This was the final report of the design project 1 (PGE 405).A project about Improved reservoir Evaluation. In this project, I discussed using different techniques in reservoir evaluation as well as using downhole fluid analysis.

1. NEAR EAST UNIVERSITY FACULTY OF ENGINEERING DEPARTMENT OF
PETROLEUM AND NATURAL GAS ENGINEERING
IMPROVED RESERVOIR EVALUATION
Project Design 1
PGE-405
Submitted to the Petroleum and Natural Gas
Engineering Department in partial Fulfillment of the
Requirements for therefore Degree of Bachelor of Science
Prepared By:
MODOU.L. JARJU
Near East University
Nicosia
December, 2017

2. i
NEAR EAST UNIVERSITY FACULTY OF ENGINEERING DEPARTMENT OF
PETROLEUM AND NATURAL GAS ENGINEERING
IMPROVED RESERVOIR EVALUATION
Project Design 1
PGE-405
Submitted to the Petroleum and Natural Gas
Engineering Department in partial Fulfillment of the
Requirements for therefore Degree of Bachelor of Science
Prepared By:
MODOU.L. JARJU
Near East University
Nicosia
December, 2017

3. ii
YAKIN DOĞU ÜNİVERSİTESİ
MÜHENDİSLİK FAKÜLTESİ
PETROL VE DOĞALGAZ MÜHENDİSLİĞİ
BÖLÜMÜ
GELİŞTİRİLMİŞ RESERVOİR DEĞERLENDİRMESİ
Petrol Mühendisliği Tasarımı I
PGE 405
Lisans Derecesi Gerekliliğinin Kısmi Yerine
Getirilmesinde
Petrol ve Doğalgaz Mühendisliği Bölümüne
Sunulmuştur
Hazırlayan
MODOU.L. JARJU
Yakın Doğu Üniversitesi
Lefkoşa
Aralık, 2017

4. iii
MODOU.L. JARJU; IMPROVED RESERVOIR EVALUATION
Approval of the Petroleum and Natural Gas Engineering Department
Prof. Dr. Cavit ATALAR
Chairman
Examining Committee in Charge
Title, Name and Surname Department Signature
Prof. Dr. Cavit ATALAR Committee Chairman, Department of
Petroleum and Natural Gas Engineering
Dr. Ersen ALP Department of Petroleum and Natural
Gas Engineering
MSc. Serhat CANBOLAT Department of Petroleum and Natural
Gas Engineering

5. iv
ACKNOWLEDGMENT
I would like to thank God, the Almighty for giving strength to undertake this amazing scholarly
adventure to expand my knowledge in the above mention topic. I would not do justice if I do not
thank and appreciate the grate and effort our honorable lecturer staff of our humble department of
petroleum engineering are putting in us. Finally, I would love to give special thanks to Mr. SERHAT
CANBOLAT for been an amazing lecturer and guiding me on becoming a better reservoir engineer
some day in the future.

6. v
ABSTRACT
Reservoir evaluation has long been a prominent practice utilized by the engineers to better understand
the reservoir especially during the exploration process. It is done for better understanding of the
exploration field. In exploration or wildcat wells, early information of the reservoir fluid compositions
and PVT properties are important to high grade the petro physical and pressure plot interpretation.
However, most of the traditional reservoir evaluation practices are straight forward and well know
but the interesting part is when there is a special case and the engineers are challenged make use of
the unconventional reservoir evaluation methods in order to get proper understanding of their
reservoir as well as ease on the side of decision making. This paper discusses some case studies where
reservoir evaluation has been used to improve the understanding of the fields to make proper decision.
1. Case Study 1 was about the use I was basically about using The NMR logging by using
CMR(Combinable Magnetic Resonance Tool) for measuring the bounding fluid and free fluid
saturation which c be use for productivity calculations.2.Case study 2 was about Downhole Fluid
Analysis (DFA) using advanced fluid analyzer. Which helps in fluid analysis in the in-situ conditions.
3.The Case Study 3 was about a history matching done which was prompted due to water influx into
one of the wells in a field in Germany and later helps in increasing the life of the field with outrunning
technique and recovery was at 69% 50MMB/D and increased to 74% 75MMB/D.4.The Fourth
case was a reservoir evaluation problem due to frequent tool plugging and as result too much rig on
time was encountered. The XLD probe (Extra Large Diameter Probe) was use to reduce the time on
rig and help facilitate on having to accomplish multiple task. However, the main objective of the
study was how the use of different reservoir evaluation practices are used in to help improve the
fields in each cases.

7. vi
ÖZET
Rezervuar değerlendirilmesi, mühendisler tarafından, özellikle de arama işlemi sırasında rezervuarı
daha iyi anlamak için kullanılmış önemli bir uygulama olmuştur. Temel olarak araştırma alanının
daha iyi anlaşılması için yapılır. Keşif veya vahşi kuyucuk kuyularında, rezervuar sıvısı
kompozisyonlarının ve PVT özelliklerinin erken bilgileri, petrofizik ve basınçlı parsellerin yüksek
dereceli yorumlanması için önemlidir. Bununla birlikte, geleneksel rezervuar değerlendirme
uygulamalarının çoğu açıktır ve iyi bilinmektedir, ancak ilginç kısım, özel bir durum olduğunda ve
mühendisler, rezervuarlarının da doğru bir şekilde anlaşılabilmesi için alışılmadık rezervuar
değerlendirme yöntemlerinden faydalanmakla yükümlü olduğu zamanlardır karar verme tarafında
kolaylık. Bu yazıda, doğru karar vermeleri için alanların anlaşılmasını geliştirmek için rezervuar
değerlendirmesinin kullanıldığı bazı vaka incelemeleri üzerinde tartışacağız. 1. Vaka Çalışması 1
temelde NMR loglama işlemini, verimlilik hesaplamaları için kullanılacak sınırlayıcı akışkan ve
serbest sıvı doygunluğunu ölçmek için CMR'yi (Combinable Magnetic Resonance Tool) kullanarak
kullanmakla ilgiliydi.2.Case study 2, İleri akışkan analizörünü kullanarak Alt Salın Akışkan Analizi
(DFA). In-situ koşullarda sıvı analizinde yardımcı olur. 3. Vaka Çalışması 3, Almanya'da bir tarlada
kuyulardan birinin su akışı ile girilen ve daha sonra uzayan teknikle alanın ömrünü uzatmaya
yardımcı olan ve geçmişe oranla% 69 oranında bir iyileşme sağlanan geçmişi eşleştirme ile ilgilidir.
50MMB / Ge ve% 74'lük bir artışla 75MMB / D.4'e yükselmiştir. Dördüncü durum, sık bir takım
tıkanması nedeniyle bir rezervuar değerlendirme problemiydi ve sonuçta çok fazla teçhizata rastlandı.
XLD probu (Extra Large Diameter Probe), teçhizat üzerindeki süreyi azaltmak ve birden fazla görevi
yerine getirmek zorunda kalmanıza yardımcı olmak için kullanılmıştır. Tüm davalarda, rezervuar
değerlendirmesinin temel olarak oluşumu anlamak için yapıldığını ve dolayısıyla ekonomide karar
verme ve alan verimliliğini arttırma yollarını belirleyebildiğini bulmuşlardır.

8. vii
TABLE OF CONTENTS
ACKNOWLEDGMENT.....................................................................................................................iv
ABSTRACT.........................................................................................................................................v
ÖZET ..................................................................................................................................................vi
TABLE OF CONTENTS...................................................................................................................vii
LIST OF FIGURES ............................................................................................................................ix
LIST OF TABLES ...............................................................................................................................x
LIST OF ABBREVIATIONS..............................................................................................................xi
CHAPTER 1 ........................................................................................................................................1
INTRODUCTION ...............................................................................................................................1
1.1What is reservoir evaluation. ......................................................................................................1
1.2Why Reservoir Evaluation? ........................................................................................................1
1.3 Economic and decision making Impact .....................................................................................1
CHAPTER 2. .......................................................................................................................................2
CASE STUDY ON WATER SATURATION EVALUATION.............................................................2
2. 1 Water Saturation Evaluation .....................................................................................................2
2.1.1NMR Interpretation..............................................................................................................2
2.1.2 NMR Permeability Relationship.........................................................................................3
CHAPTER 3 ........................................................................................................................................4
DOWNHOLE FLUID TESTER (ADVANCE FLUID ANALYZER).................................................4
3.1. Downhole Fluid Analysis (DFA) Planning ...............................................................................4
3.1.1. Fluid Discharge into Borehole ...........................................................................................4
3.1.2. CO2 Measurement in Water Based....................................................................................4
3.1.3. Wireline Formation Tester (WFT) Modules Positioning ...................................................4
3.2. Downhole Fluid Analysis (DFA) Candidate Identification.......................................................5
CHAPTER 4 ........................................................................................................................................6
EVALUATION OF WATER INFLUX IN GAS WELL ......................................................................6
4.2. Reservoir Pressure History Match ............................................................................................7
4.3 Pressure History Match Model ..................................................................................................8
4.3. Well Deliveribilties ...................................................................................................................8
CHAPTER 5 ......................................................................................................................................11
EXTRA LARGE DIAMETER PROBE.............................................................................................11
5.2 Drilling Fluid Optimization .....................................................................................................11
5.3 Optimization of Tool Configuration.........................................................................................13
CONCLUSION..................................................................................................................................14
REFERENCES...................................................................................................................................15

9. viii
LIST OF FIGURES
Figure 1: T2 distribution curve (S.J. Jacobsen, SPE, J. Phillips, et al, 1998).....................................2
Figure 2: WFT Pump-out module placed at the downstream of advanced fluid analyzer (Rozlin
Hassan, Ryan Lafferty, et al 2013).......................................................................................................4
Figure 3: confirmed Gas-Water Contact (Rozlin Hassan, Ryan Lafferty,et al 2013). ........................5
Figure 4: Well pressures and cumulative productions for history match(G. Matthes, Mobil Oil A. G.
R. F. Jackson, et al 1973). ....................................................................................................................7
Figure 5: summaries a reservoir simulation model
(http://www.intelligentsolutionsinc.com/Technology/TDM.shtml)...................................................10
Figure 6: Shows the different fluid, which were optimize (Moyosore Okuyiga, Ahmed Berrim, et al
2007). .................................................................................................................................................12
Figure 7: Shows a fluid tester, which was, plugged (Moyosore Okuyiga, Ahmed Berrim, et al
2007). .................................................................................................................................................13

10. ix
LIST OF TABLES
Table 1: how models are built for the different studies made(G. Matthes, R. F. Jackson, et al 1973) 6
Table 2: Reservoir Conditions (G. Matthes, Mobil Oil A. G. R. F. Jackson, et al 1973) ....................7

11. x
LIST OFABBREVIATIONS
SW: Water Saturation
K: Permeability
NMR: Nuclear Magnetic Resonance
RT: True Resistivity
BCF: Barrel cubic feet
DFT: Down Hole Fluid Test
WFT: Wireline Fluid Test
XLD: Extra Large Diameter

12. 1
CHAPTER 1
INTRODUCTION
Reservoir evaluation has long been a prominent practice utilized by the engineers to better understand
the reservoir especially during the exploration process all the way to the development stages. It is
done for better understanding of which paves the way for better decision-making on the field.
1.1What is reservoir evaluation.
This refers to all geological, geophysical as well as engineering techniques utilized to ensure a better
understand of the downhole formation fluid as well as rock properties for better decision-making on
the way forward on a field.
1.2Why Reservoir Evaluation?
The number one objective for reservoir evaluation is to understand the formation properties of the
reservoir for better decision making on the estimation of hydrocarbon volume, assess recoverable
reserves, and prioritize development based upon the value of the various resource classes in the asset.
This is better done by understanding the following:
1. Size
2. Shape
3. Lithology
4. Reservoir characterization of properties
(E.g. porosity, fluid composition, SW).
1.3 Economic and decision making Impact
On this paper, we shall elaborate on different formation evaluation techniques are used to improve
the condition on the field. In addition, Reservoir evaluation is very fundamental for every field and
hence a plays a very key role in the economic decision-making. The volumetric evaluations done
from the information, which are accurately acquired during the evaluation, determine the amount of
original oil in place and recoverable oil, which helps in the investment analysis, as well as overall
field Deliveribilties. These evaluations are critical for every decision taken on the field from the
exploration drilling to the field completions.

13. 2
CHAPTER 2.
CASE STUDY ON WATER SATURATION EVALUATION
Among all these case studies it was challenging for the engineers to use the conventional methods for
the formation evaluation and so they try using these methods to get a better understanding of the
formation so as to pave a way to more field development as well as ease in making economic decision.
2. 1 Water Saturation Evaluation
This case study done in Norway which was about a special case whereby water saturation is measured
using NMR logging instead of the traditional resistivity logs in conjunctions with other logs .Basically
the purpose for any studies is to get meaningful information and make good inference from that and
that definitely requires a precise methodology. In these studies, the methodology of interpretation is
based on the (.S.J. Jacobsen, SPE, J. Phillips, et al, 1998).
1. Rock type (Water-wet Rock Model): which was about the wettability of the reservoir rock.
2. NMR (Basic Interpretation and Permeability relationship).
2.1.1NMR Interpretation
This is one of the very few unique techniques use in evaluating water saturation in a more dynamic
way to determine the free fluid and bounded fluid saturation this helps so much determining the
recoverable water and hydrocarbons.
Figure 1: T2 distribution curve (S.J. Jacobsen, SPE, J. Phillips, et al, 1998).

14. 3
2.1.2 NMR Permeability Relationship
However, in this case study the resulting curve output is called “TCMR which is a porosity
measurement which is thus considered to represent approximately the same volume of fluid seen by
the resistivity tool and included in the quantity Rt, It typically has values which match core porosity
quite well. The Timur/coates formula defines the permeability relation. The relationship developed
by Coates, et al’.KTIM = a’ TCMR^4(FFI/BFV)^2……………………………...1 K Is the
permeability in mD,a is a constant(1*10^4) for sandstone ,BFV is the bound fluid volume,FFI is the
free fluid volume ,TCMR is the total porosity which is=BFV+FFI mostly except in cases like 1.gas
or light hydrocarbons prevent full NMR polarization of the large pores.2.If bound fluid logging’ has
been the acquisition mode.This results in TCMR underestimating the actual total porosity of the
formation, the deficiency coming from porosity loss in the large pores/free fluid partition. In these
cases, it is necessary to use an external porosity source such as density tool porosity with the
appropriate corrections for light hydrocarbons and grain density. Petrophysical volumetric analysis
can also be used to help in the correction. Modified equations of the previously discussed equation
(Timur/coates formula defines the permeability relation).
KTIM = a’ PHIT^4{(PHIT-BFV)/BFV}^2………………………………………………..2 PHIT is
the external porosity value, and FFI is replaced by the difference between PHIT and BFV. The
Timur/Coates permeability relationship was determined empirically in work on a large body of
sandstone core samples. A global T2cut value of 33 msec was used to partition the BFV and FFI
components of the total porosity. However, this number can change, especially as the lithology
becomes more complex l’2’G8. It must be adjusted to reflect the true bound and free fluid fractions
of the pore distribution which drive the permeability model. In specific cases further NMR core
centrifuge experiments to refine T2cutvalues are typically employed. In this study, the approach was
to consider core permeability values as a benchmark to which to compare the KTIM log outputs in
each of our examples. Procedurally, the CMR data in each of the studied wells was acquired with a
default T2cut value of 33 msec, and under either full polarization or bound fluid logging speed
conditions. TCMR processing was carried out on a workstation subsequent to the logging jobs.
( S.J. Jacobsen, SPE, J. Phillips, et al , 1998).

15. 4
CHAPTER 3
DOWNHOLE FLUID TESTER (ADVANCE FLUID ANALYZER)
This case was done in Malaysia whereby instead of the usual use of WFT to collect reservoir fluid
samples and taken to the lab for PVT analysis and others as well this time the engineers made use of
the DFT (Down Hole Fluid Tester) which make use of the Advance fluid analyzer to make analysis
in the reservoir in situ condition which is a reliability to the accuracy the results gives. There Are
many planning considerations to be made so as not to compromise the results the DFT* Advance
Fluid Analyzer*. There are different modules set for the. (Rozlin Hassan, Ryan Lafferty,et al 2013).
3.1. Downhole Fluid Analysis (DFA) Planning
In the planning as stated before the advance fluid analyzer has to be set in a way so as not to be
comprised in its analysis. The modules that are set are:
3.1.1. Fluid Discharge into Borehole
care must be taken in fluid discharging so as not to contaminate or cause an interruption of pressure
which may cause anomalies especially in gas reservoirs.
3.1.2. CO2 Measurement in Water Based
The solubility of CO2 in WBM is high which affects its measurements and therefore WBM have to
be removed. Minimum no mud filtrated is required to ensure a representative CO2 composition.
3.1.3. Wireline Formation Tester (WFT) Modules Positioning
The position of advance fluid analyzer with respect to the pump out module plays an important role
Because of the fluid analyzer is delicate and its accuracy might be tampered with if no proper planning
is done.
Figure 2: WFT Pump-out module placed at the downstream of advanced fluid analyzer
(Rozlin Hassan, Ryan Lafferty, et al 2013).

16. 5
3.2. Downhole Fluid Analysis (DFA) Candidate Identification
The selection and identification of DFA candidates in this campaign was done mainly based on the
WFT pretests and open hole logs results. The DFA candidates are identified in each of the wells of
study based on several criteria as follows: A DFA station is subsequently plan at this zone to identify
the fluid type and subsequently confirms base on the criterion. i. No pressure gradients due to tight
or thinly laminated formation. ii. Pressure Gradient Confirmation and Downhole Fluid Density
Verification. iii. Fluid Contact Confirmation. (Rozlin Hassan, Ryan Lafferty,et al 2013).
Figure 3: confirmed Gas-Water Contact (Rozlin Hassan, Ryan Lafferty,et al 2013).
It was concluded from studying this field that:1. Downhole Fluid Analysis (DFA) enables reservoir
fluid identification at the intervals where the pressure gradients are not working properly namely
thinly laminated formation, low mobility formation. and at the presence of non-hydrocarbon
component such as CO2. 2. Downhole Fluid Analysis (DFA) via advanced fluid analyzer enables the
real time optimization of logging program while doing the exploration with formation tester tool
remained in downhole. 3. CO2 composition measurement via advanced fluid analyzer is critical in
exploration phase to identify the effects of this non-hydrocarbon component on the pressure gradients,
open hole logs and conventional fluid analyzer output. 4. Downhole Fluid Analysis (DFA) via
advanced fluid analyzer permits quick reservoir study during the exploration phase by providing
required reservoir fluid information for fluid PVT properties estimation and avoids the need to wait
for downhole samples PVT laboratory results. 5. The paper demonstrates the efficiency and accuracy
of Downhole Fluid Analysis (DFA) via advanced fluid analyzer in evaluating different hydrocarbon
types ranging from low to high GOR. 6. Downhole Fluid Analyzer via advanced fluid analyzer
provides an alternative to validate the quality of PVT laboratory results for acquired downhole fluid
samples in exploration phase.

17. 6
CHAPTER 4
EVALUATION OF WATER INFLUX IN GAS WELL
This case study was about a field discovered in Germany Bierwang. The original gas in place,
determined dynamically and volumetrically, was about 156 Bcf. The gas is both sweet and dry,
permitting this reservoir to be studied as a dry gas pool with an aquifer. The size and extent of the
aquifer are not known reliably. However, the reservoir pressure behavior indicates the existence of a
strong water drive with associated water influx. To the end of to the end of 1970, five wells were
capable of gas production. However, one of these wells had exhibited water breakthrough and was
producing with a continually increasing water cut this therefore prompted a study to be done. The
objective of the study was to to 1, determine the cause of water production. 2.to predict the future
prediction deliverability of the reservoir .3.to determine the expected ultimate gas recovery. In the
cause of the study the engineers made so many studies like.(G. Matthes, R. F. Jackson, et al 1973)
Table 1: how models are built for the different studies made (G. Matthes, R. F. Jackson, et al
1973)
HISTORY MATCHING WATER PRODUCTION DELIVERABILITY
Reservoir Pressure History Match Investigation of Water Production Deliverability Study
make Model for History Matching Well Coning Behavior Deliverability History Match
Pressure Match and Water influx Make Coning Model Reservoir Pressures agreement
Coning Performance Well deliverability.
Cross-Sectional Studies
Deliverability Predictions
Individual Well Cross-Sectional
Model Total Field Cross-Sectional
Model
The problem of determining the reason for water production required the investigation of three
possible causes: (1) water influx from the aquifer overrunning the producing well (2) bottom-water
coning; or (3) channeling of water along high-permeability stringers; or some combination of these
three conditions. The history match of the observed reservoir performance revealed that water influx
could contribute to individual well water production.

18. 7
4.2. Reservoir Pressure History Match
The primary objectives of the history match were to determine the strength of the aquifer water drive
and to obtain a reservoir description that would yield good agreement between calculated and
measured pressures. This helps in making decisions on the way forward with solving the water influx
issue.
Table 2: Reservoir Conditions (G. Matthes, Mobil Oil A. G. R. F. Jackson, et al 1973).
Reservoir temperature, 0
F 122
Initial reservoir pressure, psia 2,039
Initial gas-water contact, ft subsea 3,427.6
Base water density, lb/cu ft 62.6
Water viscosity, cp 0.57
Water compressibility, vol/vol/psi 3.3 x 10-6
”
Rock compressibility, vol/vol/psi 3.0 x 10-6
Irreducible water saturation, percent 25
Residual gas saturation, percent 22
Figure 4: Well pressures and cumulative productions for history match(G. Matthes, Mobil Oil
A. G. R. F. Jackson, et al 1973).

19. 8
4.3 Pressure History Match Model
The history match of individual well pressure performance was made with a numerical simulation
model that simultaneously considers fluid flow and pressure drops in the reservoir. A two-
dimensional, two-phase gas-water model”’ was used to represent the reservoir with areal variations
in structural elevation, thickness, permeability, and porosity. To determine an optimum production
strategy, an areal two-dimensional gas-water model, cross-sectional studies, and a coning model were
used. A history match showed appreciable horizontal water influx. Wafer coning, however, would not
be a problem, and channeling could be overcome by additional perforating. Ultimate gas recovery
can be considerably increased if withdrawal rates are kept high.(G. Matthes, Mobil Oil A. G. R. F.
Jackson, et al 1973).
Figure 5: pressure curve of history match (G. Matthes, Mobil Oil A. G. R. F. Jackson, et al
1973)
4.3. Well Deliveribilties
It is important to obtain descriptions of the reservoir, production strings, and surface lines that result
in calculated performance that agrees with observed data throughout the producing history. In our
study, this deliverability history match encompassed four stages: reservoir pressure match, tubing
pressure match, surface pressure match, and well deliverability match.

20. 9
Table 3: Well Deliverability (G. Matthes, Mobil Oil A. G. R. F. Jackson, et al 1973).
Well Measured Deliverability Mcf/D Calculated
Deliverability Mcf/D
C2 32,500 33,500
C4 ---------------- ----------------
A7 35,900 34,000
C5 14,600 14,200
A9 23,500 22,200
The pressure history (TABLE 3) are used to tally with calculated reservoir pressures, which are used
to make the curve (FIGURE 4). From the curve the abandonment pressures can easily be determined
and since for a gas well with water drive the abandonment pressure is usually high which is not good
for productivity since gas wells produce by expansion and for that reason the evaluation was done to
ensure that this issue be resolved. Which was later done by outrunning technique. The program
calculates deliverability from the radial flow equation when skin and turbulence factors are provided.
In this study, for each production Well the input data included perforation intervals with skin and
turbulence factors. After reservoir and tubing pressures were matched, the calculated Deliverabilities
agreed fairly well with modifications to some well performance coefficients and minor changes in
the reservoir description. The measured and calculated data are given in Table 3.

21. 10
In this field we came to the conclusion from studies made on the wells that the water observed was
that the reservoir was acting as though a piston and water is produce. The production however if
increase (out running Technique) will increase recovery greatly. Recovery at 69% 50MMB/D was
increased to 74% 75MMB/D.
Figure 5: summaries a reservoir simulation model
(http://www.intelligentsolutionsinc.com/Technology/TDM.shtml)

22. 11
CHAPTER 5
EXTRA LARGE DIAMETER PROBE
In this case, study a new technology has been used to help the engineers overcome a plugging problem
during a reservoir evaluation. The plugging was causing so much rig time, which was not economical,
and hence it has to be resolved. The whole process of the evaluation was based on the extra-large
probe, which helps to do multiple task and as well help resolve the issue with the plugging. There
were teams from all areas required top make the whole process a success. The new wire line formation
tester technology, the Extra Large Diameter module (XLD).The utilization of XLD probe also
allowed us to significantly reduce rig time with full satisfaction of data quality and testing objectives.
Geologists ,petrophysicists, reservoir engineers, drilling engineers, as well as all other engineers
needed to make the whole evaluation process complete. And work together to come up with a solution
to the problem which was the water invasion into one of the wells. The solution must consider: 1) the
scope &objectives , 2) well bore conditions, 3) reservoir conditions, 4) rig time constraint, 5) QHSE
(such as logging in high H2S concentration environment).(Moyosore Okuyiga, Ahmed Berrim, et. al
2007).
.
5.2 Drilling Fluid Optimization
Field and drilling engineers studied the compatibilities between different mud systems with formation
tester. The results were fed back to drilling, reservoir engineers, and other geosciences in a
multidisciplinary team for job planning. The figure 6 below shows the brief summary of shop test of
different mud samples. Based on the results, mud system 1 was specifically and fatherly lowered its
solid content to a very low level, and the logging interval was replaced by optimized mud system #1
prior to the WFT operations. This was proved crucial to achieve a big success. In addition to that ,The
utilization of XLD probe allowed us to reduce the exposure of formation tester to mud from bore hole
and consequently increase packer’s and pump’s life time as well as operation efficiency. The choice
of either dual packer of XLD was fully based on thorough understanding of 1) the objectives of each
formation testing station, 2) the knowledge of reservoir rock and fluid properties, 3) the operation
conditions, and 4) the updated understanding of the facing challenges while performing real time
interpretation. The utilization of XLD probe also allowed us to significantly reduce rig time with full
satisfaction of data quality and testing objectives. Moreover, the utilization of XLD allowed us to

23. 12
use dual packer to deal with more challenging tasks such as mini-frac and sampling from low
permeability zone.
Figure 6: Shows the different fluid, which were optimize (Moyosore Okuyiga, Ahmed Berrim,
et al 2007).

24. 13
5.3 Optimization of Tool Configuration
Due to numbers of pumping stations across several individual reservoir zones, reliability and
efficiency of the WFT tool string are vital. Packer+probe(s) configuration is generally recommended.
The choice of packer or probe for each pumping station is typically based on several factors:objectives
and priority of each pumping station, rock and fluid properties (i.e., permeability, expected bubble
point or dew point. Packer+probe(s) configuration is generally recommended. The choice of packer
or probe for each pumping station is typically based on several factors:1.objectives and priority of
each pumping station, 2.rock and fluid 3.properties (i.e., permeability, expected bubble point or dew).
To reduce plugging in long time operational cases. Dual screen/filters in packer, probe(s), and
pump(s) . Two pump out modules.A big sample chamber (i.e., 6 gallon) filled with fresh water to
inflate packer or clean flowline. (Moyosore Okuyiga, Ahmed Berrim, et al 2007).
Figure 8: shows a fluid tester which was plugged (Moyosore Okuyiga, Ahmed Berrim, et al 2007).
Figure 7: Shows a fluid tester, which was, plugged (Moyosore Okuyiga, Ahmed Berrim, et al
2007).

25. 14
CONCLUSION
Reservoir evaluation is a conventional practice in the oil industry, which is done purposely to
understand the formation to pave the way forward on any development on the field. However, In
Some cases it requires some special techniques as well as new equipment's and technology in other
to get the desired results from the evaluation process. Reservoir evaluation has a very significant
impact on a field. It helps in understanding the filed as well as increase the productivity and hence
add significant value the economy. The evaluation is paramount to the life of a field and hence care
must be taken when doing it. Requires proper planning as well many technical evaluations. However,
it is done for better knowing of the conditions and parameters of the well or field at large which in
turns pave the way for increase in overall recovery from the field and hence increase value
economically.

26. 15
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