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Iraq University Interprets Buzurgan Oil Field Well Logs
1. Republic of Iraq Misan University
Ministry Of Higher Education and scientific Research College Of Engineering-Petroleum Engineering Department
Petroleum Reservoir Management
Buzurgan Well logs interpretation with interactive petrophysics
Student's Name: Ahmed Jassim Khudair
Ali Karim Salem
Mohamed Riad Abdel-Hussein
Mustafa Ibrahim Mohamed
Fourth Stage
8/4/2020
2. 1
TABLE OF CONTENTS
1. Chapter1: INTRODUCTION……………………………………………………………………2
1.2 petroPhysicalParameters………………………………………………..…………3
1.3 Cut off……………………………………………………………………………..4
1.4 log tools……….……………………………………………………………...……5
1.5 Interactive petrophysics software…………………………………………...……..6
1.6 Buzurgan Oil Field……………………………………………………….……….7
1.7 the goals of report……………………………………………………….………..7
2.Methodology and procedure…………………………………………….8
3.Result ……………………………………………………..…………….12
4.Discussion……………………………………………..…….….……….63
5.References………………………………………………...……………..63
3. 2
1.INTRODUCTION
Well logging plays an essential role in petroleum exploration and exploitation. It is used to
identify the pay zones of gas or oil in the reservoir formations. It gives continuous down hole
record and detailed picture of both gradual and abrupt changes in physical properties of
subsurface lithology Logging has a central role in the successful development of a hydrocarbon
reservoir. Its measurements occupy a position of central importance in the life of a well,
between two milestones: the surface seismic survey, which has influenced the decision for the
well location, and the production testing Logging is able to adequately reveal the whole of the
drilled sequence and has the added advantage that it measures, in situ, rock properties which
cannot be measured in a laboratory from either core samples or cuttings. From this data, it is
possible to obtain good estimates of the reservoir size and the hydrocarbons in place. According
to the measurements of well logging there are three kinds of data: electrical, nuclear and
acoustic. Electrical logging is used to analyze oil saturation and water saturation of the
formation. Nuclear logging is used to analyze the porosity and permeability. Acoustic logging
provides information about porosity and also indicates whether a liquid or gas phase occupies
the pore spaces. Logging techniques in cased holes can provide much of the data needed to
monitor primary production and also to gauge the applicability of water flooding and to monitor
its progress when activated. In producing wells, logging can provide measurements of flow
rates, fluid type, pressure, residual oil saturation. From these measurements, dynamic well
behavior can be better understood and remedial work can be planned and secondary or tertiary
recovery proposals can be evaluated and monitored. Thus no hydrocarbon can be produced
without the intervention of logs. Logging is a continuous recording of the physical properties of
rocks in the well with respect to depth. These physical properties are porosity, resistivity,
density, conductivity, saturation etc. Logging was started with simple electric logs measuring
the electric conductivity of rocks, but it is now a technically advanced and sophisticated
method. Logging plays a crucial role in exploration and exploitation of hydrocarbons. Well
logging in oil industry has its own meaning; log means “record against depth of any of the
characteristics of the rock formations traversed by a measuring apparatus in the well bore”. The
value of the measurement is plotted continuously against depth in the well . For example, the
resistivity log is a continuous plot of a formation resistivity from the bottom of the well to the
top. Generally, we go for geophysical methods for identifying the structures present beneath the
earth subsurface over a few kilometres. One of the geophysical methods, that is logging is used
to study the physical parameters of the
4. 3
formations inch by inch. Whenever an interesting zone is encountered we go for coring. This is
the direct analysis of the formations. But it is not possible to take core analysis for entire well.
So logging will give adequate data of entire well in indirect analysis. Wireline geophysical well
logs (Open-hole log) are recorded when the drilling tools are no longer in the hole. Wireline
logs are made using highly specialized equipment entirely separate from that used for drilling.
Onshore, a motorized logging truck is used which brings its array of surface recorders,
computers and logging drum and cable to the drill site. Offshore, the same equipment is
installed in a small cabin left permanently on the rig. Both truck and cabin use a variety of
inter-changeable logging tools, which are lowered into the well on the logging cable The well
log data that provide the basic information needed for reservoir characterization are used for
mapping, perforation, estimation of original oil and gas in-place, and evaluation of reservoir
perforation. The general goals of log measurements is to provide a continuous profile of:
1- identified Lithology with exact depth of formation/rock boundaries,
2- estimate Rock properties and rock composition (mineralogy); of special interest are reservoir
properties (porosity, saturation, permeability),
3- detedection Fractures and tectonic elements,
4- estimate Mechanical rock properties for stability, sanding problems, frack operations, etc.,
5-Indications or content and properties of hydrocarbons
6- Seismic-relevant parameters for integrated interpretation of seismic and log measurements,
7- detect Changes of properties; this is important particularly with respect to change of fluid
content/ saturation during production (monitoring, time lapse measurements).
1.2petroPhysicalParameters
1) Porosity: Porosity is defined as a measure of the pore spaces present in a rock. These pore
spaces within the reservoir rocksm could be filled with gas, oil or water. High porosity values
indicate high capacities of the reservoir rocks to contain these fluids, while low porosity values
indicate the opposite. Porosity is calculated as the pore volume of the rock divided by its bulk
volume. Two types of porosities can exist in a rock. These are termed as Primary porosity:
Primary porosity is described as the porosity of the rock that formed at the time of its deposition
and Secondary porosity: Secondary porosity develops after deposition of the rock. Secondary
porosity includes vugular spaces in carbonate rocks created by the chemical process of
leaching, or fracture spaces formed in fractured reservoirs. Porosity is further classified as
Total porosity: is defined as the ratio of the entire pore space in a rock to its bulk volume and
Effective porosity is the ratio of interconnected pore space to the bulk volume of the rock.
2) Permeability Permeability is a measure of the ability of a porous medium, to transmit fluids
through its interconnected pore spaces. Permeability
is three types.
a) Effective Permeability: When the pore spaces in the porous medium are occupied by more
than one fluid, the permeability measured is the Effective permeability of the porous medium to
that particular fluid. For instance, the effective permeability of a porous medium to oil is the
5. 4
permeability to oil when other fluids, including oil, occupy the pore spaces.
b) Relative Permeability: the ratio of effective permeability to absolute permeability of a porous
medium.
c) Absolute permeability: If the porous medium is completely saturated (100% saturated) with a
single fluid, the permeability measured is the absolute permeability. It is an intrinsic property of
the porous medium, and the magnitude of absolute permeability is independent of the type of
fluid in the pore spaces
3)saturation The formation saturation is defined fraction of its pore volume (porosity) occupied
by a given fluid.
1.3 Cut off
Cutoffs in petroleum engineering are limiting points at which the processing of flowing of fluid
is stopped
Porosity Cut Off :-Elimination of the portion of the formation is low porosity
and low permeability, therefore non- productive. Typically, the cutoff of porosity for
sandstones is about 8 to 10% and for limestone about 3 to 5%. Limestone’s lower porosity
cutoff values reflect the propensity for limestone’s to be highly fractured
Water Saturation Cut Off :-Remove part of the formation which contains a large amount of
water in the pore space
Clay Volume Cut Off :-Clay volume cut off mean elimination the portion of the formation
which contains large quantities of shall.
6. 5
1.4 Log tools
Lithologylogs
Sp log:- spontaneous potential is one of the earliest logs used and still in use. Spontaneous
potential response created by electric voltages arising from electrochemical factor generated by
the sum of two potential known as the membrane potential and the liquid. Detecting permeable
beds and it thickness and Determining formation water salinity and Qualitative indication of
bed shaliness and correlation between wells.
GR log:- The Gamma Ray log is a continuous measurement of the natural radioactivity of the
formation. It measures the radiation emitting from naturally occurring U, Th, and K. these
elements are concentrated in shale so the GR log indicate for shale and use to correlation
between wells and Depth control for log all logs and perforation and can use in open hole and
cased hole.
Porositylogs
Density log:- is a porosity log that measures the electron density of the formation. The density
logging tool consists of a radioactive source that emits gamma rays into the formation and one
or more gamma ray detectors, located a fixed distance from the source. use to Measures
formation bulk density (matrix and fluid density) and It is also useful in the detection of gas
reservoirs and hydrocarbon density calculations stored in layers.(with Neutron ) and The tool
has a pad so a caliper log can attached to recorded at the same time.
Neutron log:- is measured by use a neutron source to measure the hydrogen concentration of
the fluid in pores, which is directly related to porosity(the neutron log measures liquid-filled
porosity). It consisted of an isotopic source, most often plutonium-beryllium, and a detector
Sonic log:- Provide continuous record of the time taken in microsecond/foot by sound wave to
travel from the transmitter to the receiver. the sonde and Velocity of sound through a given
formation is a function of its lithological and porosity. Dense, low porosity rocks are
characterized by high velocity of sound wave and vise-versa for porous
and less dense formation
Resistivitylogs
Resistivity log:- Use to measure the resistivity of the formation, and thus the possibility of
hydrocarbon shows and A sonde sends an electrical signal through the formation and relays it
back to a receiver at the surface (induced electricity). The surface detector will measure the
formation’s resistance to the current and A rock which contains an oil and/or gas saturation
will have a higher resistivity than the same rock completely saturated with formation water.
Many types of resistivity log use , but the famous are MSFL(Micro Spherical Focused
Laterolog and DLL(Dual Laterolog Resistivity)
7. 6
Induction log:- Use to measure the conductivity of the formation, and thus the possibility of
hydrocarbon shows. A rock which contains an oil and/or gas saturation will have a lower
conductivity than the same rock completely saturated with formation water. Induction logs
use an electric coil in the sonde to generate an alternating current loop in the formation by
induction. Induction tools give best results when mud resistivity is high with respect to
formation resistivity, i.e., fresh mud or non-conductive fluid. In oil-base mud, which is
nonconductive, induction logging is the only option available.
Caliper log:- The Caliper Log is a tool for measuring the diameter and shape of a borehole. It
uses a tool which has 2, 4, or more extendable arms. The arms can move in and out as the tool
is withdrawn from the borehole and the movement is converted into an electrical signal.
1.5 Interactive petrophysics software
Well log evaluation has been achieved by using Interactive PetrophisecisTM Program (IP).
Interactive Petrophysics is a PC-based software application for reservoir property analysis and
summation. Interactive PetrophysicsTM (IP) is developed by the Production Geosciences Ltd
(PGL) (2004). IP's technical support is provided by the Schlumberger Information Solutions
(SIS). Uses such program will be very easily to determine and calculate the deterministic &
probabilistic models including porosity, water saturation, shale volumes and other properties
within user-defined zones. Also, crossplot endpoints of Petrophisecis can be determined
directly from the plots, which are significantly minimizing the keyboard entry. Advantage of
using IP to help you maximiz the value of your subsurface data. Its efficient workflows and
robust analytical functions promote productivity, rapid analysis and confident decision-making
and working to understand rock properties in the reservoir to petrophysics conducting multi
well and control of your well data analysis and is the most mathematically accurate and
petrophysical analysis tool and Using the IP Software to determine the following Petrophysical
Properties(Lithology, Porosity, Archie’s Parameters,,etc...) then calculate the water saturation
sw.after that ,Calculate the OOIP and detect the perforation zones.
8. 7
1.6 Buzurgan Oil Field
is one of the Iraqi oil fields, it is located south- east of Iraq near the Iraqi-Iranian borders, about
60 kilometers to the south-east of Al-Emara City, the center of Missan Governorate. The oil
field was discovered in 1970, and in November 1976 its development was started. The oil
field development was carried out by General Organization of South Oil – Missan Oil field
Exploration work in the Buzurgan area was started on the basis of geological and seismic
surveys. Six seismic surveys preceding exploration drilling were carried out in the period
from(14/8/1968 15/3/1969) at the area with proposed structure availability. The first BU-1
exploration well was drilled in February 1970. It found noncommercial Asmari reservoir
production and the commercial oil-bearing reservoir of the Mishirif formation as well. After
drilling the BU-1 well, which proved the availability of commercial oil in the Mishirif
formation, a detailed six-by-twelve seismic survey in was carried out from (19/12/1969-
25/3/1970) for a more detailed determination of the structure boundaries1. The drilling of the
BU-2, BU-3,and BU-4 exploration wells (July 1970-May 1971) proved the structure with oil
deposits in producing reservoirs of the Mishirif formation; determined in agreement with
seismic data. After testing the wells
were shut in. During the period from 1971 to 1975 no new wells were drilled, and all data
obtained during exploration wells drilling were investigated and analyzed in detail carried out
by ELF. The main attention in these investigations is paid to lithology and rock physical
properties1. BU-5, BU- 6, BU-7, BU-8, BU-9, BU-10, BU- 11 and BU-12 wells were drilled
between 1975-1977. As a result, stratigraphy, tectonics, and lithological physical structure of
them reservoirs were specified and detailed1. During 1977-1978 repeated seismic surveys
helped specify the deposit of the edge parts of the structure. During 1978 seven producing wells
BU-13, BU-14, BU- 15, BU16, BU-17, BU-18, and BU-19 were drilled in crest parts1. In 1981
the rate of production reached 223 STB/d from three wells in the north dome and 780 bbl/d
from the south dome.
Mishrif reservoir composes mainly of Limestone reservoir rocks from the Middle Cretaceous
Period; with moderate to good porosity value noticed in both open hole and cores. Reservoir
thickness is more than 400 meters in total. This reservoir consists of several sub units which
are: MA, MB-11, MB-12, MB-13, MB-21, MC-1, MC-2 awith barriers in between separating
those layers.
1.7 The goals of report
1- identified the lithology of formations through plot cross plot and lithology logs interpretation
2-estimate the clay volumes Depending on each tool that can calculate the clay
volume(GR,NPHI,RHOP,Resistivity,SP)
3-determine the porosity and water saturation and detect the type of fluid whithin pores
4-determine the net pay thicness.
9. 8
2.Methodology and procedure
After digitize the scanned copies of logs for studied well by software such as (didger or NeuraLog), so
the results are LAS files, which loaded to the Interactive Petrophysics software (IP V3.5, 2008), then
the reading measurements taken as one reading per 0.1524 meters. The log curves are checked to be in
depth with each other.. Environmental corrections were made using the current Schlumberger charts
(SLB, 2005), which are supplied to (IP) as the environmental correction module, actual mud
properties, calliper log, hydrostatic pressure and temperature gradient were provided for accurate
corrections. Depending on well log data the IP software had been used to calculate the petrophysical
reservoir rock properties.
The procedure:-
1-open the interactive petrophysics
program and create new database.
2-input data of well through load the data(LAS file) of well.
10. 9
3-display the well logs tracks
4- make cross plot (identified the
X and Y,Z axis to well logs) and
select the overlay line and depth
of formation
11. 10
5-determine the clay volumes by select the availible log
And enter the
depths of
formations from
geological
reports
12. 11
6-determine the porosity and water saturation. Select availibe logs and select equation of
determination of water saturation (Archie Equation )and select porosity model
7-determine the net reservoir and net pay thickness through cutoff value. Cutoff porosity It has
been calculated by core analysis ( permeability vs porosity and cuttoff porosity when 0.01
permeability) and cutoff water saturation is 0.5 and shale cutoff is 0.5
64. 63
4.Discussion
The lithology of mishrif formation mainly is limestone (carbonate reservoir) The flow of fluid
through a carbonate reservoir is a completely different process than the flows through sandstone
layers. This difference is due in large part of carbonate rocks tend to have a more complex void
system than sand rock. Much of the hydrocarbon reserves are found in carbonate rock.
However, the characterization of the carbonate reservoir is quite complex compared to sand
rock reservoirsIn the Middle East, the giant fields containing hydrocarbon are in carbonate
reservoirs, which cover about 50% of the world's hydrocarbon reserves. Appropriate
corrections (such as shale impact, opening hole conditions, invasion depth, etc.) were applied to
neutron, density and gamma-ray logs were applied before the well log analysis was done.
Current Schlumberger charts were used for Environmental corrections. Many companies have
correction models available in IP v3.5 software. The Schlumberger corrections were used to the
well records specified in the buzurgan field. Corrections are made to check true values and to
obtain them. The calculation of shale volume is important parameters that must be identified
during any explanation because it affects the values of water saturation and porosity. The
shale also controls the presence of hydrocarbons.The porosity can also be estimated depending
on three types of logs that are affected by rock porosity which are neutron, sonic and density
logs. In the porosity calculation process, the selection of well log type was based on the
borehole conditions and the good match between the log and core porosities. The most
important step in interpreting the log is the determination of water saturation. Water saturation
can be estimated from different equations by using IP software v3.5. There are many equations
to estimate water saturation such as dual water, Archie, Simandoux, Mod sinandoux,
Indonesian, Mod Indonesian, Juhaz and Waxman. Archie(we use Archie equation in calculation
of saturation) equation can be used to calculate fluid saturation for clean formation depending
on porosity (φ), the resistivity of formation water (Rw), Resistivity of formation (Rt). wells that
were interpreted by different CPI methods have used constant Archie parameters while, in fact,
these parameters have different values especially in carbonate formations which affect fluid
saturation. The constant values of Archie give low hydrocarbon saturation.
5.References
[1] Giri Prasad, R." Well Logging Importance in Oil and Gas Exploration and Production",International Journal for Research in
Applied Science & Engineering Technology (IJRASET), 2018, pp. 2154-2160.
[2] Kadhim, F.S and Samsuri, A and Idris, A.K." Calculation of Petrophysical Properties for Mishrif Carbonate Reservoir",3rd
International Conference on Fundamental and Applied Sciences, AIP Publishing LLC 978-0-7354-1258-3, 2014, pp.757-761.
https://doi.org/ 10.1063/1.4898552
[3] Schön, J." Basic Well Logging and Formation Evaluation", bookboon, 2015, pp28 ,
[4] Zughar, S.S and Ramadhan, A.A and Jaber, A.K." Petrophysical Properties of an Iraqi Carbonate Reservoir Using Well Log
Evaluation",Iraqi Journal of Chemical and Petroleum Engineering, 2020,pp 53-57. https://doi.org/10.31699/IJCPE.2020.1.8
