Sedimentology and Reservoir Characterization of the Aptian ...
Transcript of Sedimentology and Reservoir Characterization of the Aptian ...
Sedimentology and Reservoir Characterization of
the Aptian Lower Qamchuqa Formation from
Selected Wells in Bai- Hassan Oilfield/Northern Iraq
By
Sabir Subhi Shahab
Supervisor
Prof. DR. Lafta S. Kadhim Prof. Dr. Dler H. Baban
1
Chapter One
2
The Study Area
• The studied area located at Bai-Hassan Oilfield
includes three wells BH-86, BH-102 and BH-96.
• The field situated in NE-Iraq between both Kirkuk
and Qara Chuq structures that are tectonically located
at the Low Folded Zone within the unstable shelf.
3
4
A
B
5
6
Aims of the Study
1. Determining the sedimentology and petrographical properties
of Lower Qamchuqa Formation in the studied wells.
2. Detecting the paleo-depositional environment of the formation
in the study area.
3. Determining the reservoir potentiality of the formation and the
saturations of the contained fluids.
4. Subdividing the formation to reservoir units and calculating
the Net to Gross reservoir, pay, and productive ratios for the
studying formation in the studied wells.
The Data and Methodology
• Data and Sampling
The available data of each:
1. Rock samples for the Lower Qamchuqa Formation in three
studied wells at Bai-Hassan Oilfield.
2. The conventional log data of Caliper, Gamma ray, Sonic,
Density, Neutron, and Resistivity logs.
3. Porosity and permeability values from core test analysis.
4. The available thin sections were exist in NOC.7
8
Studied
Wells
Coordinate
UTM
System
Samples Lower Qamchuqa FormationThin
Sections
Cutting
and
Core
Top
m
Bottom
m
Thickness
m
NOC +
Author
BH-86Y= 139 48 227.97
X= 399 651.3821 2174 2321 147 70+21
BH-102Y= 13940 412.75
X= 4133806 2113 2154 41 24+5
BH-96Y= 139 43 321.64
X= 411 466.68 1991 2040 49 40+8
Research Methodology
• Preparing 34, with 134 thin sections by author and from NOC.
• Analysing 35 samples by Calcimetry test to determine the
calcite, dolomite, and residual materials ratios.
• Digitizing the available logs using Neural software.
• Calculating the reservoir parameters and re-plotting the
digitized curves using Excel and Grapher softwares.
• Drawing the stratigraphic columns, correlations, maps, and the
crossplots using Log Plot, GIS and Grapher softwares.
• Making lateral variation (correlation) in the studied wells for
the formation by using Petrel software.9
Lower Qamchuqa Formation
• The Qamchuqa sequence studied in its type section was represented by
massive, rather argillaceous, fossiliferous limestones, usually dolomitized,
interbedded with crystalline dolomites.
• The Lower Qamchuqa Formation thickness in High Folded Zone was about
250 to 300 m.
• The Lower Qamchuqa Formation was deposited in a purely marine neritic
environment which affected slightly by terrigenous supply.
• The formation at Bai-Hassan Oilfield is overlained unconformably by the
shale beds of Nahr Umr Formation and underlained conformably by Garagu
Formation.
• The Lower Qamchuqa Formation age considered being Early-Aptian
depending on some index fossils such as O. lenticularis, Choffatella
decipiens and Orbitolina cf with Acicularia cf.10
Chapter Two
Petrography and Diagenesis
processes
11
• This chapter focused on the thin sections
analysis which include the skeletal and non-
skeletal components, with different types of
diagenetic processes in three studied wells
BH-86, BH-96, BH-102 for Lower Qamchuqa
Formation.
12
Skeletal components
• The skeletal grains commonly consists of benthonic
foraminifer’s represented by Orbitolina, Textularia,
Meliolids, Radiolaria spines, Cyclammina lenticularis
and Chofatella, with others Echinoderm, Bioclast and
Algae (Acicularia), whereas the non-skeletal grains
included pellets and lithoclasts (extraclasts) with
Quartz grains in parts.
13
Common Diagenesis processes of Lower Qamchuqa
Carbonate Rocks
• Many types of diagenetic processes were observed in
the present study which represented by; cementation,
micritization, dissolution, mechanical and chemical
compactions (including pressure dissolution),
Stylolite, neomorphism (recrystallization and
inversion), anhydritization, and dolomitization.
14
15
This figure shows different types of diagenesis, porosities and
skeletal grains with depth for the L. Qamchuqa Fn. in the studied
well BH-86.
16
This figure shows
different types of
diagenesis, porosities
and skeletal grains
with depth for the L.
Qamchuqa Fn. in the
studied well BH-102.
17
This figure shows
different types of
diagenesis, porosities
and skeletal grains
with depth for the L.
Qamchuqa Fn. in the
studied well BH-96.
18
Orbitolina
Chofatella Radiolaria spines Cyclammina
MeliolideTextularia
19
Aciculina Pellet
BioclastsLenticulariaEchinoderm
Extraclast & Quartz grains
20
Micritization
DissolutionAnhydritization
Inversion
Common Diagenesis
Processes
Chapter Three
Microfacies and Depositional
Environments
21
• This chapter focused on the stratigraphy study.
• Detecting microfacies for the L. Qamchuqa
Formation depending on the classification of Dunham
(1962).
• Detecting the paleo-depositional environment of the
formation.
22
23
Four types of microfacies with five sub-microfacies kinds
detected in the Lower Qamchuqa Formation.
Lithological Description of Lower Qamchuqa
Formation
The lithology of the Lower Qamchuqa Formation
determined depending on:
• Optically from the microscopic study of thin sections
• From the gamma ray log.
• Calcimetry analysis for a number of selected rock
samples.
• The results checked with the descriptions done for the
formation in the final reports (NOC). 24
25
calcimetry test Showing
CaCo3
& Mg (CaCo3)2
Ratios
26
Str
atig
raph
icco
lum
nan
dm
icro
faci
eso
fth
e
Low
erQ
amch
uq
aF
orm
atio
nin
the
wel
lB
H-
86
.
27
Str
atig
raph
icco
lum
nan
dm
icro
faci
eso
fth
e
Low
erQ
amch
uq
aF
orm
atio
nin
the
wel
lB
H-
10
2.
28Str
atig
raphic
colu
mn
and
mic
rofa
cies
of
the
Low
erQ
amch
uq
aF
orm
atio
nin
the
wel
lB
H-
96
.
29
This figure representing the
microfacies correlation that
showing the vertical and
lateral facies changes in the
studied wells for the Lower
Qamchuqa Formation.
Depositional environment Model
30
Chapter Four
Shale Volume Calculation and
Porosity Log
31
32
Gamma ray log for the L.
Qamchuqa Formation
including uppermost part of
Nahr-Umr Formation in the
studied wells, BH-86, BH-
102 and BH-96.
The middle part of the
formation of being lower
gamma ray radiation than the
lower and upper parts of the
formation.
The highest recorded values
of gamma ray was around
70API.
So no pure shale beds are
expected to be exist in the
studied Lower Qamchuqa
Formation
33
*After applying the Larionov
equation the shale volume
being estimated.Vsh =0.33[2(2*IGr)-1.0] for the
rocks older than Tertiary
The upper 20-25m of the Lower
Qamchuqa Formation looks to be
generally a shaly interval followed
by around 35m clean zone with less
than 10% shale content.
Depending on standard proposed
by Ghorab, 2008 the shale content
zonation detected.
<10%...... Clean Zone
10-35%... Shaley Zone
>35%....... Shale Zone
Wells FormationDepth
Interval mZonation
Thickness
m
Avg.
V-Sh %
BH-86
Nahr Umr 2172-2174 Shaly-shale zone 2 31.67
Lower Qamchuqa
2174-2202 Shaly zone 28 24.05
2202-2237 Clean zone 35 3.63
2237-2240 Shaly zone 3 18.92
2240-2248 Clean zone 8 6.07
2248-2269 Shaly zone 21 15.91
2269-2288 Clean zone 19 8.09
2288-2295 Shaly zone 7 19.65
2295-2299 Clean zone 4 4.03
2299-2302 Shaly zone 3 14.75
2302-2309 Clean zone 7 6.57
2309-2316 Shaly zone 7 14.75
2316-2320(TD) Clean zone 4 5.30
BH-102
Nahr Umr2110-2112 Shaly zone 2 31.64
2112-2113 Shale zone 1 37.34
Lower Qamchuqa2113-2131 Shaly zone 18 16.68
2131- 2140(TD) Clean zone 9 2.45
BH-96
Nahr Umr 1989-1991 Shale zone 2 36.59
1991-2010 Shaly zone 19 18.80
34
35
• This figure shows the bulk
density recording in the
three studied wells for the
Lower Qamchuqa
Formation.
36
*For converting the recorded
bulk density to density
porosity (ΦD), the below
equation has been applied.
ΦD= (ρma-ρb) / (ρma-ρfl)
*The upper part of the
formation generally has a
porosity ranging between (6-
12) %.
*Middle part is not of
observable difference from
the upper part in well BH-86.
*Lower part (2-10%)
*Highest porosity values
observed between depths
2202 and 2212m in the well
BH-86 at which porosity
between 15 - 20%.
37
*This figure shows the
neutron porosity logs
reading for the Lower
Qamchuqa Formation in
the three studied wells,
BH-86, BH-102 and BH-
96.
*The recorded Neutron
porosity values (ΦN) are
almost the same as the
calculated porosity from
the density log.
38
*This figure displayed Δt
reading for the Lower
Qamchuqa Formation in
the three studied wells,
BH-86, BH-102 and BH-
96.
*In most parts of the
formation Δt values
ranging between 50 and
60 μsec/ft.
*Relatively higher Δt
values have been recorded
between depths 2202 and
2012m in the well BH-86.
39
*For converting the
recorded Δt to sonic
porosity (ΦS), the
below equation has
been applied
ΦS = (∆tlog-∆tma) /
(∆tfl-∆tlog)
*As no significant
difference observed
between the calculated
porosities from
density, neutron, and
sonic logs for Lower
Qamchuqa Formation
in the studied wells.
Correction of Porosity from Shale Impact
The shale impact applying by equations proposed by Dewan
(1983):
• Correction of Φ-Density: ΦDcor= ϕD- (Vsh*ρsh)
• Correction of Φ-Neutron: ΦNcor = ΦN – (Vsh* ΦNsh).
• Correction of Φ-Sonic: ΦScor = ϕS - Vsh*(Δtsh-Δtma /
Δtfl-Δtma).
• The highest reduction in the porosity values due to
correction can be seen in the upper part of the formation in
the three studied wells.
• The both ΦN and ΦS were more influenced by shale
impact than ΦD because density logging tool is less
affected by the existence of shale.40
41
43
44
45
*To further evaluating and
characterizing Lower
Qamchuqa Formation in
this study, the calculated
ΦN-Dcor values will be
mainly depended on
because this type of
measured porosity is best
representing the existed
primary and secondary
porosities.
*The North standard,1985
for evaluating porosity
ranges will be used for
describing the porosity
qualitatively in this study.
46
Permeability
• In the present study, the permeability data from core test
analysis was available for selected intervals for the Lower
Qamchuqa Formation in the three studied wells.
• To obtain permeability in mD for the whole studied
sections of Lower Qamchuqa Formation, the Multiple
Linear Regressions (MLR) method was used.
47
48
Measured permeability
from core test analysis
(green line) and the
calculated permeability
from log data using
equation (red line) for the
Lower Qamchuqa
Formation in the three
studied wells.
49
*Measured permeability
from log data using
equation for the Lower
Qamchuqa Formation in
the studied wells.
*Permeability in the L.
Qamchuqa Formation
ranged between
0.001mD to 2mD.
50
• Reservoir Units
L. Qamchuqa Formation in
the well BH-86 subdivided
into 6 RU & 2 sub-RU
depending on the shale
content, porosity, and
permeability values,
regardless which type of
fluid are stored in the
reservoir.
51
52
53
54
55
This Figure is showing a correlation
between the identified reservoir units of
Lower Qamchuqa Formation in the
three studied wells.
Chapter Five
Saturations and Reservoir
Characterization
56
57
*The used resistivity logging tools,
(MSFL),, (LLS), and (LLD)
represented by Rxo, Ri, and Rt
were recorded respectively for the
Lower Qamchuqa Formation in the
three studied wells.
*The non-separated between Rxo and Rt
curves will be an indication to
hydrocarbon bearing zones and vice
versa.
58
Water Saturation and Hydrocarbon
*The Archie equation
using to calculating water
saturation from log data.
* For better representing
the hydrocarbon
saturation, both movable
and residual hydrocarbon
percentages have been
calculated.
• Water Saturation:
• SW = 𝑛 𝐹∗𝑅𝑤
𝑅𝑡= (𝐹 ∗
𝑅𝑤
𝑅𝑡)1/n
• Movable hydrocarbon:
saturation
Shm = Sxo – Sw.
• Residual hydrocarbon
saturation
Shr = 1.0 – Sxo
59
60
*RU-6: Lowest Sh exists in the
well BH-96, whereas in the
two other wells this unit is
almost of similar Sh but the
percentages of the Shr is higher
in the well BH-86.
RU-5: is of high Sh
percentages which most of
them is movable except a
noticeable percentage of Shr in
the well BH-86.
RU-4: is almost like RU-5 in
the well BH-86 but with a
lower percentage of Sw.
RU-3 to RU-1: are of high
Shm in the well BH-86 except
some horizons in which
noticeable Shr can be seen.
61
*The Movable HydrocarbonIndex (MHI) is used to estimatethe movability of thehydrocarbons.
𝐌𝐇𝐈 =𝑺𝒘
𝑺𝒙𝒐
=
𝑹𝒙𝒐
𝑹𝒕𝑹𝒎𝒇
𝑹𝒘
*The upper part of theformation in the wells of BH-86, BH-102, and BH-96representing by RU-5 and RU-6 are totally containingmovable hydrocarbons.
*Most parts of the formation inthe well BH-86 are containingmovable hydrocarbons withnarrow horizons of non-movable hydrocarbons.
62
• The effective contribution
of fractures in flowing can
obviously be seen in most
of the reservoir units in the
three studied wells.
• The less contribution of the
fractures with matrix
porosity can be noticed in
the RU-5 in the well BH-
86.
Fluid Flow within Lower Qamchuqa Formation
63
Fo
ur
gro
ups
of
FZ
Iv
alu
es
reco
gn
ized
dep
end
ing
on
the
chan
ge
inth
esl
op
eo
fth
etr
end
lin
eso
fd
istr
ibu
ted
FZ
Isa
mp
le
po
ints
.
64
• Lower Qamchuqa Formation in the studied wells looks to own four unique
Hydraulic Flow Units (HFU) with the FZI ranges and average values
shown in the figure below.
• The less potential flow unit looked to be HFU-1 in the well BH-86 and the
best appeared to be HFU-4 in the well BH-96.
Wells FZI Range Average FZIHydraulic
Flow Units
BH-86
0-0.5 0.28 HU-1
0.5-2 1.03 HU-2
2-5 3.06 HU-3
>5 205.77 HU-4
BH-102
0 -1 0.64 HU-1
1-2 1.42 HU-2
2-5 3.23 HU-3
>5 158.34 HU-4
BH-96
0-2 0.61 HU-1
2-3 1.45 HU-2
3-5 2.96 HU-3
>5 254.63 HU-465
Net to Gross Reservoir and Pay Ratios
• Net reservoir thickness is the total thickness of the reservoir,
which Vsh, Φ, and K cutoffs are applied.
• Net pay thickness comprises those hydrocarbon bearing
reservoir intervals, additionally by log derived water saturation
cutoff.
• The thickness of the net production considered to be the
fraction of the net pay (reservoir) thickness that subjected to
the MHI cutoff.
66
67
Well
Øcutoff using
Kcutoff 0.1
%
Øcutoff using
Kcutoff 1.0
%
BH-86 4.8% for gas 16% for oil
BH-102 8.4% for gas 20% for oil
BH-96 9.9% for gas 24.9% for oil
68
Well
Swcutoff using
Øcutoff 16
%
Swcutoff using
Øcutoff 4.8
%
BH-86 17% for oil 42% for gas
BH-102 19% for oil 42% for gas
BH-96 10% for gas 26% for gas
69
Fo
rma
tio
n
Res
erv
oir
Un
its Gross
Thick.
(m)
Net
Reservoi
r
Thick.
(m)
Net
Pay
Thick.
(m)
Net
Productio
n
Thick.
(m)
N/G
Reservoi
r
(%)
N/G
Pay
(%)
N/G
Product.
(%)
Lo
wer
Qa
mch
uq
a
6 28 0.0 0.0 0.0 0.0 0.0 0.0
5 15 4 1.9 1.4 2.73 1.3 0.95
4 19 0.0 0.0 0.0 0.0 0.0 0.0
3 32 7.1 2.4 2.4 4.86 1.64 1.64
2B 20 0.6 0.4 0.4 0.41 0.27 0.27
2A 14 0.0 0.0 0.0 0.0 0.0 0.0
1 18 0.0 0.0 0.0 0.0 0.0 0.0
Total 146 11.7 4.7 4.2 8.0 3.21 2.86
Calculated N/G reservoir, pay, and productive ratios for the
Lower Qamchuqa Formation in the studied well BH-86 (case of
oil production).
70
71
Fo
rma
tio
n
Res
erv
oir
Un
its Gross
Thick.
(m)
Net
Reservo
ir
Thick.
(m)
Net
Pay
Thick.
(m)
Net
Productio
n
Thick.
(m)
N/G
Reservo
ir
(%)
N/G
Pay
(%)
N/G
Product.
(%)
Lo
wer
Qa
mch
uq
a
6 28 17.8 9.45 5.8 12.19 3.97 3.97
5 15 15 15 12 10.27 10.27 8.21
4 19 18 17.3 17.3 12.32 11.84 11.84
3 32 22.8 20.28 20.08 15.61 13.89 13.75
2A 20 13.4 10.9 10.2 9.17 7.46 6.98
2B 14 8.55 5.75 5.75 5.85 3.93 3.93
1 18 4.55 2.6 2.05 3.11 1.78 1.4
Total 146 100.1 81.28 73.18 68.52 53.14 50.08
Calculated N/G reservoir, pay, and productive ratios for the
Lower Qamchuqa Formation in the studied well BH-86 (case of
gas production).
72
73
Fo
rma
tio
n
Res
erv
oir
Un
its Gross
Thick.
(m)
Net
Reservoir
Thick.
(m)
Net
Pay
Thick.
(m)
Net
Production
Thick.
(m)
N/G
Reservoir
(%)
N/G
Pay
(%)
N/G
Productiv
e
(%)
Lo
wer
Qa
mch
uq
a
6 18 0.0 0.0 0.0 0.0 0.0 0.0
5 19 1.2 0.0 0.0 6.3 0.0 0.0
Total 37 1.2 0.0 0.0 6.3 0.0 0.0
Calculated N/G reservoir, pay, and productive ratios for the
Lower Qamchuqa Formation in the studied well BH-102 (case
of gas production).
74
1
This figure Showing
net reservoir, net
pay, and net
productive zones
with the used cutoffs
for the Lower
Qamchuqa
Formation in the
studied well BH-102.
75
Fo
rma
tio
n
Res
erv
oir
Un
its Gross
Thick.
(m)
Net
Reserv
oir
Thick.
(m)
Net
Pay
Thick.
(m)
Net
Producti
on
Thick.
(m)
N/G
Reserv
oir
(%)
N/G
Pay
(%)
N/G
Product
ion
(%)
Lo
wer
Qa
mch
uq
a 6 19 0.0 0.0 0.0 0.0 0.0 0.0
5 26 1.5 1.2 1.2 3.33 2.66 2.66
Total 45 1.5 1.2 1.2 3.33 2.66 2.66
Calculated N/G reservoir, pay, and productive ratios for the
Lower Qamchuqa Formation in the studied well BH-96 (case of
gas production).
76
1
This figure Showing
net reservoir, net pay,
and net productive
zones with the used
cutoffs for the Lower
Qamchuqa
Formation in the
studied well BH-96.
• RU-3 looked to be the most potential reservoir unit to
produce gas followed by RU-4 in the well BH-86.
• Whereas RU-1 at the lower part of the formation showed
the least potentiality for gas production among the
identified reservoir units.
• The whole penetrated part of the formation in the two wells
BH-102 & BH-96 appeared to be of no any ability to
produce oil or even to be considered as a reservoir or pay.
• The formation's greatest problem in the mentioned two
wells is the lack in the require porosity. 77
Chapter Six
Conclusions and
Recommendations
78
Conclusions
1. Depending on petrographic study, gamma ray log, and calcimetry test; the upper
part of Lower Qamchuqa Formation in the study area looks to be composed of
shaly limestone, limestone, dolomitic limestone, interbedded occasionally with
thin beds of marl. Whereas, the middle and lower part of the formation as
appeared in the well BH-86 composed of dolomite, shaly limestone, dolomitic
limestone, and limestone.
2. The skeletal components in the formation as appeared from petrography study
are mainly consist of benthonic foraminifera (Orbitolina, Textularia, Choffatella,
and Meliolids) in addition to echinoderms, bioclasts, and algae; whereas the non-
skeletal grains considered as extraclasts (Quartz grains) and pellets.
3. Diagenetic processes which affected the formation are; micritization, dissolution,
mechanical and chemical compactions (stylolite), cementation, and
dolomitization.
4. Different types of secondary porosity co-exist in the formation such as;
interparticle, intrafossils, intercrystalline, fracture, channel, vuggy, cavern, and
moldic porosities as a result of the diagenesis processes.
79
4-Lime mudstone microfacies, Dolostone microfacies, Lime
wackestone microfacies (subdivided into benthonic foraminiferals lime
wackestone sub-microfacies, benthonic foraminiferals lime mudstone /
wackestone sub-microfacies, pelloidal lime mudstone/wackestone sub-
microfacies, bioclast lime wackestone sub-microfacies, and Orbitolina
lime wackestone sub-microfacies), and Orbitolina Lime packstone
microfacies.
5. The paleo-depositional environment of the Lower Qamchuqa
Formation in the studied area is restricted and shallow open marine
environment (interior platform).
6. The formation (depending on petrophysics and log analysis study) is
of relatively low shale content (<35%), except some horizons at the
upper part of the formation in which the shale content reached to
about 70%.
80
7. The upper part of the formation in the three studied wells can be subdivided into
two reservoir units (RU-5 and RU-6). The middle and lower parts of the formation
in well BH-86 can be subdivided to four additional reservoir units (RU-1 to RU-4).
8. RU-5 is of the best reservoir property among the distinguished reservoir units of
the formation especially in the well BH-86 (average 3.135% shale content, 6.2%
porosity, and 1.75mD permeability). On the other hand, RU-1 in the well BH-86 is
of the least reservoir property with average 9.48% shale content, 3.64% porosity,
and 0.5mD permeability.
9. Almost the whole parts of the formation in the well BH-86 is containing
hydrocarbon with different saturations with being RU-6 in the well BH-96 of the
lowest hydrocarbon saturation.
10. Fractures contributed effectively in the flow of the fluids within the formation in
the three studied wells.
81
14. The fluids within the Lower Qamchuqa Formation in the studied wells are
flowing as four hydraulic flow units with different average FZI values.
15. Only about 8% of the gross 146m of the formation (in the well BH-86) is
expected to be of the required reservoir properties for oil production. The
actual productive thickness is only about 2.8%.
16. In the well BH-86 and for the case of gas production; 68% from the gross
thickness of the formation is of acceptable reservoir properties. More than 50%
as actual productive thickness from the gross 146m of the formation.
17. The whole penetrated parts of the formation in the two wells BH-102 and BH-
96 are of no any ability to produce oil or even to be considered as an
acceptable reservoir. The same is true for gas production also except about
1.2m within RU-5 in the well BH-102.
82
83
Thanks for
your attention