Sedimentological studies of marine oil ﬁelds in order to reduce drilling risk and environmental pollution: a case study of South of Iran

BOHR International Journal of Civil Engineering
and Environmental Science
2023, Vol. 1, No. 2, pp. 50–62
DOI: 10.54646/bijcees.2023.06
www.bohrpub.com
CASE STUDY
Sedimentological studies of marine oil fields in order
to reduce drilling risk and environmental pollution: a case
study of South of Iran
Samira Abbasi1, Saeid Pourmorad2*, Ashutosh Mohanty3 and Shakura Jahan4
1Department of Environment, Natural Resources Faculty, Khorramshahr University of Marine Science and Technology,
Khorramshahr, Iran
2Institute of Surface-Earth System Science, Tianjin University, Tianjin, China
3Disaster Management and Environment Madhyanchal Professional University, Madhya Pradesh, India
4Department of Environmental Sciences at Louisiana State University, Baton Rouge, LA, United States
*Correspondence:
Saeid Pourmorad,
omid2red@gmail.com
Received: 20 April 2023; Accepted: 13 May 2023; Published: 21 July 2023
Detailed studies of sedimentology and petrology of oil fields, especially oil fields located in the seas, play a
very important role in reducing the risk of danger, increasing harvest, and reducing the amount of environmental
pollution. The South Pars gas field in the waters of the Persian Gulf on the joint border line of Iran and Qatar and
on the south coast of Iran has been used as a comprehensive model for this type of study. In these studies, the
sedimentary environment and sequential stratigraphy of the Scorpion and Sarvak Formations in the South Pars
gas field in wells 1 and 3 have been investigated. Microscopic studies and analysis of gamma-ray and acoustic
diagrams of these formations have led to the identification of 9 facies in three facies belts related to wetland,
dam, and open sea. Dam facies have been identified only in Sarvak formation. This study shows that the facies
belts of the abovementioned formations in a ramp platform are also sloping. Sequence stratigraphy of Kazhdomi
and Sarvak Formations in the study wells shows that Kazhdomi Formation has one sedimentary sequence (third
category cycle) and Sarvak Formation has two sedimentary sequences. The lower boundaries of sequences 1 and
2 and the upper boundary of sequence 3 have type 1 (SB1) discontinuities, and the boundary between sequences
2 and 3 has type 2 (SB2) discontinuities.
Keywords: South Pars field, Sarvak formation, diagenetic studies, sequential stratigraphy, environmental pollution
Introduction
Sedimentological studies, especially petrographic studies,
sedimentary facies, sequence stratigraphy, and stratigraphy
of oil and gas fields, play a very important role in reducing
drilling risks and pollution (1).
Environmental pollution can be significantly prevented
with detailed geological studies and determination of ideal
locations for drilling oil wells (2).
In fact, determining the type of formation and sedimentary
characteristics of the formations being drilled plays an
important role in determining the type of drilling mud and
environmental measures, including the use of oily and non-
oily mud during drilling (3).
Sarvak Formation is known as a reservoir rock and
Kazhdomi Formation is known as a very important source
rock in most of Iran’s oil fields (4, 5). Knowing the facies
and sequences of these two formations along with their
lateral changes in understanding them better is necessary to
calculate the production and accumulation of hydrocarbons
(6, 7).
In fact, careful study of these formations will lead to
accurate paleogeographic reconstruction of albino-threonine
and the factors affecting it. In addition, understanding the
50

10.54646/bijcees.2023.06 51
depth of sea forward and backward in the samples taken and
their sequential stratigraphy can be the main objectives of this
study. In fact, in these studies, the data obtained from wells
No. 1 and 3 have been used as a model for similar studies.
Geological location of the studied
wells
South Pars gas field, the largest gas field in the world, is
located in the Persian Gulf waters on the joint border line
between Iran and Qatar, 100 km from the port of Asaluyeh,
on the south coast of Iran and 105 km northeast of the Qatar
Peninsula (Figure 1).
Research method
To study Sarvak and Kazhdomi Formations in wells No.
1 and 3 located in the South Pars gas field, paleolag data
(gamma and sonic diagrams) as well as fossil and lithological
studies on microscopic thin sections (Thinsections) have
been used. In these studies, first, all the petrographic and
diagenetic properties of the studied samples were identified,
then with the help of these data, the diagenetic properties
were analyzed, and a sedimentary model was drawn. In the
end, the sequential stratigraphic studies of the studied wells
have been investigated in detail.
In these studies, 232 microscopic thin sections were used to
identify allocums and orthoschemes and to name carbonate
rocks using Dunham’s (8) classification. Also, to determine
the facies and introduce the sedimentary model, Karuzi
method (1989) has been used.
According to this method, the type of components of facies
and their frequency were determined. The exact number of
sedimentary sequences in wells 1 and 3 was determined by
accurately determining the sedimentary environment and
constituent facies.
FIGURE 1 | Location of South Pars field adjacent to other oil and gas
fields in the Persian Gulf and relative to the collapse of Dezful (9).
Discussion
Sarvak Formation in the sample section is 821.5 m and
consists of fine-grained clay limestones and iron-bearing
limestones (Figure 2) (10). This formation is divided into two
members in the South Pars gas field from bottom to top based
on lithological and reservoir properties: Madoud (dolomitic
limestone) and Ahmadi (Chile-Marni).
Also, Ilam Formation is composed of dolomitic
limestone and includes limestones of the
Santonine-Campanian age (11).
Petrography of components
To identify and name microfacies and interpret the
sedimentary environment, as well as to study diagenetic
processes in order to interpret the diagenetic history,
it is necessary to know the components in the studied
samples (12).
The components in the microfacies of these two
formations were classified into three groups including
FIGURE 2 | Lithological column of Sarvak Formation in sample
section in Bangestan anticline (James and wynd, 1965 with some
changes).

52 Abbasi et al.
non-skeletal carbonate components, skeletal carbonate
components, and non-carbonate and detrital components.
Non-skeletal carbonate components
The most important non-skeletal carbonate components
observed include ploids and intraclasts. The size of peloids
observed in Sarvak Formation is about 0.3–0.5 mm without
internal structure. These ploids make up about 30–35%
of the non-skeletal carbonate components in the observed
samples (Figure 3A). The presence of ploids indicates
shallow tropical and subtropical marine environments,
but can also be found on continental slopes and in
basins (13).
In the studied samples of Sarvak and Kazhdomi
Formations in the underground sections of the South
Pars gas field, intraclasts without very good sorting and
in different sizes (0.3–0.7 mm) have been observed (3-B).
FIGURE 3 | Microscopic images of the studied samples.
(A) Examples of ploids (blue arrow) and intraclasts (red arrow)
in Sarvak Formation (underground section No. SP3 of Sarvak
Formation South Pars gas field, depth 1172 m, xpl light). (B) A sample
of ploids of Kozhdami Formation (underground section No. SP3 of
Kozhdami Formation, South Pars gas field, depth 1245 m, xpl light).
(C) Sample of millivolts of Sarvak Formation (underground section
No. SP1 of Sarvak Formation South Pars gas field, depth 918 m,
xpl light). (D) Trocholina altispira foraminifera in samples of Sarvak
Formation (underground section No. SP3 of Kozhdami Formation of
South Pars gas field, depth 1245 m, xpl light). (E) Benthic foraminifera
Trocholina altispira in Kozhdami Formation (underground section No.
SP1 Kozhdami Formation South Pars gas field, depth 1006 m, xpl
light). (F) Hemicyclamine benthic foraminifera in Kozhdami Formation
(underground section No. SP1 of Kozhdami Formation, South Pars
gas field, depth 1006 m, xpl light).
Intraclasts are fragments of a loose sedimentary bed that are
re-transported and deposited within the sedimentary basin
(14, 15).
Skeletal carbonate components
(foraminifera)
The most important carbonate components identified
include Foraminifers, Ostracoda, Bivalvia, Gastropoda,
Algae, Cnidaria, and Echinodermata. The most abundant
foraminifera in Sarvak and Kazhdomi Formations can be of
different types of miliolids (Figure 3C). Other foraminifera
in Sarvak and Kazhdomi Formations include Orbitolina
gr. concava. Miliolite and Nazaara are indicators of the
swamp environment.
Orbitolina is found in the area of lagoons and dams
and is in the form of wide cones that are seen in both
Sarvak and Kazhdomi Formations. In the Sarvak Formation,
pelagic foraminifera including lenticulina and allogesthina
were also observed (Figure 3D). Foraminifers are composed
of low or high magnesium calcite and rarely aragonite (16).
Ostracodes in Sarvak and Kazhdomi Formations constitute
about 5% of skeletal carbonate components. These ostriches
are generally benthic and no pelagic types of ostracodes have
been observed in this formation. Their average size is about
0.2 mm (Figure 3D).
Ostriches are valuable representations of ancient
environmental conditions such as salinity, oxygen
production, bed bottom, and water depth (17).
In the study areas, bivalve crust fragments with a frequency
of about 5% of skeletal carbonate components have been
observed. The size of these bivalves has been observed from
about 0.5 mm to several millimeters. Two rudist spheres have
also been observed in the Sarvak Formation (Figures 3E, 4A).
The shell of most bivalves is composed of aragonite, and some
have mixed mineralogy (18, 19).
Gastropods are one of the many components of lime-
stone (20, 21). Gastropods are not very common in Sarvak
and Kazhdomi Formations and have been seen in lagoon
sections along with other fossils in the form of longitudinal
and transverse sections (Figures 5B, C). The average size of
observed gastropods has been about 0.5 mm.
Red algae are not seen in the studied underground areas
and green algae are also observed to a small extent. These
algae are usually located in the lagoon section (Figure 5D).
Algae live mainly in shallow and warm environments (neritic
part) of the sea and are less present in deep environments
(14, 22).
Cedaria in Sarvak and Kazhdomi Formations in the
studied sections form a very small part of the components
(Figure 5E). Cedarias include anthozoans (corals) that often
live in the sea and are attached to the floor (14).
Examples of this echinoderm have been observed in
Sarvak and Kazhdomi Formations (Figure 5F). Fragments

10.54646/bijcees.2023.06 53
FIGURE 4 | Microscopic images of the studied samples. (A) A sample
of Benzicine Nazazata foraminifera (underground section No. SP1
of Sarvak Formation, South Pars gas field, depth 936 m, xpl light).
(B) An example of benthic foraminifera in Sarvak Formation. The blue
arrow indicates a sample of milliolides (underground section No. SP3
of Sarvak Formation, South Pars gas field, depth 1168 m, xpl light).
(C) Framinifer benthic textularia (underground section No. SP1 of
Sarvak Formation South Pars gas field, depth 1165 m, xpl light). (D) A
sample of pelagic foraminifers in Sarvak Formation (underground
section No. SP3 of Sarvak Formation, South Pars gas field, depth
of 1172 m, xpl light). (E) Bentic ostracod in Sarvak Formation
(underground section No. SP3 of Sarvak Formation South Pars gas
field, depth 1165 m, xpl light). (F) Fragments of two layers of Sarvak
Formation (underground section No. SP3 of Sarvak Formation South
Pars gas field, depth 1165 m, xpl light).
of crinoid spines have also been observed in some sections
(Figure 6A). Echinoderm fragments are present in lime-
stone formed in shallow marine environments plus deep
marine environments (23).
Non-carbonate components
The most important non-carbonate components in the
Sarvak and Kazhdomi Formations are quartz and glauconite.
These components appear to be mostly of diagenetic origin
(Figures 6B, C).
Diagenesis
The diagenesis of carbonates is associated with various
processes that take place in near-sea and metallurgical
environments and down to the deep burial environment (24).
The types of diagenetic processes identified in the Sarvak
and Kazhdomi Formations in the South Pars gas field
identified include the following:
FIGURE 5 | Microscopic images of the studied samples. (A) A piece
of two-story road in Sarvak Formation (underground section No. SP1
of Sarvak Formation South Pars gas field, depth 918 m, xpl light).
(B) Longitudinal section of a gastropod (underground section No.
SP3 No. Sarvak Formation South Pars gas field, depth 1172 m, xpl
light). (C) Transverse section of a gastropod (underground section
No. SP1 No. Kozhdami Formation of South Pars gas field, depth
1026 m, xpl light). (D) Green algae in samples of Sarvak Formation
(underground section No. SP1 of Sarvak Formation South Pars gas
field, depth 986 m, xpl light). (E) An example of a coral in Kozhdemi
Formation (underground section No. SP3 of Kozhdami Formation,
South Pars gas field, depth 1212 m, xpl light). (F) Echinoderm
section in Sarvak Formation (underground section No. SP3 of Sarvak
Formation South Pars gas field, depth 1165 m, xpl light).
Cementing
In Sarvak and Kazhdomi Formations, the most important
and abundant cement is calcite cement.
Cementation is a diagenetic process by which deposited
minerals settle in the sediment voids and cause the sediments
to become rocky Burley and Worden (25, 26).
Platy calcite cement
This cement is one of the most abundant cements in the
samples and has been observed in most of the fractures and
cavities in the sections and is composed of large and clear
calcite crystals (Figure 7A).
Equant calcite mosaic cement
In the studied samples, the presence of such cements with
equal crystals in the distances between the grains and also as
a fracture filler has been observed (Figure 7B). This cement

54 Abbasi et al.
is common in meteoric and burial diagenetic environments
and is the result of a slow growth rate (27).
Drusy cement
This cement with its shaped to semi-shaped crystals in some
cases has filled the inside of oysters of different organisms
in the Sarvak and Kazhdomi Formations (Figures 7C, D).
This cement fills some cavities, intergranular pores, and
sometimes mold pores and fractures in the studied sections
Bathurst (28).
Compression and compression
dissolution
Compression and compression dissolution are the two main
diagenetic processes that generally depend on the depth of
sediment burial (29, 30). The most common structures due
to compression dissolution (chemical compaction) in Sarvak
and Kazhdomi Formations are stylolites (Figures 8C, D).
Neomorphism or neoplasm
The neomorphism observed in Sarvak Formation is an
incremental neomorphism. In this case, dolomicrite (less
than 5 microns) is converted into dolomicrospar (5–30
microns) or dolomicrospar into pseudospar (larger than 30
microns) (Figure 8E).
The phenomenon of neomorphism is associated with
changes in the mineralogy or fabric of sediment (31, 32).
Dolomitization
Dolomites often form suitable hydrocarbon reservoirs
because of this process, which increases porosity Allen and
Wiggins (33). Different types of dolomites in the Sarvak and
Kazhdomi Formations can be determined according to the
shape of the crystal border (flat or non-flat) and the size of
the crystals:
Microcrystalline dolomites or
dolomicrosparite
This type of dolomite is more abundant than the first type of
dolomite in terms of abundance in the Sarvak and Kazhdomi
Formations (Figure 9B). Dolomicosparites are histologically
the same size and their crystals are semi- shaped to shaped
with planar’s borders.
In this type of dolomite, the size of the crystals is 62–250
microns and they are composed of crystals of different sizes,
dense, semi-shaped to amorphous, and uneven crystalline
borders. These types of dolomites have a lower frequency
than dolomicospars in Sarvak Formation.
(Figure 9C) and they were not observed in the
Scorpion Formation.
Ironing
Iron compounds (hematite and limonite) have been observed
more abundantly in some specimens of Sarvak and
Scorpion, especially in the intercrystalline pores between
dolosparite crystals and dolomicrospars (Figures 10A, B).
Iron compounds have also been observed along acetylides
and in fossil cells (mostly foraminiferal cells). Ironmaking is
generally associated with burial diagenesis.
Porosity
The types of porosities in the samples of Sarvak and
Kazhdomi Formations in the South Pars gas field include the
following:
FIGURE 6 | Microscopic images of the studied samples. (A) An example of Echinoderm thorn in Sarvak Formation (underground section No.
SP1 of Sarvak Formation South Pars gas field, depth 1172 m, xpl light). (B) Gluconite grain as one of the non-detrital components in Sarvak
and Kozhdami Formations (underground section No. SP3 of Sarvak Formation South Pars gas field, depth 1168 m, xpl light). (C) Destructive
quartz grains as non-destructive components observed in Sarvak Formation (underground section No. SP1 of Sarvak Formation South Pars
gas field, depth 1172 m, xpl light).

10.54646/bijcees.2023.06 55
FIGURE 7 | Microscopic images of the studied samples. (A) Cal-
cite plate cement—pay attention to the large crystals of this cement
(underground section No. SP3 No. Kozhdami Formation of South
Pars gas field, depth 1228 m, xpl light). (B) Calcite all-dimensional
cement—pay attention to crystals approximately the same size as
cement (underground section No. SP3 of Kozhdami Formation of
South Pars gas field, depth 1250 m, xpl light). (C) Druze calcite
cement—pay attention to the large crystals of this cement in
the center of the hole (underground section No. SP3 No. Sarvak
Formation South Pars gas field, depth 1172 m, xpl light). (D) Calcite
Druze Cement (underground section No. SP3 of Kozhdami Formation
of South Pars gas field, depth 1224 m, xpl light). (E) Calcite drossite
cement can be seen in a cavity of Sarvak Formation. The direction
of the arrow shows an increase in the size of the cement crystals
(underground section number SP3 of Sarvak Formation, South Pars
gas field, depth of 1165 m, xpl light).
Porosity between crystals and particles
This type of porosity is the type of primary porosity
(34). This porosity is observed among dolomite crystals
in Sarvak Formation, which is sometimes filled with iron
oxide (Figure 10C).
Cavity porosity
In the study samples, this type of porosity, which is one of
the types of secondary porosity (35), is the loss of unstable
and soluble parts such as skeletal parts and shell fragments.
It has created these porous pores, which are sometimes
filled with anhydrite and calcite cements. This porosity is
the most common type of porosity in the studied sections
(Figures 10D, E, 11A).
FIGURE 8 | Microscopic images of the studied samples. (A) Cement
is also calcite dimension (blue arrow) which contains amorphous
dolomite crystals (underground section No. SP3 of Sarvak Formation
of South Pars gas field, depth 1172 m, xpl light). (B) Calcite drossite
cement (blue arrow) that surrounds a hole (underground section No.
SP3 of Sarvak Formation, South Pars gas field, depth 1168 m, xpl
light). (C) Stylolite in Sarvak Formation which is filled with organic
matter (underground section No. SP3 No. Sarvak Formation South
Pars gas field, depth 1172 m, xpl light). (D) Stylolite in Kozhdami
Formation which is filled with organic matter (underground section
No. SP3 Kozhdami Formation South Pars gas field, depth 1245 m,
xpl light). (E) An example of the phenomenon of neomorphism
in Sarvak Formation which has caused the transformation of
dolomicrite crystals into dolosparite (underground section No. SP3
of Sarvak Formation South Pars gas field, depth 1165 m, xpl light).
Moldic porosity
In the studied samples, this porosity, which is selected by the
stone fabric and is secondary Bathurst (28) is mostly filled
with ferrous materials or cement (Figures 10B, 11B).
Fracture porosity
Fracture porosity in carbonate rocks occurs after sediment
burial (34, 36). In the studied samples, this type of porosity is
observed in the fracture space along with cementation, which
generally has calcite mineralogy (Figures 11B, C).
Diagenetic sequences in Sarvak and
Kazhdomi Formations
According to the studies, Sarvak and Kazhdomi Formations
have been affected by different diagenetic processes over time.
Considering that the observed diagenetic processes for both
formations were almost similar.

56 Abbasi et al.
FIGURE 9 | Microscopic images of the studied samples.
(A) Microcrystalline dolomite as one of the types of dolomites
in Kozhdami Formation which is becoming coarser crystalline
dolomites (underground section No. SP3 Kozhdami Formation South
Pars gas field, depth 1165 m, Noor xpl). (B) The rhomboid crystals
of dolomicrosparite in the background of the rock are known to
be selectively formed (underground section No. SP3 No. Sarvak
Formation South Pars gas field, depth 1165 m, xpl light). (C) Dolbo
microsparite rhombohedral crystals in the microstatic background
of Sarvak Formation (underground section No. SP3 of Sarvak
Formation South Pars gas field, depth 1168 m, xpl light). (D) In
this picture, semi-shaped crystals of dolosparite in Sarvak Formation
(underground section No. SP3 of Sarvak Formation, South Pars gas
field, depth 1204 m, xpl light). (E) Amorphous crystals of Dolosparite
in samples of Sarvak Formation (underground section No. SP3 of
Sarvak Formation South Pars gas field, depth 1172 m, xpl light).
Sedimentary Facies
Facies of Kazhdomi Formation
Studies on the facies of this formation have led to
the identification of two facies belts of wetland (A)
and open sea (C).
Facies of Sarvak formation
The facies of this formation have been identified by studying
microscopic samples, which has resulted in the identification
of three facies belts of wetland (A), dam (B), and open sea (C)
as follows:
Collection of microscopic facies of wetland
environment (A)—(Lagoon facies belt)
The environment of the lagoon is limited and salinity
increases due to its location behind the Reef/Greenstone
dams. The diversity of organisms in this environment is low
but its frequency is high (37).
FIGURE 10 | Microscopic images of the studied samples. (A) Iron
oxides (brown in color) and organic matter (dark in color)
surround cavities, intercrystalline porosities of dolomites (under-
ground section No. SP3, Sarvak Formation, South Pars gas field,
depth 1168 m, xpl light). (B) Mold porosity in foraminifera filled
with iron oxides (underground section No. SP3 of Sarvak Formation,
South Pars gas field, depth 1204 m, xpl light). (C) Intercrystalline
porosities in dolomites of Sarvak Formation (underground section
No. SP3 of Sarvak Formation South Pars gas field, depth 1168 m, xpl
light). (D) Pore porosity in the calcareous field of Kozhdami Formation
(underground section No. SP3 Kozhdami Formation of South Pars
gas field, depth 1244 m, xpl light). (E) Cavity porosity in Sarvak
Formation (underground section No. SP3 of Sarvak Formation South
Pars gas field, depth 1165 m, xpl light).
Facies A1 (Madstone/Vexton bioclast with
ostracod)
This facies contains various biocells. Orbiotulin and other
benthic foraminifera form the most important skeletal
components in this subfacial. This facies is equivalent
to the standard facies 18 for Flugel carbonate platforms
(Figures 12A, B).
Facies A2 (Bioclast and Weston)
These vesicular facies contain skeletal components such as
gastropods in the form of longitudinal and transverse cuts
and bivalve fragments in large quantities. Other components
include green algae. Diagenetic processes in this facies
include advanced porosity due to fracture and cementation
of skeletal components (Figure 12C).
Facies A3 (Paxton Bioclast)
The most important skeletal components of this facies
include echinoderm, orbitulin, and trocholine. The amount

10.54646/bijcees.2023.06 57
FIGURE 11 | Microscopic images of the studied samples. (A) In this picture, examples of cavities in the microcrystalline field in Sarvak Formation
can be seen (underground section No. SP3 of Sarvak Formation, South Pars gas field, depth 1165 m, xpl light). (B) Porosity due to fracture
(blue arrow) and mold porosity (red arrow) (underground section No. SP3 of Sarvak Formation, South Pars gas field, depth of 1165 m, xpl light).
(C) Porosity due to fracture (blue arrow) (underground section No. SP3 No. Kozhdami Formation of South Pars gas field, depth 1208 ms, xpl
light).
FIGURE 12 | Microscopic images of the studied samples. (A) Facade A1: Madstone/Westxton with extruded. It has an astra code and two
cups. (B) Facade A1: Madstone/Waxton Bioclast. It has ostracods and bivalve crumbs. (C) Subfacial A2: Bioclast Wexton, bivalve, green algae
gastropod.
FIGURE 13 | Microscopic images of the studied samples. (A) Facade A3: Paxton bioclast contains trocholine, bilayer, and echinoid. (B): Facade
A3: BioClast Paxton contains ecoinoids, bivalves, and benthic fragments. (C) Facade A4: Paxton myloid ploidy contains benthic foraminifera
such as myeloid and nearly matched ploid grains.
of orbitulin and trocholine reaches a maximum of 50%
and echinoderm up to 20% (Figures 13A, B). This facade
is equivalent to the standard Facelog No. 20 for Rug
platforms (RMF20).
Facies A4 (Paxton Myeloid Ploid)
Most of this facies contains benthic foraminifera such as
myeloid and almost matched ploid granules. Bifurcated
fragments have also been seen in this facies. This facade is
equivalent to Flogel Standard Facility No. 16 for ramp type
carbonate platforms. Cementation phenomena have been
observed in these facies and porosity has not been observed
much in these facies (Figure 13C).
Interpretation of sedimentary environment
of wetland facies belt
Group A1 and A2 facies are deposited in the low-energy
part of the wetland, which mainly covers the land-facing
part. Evidence of this is the presence of limestone in large
quantities in its facies. In addition, the presence of skeletal
components of organisms that live in the low-energy part of
the lagoon, such as gastroparesis, miliolids, and green algae,
is another reason for the deposition of A2 and A1 facies in
the low-energy part of this environment.
The presence of ploidy in the A3 facies of this group is
also important for non-skeletal granules. These non-skeletal
grains are more abundant in quiet parts of the lagoon. Ploids

58 Abbasi et al.
FIGURE 14 | Microscopic images of the studied samples. (A) Facial
B1: Greenstone ploidal intracellular containing ploid and semi-
matched intracellular. (B) Facade B2: This facies includes echinoid
fragments, orbitolin foraminifera, and non-skeletal components such
as intraclasts and biceps components.
are either created by organisms or created by the crushing of
intercal near the dam and have entered the lagoon.
Barrier facies belt (B)
The facies belt of the dam is located between the two belts of
the facies of the wetland behind the dam and the open sea
and includes the following facies:
B1 loss (Ploidal intracellular greenstone)
Most of its components include ploid in the range
of 50–60% and intracellular in the range of 10–15%.
Ploids and intraclasts are semi-matched. This facies is
equivalent to the standard microfacies No. 27 of Flugel. The
phenomenon of dolomitization in this facies is sometimes
observed (Figure 14B).
B2 facies (greenstone bioclast)
The components of this facies include echinoid fragments,
orminitic foraminifera, non-skeletal components such as
intraclasts, and biceps fragments (Figure 12C). The absence
of a mud matrix indicates the energetic conditions in the
deposition of this microfacies. The presence of echinoderm
can indicate the part close to the open sea of the dam.
This facade is equivalent to the standard 26 Flugel facies for
carbonate ramp (RMF 26) platforms.
Interpretation of the sedimentary
environment of the dam facies belt
Facies B1 and B2 are related to the energetic environment of
the dam due to the grain size, the presence of cement, and the
absence of carbonate mud.
The semicircular of the intracellular grains in the B1
facies also indicates a high-energy environment. These grains
can be formed by the erosion of canal walls in a barrier
medium (38). Micritic cover around skeletal grains indicates
sedimentation in the area of light penetration and depth less
than 100–200 m Enos (39) and Selwood (40).
Open marine facies belt
The offshore facies belt extends at the end of the carbonate
platform toward the sea of dam facies/submarine hills (41).
Offshore facies include the following facies.
FIGURE 15 | Images of microscopic facies C1 (A) and C2 offshore (B,C).
FIGURE 16 | Destructive facies in Scorpion and Sarvak structures. (A) Chilean facies at the base of Kazhdomi Formation, and (B,C). Sandstone
facies in Sarvak (B) and Kazhdomi (C) Formations.

10.54646/bijcees.2023.06 59
FIGURE 17 | Facies model of the studied formations, which is in
accordance with the facies of a carbonate ramp, including inner and
middle ramps.
Facies C1 (Madstone Bioclast): In this facies, components
such as echinoderm fragments and bilayer fragments are
observed. Echinoid fragments usually make up the largest
number of fragments. This facade is equivalent to the
standard facelift number 9 of Flugel. This facade is related
to the initial parts of the middle ramp (Figure 15A).
Facies C2 (vextone bioclast): This facies includes fragments
of the echinoderm, sponge needle, and a limited number of
pelagic foraminifera. This facade is equivalent to Standard
Flogel Facility No. 5 for ramp-type carbonate platforms.
These facies can be related to the end parts of the middle
ramp facies (Figures 15B, C).
Detrital facies in Kajdomi and Sarvak
Formations Shale damage
This facies is mostly observed at the base of Kazhdomi
Formation. Ahmadi Shale exists as an interlayer between the
limestones of this section (Figure 14A).
Sandstone facies
These facies have been observed sparsely in some depths
of Sarvak and Kajdomi Formations (Figures 14B, C).
Arnite quartz facies can be seen in the base parts of
Kazhdomi Formation.
Interpretation of the offshore
sedimentation environment C
The presence of echinoderms and spongy needles in these
facies and the absence of wetland organisms such as
gastropods, even in small numbers, indicate their transport
to the deep parts of the open sea environment. Group C
is similar to today’s deep sediments of the Florida platform
FIGURE 18 | Sequential stratigraphic column of Kazhdomi Formation
in well No. 1 of South Pars gas field (top left figure) and sequential
stratigraphic column of Sarvak Formation (Madoud and Ahmadi) in
well No. 1 of South Pars gas field (top right figure) And finally the
guide form of stratigraphic sections (bottom figure).
FIGURE 19 | Sequence stratigraphic column of Kozhdami Formation
in well No. 3 of South Pars gas field (right figure) and sequence
stratigraphic column of Sarvak Formation (Madoud and Ahmadi) in
well No. 3 of South Pars gas field.
Enos (39) and Selwood (40) and the Bahamas platform
Shin (42).
Sedimentary model
Based on the data obtained from the mentioned studies,
calcareous facies of Kazhdomi Formation have been
deposited in the above areas in the wetland and open sea
environment. The facies of Sarvak Formation of well No. 3
have also been deposited in the wetland and open sea facies
belt, but this formation in well No. 1 includes the wetland
facies belt, dam, and open sea.

60 Abbasi et al.
A lack of growth of dam reefs, a lack of turbidite facies,
gradual changes of facies in the stratigraphic column, a lack
of continuity of reef processes, and absence of aggregate
grains are in accordance with a ramp-type carbonate
platform (Figure 17).
Sequential stratigraphy
Sequence stratigraphy is based on the knowledge of
sedimentology and stratigraphy (43, 44). In the following
section, the sequential stratigraphy of the two wells studied
is introduced as a model for this type of study:
According to the obtained evidence, the discontinuity of
the top of the Darian Formation to the Apsin age in this
region separates this formation from Kozhdi Formation of
the Albin age. Sequence (I) in Kozhdi Formation is 43 m thick
at the age of Albin. The time and presence of gluconite and
iron oxide minerals have been determined (45, 46).
In fact, it can be said that this section was deposited as
a result of the significant advance of the sea on the level of
discontinuity of the Apsin end. As the sea progresses on the
discontinuous surface, the TST section of this sequence is
formed and includes a group of open sea facies. This part,
which is 22 m thick, has a sponge needle and small amount
of planktonic foraminifera. The highest MFS advanced level
is located at 22 m at the base of this formation and is located
between the shale layers and the open sea facies.
The HST section is 21 m thick and consists of wetland
facies. Orbitolina has been seen in abundance in this section.
Trocholine fossils have also been found in small amounts.
The upper boundary of the sequence is due to the change of
time and change of lithology of SB2 type and is located at the
top of Kazhdomi Formation (Figure 16).
Sequential stratigraphy of Sarvak Formation in well No.
1 of South Pars gas field: Sequence II in this formation
has a thickness of 53 m and is of Cenomanian age. The
lower boundary of this sequence is of SB2 type according
to the reasons mentioned above and is located at the top of
Kazhdomi Formation. The TST facade handle is 38 m thick.
The maximum flood level (MFS) is located at a depth of 38 m
in the Madoud section.
The HST facies series includes calcareous sediments of the
wetland and dam environment with a thickness of 15 m and
its most important benthic foraminifera are orbitulin and
trocholine. This group of facies is also located in the mud
section of Sarvak Formation. The upper boundary of this
sequence is SB1 due to the presence of laterite in thin sections
and is located at 1 m at the base of Ahmadi Shale. Sequence
2, which is located in Ahmadi section, is 33 m thick.
The TST facies category is 11 m thick and includes the
open sea facies. The maximum advanced level (MFS) in this
sequence is located at 11 m at the base of Ahmadi Sarvak
section and between the layers of limestone. The HST facies
category is 22 m thick and includes the wetland facies. The
upper boundary of the sequence is SB1 and is located at
the apex of the Ahmadi Shale and the level of the threonine
discontinuity (Figure 16).
Sequential stratigraphy of Kazhdomi
Formation in well No. 3 of the South Pars
gas field
Kazhdomi Formation 41 in well No. 3 of South Pars is 41 m
thick. Sequence 3 in Kazhdomi Formation, well No. 3, similar
to this formation in well 1, is of Albin age. The SB1-type
sequential boundary is located on the Darian Formation
(discontinuous surface between Apsin and Albin).
Sequence I is 41 m thick. The TST facies group, which
consists of offshore facies, is 16 m thick. The highest
advanced level (MFS) is located between the Chilean layers
and at a depth of 16 m at the base of the Scorpion. The HST
facies category is 25 m thick and includes wetland facies.
The upper boundary of the sequence is of type SB2 and is
located between the layers of Chile Scorpion and Dolomite
Modoud (Figure 17).
Sequential stratigraphy of Sarvak
Formation in well No. 3 of South Pars gas
field
Sequence 1, which is the age of Cenomanian, is 23 m thick.
The TST facies handle is 4 m thick and includes open sea
facies. The maximum advanced level (MFS) is located 4 m
from the base of the head (Modoud section). The HST facies
category is also located in the module section.
This category of facies is 19 m thick and includes the facies
of the lagoon. Tricholine and orbitulin are abundant in these
facies. The upper bound of the sequence II, as mentioned in
well No. 1, is due to the presence of SB1- type laterite and
is located at the base of Ahmadi Shale. Sequence 24 is 24 m
thick and is located in Ahmadi Shale.
The TST facies category in this sequence is 6 m thick
and includes open sea facies. Rotalia facies has also been
“seen” in this category. The level of maximum progress in this
sequence is located at a depth of 6 m at the base of the Ahmadi
Shale. The HST facies handle has a thickness of 20 m, which
has a wetland facade. The upper bound of sequence III is of
the SB1 type due to the discontinuity between cenomanine
and threonine (Figure 17).
Conclusion
The most important results of these studies, which have been
used as a model for similar studies, include the following:
–Studies of Kajdomi and Sarvak Formations have led to the
identification of wetland facies belts behind the dam, dam,

10.54646/bijcees.2023.06 61
and returned sea, which are divided into facies and subfacies
in more detail based on their texture and components.
–Sedimentary model for Kazhdomi and Sarvak
Formations located in the South Pars gas field has been
determined based on the sequence of identified facies of
ramp-type platform with one-way slope.
–Based on sequential stratigraphic studies of Scorpion and
Sarvak structures, three third-cycle sedimentary sequences
have been identified for the deposits of these two formations,
including sequence I of the former Albino age, which is
located in the lower and middle part of Scorpion Formation.
Sequence II is of Late Albian-Early Cenomanian age, which
is located from the apex of the Kazhdomi Formation to the
apex of the Modoud section of the Sarvak Formation.
–The upper boundary of the Sarvak sequence is
characterized by erosion discontinuities and longtime
gaps. According to paleontological studies, the age of Sarvak
Formation in the well (Nos. 1 and 3) is probably up to the
end of Cenomanian and immediately on it; Ilam Formation
is of Santonian age.
The presence of such a large discontinuity confirms the
protrusion of the platform due to tectonic movements of salt
(salt domes) or self-fault or activation of foundation faults.
References
1. Pourmorad S, Harami RM, Solgi A. Sedimentological, geochemical
and Hydrogeochemical studies of alluvial fans for mineral and
environmental purposes (case study of Southwestern Iran). Lithol Miner
Resour. (2021) 56:89–112. doi:
2. Pourmorad S, Abbasi S, Patel N, Mohanty A. Investiga- tion and
potential identification of karsts as groundwater resources with the help
of GIS studies, a case study of western Iran. Lithol Min Resour. (2022).
3. Pourmorad S, Jokar A, Jahan S. Determination of key beds from the cap
rocks of oil reservoirs using a novel method, case study: the Gachsaran
Formation, Southwest Iran, Lithology. (2021).
4. Jamalpour M, Bahauddin H, Armoon A. Lithostratigraphy and
biostratigraphy of the sarvak formation in Wells No. 2, 16 and 66
of Rag-e-Safid oilfield in the Southwest of Iran. Open J Geol. (2017)
7:806–21.
5. Yazdi-Moghadam M, Schlagintweit F. Persiconus sarvaki n. gen., n. sp.,
a new complex orbitolinid (Foraminifera) from the Ceno- manian of
the Sarvak Formation (SW Iran, Zagros Zone). Cretaceous Res. (2020)
109:104380.
6. Jino Park J, Lee J, Joo Choh S. Facies analysis of the upper
Ordovician Xiazhen formation, southeast China: implications for
carbonate platform development in South China prior to the onset of
the Hirnantian glaciation. Facies. (2021) 67:18.
7. Sajadi S, Rashidi R. Paleoecology and sedimentary environments of
the Oligo-Miocene deposits of the Asmari Formation (Qeshm Island, SE
Persian Gulf). London: IntechOpen (2019).
8. Dunham RJ. Classification of carbonate rocks according to depositional
texture. AAPG Mem. (1962) 1:108–21.
9. Insalaco E, Virgone A, Courme B, Gaillot J, Kamali M, Moallemi A,
et al. Upper Dalan member and Kangan formation between the zagros
mountains and offshore Fars, Iran: depositional system, biostratigraphy
and stratigraphic architecture. GeoArabia11, Gulf PetroLink, Bahrain.
(2006):75–176.
10. James G, Wynd GG. Stratigraphic nomenclature of iranian oil
consortium agreement area. AAPG Bull. (1965) 49:2182–245.
11. Soleimani S, Aleali M. Microfacies patterns and depositional
environments of the Sarvak Formation in the Abadan Plain, South-
west of Zagros, Iran. Open J Geol. (2016) 6:201–9.
12. James N, Narbonne G, Armstrong A. Aragonite depositional facies in
a Late Ordovician calcite sea. Eastern Laurentia. Sedimentology. (2020)
67:3513–32.
13. Kroger B, Penny A, Shen Y, Munnecke A. Algae, calcitarchs and the
late Ordovician Baltic limestone facies of the Baltic Bain. Facies. (2020)
66:12. doi: 10.1007/s10347-019-0585-0
14. Flugel E. Microfacioes of Carbonate Rocks, Analysis, Interpre- tation and
Application. Berlin: Springer (2004). 976 p.
15. Lee M, Elias R, Choh S, Lee D. Disorientation of corals in Late
Ordovician lime mudstone: a case for ephemeral, biodegradable
substrate? Palaeogeogr Palaeoclimatol Palaeoecol. (2019) 520:55–65.
16. Sariaslan N, Langer M. Atypical, high-diversity assemblages of
foraminifera in a mangrove estuary in northern Brazil. Biogeo Sci. (2021)
18.
17. Kalpana R, Saravana Bhavan P, Udayasuriyan R, Sheu J, Jayakumar T,
Fong T. First record of a seed shrimp (Ostracoda: Podocopida) Cypretta
campechensis (Cyprididae) in a perennial lake (Coimbatore, India): its
molecular identification. Int J Fauna Biol Stud. (2021) 8.
18. Khalil M, Ezraneti R, Rusydi R, Yasin Z, Hwai Tan S. Biometric
relationship of Tegillarca granosa (Bivalvia: Arcidae) from the Northern
Region of the Strait of Malacca. Ocean Sci J. (2021) 56:156–66.
19. Ramesha M, Sophia S. Morphometry, length-weight relationships
and condition index of Parreysia favidens (Benson, 1862) (Bivalvia:
Unionidae) from river Seeta in the Western Ghats. India Indian J Fish.
(2015) 62:18–24.
20. Malaquias M, Stout C, Brenzinger B, Gosliner T, Valdeś A. Molecular
and morphological analyses reveal pseudocryptic diversity in Micromelo
undatus (Bruguie‘re, 1792) (Gastropoda: Heterobranchia: Aplustridae).
Syst Biodivers. (2021):1–25. doi: 10.1080/14772000.2021.1939458
21. McCarthy JB, Krug PJ, Valdes A. Integrative systematics of Placida
cremoniana (Gastropoda, Heterobranchia, Sacoglossa) reveals multiple
pseudocryptic species. Mar Biodivers. (2019) 4.
22. Ragazzola F, Kolzenburg R, Adani M, Bordone A, Cantoni C, Cerrati
G, et al. Carbonate chemistry and temperature dynamics in an alga
dominated habitat. Reg Stud Mar Sci. (2021) 44.
23. Petrov N, Vladychenskaya I, Drozdov A. Molecular genetic markers
of intra- and interspecific divergence within starfish and sea urchins
(Echinodermata). Biochemistry. (2016) 81:972–80.
24. Tucker ME. Sedimentary petrology: an introduction to the origion of
sedimentary rocks. London: Blackwell, Scientific Publication (2001).
260 p.
25. Burley and Worden (2004).
26. Nikbakht S, Rezaee P, Moussavi-Harami R, Khanehbad M, Ghaemi F.
Facies analysis, sedimentary environment and sequence stratigraphy
of the Khan Formation in the Kalmard Sub- Block, Central Iran:
implications for Lower Permian palaeogeography. Neues J Geol
Palaontol. Abhandlungen. (2019) 292:129–54.
27. Xie D, Yao S, Cao J, Hu W, Qin Y. Origin of calcite cements and their
impact on reservoir heterogeneity in the Triassic Yanchang formation,
Ordos Basin, China: a combined petrological and geochemical study.
Mar Petrol Geol. (2020) 117:118–32. doi: 10.1016/j.marpetgeo.2020.
104376
28. Bathurst (1975).
29. Ehrenberg S, Baek H. Deposition, diagenesis and reservoir quality of
an Oligocene reefal-margin limestone succession: Asmari formation,
United Arab Emirates. Sed Geol. (2019) 393:105535.
30. Moghaddas Y, Mahari R, Shabanian R, Najafzadeh A. Sedimentary
environment, sequence stratigraphy, diagenesis and geochemistry of the
carbonate Ruteh Formation in north of Mahabad section. J Stratigr
Sedimentol Res Univer Isfahan. (2019) 35:73–108.
31. Chafeet H, Raheem M, Dahham N. Diagenesis processes impact on the
carbonate Mishrif quality in Ratawi oilfield, southern Iraq. Model Earth
Syst Environ. (2020) 6:2609–22.

62 Abbasi et al.
32. Gharechelou S, Amini A, Bohloli B, Swennen R. Relationship between
the sedimentary microfacies and geomechanical behavior of the Asmari
Formation carbonates, southwestern Iran. Mar Petrol Geol. (2020)
116:104306.
33. Allen and Wiggins (1993).
34. Wu W, Li W. Porosity of bimodal sediment mixture with particle filling.
Int J Sediment Res. (2017) 32:253–9.
35. Gamal H, Elkatatny S, Alsaihati A, Abdulraheem A. Intelli- gent
prediction for rock porosity while drilling complex lithology in real time.
Comput Intell Neurosci. (2021) 2021:12. doi: 10.1155/2021/9960478
36. Hosseini Asgarabadi Z, Khodabakhsh S, Mohseni H, Abbassi N,
Halverson G, Hao Bui T. Microfacies, geochemical characters and
possible mechanism of rhythmic deposition of the Pabdeh formation in
SE Ilam (SW Iran). Geopersia. (2019) 9:89–109.
37. Sebok S, Csato I, Nemes L. Sedimentology and depositional system of
a transitional shallow marine – coastal complex. Lower Visean deposits
in the Central Volga-Ural Petroleum Province, Oren- burg. Central Eur
Geol. (2021) 64:113–32.
38. Tucker ME, Wright PV. Carbonate sedimentology. London: Blackwell,
Scientific Publication (1990). 482 p.
39. Enos (1986).
40. Selwood (1996).
41. Karami S, Ahmadi V, Sarooe H, Bahrami M. Facies analysis
and depositional environment of the Oligocene–Miocene Asmari
Formation, in Interior Fars (Zagros Basin, Iran). Carbonates Evaporites.
(2020) 35:118–26.
42. Shin (1986).
43. Abdulnaby W. Structural geology and neotectonics of Iraq. Northwest
Zagros: Elsevier (2019). 320 p.
44. Moussavi-Harami R, Naseri-Karimvand F, Mahboubi A, Ghabeishavi A,
Shabafrooz R. Depositional environment and sequence stratigraphy of
the oligocene–Miocene deposits North and East of Dehdasht, Izeh Zone,
Zagros Basin, Iran. J Sci Islam Repub Iran. (2019) 30:143–66.
45. Abyat Y, Abyat A, Abyat A. Microfacies and depositional environment
of Asmari formation in the Zeloi oil field, Zagros basin, south-west Iran.
Carbonates Evaporites. (2019) 34:1583–93.
46. Aiello G. Introductory chapter: an introduction to the stratigraphic
setting of Paleozoic to Miocene deposits based on paleoecology, facies
analysis, chemostratigraphy, and chronostratigraphy- concepts and
meanings. (2019):1–14.
47. Pourmorad S, Abbasi S, Ashutosh M, Moein Z. Geochemical and remote
sensing in sedimentary mine Explorations. Germani: Lambert publication
(2022). 480 p. .
48. Pourmorad S, Ashutosh M. Alluvial fans in Southern Iran: geological,
environmental and remote sensing analyses. Singapore: Springer Verlag
(2022). 209 p. .
49. Pourmorad S, Mostofa K, Li SL, Liu CQ, Moein Z. Drilling Engineering
(Geology and Mud Engineering). Germani: Lam- bert publication (2021).
480 p. .
50. Read JF. Carbonate platfoprms of passive (extensional) continental
margins: type characteristics and evolution. Tectonophysics. (1982)
81:195–212.

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