Dipmeter Interpretation - More Accurate Structural Definition of the

GEOL . CROAT.
49/2
283 - 288
5 Figs. I
I
I ZAGREB 1996 I
Scientific paper
Dipmeter Interpretation - More Accurate Structural Definition
of the Ponti an Sandstones of Lipovljani and Jamarice
Jurica NOV AK ', .Josipa VELIC', Bozidar JANCIKOVIC' and Bruno SAFTIC'
Key words: Dipmclcr inte rpre tation, Descriptive stat isti cs, Orientation of fauil s, Fault characterisation,
Pontian sand stones, Lipovljani, Jamarice, Sava
dep ression, Croatia.
PROCEED INGS
Kljucne rijeci: interpre tacija dipmetra, deskriptivna
statistika, orijentacija rasjeda, karakterizacija rasjecia, pontski pjescenjaci, Lipovljani, Jamarice, savska
depresija, f-Irvatska.
Abstract
Sazetak
Two pairs of wel ls have been chosen from the L i povljani and
Jamaricc oil field s in lhe Sava depression il1111e south-west part of the
Pannonian basin. Both we ll s from each field have a measu red E-log,
and one al so has a high-quality diplog. T he reservo ir rocks afC represent ed by folded and faulted Pontian sandstones . A combination of
grap hical int erpre tation and SCAT (Sta ti stical Curvature Analy sis
Tec hniqu cs) has allowcd identification of both structural and fault
plane dips . Defining the position of fault plancs cnabled thc characterisation of normal and reverse faults, incli ncd in thc direc lion of
stmctural dip (or against il) , a nd positioned either longi tudinal , transverse or d iagonal to the st ruclllre. The d cscribcd tcchnique can bc fully utilised in the crea tion of a gco log ical modcl aimcd to finding the
bypassed oil.
S naftnih potja Lipov lj ani i J am aric e iz savs ke d epre sije u
jugozapadnom dijclu panon sk og bazena odabranc s u po dvij c
bU SOlinc s c leklrokarOlazn im dijagramima od kojih po jedna ima jos i
vrlo kva litetan diplog. Ovdje su ko le ktori, po ntsk i pjescenjaci, bor-ani
i rasjedan i. Kompteksnom interpre tac ijom - g rafickom i statistickom
(SCAT) , razlu ce ni Sll nag ibi sloj eva od nagiba paraklaza. Ulv rd e ni
cleme nti orijentacije rasjeda omogucili su njihovu karakt e rizacij u na
normalne iii reverznc, na prolusmjernc ii i iS losmjernc, te na uzcluznc,
poprecne iii dijagonalne. Tako dobivena !j esenja nezaob ilazna su pri
kreiranju geolos kog modet a s ciljem pronalazenja 7.aostalc !lafte.
I,
INTRODUCTION
Fro m th e late seven ties to th e early eighti es INA ,
the Croatian national oi l-company purchased logging
equ ipment from " W es tern Atlas", including the fourpad high -reso lution dipmeter. In addition to giving an
ana lo gue output recorded on film , thi s equipment is
capa ble of digital recordin g of data, and thus enables
computer data- process ing.
Dipilleter measurements were taken in several well s
of Li povljan i and Jamarice fie ld s. The physical and
lithological charac te ri sti cs of th e Pontian sandstones,
reservoir rocks in the aforementioned fi elds, res ulted in
good quality data with very c losely spaced dip measurements. Thi s suggested a mcthod for thc recognition
and more accurate location of faults , and th e ir orien tation and influ e nce on the gco mctry of resc rvoir rocks.
Two Iypical we ll s from each field have bcen chosen to
illustratc the mc th od. The results of various statistical
c urvature analysis tec hniques arc given, and show th e
success ful de fin ition of structural dips (d ips of bedding
planes), and their separation from differently spaced
planes caused by tectonic deformation - fa ult planes
presen ted by e ither simple surfaces or fault zones.
The oil fields of Lipovljani and Jamaricc arc located
some 90 km east of Zagre b (Fig. Ib), in th e so uth western part of th e Pannonian basin, in the Sava depres sion. In J 932 the first oil and gas ex plorati ons took
place th ere . Uplifted structures were defined by seismi c
reflection lines in 1959. The drilling on Lipovljani commcnced in 1960, and on .Tamaricc in 1964. I n accordance with re gional lithostratigraphic s ubdivi sion th e
productive hori7.on s were named Janj a Lipa, Kozarica
and Bujavica sand stone s (Figs. la, 4a), which chronostratigraphi ca lly fairly closcly rcspond to the Ponti an
deposits.
The observabl e signs of fauliing in the m enti o ned
fie lds had prcviollsly drawn thc attention o f explorationi sts durin g th e ea rl y 1970 's. This was then docllmented by a detailed study of conventional E-Iogs, a nd
the cases where the same layers were be ing repeatedly
drilled th rough in one wcll, or an apparent hiatus in a
I
lNA -Naftap lin. Subiceva 29, HR- t 0000 Zagrcb, Cro;Jl ia.
2
University of Zagreb, Facul!y of Mining , Geology & Petroleum Engi neering , Pi erotlijeva 6, P.O. Box 186, HR -I 0000 Zagrcb, Croatia.
Geologia Croalica 49/2
284
Lip-63
LOCAT I ON
lip-123
MAP
seA l E
~oom.
l .b .
LlPOVLJANI
Up.-123
R, POLAR PLOT
AZIMUTH DIP
270
1----------. 1000-1063 . ' 1064-1080 . 1081-115~
l.c.
DEPTH INTERVAL m
LlPOVLJANI
Lip-123
R2POLAR PLOT
AZIMUTH DIP
270
1_ 1230-1281 . 1282-1312 . 1312-1360
1.d.
DEPTI-IINTERVAL (m)
-R--
well nearby were explained by tectonics (TUFEKCIC ,
1970; HERNITZ & SIMON, 1975; JANCIK OYIC,
1977)_
2. RESULTS OF DIPMETER ANALYSIS
The dip log of we ll Li p-123 has been chosen fro m
the field Li pov ljani to gether with E-log of Lip -63 fo r
correlalion purposes . The depth interval from 1000 to
1350 m is shown (Fig. La). Co rrelation of log-meas urements (NI6, N64, SP) from these closely spaced wells
depicts substan tial differences in the lit hol ogical COtn-
I
LEGEND
BUJAVICA SANDSTON E
KOZARICA SANDSTONE
JANJA LlPA SANDSTONE
REPEAT SECTION
FAULT
Fig. I a) Correl31ion scheme Lip63 Wel! - Lip-123 Well; b)
location map: c) Lip- 123 Well
R, Azimuth Dip Plol: d) Lip123 Well R2 Azimuth Dip
Plot.
position and thickn ess of individual sandstone bodies. It
is, [or example, not iceable that th e Bujavica sandstone
drilled by Lip-63 well was totally absen t in Lip-123 _ In
contras t, the Janja Li pa sandstone is some 20 m thi nner
in Lip-63 than Li p-123. The dip plot of Lip-123 clearly
shows a change of dip angle and az im uth in two pos itions (Fig. I a) . On the polar plots o[ az imut h and dip o[
plana r eiemems fro m c hosen intervals (Figs. 1c and I d)
a concentrati on of patte rns is apparen t, illus trati ng the
structural dip in the hanging wa ll and in the footwall,
toge ther wi th the orientation of the fau lt plane itself.
This way of dip plotting doesn '1 show the depth of indivi dual di ps, wh ich is possibly co nfusing to less experi-
Novak. Velie. Jaocikovic & Saftic : Dipmeler Inlerprel;llio n - More Aeeur:lIe SlruClllr;t1 Definition ...
285
23
SCAT and Stick Plot
,.,
,",~"'H
,~"
IIIP
,'~
Ill""',.
"
I ~ I'I'I
VI l W ..... ,
~'s
I.':;" '"
v a"
I fIQn
"oS
,"~
Fig. 2 Lip - 123 Well R , SCAT a nd Slick
Plm.
e nced analysts. The "azimuth vs. dip" cross- plot allows
singular dip s to be traced to their precise depth so that
the ir "ori gin" ca n be controlled. Generall y speaking, in
th is way patterns analysed with th e help of" a cross-plol
will show a Gauss norma l distribution , where by dips
from one side of the [aull or another are put into one or
more stochasti c groups. In the case of Lip- 123, not only
a ve rt ical but al so a horizontal di splace me nt can be
deduced from th e differences in th e dip azimuth (Fig.
2). Furthe011ore, it is only possible by c ross-plot to precisely define the position of the transverse and longitudi nal plane, marked by st ruc lUral d ip and we ll axis. A
se ri es of related c ro SS-pIOIS is shown on Fig. 2. These
a rc: Mercator projection of azimuth vs. de pth, "dip vs.
dept h", the transve rse and longitudinal dip component
vs. depth and the two most characteristic perpendicular
sti ck plot s vs. de pth . Thorough analysis of th e c ro ssplot s allowed ca lc ulation of the thi c kn ess of th e
defo rm ed inlervals and, more importa ntly, the dip and
azi muth of fault planes. ]n Lip ~ 123 two faults are document ed - R, with a fault plane 125/50 on 1070 m and R,
positioned 190/60 on 1298 m. The first fault is younge r,
nonnal , inclined against the structu ral dip and diagonal
to the stru c tu re (Fig. 3), the o ther is o lde r, probably
reverse, inclined in the same direc tion as the st ruc tural
dip but steeper than bedding dip values.
We ll -log correlation be twee n 1am -74 and J am- 160
showed marked differences in sandstone thickness (Fig.
4a). The dip plot of Jam - 160 shows well-marked di scontinuities of both dip and az imuth al deplhs co rresponding 10 th e pos iti ons of reduced sandstone thickness as defi ned by E-Iog correlati on with Jam-74. These
di sco ntinuities are also observabl e on the Mercator projec tion of azimuth vs. depth, as we ll as on the "d ip vs.
depth " plot (Fig. 5). It is al so noti ceable that both th e
transverse and longitudinal dip component ha ve similar
di scon tinuities at the same depth s. The pattern s at J203
and 1250 m have an inclination opposite to the di sconti -
Geologia Cwatica 49(2
4. REFERENCES
CROSS SECTION Lip-63 - Lip-123
lip-63
lip-1 23
BASSIOUNI, Z. & YELIC, J. (1996): Prospecting for
Bypassed Oil and Gas.- Geol. Croat., 49/2, Proceedings of I st Internat ional Symposium of Petroleum
Geology, 1.97-202.
HERNlTZ, Z. & SIMON, J. (1975): Rasjedi i izrada
karata debljina naslaga (Faults and Preparalion of
Isopach Maps). - Zbornik radova Rud arsko -gco losko-naftno g fakulteta Sveucilista u Zagrcbu u povodu 35 god. rada, 77 -85, Zagreb.
D
SUJAVICA
SANDSTONE
I ? 1NORMAl
»" fAULT
_
SA NDSTONE
~ JANJALIPA
!L..±2:lISANDSTONE
t.:-.-'::-.
:
IREVERSE
~ REPEAT
Iiiiiiiiiii KOlARICA
FAULT
_
SECTION
Fig_ 3 Cross sec Lion Lip-63 Well - Lip-123 Well.
nuities located at 1280. 1308 and 1355 m respectively.
This is due to the spatial position of faults that arc
appropriately shown in the chosen sections . Figures 4b,
c, d, e and f show azimuth vs. dip cross-plots from Jam160. The positions of fault planes are as fol1ows: R]
with 220/55 at 1203111, R2 with 290/45 at 1250 m, R3
with 145/50 at 1280 m, R4 with 75/45 at 1308 m and R,
with 90/65 at 1355 m. Based on the relationship
between the structural dip and orientation of fault
planes, faults R] and R2 arc diagonal with fault planes
inclined in the same direction as the structural dip, R3
and R" are diagonal with inclination aga in st the structural dip, while rault Rs is longitudinal to the structure
and inclined against the structural dip. All the faulls
have 110rmal displacement. These solutions are essential
in finding the so-called "bypassed oil", especially in the
phase of building a complex geological model
(BASSIOUNI & YELIC, 1996; PRELOGOYIC et aI.,
1995) in order to explore for oil and gas morc economically.
3. CONCLUSION
The interpretation of very dense dipmeter data
requires certain skill and experience. Only by utilisation
of a number of graphical and statistical techniques can
satisfactory and unambiguous results be obtained.
Examples of two pairs of wells from the Lipovljani and
Jamarice fields, with intensively rolded and faulted
sandstone reservoirs, are uscd for Ihe illustration of how
structural dips can be discerned from the fault planes;
how the fault plane OrieJ1lalion can be defined; and
finally how the character of a fault can be deduccd.
JANCIKOYIC , B. (1977): Principi mjerenja pad a slojeva u busotinama i mogucnost definiranja prostorne
orijcntacije rasj eda u neogenim slojevima jugozapadnog dijcJa Panonskog bazena (Principles of Dip
Logging and the Possibility of Determining the Spatial Orientation of Faults in Neogenc Deposits in the
South-western Part of the Pannonian Basin).Zborn ik radova Ill. godiSnjeg skupa Znanstvcnog
savjeta za naftu Jugoslavenske akademije znanosli i
umjetnosti, 171-207, Novi Sad .
PRELOGOVIC, E., JAMICIC, D., ALJINOY IC, B.,
YELlC, .T., SAFTIC, B. & DRAGAS, M. (1995):
Dinamika nastanka struktura juznog dijela Pan onskog bazena.- In: YLAHOYIC, I., YELIC, I. &
SPARICA, M. (cds.): First Croatian Geological
Congress, Proceedings, 2,481-486, Zagreb.
TUFEKCIC, D. (1970): 0 revcrsnom rasjedanju struklure Lipovljani (Compression Type of Reverse
Faulting in Lipovljani Structure).- Nafta, 21/3, 99104, Zagreb.
287
Nova\... Velie. J:lIlc ikovic & . Sanie: Diplllclcr Imcrprc[:l[ion - More Accurate Stnlcturnl Derini[ ion ..
------- - - - - -- - - - - -- - - -------
Jom-74
SP
' 00
~
o
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o
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20.2
JAMARICE
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Jam-160
AZIMUTH VII DIP CROSS PLOT
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. 11~'W3
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I'H E RVAL
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AZI MUTH ys DIP CROSS PLOT
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to
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DIP AI IM U TIi
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OEPTH I NTER VAL 1tI'}
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JAMARICE
Jam -t OO
AZIMUTH V5 DIP CROSS PLOT
R,
•
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•"
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•
4.d.
'I
, .;--~=;-~.~
D IP A7. IMIHH
1~12 7 e
• 1271-12S ,
. '2B2· , :lQ2
DEPTIi INTERVAL (m·
JAMARICE
JAM-t60
AZ IMUTH VII, DIP CROSS PLOT
R,
~l
J
.
..
'.
•
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D IP AIIIIIUTII
".
JAMARICE
Jam-160
AZIMUTH VII. DIP CROSS PLOT
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·:.. ..'0 .-
LEGEND
CJ
BUJAVtCA SANDSTONE
Cd
KOZARICA 2 SANDSTONE
c::J
KOZARICA 1 SAN DSTONE
G:;gJ
JANJA L1PA SANDSTONE
R
-
-
'.
fAun
-
4 ,I.
.
•
'"
DIP AZ IMUT H
D EP TH INTERVAL (.,1
Fi g. 4 a) Corre lation scheme
Jam -74 We ll - Jarn-160
Well:
b) Jam- 160 Wel l R I azimut h
vs. dip cross plol:
c) Jam-l 60 Well R2 az imuth
vs. dip Cross Plot:
eI) Jam -160 We ll RJ<lzimut h
vs. clip cross plot:
c) Ja111-l60 We i) R" az imuth
vs. dip cross pial;
f) Jarn- 160 We ll Rs azim uth
vs. dip cross 1'101.
( It!olog la Cro,lI u.:a 4'J(l
Jam-160
SCAT and Stick Plot
nn
Fig. 5 Jalll- 160 W ell Rj- Rt -R,l SCAT
and Slick PI OL

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