Lithofacies and Petrophysical Properties Interpretation of ...understanding the sedimentological characteristics of a reservoir rock such as grain sizes, shapes, degree of sorting,

International Journal of Scientific Research and Engineering Development-– Volume 3 Issues 2 Mar- Apr 2020

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Lithofacies and Petrophysical Properties

Interpretation of Reservoir Rocks: A Case Study of

Shaka field, Onshore Niger Delta. Joshua O. Mene*, Kingsley O. Okengwu* and Eric U. Eche**

*Department of Geology, University of Port Harcourt, Choba Rivers State, P.M.B. 5323, Nigeria. **Center for Petroleum Geoscience, University of Port Harcourt, Choba Rivers State, P.M.B. 5323, Nigeria.

Correspondence email: [email protected]

Abstract:

This research covers lithofacies and petrophysical interpretation of reservoir rocks using well logs and core data from Well SHA-001 to

understand the reservoir quality with respect to their depositional environments. Analysis was carried out on core sample of 84.3 feet

from a depth range of 7176 ft – 7260.3 ft in well SHA-001 to identify and interpret lithofacies depositional environments. Six (6)

Lithofacies were identified; these were Planar/Parallel laminated Sandstone, Cross-bedded coarse gravely Sandstone, Cross-bedded

medium to fine grain Sandstone, Wavy-rippled Sandy-Heteroliths, Wavy-rippled Muddy-Heteroliths and Parallel-laminated mudstone.

Bioturbations in core ranges from barren to rare with observable Ophiomorpha, Skolithos and Planolites ichnofossils which depicts

mainly costal depositional settings. Three (3) Lithofacies associations were identified; these were Coastal Plain Heterolithics, Tidal

Channel Sandstones and Fluvial Channel Sandstones. Petrophysical analysis was carried out on identified lithofacies in Well SHA-001.

From petrophysical results, Lithofacies deposited with in the Fluvial Channels and Tidal Channels depositional environments (SmX,

SP, and ScX) exhibited good to excellent reservoir qualities, these includes good to excellent effective porosity (0.15 – 0.34), permeability

(877.6mD – 3353.7mD), hydrocarbon saturation (0.62 – 0.77) and poor water saturation (0.22 – 0.37). While lithofacies deposited within

the Coastal Plains depositional environment (HsW, HmW and MP) exhibited very poor to average reservoir qualities regardless

exhibiting average to excellent hydrocarbon saturation (0.54 – 0.70) as they exhibited very poor effective porosity (0.21 – <0.0) and

permeability (310.6mD – 1452.6mD) which are very important factors of reservoir quality. This research has therefore explained how

the depositional environment affects reservoir qualities, hence a fundamental component to consider during the exploration and

production of hydrocarbon.

Keywords- Lithofacies, Petrophysical Interpretation, Reservoir Rocks, Depositional Environments.

I. INTRODUCTION

A reservoir is simply a geologic subsurface feature by nature of

its porosity, permeability and thickness (both lateral and vertical) can

accumulate and transmit a commercial volume of hydrocarbon

provided all entrapment conditions are in place. Being a subsurface

geologic feature, one cannot simply understand its sedimentological

characteristics such as lithofacies (composition and textures),

biofacies (flora and fauna composition) and ichno facies (biogenic

sedimentary structures) as well as its intrinsic characteristics such as

porosity, permeability, net-gross, geometry, trapping styles, shapes or

lateral continuity at the surface level only (outcrops and exposures).

One must apply several standard techniques as well as procedures in

understanding these characteristics at subsurface level in other to

accurately interpret their various depositional environments, knowing

fully well that every depositional environment has its own unique

petroleum play significance which influences the exploration and


Lithofacies identification and interpretation helps in

understanding the sedimentological characteristics of a reservoir rock

such as grain sizes, shapes, degree of sorting, colours, textures,

sedimentary structures (physical, chemical and biological structures),

etc. This will enable proper interpretation of reservoir rocks as well as

in the determination of their depositional environments [1]. These

attributes from lithofacies could also be well utilized when carrying

out petrophysical analysis on reservoir rocks, this will aid proper

interpretation of reservoir rocks intrinsic properties such as porosity

(Φ), permeability (K), net to gross (NTG), water saturation (Sw),

hydrocarbon saturation (S-Hc) etc [2]. This will also enable proper

RESEARCH ARTICLE OPEN ACCESS




analysis during hydrocarbon volumetric calculations as well as in the

production of hydrocarbon. Lithofacies and petrophysical

interpretation of reservoir rocks therefore tends to be key players

during exploration and production of hydrocarbon. This research is

centered on the lithofacies and the petrophysical properties of

reservoir rocks from well logs and core data obtained from SHA-001

well of Shaka field, Costal Swamp Depobelt, onshore eastern Niger

Delta, Nigeria.

The Study Area (Shaka Field) is located within the Central

Swamp Depobelt of Miocene age in the Niger Delta Basin, consisting

of four (4) wells designated SHA-001, SHA-002, SHA-003 and SHA-

004 which cover an area of about 10,863.02 km2 with wells having a

distance of about 0.61km, 1.27km and 4.49km apart from each other

respectively (See Fig. 1). This research is centered mainly on Well

SHA-001 being the only cored section. References [3], [4] have all

carried detailed research and publications on the Niger Delta

sedimentary basin as regards to its geology, tectonic history and

evolution. The Niger Delta is located within the Gulf of Guinea,

Equatorial West Africa at the southern end of Nigeria bordering the

Atlantic Ocean between latitude 4o and 6o N and longitude 3o and 9o

E and extends throughout the Niger Delta province [3]. Reference [4]

suggested an area of about 75,000km2 and has an average sediment

thickness of about 12,000m. The Niger Delta sedimentary basin was

formed at the site of a rift triple junction related to the opening of the

Southern Atlantic starting in the Late Jurassic and continuing into the

Cretaceous [5]. It properly began to develop during the Eocene epoch,

accumulating sediments that now are over 10 kilometers thick,

depositing first the marine shales of the Akata formation, followed by

the intercalation of sands and shales of the Agbada formation before

the deposition of the continental sands of the Benin formation [5] (See

Fig. 2).

Fig. 1: Base Map of the Study Area

Fig. 2: Stratigraphic column showing the three formations of the Niger Delta

Basin [3].

II. MATERIALS AND METHODS

A. Samples and sampling

The data set for this research was provided by Shell Petroleum

Development Company (SPDC) under the approval from the

Department of Petroleum Resources (DPR), Nigeria. The materials

used for this research were Well logs data which included; Gamma




Ray logs, SP logs, Gamma Ray Index logs, Resistivity logs, Density

logs and Petrophysical logs (Total Porosity logs, Effective Porosity

logs, Water Saturation logs, Hydrocarbon Saturation logs,

Permeability logs). Core data set was also utilized for this research.

B. Core Description

Core description entails a close observation and interpretation of

the sedimentological properties of the cores to understand the

lithology, texture, sedimentary structures, macroscopic digenetic

features, etc. This would enable sedimentologist to identify unique

facies, group facies that are genetically related into facies associations

as well as understanding the continuous lateral / vertical changes in

facies attributes (facies succession). From these analysis and

descriptions, the depositional environments of cored sections as well

as the whole reservoir sands within that zone could be reconstructed.

Detailed core description was carried out on 84.3 feet of 1/3rd slabbed

core photos provided from well SHA-001 at depth range from 7176 ft

– 7260.3 ft. Core description was carried out using the standard SPDC

reservoir lithofacies and genetic unit scheme as published in [6] (See

Table 1) to organize lithofacies into lithofacies associations for

accurate interpretation and reconstruction of the depositional

environments of reservoir sand.

Table 1: SPDC Recognized Lithofacies and Genetic Units Scheme [6].

Lithology Dominant

Grain Size

Dominant

Sedimentary

Structure

Secondary

Sed.

Structure

Lithofacies

Codes/

Examples

> 90%

Sand

50 - 90%

Sand

50 - 90%

mud

(10 - 50%

sand)

Sandstone (S)

c-Coarse

m- Medium

f- Fine

Sandy

Heterolith

(Hs)

Massive (M)

Cross bedded

(X)

Planar, Parallel

bedded (P)

Hummocky,

Shaley cross

bedded (H)

Wave rippled

(W)

Current rippled

(C)

Bioturbated (B)

Rooted (R)

Fossiliferous

(F)

Organic-

Carbonaceous

(O)

Cement-

general

(c)

Siderite

(s)

Deformed

(d)

ScM

ScX

SmP

SmH

SfW

SC

SmB

SR

SF(c)

HsH

HsC

HsW

HmC

HmW

HmB

> 90 %

Mud

(< 10

Sand)

Mudstone (M) MPs, MP,

MF, MO

C. Concept of Facies

Facies can simply be defined as the sum characteristics of a

sedimentary unit whose physical, chemical and biological attributes

are distinct from adjacent neighboring sedimentary units [1]. The

physical sedimentary attributes such as texture (grains sizes and

shapes), physical sedimentary structures (cross bedding, lamination,

etc.) as well as the chemical sedimentary attributes such as colour,

chemical sedimentary structures (stylolites, etc.) of a sedimentary unit

make up a lithofacies unit. Also, the biological characteristics of a

sedimentary unit such as fauna and flora distributions make up a

biofacies unit while the imprints of biological activities such as

burrows, tracks, etc. make up an inchofacies unit.

These attributes enable a total description of sedimentary rocks,

depending on the area of concentration for rock descriptions (litho,

bio or ichno). However, the combination of all these characteristics

makes up sedimentary facies.

D. Facies Analysis, Facies Association and Facies

Succession

Facies analysis involves a detailed review of all sedimentological

attributes of reservoirs in order to interpret and reconstruct the manner

in which these reservoirs materials or components were transported

and deposited, hence helping in reconstruction the depositional

environment [1]. The concept of facies comes in play during facies

analysis in identifying and analyzing physical, chemical and

biological attributes of a sedimentary unit which will facilitate an

accurate interpretation and reconstruction of the sedimentary

depositional environment. It is worth mentioning that facies analysis

covers a wide range of sedimentary scale down to the smallest

laminae of a sedimentary unit, as the smallest unit of a sedimentary

laminae should possess all attribute necessary for facies analysis.

After the sedimentary attribute of a stratum has been identified, strata

with similar facies attributes that are genetically related with a

significant depositional environment can be group as beds and bedsets

[1]; likewise, beds and bedsets with similar facies attributes that are

genetically related with also a significant depositional environment

can be grouped as formations [1]. This is known as facies association

and it is utilised in interpreting and reconstructing the depositional

environments of reservoirs during facies analysis. Facies analysis also

monitors a significant trend (changes) either laterally or vertically in

facies attributes; this is known as facies succession and it is also used




in the interpretation and reconstruction of reservoirs depositional

environments.

E. Petrophysical Evaluation of Reserviors

Petrophysical evaluation is basically the study of the physical

properties of the rocks such as grain sizes, shapes, framework that

influence reservoir attributes such as porosity, permeability, fluid

saturation, etc. It is worth mentioning that the petrophysical attributes

of reservoir sands are highly influenced by the sedimentological

attributes that is dominant in the environment of deposition. This

implies that, as the sedimentological attributes of reservoir sands

change across wells (reservoir heterogeneity), the petrophysical

attributes also change in the same manner. The identified lithofacies

in cored descriptions was integrated into the petrophysical attributes

within the core section (appendix table A1-A3) to understand how the

sedimentological attributes of these reservoirs affect its petrophysics

and reservoir quality which is associated with the depositional

environments of the reservoirs.

Some of the derivatives of these petrophysical attributes include;

1. Gamma ray index (IGR)

Equation after [7], Where;

IGR = Gamma ray index that describes a linear response to shale

content

GRlog = Log reading at depth interest

GRmin = Gamma ray value in a nearby clean sand zone

GRmax = Gamma ray value in a nearby shale.

2. Volume Shale (VSH)

Equation after [8] of non-linear relationship for Tertiary rocks, where;

VSH = Volume of shale

IGR = Gamma ray index that describes a linear response to shale

content

3. Total Porosity (POROT)

Where; ØT = Total porosity, ρma = Matrix density = 2.65, ρbulk = Bulk

density,

ρfl = Fluid density (0.74 for gas, 0.9 for oil and 1.0 for water)

4. Effective Porosity (POROE)

e =

Where; Øe = Effective porosity, Øtsh = Total shale porosity, ØT =

Total porosity,

VSH = Volume of shale

5. Water Saturation (Sw)

Equation after [9] empirical model,

Where; Sw = Water saturation, Ro = Resistivity of the oil leg, Rt =

True resistivity reading

6. Hydrocarbon Saturation (SH)

Where; SH = Hydrocarbon saturation, Sw = Water

saturation

7. Permeability (K)

Equation after [10]

where; K(mD) = Permeability in milliDarcy, Øe = Effective

porosity, Sw = Water saturation

III. RESULTS AND DISCUSSIONS

A. Cored Depth Range

Detailed core descriptions were carried out on 84.3 feet of 1/3rd

slabbed core provided from well SHA-001 at depth range from 7176

ft – 7260.3 ft which covers parts of reservoir C (See Fig. 3). Core

description was achieved using the standard SPDC reservoir

lithofacies and genetic unit scheme [6].




Fig. 3: Cored Sections Parts of Reservoir C

B. Depth Shift

Depth shift was carried out on cored section along with wireline

logs to correct the difference between driller’s depths to which the

core was referenced from and that of the logger’s depths to which the

wireline was referenced from. The difference between these depths

creates a depth shift which might be positive or negative, increasing

the accuracy of cores when compared along with gamma ray log for

this research. Table 2 further shows the depth shift conversion

between cores and wireline logs.

Table 2: Depth Shift Correction of Core Depth with Wireline Log Depth

S/N

DEPTH (ft)

SHIFT

(ft) CORE WIRELINE

1 7176.00 – 7183.00 7178.35 – 7185.35 +2.35

2 7183.40 – 7184.30 7183.48 – 7184.38 +0.08

3 7191.00 – 7194.00 7191.97 – 7194.97 +0.97

4 7203.00 – 7206.00 7205.00 – 7208.00 +2.00

5 7209.00 – 7212.00 7211.08 – 7214.08 +2.08

6 7212.00 – 7213.00 7213.01 – 7214.01 +1.01

7 7221.00 – 7224.00 7222.10 – 7225.10 +1.10

8 7227.00 – 7230.00 7228.03 – 7231.03 +1.03

9 7230.20 – 7230.80 7230.64 – 7231.24 +0.44

10 7247.80 – 7253.80 7247.89 – 7253.89 +0.09

11 7259.15 – 7259.45 7259.16 – 7259.46 +0.01

12 7259.45 – 7260.00 7259.48 – 7260.03 +0.03

C. Lithofacies Identification

Six (6) lithofacies were identified from inspection and

description of the cored section using the standard SPDC reservoir

lithofacies and genetic unit scheme [6]. The identified lithofacies

were;

1. Planar/Parallel laminated sandstone, SP

2. Cross-bedded coarse-gravely sandstone, ScX

3. Cross-bedded medium to fine sandstone, SmX

4. Wavy-rippled sandy heteroliths, HsW

5. Wavy-rippled muddy heteroliths, HmW

6. Parallel-laminated mudstone, MP

Table 3 further summarizes the characteristics of identified lithofacies

as well as their percentage distribution. The percentage distribution of

identified lithofacies was obtained from the percentage ratio between

the lengths of individual lithofacies to the length of the whole cored

section. Fig. 4 shows a graphical percentage distribution of identified

lithofacies within the cored section.

Table 3: Lithofacies Distributions of Cores [6]

Lithology Lithofacies SPDC

Code

%

Distribution

Length

(ft)

Sandstone Planar/Parallel

laminated

sandstone

SP 10.6 8.9

Cross-bedded

coarse-gravely

grained

sandstone

ScX 14.2 12

Cross-bedded

medium to fine

grained

sandstone

SmX 55 46.4

Heteroliths Wavy-rippled

sandy

heteroliths

HsW 19 16

Wavy-rippled

muddy

heteroliths

HmW 0.4 0.3

Mudstone Parallel-

laminated

mudstone

MP 0.8 0.7

Total 100 84.3




Fig. 4: Graphical Interpretation of Percentage Distribution of Lithofacies of

Cores [6]

D. Lithofacies Descriptions and Interpretations

Identified lithofacies of cores were described and interpreted also

using the standard SPDC reservoir lithofacies and genetic unit scheme

[6], noting observable sedimentological characteristics such as grain

sizes, grain shapes, physical sedimentary structures and biological

sedimentary structures. Lithofacies descriptions were as follows;

1) Sandstones

i. Planar/Parallel Laminated Sandstone (SP)

This lithofacies consists of about 10.6% (8.9ft in length) of the

cored section in well SHA-001 (See Plate 1). The lithofacies is

moderately to well-sorted, medium to fine-grained sandstones, with a

dominance of fine grains. Colours identified within this lithofacies

ranges from light brown - grey with good oil stains. Sedimentary

structures were unidirectional, low angle, planar to parallel-laminated

strata bases. The internal laminae were of mm-cm thickness and

displayed weak grading. Bioturbation intensity ranges from absent to

moderate with observable signatures of Ophiomorpha and Skolithos.

The observed moderately to well sorted sandstones, with sparsely

distributed marginal marine ichnofauna assemblages showed how

these sediments were possibly deposited and reworked by the

influence of waves/tidal processes in an intermediate to high energy

flow regime within the shallow marine depositional environment. The

wave/tidal influence constantly erodes and re-deposits these sediments

at different energy intervals causing the development of low angle

planar to parallel laminated surfaces (See Plate 1). The activities in

these flow regimes also discourages the visualization of ancient

biological activities as observed by the sparsely distributed

ichnofacies signatures of Ophiomorpha and Skolithos that depicts

coastal depositional settings. This lithofacies exhibits similar

characteristics with facies deposits of the tidal channels within the

coastal depositional environment settings.

Plate 1: Planar/Parallel Laminated Sandstone (SP)

ii. Cross-bedded Coarse-Gravely Grained Sandstone (ScX)

This lithofacies consists of about 14.2% (12ft in length) of the

cored section in well SHA-001 (See Plates 2 and 3). The lithofacies is

poorly sorted, fine to very coarse-grained but predominantly coarse-

grained sandstone. Colours ranges from grey to brownish-red with

good oil stains. Sedimentary structures were massive to low-angled

cross stratifications with fine-grained to very fine-grained lamina and

sharp basal contacts between bed sets. The identified pebbles and

granules commonly form lags or are aligned on the foresets but may

also be dispersed throughout the lithofacies. Bioturbation intensity

ranges from absent to moderate with observable signatures of

Ophiomorpha and Skolithos.




The poorly sorted, cross-bedded coarse-grained sands with sharp

erosive bases often reflects a high energy flow regime characteristic of

a fluvial depositional system. The observed coarse-gravely size clasts

were transported mostly by saltation / rolling along the channel and

were gradually deposited discretely to form quartz / gravel lags as the

energy of the flow reduces, the finer sediments were also gradually

deposited as the flow energy continues to reduce along the channel

(See Plates 2 and 3). The sediments in this lithofacies continues to

deposit in this manner forming massive to low angle cross

stratifications in a downstream direction which is diagnostic of a

fluvial system [1]. The constrained marginal marine ichnofauna

assemblages observed were indicative of a coastal environmental

setting. This lithofacies is said to exhibits similar characteristics with

sands deposits of the fluvial-dominated estuarine channel.

Plate 2: Cross-bedded Coarse-Gravely Sandstone (ScX)

Plate 3: Cross-bedded Coarse-Gravely Sandstone (ScX)

iii. Cross-bedded Medium-fine Sandstones (SmX)

This lithofacies consists of about 55% (46.4ft in length) of the

cored section in well SHA-001 (See Plates 4 and 5). This lithofacies is

moderately to well sorted, fine to medium-grained but predominantly

medium-grained sandstones. Colours ranges light to moderate

yellowish-brown to grey with good oil stains. Sedimentary structures

were unidirectional, horizontal to low angled inclined cross-

stratifications bounded by sharp erosional surfaces with argillaceous

laminae /coal bands abundance. The coarse-grained sands / granules

occurred occasionally either as sparsely disseminated to locally

concentrated. There were also mud pebbles/rip mud clast distributed

discretely within the lithofacies. Bioturbation intensity ranged from

barren to low with observable signatures Ophiomorpha, and

Diplocraterion burrows.




Plate 4: Cross-bedded Medium-fine Sandstones (SmX)

Plate 5: Cross-bedded Medium-fine Sandstones (SmX)

2) Heteroliths

i. Wavy-rippled Sandy Heteroliths (HsW)

This lithofacies consists of about 19% (16ft in length) of the

cored section in well SHA-001 (See Plates 6 and 7). The lithofacies is

a heterolithic mixture of sands, silts and muds but predominantly

sands. The Sands were very well sorted, very fine to fine grained but

predominantly very fine grained that were rounded to sub-rounded.

Colours ranges from light to medium yellowish brown to grey.

Sedimentary structures were wavy rippled to sub-parallel laminated

fine-grained sandstones interbedded with wavy shale laminations and

sharp erosive bases between individual laminae. Bioturbation is

generally rare with recognisable traces of Planolites and

Ophiomorpha ichnofossils.

The restricted marginal marine ichnofaunal assemblages and

heterolithic texture of this facies indicates deposition in a low energy,

shallow marine setting which is categorized by alternating suspension

and bedload sediments. The sedimentary structures on this lithofacies

were due to the constant erosion and re-deposition of the sediments by

low waves energy. Marine sediments were possible carried by these

low wave energies, deposited on the previous sediments that were

equally reworked at the same time as the wave energy attenuates. This

lithofacies exhibits similar characteristics with sediments deposits of

the estuarine channel margins or bays depositional environments.




Plate 6: Wavy-rippled Sandy Heteroliths (HsW)

Plate 7: Wavy-rippled Sandy Heteroliths (HsW)

ii. Wavy-rippled Muddy Heteroliths (HmW)


cored section in well SHA-001 (See plate 8). The lithofacies is a

heterolithic mixture of sands and muds but predominately muddy

sediments. Colours ranges from light to medium dark grey.

Sedimentary structures were traces of small scaled wavy, current

rippled, planar laminations with traces of organic debris and tiny

discrete shell fragments. Bioturbation is generally rare with

recognisable traces of Planolites and Ophiomorpha ichnofossils.

The restricted marginal marine ichnofaunal assemblages and

heterolithic texture of this facies indicates deposition in a low energy,

shallow marine setting which is categorized by alternating suspension

and bedload sediments, but predominantly suspension sediments. The

deposition of this lithofacies is similar with that of the Wavy-rippled

Sandy Heteroliths (HsW) in Plates 6 and 7. The difference could be

accounted by the flow energy regime of the transporting medium, this

lithofacies was deposited in a lower energy that allowed very fine

grain sediments to coagulates and deposit as mudstone within the

lithofacies (See Plate 8). This lithofacies exhibits similar

characteristics with sediments deposits of the estuarine channel

margins depositional environments.

Plate 8: Wavy-rippled Muddy Heteroliths (HmW)

3) Mudstone

i. Parallel Laminated Mudstone (MP)


cored section in well SHA-001 (plate 9). The lithofacies consists of

shales with bands of silty sand lamina with varaible thickness.

Colours ranges from light brown, medium to dark grey. Sedimentary

sturctures were parallel to sub-parallel laminated with very fine

sandstones/siltstones that were planar laminated. Traces organic

debris were obsereved in the mudstone. Bioturbation intensity ranged

from rare to absent with discrete small scale borrows.




The fine-grained textures were indicative of sediments deposited

under low hydraulic energy conditions mostly by suspensions. The

presence of silty sands lamina were indicative of a more energetic

storm wave deposits than that which initially deposited the muds. The

restricted marginal marine ichnofaunal assemblages suggested a

reduction in the amounts of oxygen associated with organic material

in a quiet water setting. This lithofacies exhibits similar characteristics

with sediments deposits of the coastal depositional settings in

particular the lagoon depositional environments.

Plate 9: Parallel Laminated Mudstone (MP)

E. Lithofacies Associations

Lithofacies associations are groups of genetically related

lithofacies having the same depositional environment significances

[1]. Lithofacies associations were carefully recognized using the

standard SPDC reservoir lithofacies and genetic unit scheme [6]. The

complete details of lithofacies association were displayed in appendix

A1 and A2, the recognized lithofacies associations were as follows;

1) Tidal Channel Sandstones

Lithofacies grouped under this association were the Cross-

bedded medium to fine grain sandstone (SmX) and the Planar/Parallel

laminated sandstone (SP) (See Fig. 5 and 6). This was categorized by

moderately to very well sorted medium to fine-grained sandstones that

exhibits an observable unidirectional horizontal to low angle cross-

stratifications as well as planar to parallel-laminations bounded by

subtle to sharp erosional surfaces. Evidence of tidal influence are

observed from the presence of argillaceous lamina / coal lamina of

mm-cm thickness as well as mud pebbles/rip mud clast at several

intervals within the lithofacies. Bioturbations level of occurrence was

from rare to moderate whose ichnofacies assemblages consists mainly

of Skolithos, Ophiomorpha with rare traces of Diplocraterion which

indicates the littorals zones along the sandy shorelines that are tidally

influenced.

Figure 5: Lithofacies Log Description of the Tidal Channel Sands – A

Figure 6: Lithofacies Log Description of the Tidal Channel Sands – B

2) Fluvial Channel Sandstones

Lithofacies grouped under this association were mainly Cross-

bedded coarse gravely sandstone (ScX) and Cross-bedded medium




sandstone (SmX) (See Figure 7 and 8). This is categorized by poorly

sorted fine to predominantly very coarse-grained sandstones that

exhibits observable unidirectional massive to low-angled cross

stratifications with fine-grained to very fine-grained lamina of which

observed pebbles and granules form lags, or are aligned on the

foresets but may also be dispersed throughout the lithofacies with

sharp basal contact between bedsets. These are evidence of fluvial

influence in which sands deposition was in sinuous to straight crested

dunes migrated by high energy fluvial currents. Regardless of these

fluvial influences, observable traces of marginal marine depositional

settings are exhibited as indicated by the observed barren to low

bioturbation levels often cause by Ophiomorpha borrows which

indicates deposits closeness to the coastal depositional settings,

comparable depositional environments are of the fluvial-dominated

estuarine channels.

Figure 7: Lithofacies Log Description of the Fluvial Channel Sands – A

Figure 8: Lithofacies Log Description of the Fluvial Channel Sands – B

3) Coastal Plain Heteroliths

Lithofacies grouped under this association were mainly Wavy-

rippled sandy heteroliths (HsW), Wavy-rippled muddy heteroliths,

(HmW) and Parallel-laminated mudstone (MP) (See Fig. 9). This is

categorized by a heterolithic mixture of sands, silts and muds. Sands

and silts are very well sorted, very fine to fine grained that exhibits

wavy rippled to sub-parallel laminations with wavy shale laminations

with sharp erosive bases between lamina. Shales are moderately fissil

and parallel to sub-parallel laminated with very fine

sandstones/siltstones that are planar laminated. Observable organic

debries and well as tiny discrete shell fragments are exhibited on the

shales which is an indicator of an energy low and oxygen depleted

environment. Bioturbation occurrence is rare to absent with

observable ichnofossils assemblages consisting mainly of Planolites,

Skolithos and Ophiomorpha borrows which indicates the littoral to

sub-littoral zones along the sandy shorelines to the shoreface

depositional settings. Generally, this unit is erosively overlain by

channelized sandstones of the tidal channel depositional settings

(lithofacies succession). Table 4 generally shows a summary of

interpreted depositional environments of cored section from

interpreted lithofacies associations.

Figure 9: Lithofacies Log Description of the Coastal Plain Heterolithics




F. Petrophysical Interpretation of Lithofacies

From the effective porosity-permeability graph shown in figure

10, it was observed that lithofacies of the Cross-bedded Coarse

Gravely Sandstone (ScX) showed permeability range values from

3353.7mD – 3017.5mD and effective porosity range values from 0.34

– 0.32, this is an indicative of excellent permeability and effective

porosity attributes. The lithofacies of both Cross-bedded Medium to

Fine Sandstone (SmX) and Planar/Parallel Laminated Sandstone (SP)

showed permeability range values from 2318.5mD – 877.6mD and

effective porosity range values from 0.28 – 0.15, this is an indicative

of good to moderate permeability and effective porosity attributes.

Lithofacies of the Wavy-rippled Sandy Heteroliths (HsW) showed

permeability range values from 1452.6mD – 371.5mD and effective

porosity range values from 0.21 – 0.05, this is an indicative of

moderate to poor permeability and effective porosity attributes. The

lithofacies of both Wavy-rippled Muddy Heteroliths (HmW) and

Parallel-laminated Mudstone (MP) showed permeability range values

from 312.7mD – 310.6mD and effective porosity range values from

<0.0, this is an indicative of very poor permeability and effective

porosity attributes.

Table 4: Summary of Interpreted Depositional Environments of Cored Section

Cored Depth (ft) Depositional

Environments

Lithofacies

7176.0 – 7183.5 Tidal Channel

Sandstones

SP and SmX

7183.5 – 7192.4 Fluvial Channel

Sandstone

SmX, ScX

and HsW


Sandstones

SmX, ScX

and HsW

7215.6 – 7230.0 Fluvial Channel

Sandstones

ScX and SmX


Sandstones

SmX, ScX

and HsW

7247.2 – 7260.3 Coastal Plain

Heterolithics

HsW, MP and

HmW

Figure 10: The Relationship Between Effective Porosity and Permeability as a

Function of the Reservoir Qualities of Identified Lithofacies.

From the hydrocarbon saturation-permeability graph shown in

figure 11, it was observed that lithofacies of the Cross-bedded Coarse

Gravely Sandstone (ScX) showed hydrocarbon saturation (Sat.HC)

range values from 0.77 – 0.74 (77% - 74%), this is an indicative of

excellent hydrocarbon saturation attributes. The lithofacies of both

Cross-bedded Medium to Fine Sandstone (SmX) and Planar/Parallel

Laminated Sandstones (SP) showed hydrocarbon saturation (Sat.HC)

range values from 0.72 – 0.62 (72% - 62%), this is an indicative of

good to excellent hydrocarbon saturation attributes. The lithofacies of

Wavy-rippled Sandy Heteroliths (HsW) showed hydrocarbon

saturation (Sat.HC) range values from 0.70 – 0.58 (70% - 58%), this is

also an indicative of average to excellent hydrocarbon saturation

attributes. While lithofacies of Wavy-rippled Muddy Heteroliths

(HmW) and Parallel-laminated Mudstone (MP) showed hydrocarbon

saturation (Sat.HC) range value ranges from 0.56 – 0.54 (56% - 54%),

this is indicative of average hydrocarbon saturation attributes.




Figure 11: The Relationship Between Hydrocarbon Saturation and

Permeability as a Function of the Reservoir Qualities of Identified Lithofacies.

From the water saturation-permeability graph shown in figure 12,

it was observed generally that lithofacies of the Cross-bedded Coarse

Gravely Sandstone (ScX), Cross-bedded Medium to Fine Sandstone

(SmX) and Planar/Parallel Laminated Sandstones (SP) showed water

saturation (Sw) range values from 0.22 – 0.37 (22% - 37%) while the

lithofacies of Wavy-rippled Sandy Heteroliths (HsW), Wavy-rippled

Muddy Heteroliths (HmW) and Parallel-laminated Mudstone (MP)

showed water saturation (Sw) range values from 0.30 – 0.46 (30% -

46%).

Figure 12: The Relationship Between Water Saturation and Permeability as a

Function of the Reservoir Qualities of Identified Lithofacies.

From the above petrophysical results of lithofacies, it was

observed that lithofacies deposited with in the Fluvial Channels and

Tidal Channels depositional environments (SmX, SP, and ScX)

exhibited good to excellent reservoir qualities, these includes good to

excellent effective porosity, permeability, hydrocarbon saturation and

poor water saturation. While lithofacies deposited within the Coastal

Plains depositional environment (HsW, HmW and MP) exhibited very

poor to average reservoir qualities although they exhibited average to

excellent hydrocarbon saturation. This was due to the fact that they

exhibited very poor effective porosity and permeability which are

very important factors of reservoir quality during the exploration and


IV. CONCLUSION

After a total review of the identified lithofacies attributes, it was

therefore concluded that lithofacies within this reservoir were

deposited in a coastal depositional setting that was evidently incised

by estuarine channels of both fluvial and tidal backgrounds and

possibly adjacent to a swamp land paleo-environment. The

petrophysical attributes of identified lithofacies within this reservoir

has facilitated the differentiation of highly productive zones from the

less productive zones (reservoir compartmentalization). The highly

productive zones within this reservoir were lithofacies that were

deposited within the Tidal and Fluvial Channels depositional

environment as they exhibited good to excellent reservoir quality

while the less productive zones within this reservoir were lithofacies

that were deposited within the Coastal Plains depositional

environment as they exhibited very poor to average reservoir quality.

This was compared with other fields studies within the Niger Delta

such as the D2 Sands of Greater Ughelli Depobelt [2] whose high

productive zones were in the Upper Shoreface and Channel

depositional environments, and least productive zones in the Tidal

flats and Lower Shoreface. Other reservoir studies within the Niger

Delta such as that of [11], [12] was also compared with results gotten

from the study area. This research has therefore explained how the

depositional environment affects reservoir qualities, hence a

fundamental component to consider during the exploration and





ACKNOWLEDGMENTS

The authors hereby acknowledge the assistance of Shell

Petroleum Development Company (SPDC) through the Department of

Petroleum Resources (DPR) for the provision of available dataset for

this work. Also, the Department of Geology, University of Port

Harcourt for the provision of workstations and laboratory for this

research.

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[8] V. Larionov. Borehole Radiometry. Moscow, USSR,

Nedra, 1969.

[9] G.E. Archie. "Classification of carbonate reservoir

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[11] O. W. Osayande and K. O. Okengwu. “Lithofacies

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[12] R. O. Oyanyan, C. G. Soronnadi-Ononiwu and A. O.

Omoboriowo. “Depositional environments of sam-bis

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pp:1624-1638, 2012.




APPENDIX

Figure A1: Sedimentary Log and Description of Cored Section-A




Figure A2: Sedimentary Log and Description of Cored Section-B




Table A1: Petrophysical Attributes of Reservoir C in Well SHA-001 (Cored Section)

MD (Ft) Gamma

(API)

R

(ohm.m)

K (mD) RHOB

(g/cm3)

IGR

(gAPI)

VShale

(%)

Por.Tot.

(m3/m3)

Por.Eff.

(m3/m3)

Sw Sat.HC

7175 89.51 11.9766 400.753 2.32 0.88 0.7029 0.2 0.0594 0.40997 0.59

7175.5 82.64 14.2422 541.2903 2.3011 0.8 0.5558 0.2115 0.0939 0.38775 0.6123

7176 75.69 16.8281 733.0885 2.2801 0.71 0.435 0.2242 0.1267 0.36573 0.6343

7176.5 71.3 19.4219 877.5999 2.2656 0.66 0.3707 0.2329 0.1466 0.35201 0.648

7177 70.66 22.6562 900.0878 2.2635 0.65 0.362 0.2343 0.1495 0.35002 0.65

7177.5 73.77 25.8906 793.9816 2.2739 0.69 0.4059 0.228 0.1354 0.35973 0.6403

7178 74.41 23.2969 773.3079 2.276 0.7 0.4154 0.2267 0.1325 0.36173 0.6383

7178.5 73.77 18.4531 793.9816 2.2739 0.69 0.4059 0.228 0.1354 0.35973 0.6403

7179 73.77 15.5312 793.9816 2.2739 0.69 0.4059 0.228 0.1354 0.35973 0.6403

7179.5 75.05 11.6484 753.0113 2.278 0.71 0.4251 0.2254 0.1296 0.36373 0.6363

7180 75.05 9.0625 753.0113 2.278 0.71 0.4251 0.2254 0.1296 0.36373 0.6363

7180.5 71.94 7.7656 855.4827 2.2678 0.67 0.3795 0.2316 0.1437 0.354 0.646

7181 70.66 7.4453 900.0878 2.2635 0.65 0.362 0.2343 0.1495 0.35002 0.65

7181.5 65.63 9.7109 1090.449 2.2455 0.6 0.2994 0.2452 0.1718 0.33447 0.6655

7182 58.08 15.8594 1423.487 2.2154 0.51 0.2215 0.2634 0.2051 0.31131 0.6887

7182.5 50.53 46.9375 1825.414 2.1806 0.42 0.1595 0.2845 0.2391 0.28821 0.7118

7183 43.02 91.5625 2318.533 2.1395 0.33 0.1103 0.3094 0.2752 0.26505 0.735

7183.5 34.84 107.3125 3017.545 2.0843 0.23 0.068 0.3428 0.3195 0.23919 0.7608

7184 31.09 211.625 3423.072 2.0538 0.19 0.0518 0.3613 0.3426 0.22695 0.773

7184.5 32.32 234.125 3281.781 2.0643 0.2 0.057 0.3549 0.3347 0.23102 0.769

7185 36.08 239.5 2897.448 2.0936 0.25 0.0738 0.3372 0.3123 0.24316 0.7568

7185.5 37.99 249.25 2722.754 2.1072 0.27 0.0831 0.329 0.3016 0.24926 0.7507

7186 38.59 257.5 2670.73 2.1113 0.28 0.0861 0.3265 0.2984 0.25116 0.7488

7186.5 39.87 276 2563.512 2.1198 0.29 0.0928 0.3213 0.2915 0.25519 0.7448

7187 41.11 294.25 2464.207 2.1277 0.31 0.0995 0.3165 0.285 0.25907 0.7409

7187.5 42.39 288.75 2366.054 2.1357 0.32 0.1066 0.3117 0.2785 0.26306 0.7369

7188 44.9 273.5 2184.494 2.1505 0.35 0.1216 0.3027 0.2659 0.27087 0.7291

7188.5 46.78 278.5 2058.108 2.161 0.37 0.1335 0.2964 0.2568 0.27667 0.7233

7189 50.53 303 1825.414 2.1806 0.42 0.1595 0.2845 0.2391 0.28821 0.7118

7189.5 50.53 312 1825.414 2.1806 0.42 0.1595 0.2845 0.2391 0.28821 0.7118

7190 49.93 276 1860.902 2.1775 0.41 0.1551 0.2863 0.2419 0.28638 0.7136

7190.5 50.53 243.25 1825.414 2.1806 0.42 0.1595 0.2845 0.2391 0.28821 0.7118

7191 51.81 232.375 1751.64 2.1869 0.43 0.169 0.2807 0.2333 0.29213 0.7079

7191.5 54.33 223.875 1613.568 2.1987 0.46 0.1889 0.2735 0.2218 0.29983 0.7002

7192 56.2 219.125 1516.279 2.2072 0.48 0.2047 0.2683 0.2134 0.30557 0.6944

7192.5 57.48 220.75 1452.634 2.2128 0.5 0.216 0.265 0.2077 0.30948 0.6905

7193 56.2 219.125 1516.279 2.2072 0.48 0.2047 0.2683 0.2134 0.30557 0.6944

7193.5 53.69 208.75 1647.773 2.1958 0.46 0.1837 0.2753 0.2247 0.29788 0.7021

7194 50.53 202 1825.414 2.1806 0.42 0.1595 0.2845 0.2391 0.28821 0.7118

7194.5 48.66 202 1938.627 2.171 0.4 0.1461 0.2903 0.2479 0.28245 0.7175

7195 48.06 216.125 1976.051 2.1678 0.39 0.142 0.2922 0.2507 0.28061 0.7194

7195.5 48.06 208.75 1976.051 2.1678 0.39 0.142 0.2922 0.2507 0.28061 0.7194

7196 48.06 190.75 1976.051 2.1678 0.39 0.142 0.2922 0.2507 0.28061 0.7194

7196.5 49.93 163.5 1860.902 2.1775 0.41 0.1551 0.2863 0.2419 0.28638 0.7136

7197 52.45 149.25 1715.698 2.1899 0.44 0.1739 0.2788 0.2303 0.29409 0.7059

7197.5 52.45 142.375 1715.698 2.1899 0.44 0.1739 0.2788 0.2303 0.29409 0.7059

7198 50.53 141.75 1825.414 2.1806 0.42 0.1595 0.2845 0.2391 0.28821 0.7118

7198.5 48.66 139.875 1938.627 2.171 0.4 0.1461 0.2903 0.2479 0.28245 0.7175

7199 44.26 128.75 2229.228 2.1468 0.34 0.1177 0.305 0.2691 0.26889 0.7311

7199.5 41.11 114.4375 2464.207 2.1277 0.31 0.0995 0.3165 0.285 0.25907 0.7409

7200 37.99 113.625 2722.754 2.1072 0.27 0.0831 0.329 0.3016 0.24926 0.7507

7200.5 37.99 112.75 2722.754 2.1072 0.27 0.0831 0.329 0.3016 0.24926 0.7507

7201 39.23 118.875 2616.499 2.1156 0.29 0.0894 0.3239 0.2949 0.25317 0.7468

7201.5 41.75 123.125 2414.599 2.1317 0.31 0.103 0.3141 0.2817 0.26107 0.7389

7202 44.26 128.75 2229.228 2.1468 0.34 0.1177 0.305 0.2691 0.26889 0.7311

7202.5 44.9 134.375 2184.494 2.1505 0.35 0.1216 0.3027 0.2659 0.27087 0.7291

7203 46.14 133.25 2100.328 2.1575 0.37 0.1294 0.2985 0.2599 0.2747 0.7253

7203.5 46.14 131.5 2100.328 2.1575 0.37 0.1294 0.2985 0.2599 0.2747 0.7253

7204 46.14 144.375 2100.328 2.1575 0.37 0.1294 0.2985 0.2599 0.2747 0.7253

7204.5 46.14 161 2100.328 2.1575 0.37 0.1294 0.2985 0.2599 0.2747 0.7253

7205 46.14 186.125 2100.328 2.1575 0.37 0.1294 0.2985 0.2599 0.2747 0.7253





MD (Ft) Gamma

(API)

R

(ohm.m)

K (mD) RHOB

(g/cm3)

IGR

(gAPI)

VShale

(%)

Por.Tot.

(m3/m3)

Por.Eff.

(m3/m3)

Sw Sat.HC

7206 45.54 160.125 2140.65 2.1541 0.36 0.1256 0.3005 0.2628 0.27285 0.7271

7206.5 48.06 133.75 1976.051 2.1678 0.39 0.142 0.2922 0.2507 0.28061 0.7194

7207 52.45 107.6875 1715.698 2.1899 0.44 0.1739 0.2788 0.2303 0.29409 0.7059

7207.5 54.33 87.375 1613.568 2.1987 0.46 0.1889 0.2735 0.2218 0.29983 0.7002

7208 56.84 87.375 1484.203 2.21 0.49 0.2103 0.2666 0.2106 0.30753 0.6925

7208.5 60 32.0312 1333.053 2.2234 0.53 0.2396 0.2585 0.1966 0.31718 0.6828

7209 63.75 23.625 1167.687 2.2384 0.57 0.2783 0.2495 0.18 0.32869 0.6713

7209.5 66.9 15.5312 1039.837 2.2502 0.61 0.3144 0.2423 0.1661 0.33841 0.6616

7210 70.66 11.6484 900.0878 2.2635 0.65 0.362 0.2343 0.1495 0.35002 0.65

7210.5 72.57 9.7109 833.7409 2.2699 0.68 0.3885 0.2303 0.1408 0.35599 0.644

7211 73.21 9.3828 812.3726 2.272 0.68 0.3977 0.2291 0.138 0.35798 0.642

7211.5 71.94 7.4453 855.4827 2.2678 0.67 0.3795 0.2316 0.1437 0.354 0.646

7212 68.18 6.7969 990.7844 2.2548 0.63 0.33 0.2395 0.1605 0.34235 0.6576

7212.5 63.75 8.4141 1167.687 2.2384 0.57 0.2783 0.2495 0.18 0.32869 0.6713

7213 57.48 14.2422 1452.634 2.2128 0.5 0.216 0.265 0.2077 0.30948 0.6905

7213.5 53.69 25.8906 1647.773 2.1958 0.46 0.1837 0.2753 0.2247 0.29788 0.7021

7214 47.42 43.375 2016.693 2.1644 0.38 0.1377 0.2943 0.2538 0.27864 0.7214

7214.5 41.11 78 2464.207 2.1277 0.31 0.0995 0.3165 0.285 0.25907 0.7409

7215 34.84 95.5 3017.545 2.0843 0.23 0.068 0.3428 0.3195 0.23919 0.7608

7215.5 33.6 139.875 3143.976 2.0747 0.22 0.0625 0.3487 0.3269 0.23519 0.7648

7216 34.2 157.625 3081.969 2.0794 0.23 0.0651 0.3458 0.3233 0.23713 0.7629

7216.5 36.08 134.375 2897.448 2.0936 0.25 0.0738 0.3372 0.3123 0.24316 0.7568

7217 38.59 117.9375 2670.73 2.1113 0.28 0.0861 0.3265 0.2984 0.25116 0.7488

7217.5 41.75 76.6875 2414.599 2.1317 0.31 0.103 0.3141 0.2817 0.26107 0.7389

7218 46.14 52.75 2100.328 2.1575 0.37 0.1294 0.2985 0.2599 0.2747 0.7253

7218.5 51.17 34.3125 1788.206 2.1837 0.43 0.1642 0.2826 0.2362 0.29017 0.7098

7219 56.2 18.125 1516.279 2.2072 0.48 0.2047 0.2683 0.2134 0.30557 0.6944

7219.5 61.23 14.2422 1276.854 2.2285 0.54 0.2519 0.2555 0.1911 0.32097 0.679

7220 65.63 14.2422 1090.449 2.2455 0.6 0.2994 0.2452 0.1718 0.33447 0.6655

7220.5 68.18 16.5 990.7844 2.2548 0.63 0.33 0.2395 0.1605 0.34235 0.6576

7221 62.47 20.7188 1222.31 2.2334 0.56 0.2646 0.2525 0.1857 0.32477 0.6752

7221.5 56.84 24.5938 1484.203 2.21 0.49 0.2103 0.2666 0.2106 0.30753 0.6925

7222 53.69 29.4531 1647.773 2.1958 0.46 0.1837 0.2753 0.2247 0.29788 0.7021

7222.5 51.17 36.5625 1788.206 2.1837 0.43 0.1642 0.2826 0.2362 0.29017 0.7098

7223 48.66 32.0312 1938.627 2.171 0.4 0.1461 0.2903 0.2479 0.28245 0.7175

7223.5 49.29 26.2188 1899.413 2.1743 0.4 0.1506 0.2883 0.2449 0.28441 0.7156

7224 51.81 16.5 1751.64 2.1869 0.43 0.169 0.2807 0.2333 0.29213 0.7079

7224.5 54.96 13.2656 1579.925 2.2017 0.47 0.1942 0.2717 0.219 0.30179 0.6982

7225 58.08 15.8594 1423.487 2.2154 0.51 0.2215 0.2634 0.2051 0.31131 0.6887

7225.5 62.47 14.5625 1222.31 2.2334 0.56 0.2646 0.2525 0.1857 0.32477 0.6752

7226 66.27 11 1064.947 2.2478 0.6 0.3068 0.2437 0.169 0.33644 0.6636

7226.5 64.39 11.3281 1141 2.2408 0.58 0.2853 0.248 0.1772 0.33066 0.6693

7227 61.23 14.2422 1276.854 2.2285 0.54 0.2519 0.2555 0.1911 0.32097 0.679

7227.5 57.48 21.6875 1452.634 2.2128 0.5 0.216 0.265 0.2077 0.30948 0.6905

7228 49.93 35.9375 1860.902 2.1775 0.41 0.1551 0.2863 0.2419 0.28638 0.7136

7228.5 43.02 78.3125 2318.533 2.1395 0.33 0.1103 0.3094 0.2752 0.26505 0.735

7229 34.2 94.1875 3081.969 2.0794 0.23 0.0651 0.3458 0.3233 0.23713 0.7629

7229.5 32.32 111.9375 3281.781 2.0643 0.2 0.057 0.3549 0.3347 0.23102 0.769

7230 31.68 124.625 3353.709 2.059 0.2 0.0543 0.3582 0.3387 0.22893 0.7711

7230.5 31.09 94.5 3423.072 2.0538 0.19 0.0518 0.3613 0.3426 0.22695 0.773

7231 32.32 38.8438 3281.781 2.0643 0.2 0.057 0.3549 0.3347 0.23102 0.769

7231.5 35.48 23.9531 2954.806 2.0892 0.24 0.071 0.3399 0.3158 0.24124 0.7588

7232 38.59 16.1875 2670.73 2.1113 0.28 0.0861 0.3265 0.2984 0.25116 0.7488

7232.5 43.02 15.8594 2318.533 2.1395 0.33 0.1103 0.3094 0.2752 0.26505 0.735

7233 48.66 17.1562 1938.627 2.171 0.4 0.1461 0.2903 0.2479 0.28245 0.7175

7233.5 54.33 19.7344 1613.568 2.1987 0.46 0.1889 0.2735 0.2218 0.29983 0.7002




MD (Ft) Gamma

(API)

R

(ohm.m)

K (mD) RHOB

(g/cm3)

IGR

(gAPI)

VShale

(%)

Por.Tot.

(m3/m3)

Por.Eff.

(m3/m3)

Sw Sat.HC

7234 53.69 23.9531 1647.773 2.1958 0.46 0.1837 0.2753 0.2247 0.29788 0.7021

7234.5 51.81 29.7812 1751.64 2.1869 0.43 0.169 0.2807 0.2333 0.29213 0.7079

7235 48.06 35.9375 1976.051 2.1678 0.39 0.142 0.2922 0.2507 0.28061 0.7194

7235.5 47.42 26.8594 2016.693 2.1644 0.38 0.1377 0.2943 0.2538 0.27864 0.7214

7236 49.29 20.7188 1899.413 2.1743 0.4 0.1506 0.2883 0.2449 0.28441 0.7156

7236.5 53.69 21.3594 1647.773 2.1958 0.46 0.1837 0.2753 0.2247 0.29788 0.7021

7237 60 17.4688 1333.053 2.2234 0.53 0.2396 0.2585 0.1966 0.31718 0.6828

7237.5 66.27 13.2656 1064.947 2.2478 0.6 0.3068 0.2437 0.169 0.33644 0.6636

7238 68.74 14.8906 969.8051 2.2568 0.63 0.337 0.2383 0.158 0.34408 0.6559

7238.5 75.69 15.2109 733.0885 2.2801 0.71 0.435 0.2242 0.1267 0.36573 0.6343

7239 82 10.6797 556.962 2.2992 0.79 0.5436 0.2126 0.097 0.38571 0.6143

7239.5 85.11 7.7656 484.5798 2.3081 0.82 0.6054 0.2072 0.0818 0.3957 0.6043

7240 88.87 6.4727 411.5251 2.3183 0.87 0.6879 0.201 0.0627 0.40788 0.5921

7240.5 98.29 5.8242 310.173 2.3419 0.98 0.9414 0.1867 0.0109 0.43921 0.5608

7241 105.88 5.8242 341.6443 2.3592 1.07 1.205 0.1762 -0.0361 0.46532 0.5347

7241.5 101.49 6.1484 308.7932 2.3494 1.02 1.0451 0.1822 -0.0082 0.4501 0.5499

7242 92.62 8.4141 355.7768 2.328 0.91 0.7804 0.1951 0.0429 0.42022 0.5798

7242.5 85.75 13.2656 471.0101 2.3098 0.83 0.6188 0.2062 0.0786 0.39776 0.6022

7243 80.72 18.7656 589.5322 2.2955 0.77 0.5199 0.2149 0.1032 0.38163 0.6184

7243.5 76.97 23.2969 694.373 2.2841 0.73 0.4554 0.2218 0.1208 0.36975 0.6303

7244 67.54 26.5312 1015.117 2.2525 0.62 0.3221 0.2409 0.1633 0.34038 0.6596

7244.5 61.87 29.125 1248.5 2.231 0.55 0.2584 0.2539 0.1883 0.32293 0.6771

7245 60 30.75 1333.053 2.2234 0.53 0.2396 0.2585 0.1966 0.31718 0.6828

7245.5 61.23 30.0938 1276.854 2.2285 0.54 0.2519 0.2555 0.1911 0.32097 0.679

7246 60 28.1562 1333.053 2.2234 0.53 0.2396 0.2585 0.1966 0.31718 0.6828

7246.5 58.08 25.25 1423.487 2.2154 0.51 0.2215 0.2634 0.2051 0.31131 0.6887

7247 58.72 23.625 1392.872 2.2181 0.51 0.2274 0.2618 0.2022 0.31327 0.6867

7247.5 58.72 23.9531 1392.872 2.2181 0.51 0.2274 0.2618 0.2022 0.31327 0.6867

7248 60 23.9531 1333.053 2.2234 0.53 0.2396 0.2585 0.1966 0.31718 0.6828

7248.5 61.23 21.3594 1276.854 2.2285 0.54 0.2519 0.2555 0.1911 0.32097 0.679

7249 63.75 19.0938 1167.687 2.2384 0.57 0.2783 0.2495 0.18 0.32869 0.6713

7249.5 66.27 16.8281 1064.947 2.2478 0.6 0.3068 0.2437 0.169 0.33644 0.6636

7250 68.74 14.8906 969.8051 2.2568 0.63 0.337 0.2383 0.158 0.34408 0.6559

7250.5 71.3 13.5938 877.5999 2.2656 0.66 0.3707 0.2329 0.1466 0.35201 0.648

7251 74.41 11.6484 773.3079 2.276 0.7 0.4154 0.2267 0.1325 0.36173 0.6383

7251.5 78.8 10.3594 641.3885 2.2897 0.75 0.486 0.2183 0.1122 0.37555 0.6245

7252 85.75 9.3828 471.0101 2.3098 0.83 0.6188 0.2062 0.0786 0.39776 0.6022

7252.5 91.42 8.0938 371.5493 2.325 0.9 0.7497 0.197 0.0493 0.41627 0.5837

7253 95.81 7.1211 323.8305 2.336 0.95 0.8677 0.1903 0.0252 0.43087 0.5691

7253.5 100.21 6.7969 307.0054 2.3464 1 1.0024 0.184 -0.0004 0.44572 0.5543

7254 104.6 6.4727 327.5264 2.3564 1.05 1.1563 0.1779 -0.0278 0.46086 0.5391

7254.5 105.24 6.4727 334.09 2.3578 1.06 1.1804 0.1771 -0.0319 0.46309 0.5369

7255 103.32 6.4727 317.2562 2.3536 1.04 1.1094 0.1797 -0.0197 0.45643 0.5436

7255.5 100.21 6.7969 307.0054 2.3464 1 1.0024 0.184 -0.0004 0.44572 0.5543

7256 99.57 6.7969 307.3034 2.345 0.99 0.9817 0.1849 0.0034 0.44355 0.5565

7256.5 102.04 6.7969 310.6123 2.3507 1.02 1.0643 0.1814 -0.0117 0.45202 0.548

7257 103.32 7.1211 317.2562 2.3536 1.04 1.1094 0.1797 -0.0197 0.45643 0.5436

7257.5 101.49 7.1211 308.7932 2.3494 1.02 1.0451 0.1822 -0.0082 0.4501 0.5499

7258 100.85 7.1211 307.4944 2.3479 1.01 1.0236 0.1831 -0.0043 0.44791 0.5521

7258.5 103.32 7.1211 317.2562 2.3536 1.04 1.1094 0.1797 -0.0197 0.45643 0.5436

7259 103.96 7.1211 321.9245 2.355 1.05 1.1326 0.1788 -0.0237 0.45864 0.5414

7259.5 102.04 7.1211 310.6123 2.3507 1.02 1.0643 0.1814 -0.0117 0.45202 0.548

7260 99.57 7.4453 307.3034 2.345 0.99 0.9817 0.1849 0.0034 0.44355 0.5565

7260.5 97.65 7.4453 312.7029 2.3404 0.97 0.9219 0.1876 0.0147 0.43705 0.563


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Lithofacies and Petrophysical Properties Interpretation of ...understanding the sedimentological characteristics of a reservoir rock such as grain sizes, shapes, degree of sorting,