
y coincidem P and S wave seismic sequences. Note that even
mough each sequence spans three identical black peaks on
me
right si de
of
each image, the internal architecture
of
the S wave sequence allows providing
more
in
f
onna
tion about reservoir flow paths and compartmem boundaries.
(Hardage, 1996)
4.7
4.8
4.
5 .0
51
5 2
5.3
5.4
4.7
4.8
4.
5 .0
5. 1
5.2
5 3
5.4
Fig. 4. S and 8
2
images across [he Austin Chalk. The 8
2
reflect
io
n is delayed
by
about 50msec rclative lo S. reflection. No
te
the prominent amplitude
anomaly towards the middl
e.
This represents a highly fractured zone 250m
wide. This efTect appears with consistent ampl itude on
me
S.. whereas on the
S
section, the Austin Cha
lk
shows laterally variant amplitudes (Mueller, 1992)
8/9/2019 Dynamic Reservoir Characterization
10/14
Fig
5. Velocity ratio map
VpfVs
computed from
th
e
S
and P datasets)
for Nisku carbonate reservoir interval, Joffre Field, Albena, Canada. Core
porosity contours overlap VpfVs. B
lu
e and magenta colors show higher
VpfVs zones which strongly agree with the highesl porosity v
lu
es.
Areslad, 1996)
8/9/2019 Dynamic Reservoir Characterization
11/14
g 6 Location map o Vacuum Field. Lea County, New Mexico.
Colorado School ofMines, 98)
8/9/2019 Dynamic Reservoir Characterization
12/14
,
. , 1 '- t:'.H ~ f 1 1 ' 1 1 ~ 3 '
I - _ ..
- I _
' < . ~ ~
"
; 1
." . ...
'.
n '
: - r ~
1 1) : _ I
' " ;
1
111
1
t -, '' ' . , ' I : : ; ~ 1 ~ _ .
~ . ,
.... ..
' I ~ I V ' ' ' ' ' ' ' : ; ; ; ; J .
,... - "
L
___
- - I _ _
li r,] - , ,:t
(a)
J..... : : : : .... ~ , . . , : : . : : - ~ : : ' : : ' , , : ~
::
f ; ~ E i ~ ,
J
~ + t : ~ ' ~
-
: - -.
- 'O- ..... _
(b)
-
= " ~ - = : ~
: - ~ : : _ .
. . ~ : ... :i; .;.;.
,-ir
~ ~ ~ f H f ~ ~
I
~ r ~
~ \ :
-r ..
~ ' . :
- - : ..c. ..
(e)
Fig. 7. lnline 69 (migrat
ed
sections). (
a)
P
wave
from
the in itial and
re
peat surveys
(0 .1 0
10
1.65s);
(b)
SI wave (po larizati
on:
118) and S2 wavc (polarization: 28)
from
the initial survey (0.5
to
3.25s); (e)
SI
wa ve
(polarization: 118) and S2
wave
(polarization: 28)
from
the rcpeal survey
(0 .5 to 3.25s). (Davis, 1997)
8/9/2019 Dynamic Reservoir Characterization
13/14
8/9/2019 Dynamic Reservoir Characterization
14/14