PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
A Study On The Reservoir Rocks Of Qishn Formation (Masila Block 14)
1. REPUBLIC OF YEMEN
MINISTRY OF OIL AND MINERAL RESOURCES
PETROLEUM EXPLORATION AND PRODUCTION AUTHORITY
A STUDY ON THE RESERVOIR ROCKS OF QISHN
FORMATION (Masila Block 14)
By: Dr. Eng. Mohammed Darsi Abdulrahman Nedham
Doctor of Science (Geologist), PEPA ’s Office (Aden)
Aden (June 2oo3)
2. WHAT MASILA BLOCK AND QISHN FORMATION
MEANS FOR CANADIAN NEXEN INC.?
First of all, and before I am going to write any word as an introduction to my study on
the reservoir rocks of Qishn Formation in Masila Block (14). I would like to draw the
attention of all people, who work as decision makers in the Ministry of Oil and
Minerals (MOM) and the Petroleum Exploration and Production Authority (PEPA) on
the great importance of answering the above-mentioned question.
We must know, that Masila Block (See, Fig. (1)) has a great meaning for Nexen
Company, because of the following reasons:
1. Approximately 44% of Nexen's overall production comes from the Masila Block
(Yemen), which representing just over one third of the company's cash flow.
2. Nexen has a 52% working interest in and operate the Masila Project, which is the
largest single source of oil production in Yemen and has grown steadily since
discovery in 1990.
3. To date, the 15 fields that comprise the Project have produced over 665 million
gross barrels of oil from total gross recoverable reserves of just over one billion
barrels.
4. Nexen has the right to produce oil from the Masila fields until 2011 and the right
to negotiate a five-year extension.
5. During 2002, $402 million ($209 million net) was invested to drill and equip 74
new development wells and expand existing infrastructure. Gross production was
maintained throughout the year at approximately 226,900 barrels per day.
6. The economics of Masila production are attractive. Historic finding and
development costs are approximately US $2 per barrel and operating costs have
averaged US $1 per barrel, resulting in excellent returns for shareholders!
All the above mentioned reasons makes Nexen not just take care of Masila Block and
Qishn Formation, (I mean the Qishn clastic member, which is the main producing
reservoir in this area and the main subject of this study), but also to work actively on
exploring outside the Masila Block. In my opinion, the strategic point of view and the
excellent steps taken by the heads of Nexen Inc. led to the following main result and
present fact:
(Nexen, NOW, hold interests in seven exploration licenses (Block 50 Block 51
Northern Blocks 11, 12, 36, 54 and 59) comprising over 20 million acres of
undeveloped land, the majority of which are located in northeastern Yemen close to
the Saudi Arabian border. (See Fig. (2))
Due to what mentioned above I am sure that we in Yemen are highly in need for
building not just the high qualified Yemeni oil team but also for building the first
National Oil Exploration Company. Am I right? Now, it is the suitable time for
Yemeni specialists, who found a great chance to work with those kind of high-
qualified and experienced foreign specialists, to learn from the newest in their field of
specialization. Our scientific cooperation and friendship must continue with all and
forever. If we really want to see the whole plains clearly, we must climb the highest
mountain. i
3. Fig. (1) Masila Location (Nexen Inc., Data)
<
Fig. (2) Nexen Blocks in Yemen (Nexen Inc., Data)
ii
4. INTRODUCTION
Masila Block 14 is operated by Canadian Occidental Petroleum Yemen on behalf of
its partners Occidental Peninsula, Inc. and Consolidated Contractors International,
Ltd., (CANADIAN NEXEN PETROLEUM YEMEN as known now), and is located
in the Hadhramaut region, in east-central Republic of Yemen. Oil was first discovered
on the Block in late 1990 with Commerciality declared in late 1991. Oil production at
Masila began in July 1993.
There are now 15 oil fields known in Masila, Block 14: (See, Fig. (3)) 1. Camaal (C),
2. North Camaal (NC), 3. Sunah (S), 4. Northeast Sunah (NES), 5. Heijah (HJ), 6.
Hemiar (HR), 7. South Hemiar (S.HR), 8. West Hemiar (W.HR), 9. Tawila (T), 10.
Haru (HU), 11. Nazeia (NZ), 12. Dahban (D), 13. Bainoon (ND), 14. Qataban (QAT),
and 15. Gabal-Isbeel, containing 56 pools within the Masila Block. Total proven
ultimate recoverable oil reserves are approaching 900 million STB. Proven, probable
and possible reserve estimates are in excess of one billion barrels of recoverable oil.
The Masila fields are in the Jurassic- to Lower Cretaceous-aged, Saar Graben. Almost
90% of the Masila reserves are reservoired in the Qishn Formation of the Lower
Cretaceous Upper Qishn Clastics Member. Oil is also found in at least seven other
reservoirs consisting of Lower Cretaceous and Middle to Upper Jurassic age clastics
and carbonates as well as fractured granitic basement.
In this study I used real subsurface data related to 93 wells, penetrated the productive
and non-productive fields of the studied area. All above-mentioned wells penetrated
Qishn formation the main subject of this study, where I made geostatistical
calculations and analysis, to explain the process of sedimentation mathematically for
Qishn formation generally and its subdivision in detail. Showing the maximum,
minimum and the average of Qishn formation thickness, its members, sub members,
units and sub units in detail for every well, for every productive field and for Masila
Block as a whole.
The most important thing I have done during my study to the pervious and the present
data, informations and published materials on the reservoir rocks of Qishn Formation
is that I focused on the main producing horizon (the Upper Qishn Clastics Member).
The Upper Qishn represents an upward transgressive sequence from braided river
deposits into tidally influenced shorelines, overlain by subtidal and shelf deposits.
Important Notices:
1. Yemeni reserves of raw oil were estimated to be about 4 billion barrels, of which
1380 million barrels are found in Marib, 1580 billion barrels in Masila, 250
million barrels in Shabwah, and 750 million barrels in Gannah.
2. Arab investment in Yemen heading toward $1 billion Yemen, Economics,
9/23/1997
iii
6. MAIN TOPICS OF THIS STUDY
The main topics of this study on the reservoir rocks of Qishn Formation (Masila
Block 14) are the following:
1. To show the great importance of Masila (Block 14) and the
reservoir rocks of Qishn Formation for Nexen Inc.
2. To give a brief on the whole pervious activities done on studying
the Geological Research History Work of the eastern part of the
Republic of Yemen (the study area and the adjacent areas).
3. To follow Qishn formation location on the whole surface, to study
it in the sub surface of the studied area and to highlight the upper
Qishn clastics rocks stratigraphy.
4. To study the Qishn Formation in Masila Block 14 as whole and in
detail, its subdivision, ages, sequence stratigraphy, general
lithology, lithology, its drilling parameters averages, mud
parameters, its Paleogeography, and its sedimentation thicknesses
in the study area by making 20 tables on Qishn formations and it
sub sequences.
5. To explain the petroleum system of Qishn Formation, its source
rocks, maturation, migration, reservoir rocks, traps and seals.
v
7. NATURE OF THIS STUDY
Prompted largely by this interest, my research study plan on studying the reservoir
rock of Qishn Formation was concentrated on its achievement on the following
important point:
1. Study and examination of all primary information connected with the subject from
various sources.
2. Sorting of this information in accordance with its importance.
1. Making number of tables and maps.
2. Checking of all data and making necessary tests on them.
3. Follow-up of the historical development of the reservoir rocks of Qishn Formation
through the making of varying geostatistical and mathematical calculation for the
interested section of Qishn formation and its subdivision from its bottom till the
surface.
AIM OF THIS STUDY
The study was aimed at the problems outlined in the previous two sections. This study
is the first investigation work-study, done by me on the reservoir rocks of Qishn
formation of Masila Block 14, which aims to:
1. Help understanding of the great importance of the studied area.
2. Help understanding of the pervious and present geological activities in the area.
3. Help understanding of the reservoir rocks of Qishn formation, surface, sub surface
geology and the upper Qishn stratigraphy.
4. Help understanding of Qishn formation sequence stratigraphy.
5. Help understanding of Qishn formation (Masila, Block 14) petroleum system.
6. Give new discussions points, recommendations and conclusions.
vi
8. CONTENTS
WHAT MASILA BLOCK AND QISHN FORMATION MEANS FOR
CANADIAN NEXEN INC.? --------------------------------------------------------------i
INTRODUCTION --------------------------------------------------------------------------iii
MAIN TOPICS OF THIS STUDY ------------------------------------------------------v
NATURE OF THE PROBLEM ---------------------------------------------------------vi
AIM OF THIS STUDY --------------------------------------------------------------------vi
CONTENTS ---------------------------------------------------------------------------------vii
LIST OF FIGURES ------------------------------------------------------------------------ix
LIST OF TABLES --------------------------------------------------------------------------x
CHAPTER 1: THE EASTERN PART OF THE REPUBLIC OF YEMEN
GEOLOGICAL RESEARCH HISTORY WORK
1.1 PERVIOUS ACTIVITIES IN MASILA BLOCK AND ITS ADJACENT
AREAS -------------------------------------------------------------------------------1
1.1.1 INRODUCTION
1.1.2 PERVIOUS WORKS BASED ON MY
CLASIFICATION AND DIVISION
CHAPTER 2: THE RESERVOIR ROCKS OF QISHN FORMATION
(MASILA, BLOCK 14) – GEOLOGY
2.1 INTRODUCTION --------------------------------------------------------------3
2.2 QISHN FORMATION RESERVOIR GEOLOGY
2.3 UPPER QISHN CLASTICS – STRATIGRAPHY -------------------------9
CHAPTER 3: QISHN FORMATION AND ITS SUBDIVISION (IN DETALS)
3.1 INTRODUCTION -------------------------------------------------------------10
3.2 QISHN FORMATION IN THE OUTCROP
3.3 QISHN FORMATION IN THE SUBSURFACE (IN DETAILS)
3.3.1 Qishn Carbonate Member ------------------------------------------21
3.3.1.1 Qishn Carbonate Member - Age
3.3.1.2 Qishn Carbonate Member - Lithology in General
3.3.1.3 Qishn Carbonate Member - Lithological Description
3.3.1.4 Rate of Penetrations for Qishn Carbonate Member
3.3.1.5 Gases in Qishn Carbonate Member
3.3.1.6 Drilling Parameters for Qishn Carbonate Member
3.3.1.7 Qishn Carbonate Member – Subdivision ------------24
3.3.1.7. 1 C1
3.3.1.7.2 C2
3.3.1.7.3 RS (Red Shale)
3.3.1.7.4 C3
3.3.2 Qishn Clastic Member ----------------------------------------------26
3.3.2.1 Qishn Clastic Member - Age
3.3.2.2 Qishn Clastic Member - Lithology in General
3.3.2.3 Qishn Clastic Member - Lithological Description
vii
9. 3.3.2.4 Rate of Penetrations for Qishn Clastic Member
3.3.2.5 Gases in Qishn Clastic Member
3.3.2.6 Oil Shows in Qishn Clastic Member
3.3.2.7 Drilling Parameters for Qishn Clastic Member
3.3.2.8 Qishn Clastic Member – Subdivision ----------------29
3.3.2.8.1 Upper Qishn Clastic Sub Member ----------30
3.3.2.8.1.1 S1 ------------------------------------31
3.3.2.8.1.1.1 S1A
3.3.2.8.1.1.2 S1B
3.3.2.8.1.1.3 S1C
3.3.2.8.1.2 S2 ------------------------------------33
3.3.2.8.1.2.1 S2A
3.3.2.8.1.2.2 S2B
3.3.2.8.1.2.3 S2C
3.3.2.8.1.2.4 S2D
3.3.2.8.1.3 S3 ------------------------------------35
3.3.2.8.2 Lower Qishn Clastic Sub Member -------- -36
3.3.2.8.2.1 LQ1
3.3.2.8.2.2 LQ2
3.3.2.8.2.3 LQ3
3.3.2.8.2.4 LQ4
CHAPTER 4: QISHN FORMATION PETROLEUM SYSTEM -----------------40
4.1 INTRODUCTION
4.2 SOURCE ROCKS
4.3 MATURATION
4.4 MIGRATION
4.5 RESERVOIR ROCKS
4.6 TRAPS AND SEALS
CHAPTER 5: DISSCUSION POINTS, RECOMMENDATIONS AND
CONCLUSION
5.1 DISSCUSION POINTS --------------------------------------------------------41
5.2 RECOMMENDATIONS ------------------------------------------------------42
5.3 CONCLUSIONS ----------------------------------------------------------------43
ACKNOWLEDGEMENTS -----------------------------------------------------------------44
REFERENCES -------------------------------------------------------------------------------45
ABOUT THE AUTHOR --------------------------------------------------------------------46
viii
10. LIST OF FIGURES
Fig. (1) Masila Location ---------------------------------------------------------------------ii
Fig. (2) Nexen Blocks in Yemen -----------------------------------------------------------ii
Fig. (3) Masila Block Oil Fields ------------------------------------------------------------iv
Fig. (4) Regional Stratigraphy (showing our study area) --------------------------------4
Fig. (5) Regional Frame Work (showing Masila Block Location due to Say’un al-
Masila Basin -----------------------------------------------------------------------------------5
Fig. (6) Regional Setting (showing Masila Block Location, due to Masila High) ---6
Fig. (7) Stratigraphy of Masila (showing Qishn Clastics Member and its related
subdivision) -----------------------------------------------------------------------------------7
Fig. (8) Regional cross section between Tawila-1, Tawila-17, Heijah-2, Camaal-3
and Sunah-3 wells -----------------------------------------------------------------------------8
Fig. (9) Qishn Carbonate Member, Thickness Map -------------------------------------22
Fig. (10) Qishn Carbonate Member, Three Dimension Model -------------------------23
Fig. (11) Qishn Clastics Member, Thickness Map ---------------------------------------27
Fig. (12) Qishn Clastics Member, Three Dimension Model ----------------------------28
Fig. (13) Qishn Formation, Thickness Map -----------------------------------------------38
Fig. (14) Qishn Formation, Three Dimension Model -----------------------------------39
ix
11. LIST OF TABLES
Qishn Formation of Masila Block, its Subdivision Tops and Thicknesses
Table (1) Qishn Carbonate of Masila, Block 14 Thicknesses ----------------------11
Table (2) Qishn Carbonate (C1) of Masila, Block 14 Thicknesses --------------------14
Table (3) Qishn Carbonate (C2) of Masila, Block 14 Thicknesses --------------------15
Table (4) Qishn Carbonate (RS) of Masila, Block 14 Thicknesses --------------------15
Table (5) Qishn Carbonate (C3) of Masila Block 14, Thiknesses ---------------------16
Table (6) Qishn Clastics of Masila, Block 14 Thicknesses --------------------------19
Table (7) Upper Qishn Clastics of Masila, Block 14 Thicknesses -----------------20
Table (8) Upper Qishn Clastics (S1A) of Masila, Block 14 Thicknesses -------------21
Table (9) Upper Qishn Clastics (S1B) of Masila, Block 14 Thicknesses -----------22
Table (10) Upper Qishn Clastics (S1C) of Masila, Block 14 Thicknesses -----------22
Table (11) Upper Qishn Clastics (S2A) of Masila, Block 14 Thicknesses -----------23
Table (12) Upper Qishn Clastics (S2B) of Masila, Block 14 Thicknesses -----------24
Table (13) Upper Qishn Clastics (S2C) of Masila, Block 14 Thicknesses -----------24
Table (14) Upper Qishn Clastics (S2D) of Masila, Block 14 Thicknesses -----------25
Table (15) Upper Qishn Clastics (S3) of Masila, Block 14 Thicknesses -------------25
Table (16) Lower Qishn Clastics of Masila, Block 14 Thicknesses ---------------26
Table (17) Lower Qishn Clastics (LQ1) of Masila, Block 14 Thicknesses ----------26
Table (18) Lower Qishn Clastics (LQ2) of Masila, Block 14 Thicknesses ----------27
Table (19) Qishn Formation of Masila, Block 14 Thicknesses ---------------------27
Important Notice:
All above-mentioned tables done by me based on my study to:
1. The Masila Block Field Development Location Map in General.
2. Sunah, Heijah, Camaal, Hemiar, … ,Haru and Naziah Fields
3. The Geological Summary of the Masila Block
4. The Masila Block Stratigraphic Column
5. The Geological Sections done by me for Sunah-1, Naar-1, Maljan-1, Ressib-1,
Deelun-1 Wells.
6. Masila Block Formation Tops and Thicknesses (The table done in 1993, 1997 and
updated in 2002, by Nexen Inc.)
7. An old table done by me as a part of my study to Masila Block in the past. The
main aim of the above mentioned table is to give interested persons in Masila
Block general informations (such as: Block Area, Productive and non-productive
fields, No. of wells in every Productive and non-productive fields and the
Sedimentary Cover) and also geological informations (such as: the stratigraphical
sections, thicknesses, lithology, source rocks characteristics and reservoir rocks
characteristics)
x
12. CHAPTER 1
THE EASTERN PART OF THE REPUBLIC OF
YEMEN GEOLOGICAL RESEARCH
HISTORY WORK
1.1 PERVIOUS ACTIVITIES IN MASILA BLOCK AND ITS ADJACENT
AREAS
1.1.1 INRODUCTION
The Republic of Yemen is beside the richest hydrocarbon province in the world. Oil
only discovered in the early 1980’s in the offshore (Sharmah Well). It is known, that
Nexen Inc. (formerly known as Can Oxy Company) discovered oil in Masila Block in
1990 in the Qishn Clastics Member of Qishn Formation.
The Masila Block has 1250 km2 in size. The Estimated Reserves is 1.1 billion barrels
recoverable and the Cumulative Production is 600,000,000 barrels (Due to March
2002 wells production reports), where the daily production was 230,000 b/d.
1.2 PERVIOUS WORKS BASED ON MY CLASIFICATION AND DIVISION
According to my new classification and first division to the whole geological research
history work in the Republic of Yemen to four stages (See Yemen Times Newspaper.
Issue 2-January 10th through January 16 2000, Vol. IX Culture Page, Issue 10 -
March 6 through March 12 2000, Vol. X, Culture Page and Issue 15 - April 10
through April 16 2000, Vol. X, Culture Page). It is so clear now, that:
1. On the First Stage (The First Systematic Geological Observation Stage or
Carter’s Stage), 1852-1901:
No kind of geological studies had been detected in the Masila area.
2. On the Second Stage or the Hinterland Studies Stage, (1902-1946) and the
Third Stage (The First Systematic more detailed Stratigraphic and Geological
Studies Stage or Beydoun, Z.R.'s Stage, (1947-1967):
The Petroleum Concessions Ltd, one of the Iraq Petroleum Company and associated
companies (IPC and Associated companies) had carried out little exploration work in
the area between 1937 and 1960. During that time they made geological field
mapping, investigation, supplemented by aerophoto studies, photogeologic and
mapping covering the entire territory were carried out.
1
13. 3. On The Third Stage (The First Systematic more detailed Stratigraphic and
Geological Studies Stage or Beydoun, Z.R.'s Stage), 1947-1967:
During this stage the adjacent areas started to be studied by scientist and oil
companies. Bunker, D.G. wrote about the southwest Borderlands of Rub al Khali, in
1953. From 1961 to early 1967, Pan American International Oil Company through a
subsidiary, Pan American Hadhramawt Oil Company (PAHOC) drilled four wells
(Hoowarin, Tarfayt and Core Hole 88 reached Precambrian basement and the forth
was abandoned in the Cretaceous sediments).
4. The Forth Stage or The Yemeni Geologists Stage (1968 – until Today):
During this stage many important scientific works happened in Yemen, which at the
end led to the creation of the concision map of Yemen, the birth of Masila Block and
its oil discoveries.
It is known that, the Petroleum and Minerals Board (the PMB) was established, in
1970 in former South Yemen. During the period from 1970 to 1973, the joint of
former South Yemen-Algerian Petroleum Company (SYAPCO) drilled Taur-1 in
1974 and Taur-2 was commenced. In 1974, a group of experts from Cuba assumed the
drilling operation from SYAPCO and with former PMB completed Taur-2, Taur-3
and drilled Thamud-1 and Hathout-1. In September 1976, the functions of the PMB
were broadened and the Petroleum Exploration Board (the PED) was created (The
Petroleum Exploration and Production Board, Aden Branch – As known now), was
led different activities on studding the geology of this area. As a result of their work
on the Yemeni sector of Rub al Khali basin, wells as Taur-2, Taur-3 and Hathout-1
was drilled. A group of the P.E.D.’s Engineers, Technician and workers, work hard on
this area, their work is highly appreciated.
Between 1975 and 1979, as a part of its assistance program, TechnoExport, the former
Soviet Technical Assistance Organization, had recorded aeromagnetic surveys
covering most of former South Yemen and also a gravity survey had been conducted
over specific areas of interest.
On Mar. 27 1979, B. Kuzin and Mohammed Ba’abad made a Stratigraphic
Correlation, for wells drilled in that area correlative with wells located in the adjacent
area at that's time.
The field investigation had been augmented from time to time by Czechoslovakian
and German technical personnel.
Agip SpA (from 1978 to 1980): conducted landsite airphoto interpretation and a field
mapping project along the coastal outcrop belt as part of its offshore exploration effort
in the Sayhut Block. On 1981 Agip recorded 110 km of seismic on the coastal plain
east of Mukalla.
Petroleo Brasileiro SA (Petrobras): shot a regional seismic program and drilled three
unsuccessful test wells in the area to the north of the Masila Block in Jeza syncline
and relinquished the area in 1987.
2
14. CHAPTER 2
THE RESERVOIR ROCKS OF QISHN FORMATION
(MASILA, BLOCK 14) – GEOLOGY
2.1 ITRODUCTION
It is known, that oil trapped in sands of the Qishn Formation, the main subject of this
study, in the following structures: Camaal, North, Sunah, North East Sunah, Heijah,
Hemiar, South Hemiar, West Hemiar, Tawila, Haru, Nazeia, Dahban, North Dahban,
Qataban, and Gabal-Isbeel.
Note 3: Oil has also been discovered in the Kohlan Formation (at Sunah; for
example), in addition there have been significant oil shows from fractured basement
(at Sunah; for example) and the Saar Formation (at Camaal; for example). In my
opinion ongoing exploratory drilling is expected to inhance present discoveries and to
find oil in additional horizons and traps.
Subsidence in the Masila area began with a marine transgression in Upper Jurassic
time over the Pre Cambrian basement peneplain. The Kohlan Formation sands were
deposited as a transgressive lag that passes gradationally upwards into the shallow
marine carbonates of Shuqra Formation. A period of rifting in the late Jurassic led to
restricted conditions and deposition of the Madbi shales, the oil source rocks for the
discoveries. The Madbi shales are overlain by the deep-water limestones of the Naifa
Formation of uppermost Jurassic to lowermost Cretaceous age. Lower Cretaceous
shales and carbonates of the Saar Formation and the clastics and carbonates of the
Qishn Formation, the main subject of this study, were deposited. The Upper
Cretaceous and the Lower Tertiary sediments are predominantly clastic with
interbedded carbonates becoming more carbonate rich into the Tertiary.
The Masila area has undergone several periods of rifting, resulting in a complexly
faulted basement structure. Uppers Jurassic rift basins are bounded by the basement
high blocks over which the Jurassic has been eroded and is either thin or absent.
Subsequent periods of rifting led to reactivation of the basement faults and normal
faulting through the Cretaceous (the Lower Cretaceous age of Qishn Formation) and
the Tertiary section over the basement highs.
2.2 QISHN FORMATION RESERVOIR GEOLOGY
The Qishn reservoir sandstones have both high porosity (18-21%), and high
permeability (<10 Darcies). They are relatively homogenous and continuous in the
lower section and are more heterogeneous in the middle-upper section. The uppermost
marine sandstones are mature and very homogeneous. The major field accumulations
are tilted, normal, fault block structures located over basement paleohighs, and are
dependent upon juxtaposition against overlying Qishn carbonates. The carbonate-
dominated pre-Qishn section, including the source rock, is not present on the paleo-
highs, and is thickest in the basement lows.
3
15. This Study
Fig. (4) Regional Stratigraphy, showing our study area
(Beydoun et al., 1998)
4
16. This study
Fig. (5) Regional Frame Work, showing Masila Block Location due to
Say’un al-Masila Basin (Nexen Inc., Data)
5
17. Fig. (6) Regional Setting, showing Masila Block Location due to
Masila High (Nexen Inc., Data)
6
18. Fig. (7) Stratigraphy of Masila, showing Qishn Clastics Member and its
related subdivision (Nexen Inc., Data)
7
19. Fig. (8) Regional cross section between Tawila-1, Tawila-17, Heijah-2,
Camaal-3 and Sunah-3 Wells (Nexen Inc., Data)
8
20. 1. The Upper Qishn Clastics of Cretaceous age are the primary producing reservoirs
in the Masila Block Development area.
2. Cretaceous Qishn Clastics Member, Yemen, was deposited in a rift basin connected
to the Paleo-Indian Ocean - an ideal set-up for tidal amplification and domination.
Recoverable hydrocarbon reserves are 1.1 bbl. Facies associations are consistent with
an estuarine system – sand shoals, tidally influenced point bars, mud flats, etc.
Lower Qishn onlap resulted in deposition of tidal estuarine to bay-facies. A sequence
boundary truncates the Lower Qishn at the base of the S3, a low-accommodation
braidplain deposited close to the shoreline. A flooding surface at the top of the S3
heralds S2 progradational, tide-dominated deltaic deposits. Delta progradation
culminated in clastic dolomitic deposits on the coastal plain. With subsequent
transgression, S1C deposits show rising water table and a nonmarine flooding surface,
overlain by tidal-flat/inlet deposits. Ongoing transgression resulted in wave-
ravinement overlain by shallow shelf clastics and deeper shelf carbonates of the S1B.
The overlying S1A comprises bioturbated, clastic shelf deposits related to a drop in
sea level. Accommodation was relatively high, except for low accommodation
associated with regional sheet sandstone of the S3. Qishn Clastic sediments meet the
criteria of a macrotidal, tide-dominated estuary, yet a more appropriate analog is the
Tigress-Euphrates River and delta flowing into the Arabian Gulf. Is the latter a tidally
influenced delta flowing into a gulf - or a large bayhead delta? Application of existing
terminologies - estuaries, syn-rift clastics, deltaic, strait, Gulf, bay - is confusing to the
practicing explorationist, particularly when attempting to convey a mental image of
the environmental setting of the reservoir.
2.3 UPPER QISHN CLASTICS – STRATIGRAPHY
The Upper Qishn Clastics have been proven productive over the Sunah, Heijah,
Camaal and other productive structures. The interval is defined as the predominantly
sandstone section abruptly overlying the shalier Lower Qishn Clastics and underlying
the sealing Qishn Carbonates. It ranges in thickness from 61 meter in Heijah-1 to 76
m in Sunah-1.
Important Notice: We are highly in need to make a restudy on all Upper Qishn
Clastics samples cored in productive structures. Through standard core analysis and
special core analysis and petrographic analysis, we can give a full more detailed
restudy on the Upper Qishn Clastics reservoir geology and petrophysics.
The Upper Qishn Clastics is subdivided into three lithostratigraphic units, which in
descending order are SI, S2 and S3. Each sequence contains reservoir quality sands
and in my opinion it must be correlated not just in specific structures, but amongst all
above mentioned Upper Qishn Clastics productive structures.
9
21. CHAPTER 3
QISHN FORMATION AND ITS SUBDIVISION
(IN DETALS)
3.1: INTRODUCTION
It is known that Qishn Formation (Lower Cretaceous Age) is synonym to Lower
Cretaceous part of Little, 1925. It is equivalent to Shuaiba Formation (Present in the
Kingdom of Saudi Arabia and the United Arab Emirates). In this study I used 93 wells
penetrated Qishn Formation in different productive and non-productive fields of
Masila Block, where I concentrated my study on the reservoir rocks of Qishn
formation. (See, Table (1))
3.2 QISHN FORMATION IN THE OUTCROP
• In Mahra Province at Ras Sharwayn near Qishn town as the name implies. Thickness 411
m, from base upwards mainly limestone and marl.
• Near Al-Mukalla at Jabal ar Rays. Thickness 32 m, from base upwards mainly sandstone,
marls and limestone.
• In Wadi Masila near Qalana (Thickness 628 m, for the first section 338 m and for the
second section 290 m), from base upwards mainly sandstones, dolomites and lime-
mustone for the first section mainly marls and marly limestone.
• In Masila – Thickness 498 m. Mainly limestone, with several sandstone, marl and shale
zones in the lower part.
• Jabal Ghuba (near Brum) – Thickness 63 m. mainly of sandstones and gypsiferous marls
and siltstone and some conglomeratic layers, is capped by the fossiliferous limestone
carrying orbitolinas.
• Jabal Billum – the Jurassic Qishn contact is marked by sandy dolomitic limestone.
• Al-Mintaq – The base is marked by a thick conglomerate or sandstone with some pebbles
generally locally derived from the under lying Jurassic or basement, this marks the advent
of the Cretaceous Sea.
3.3 QISHN FORMATION IN THE SUBSURFACE (IN DETAILS)
It is known, that Qishn formation in Yemen is subdivided into three members:
1. Qishn Carbonate Member
2. Qishn Clastic Member
3. Sa’af Member
Due to my study to the above mentioned area I gave more attention to the following
subdivision of Qishn Formation:
3.3.1 Qishn Carbonate Member
3.3.2 Qishn Clastic Member
10
22. 3.3.1 Qishn Carbonate Member: (See, Table (1), Figs. (9) and (10))
3.3.1.1 Qishn Carbonate Member - ge: (Barremian to Aptian but in the extreme east
may go down to Late Hauterivian and up to ?Early Albian Age)
3.3.1.2 Qishn Carbonate Member - Lithology in General: Principally carbonates as
the name implies but includes subordinate shales and occasional sands and generally
reflect a nertic environment.
3.3.1.3 Qishn Carbonate Member - Lithological Description: In my study area,
Qishn Carbonate Member ’s lithology is mainly of Lime-Mudstone to Lime-
Wackstone with thin streaks of Shale.
Limestone: Mudstone to Wackstone, occasionally Packstone, white to grayish white,
pale yellow brown, cryptocrystalline to occasionally microcrystalline, moderately
hard to hard, chalky, argillaceous grading to marly Limestone, with pyrite crystals.
Shale: Dark bluish grey, olive grey, reddish brown, firm, fissile, calcareous in places,
with abundant pyrite.
Table (1) Qishn Carbonate of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Qishn Car. Qishn Car. Qishn Car.
Name Thickness Thickness Thickness
(Max. (ft (Min. (ft (Aver. (ft
Sunah 455 (S-11) 144 (S-8 D2) 367.6
NE Sunah 424 (NES-1) 418(NES-2) 421
Heijah 377 (HJ-11) 340 (HJ-6) 356.3
Camaal 402 (C-14) 128 (C-21) 343.1
North Camaal 419 (NC-2) 392 (NC-1) 405.5
Hemiar 422 (HR-1) 407 (HR-2) 413.9
S.Hemiar 546 (S.HR-1) 117 (S.HR-3) 360.3
W.Hemiar 415 (W.HR-3) 117(W.HR-1) 308
Tawila 373 (T-9) 129 (T-11) 285.4
Masila Block (Thickness Max.) 546 (S.HR-1) 418 (NES-2) 421
Masila Block (Thickness Min.) 373 (T-9) 117 (S.HR-3 285.4
& W.HR-1)
Masila Block (Thickness Ave.) 425.7 243.6 361.1
11
23. 1 .1 0
1 .0 0
45
0 .9 0
0 .8 0
40 0 .7 0
0 .6 0
0 .5 0
35 0 .4 0
0 .3 0
0 .2 0
30
0 .1 0
0 .0 0
25 -0 .1 0
20 30 40 50 60 70
Fig. (9) Qishn Carbonate Member, Thickness Map
(Taking in account the whole eastern part of the Republic of Yemen, the western part
of Sultanate of Oman border and the Kingdom of Saudi Arabia border with the
Yemeni sector of Rub al-Khali Basin; Done by: Dr. Mohammed Darsi)
12
24. 1 .1
1 .0
0 .9
0 .8
0 .7
0 .6
0 .5
0 .4
0 .3
0 .2
0 .1
0 .0
-0 .1
Fig. (10) Qishn Carbonate Member, Three Dimension Model
(Taking in account the whole eastern part of the Republic of Yemen, the western part
of Sultanate of Oman border and the Kingdom of Saudi Arabia border with the
Yemeni sector of Rub al-Khali Basin; Done by: Dr. Mohammed Darsi)
13
25. 3.3.1.4 Rate of Penetrations for Qishn Carbonate Member:
Average ROP in Limestone 28 Min/M.
Average ROP in Shale 22 Min/M.
3.3.1.5 Gases in Qishn Carbonate Member:
Background gas levels averaged 0.1 units.
3.3.1.6 Drilling Parameters for Qishn Carbonate Member:
WOB 20-25 klbs
RPM 90-100
SPM 540 gpm
SPP 1500 psi
MW 9.4 PPG
FW 42-43
3.3.1.7 Qishn Carbonate Member - Subdivision: In Masila Block, Qishn Carbonate
Member subdivided into the following units:
3.3.1.7. 1 C1 (See, Table (2))
3.3.1.7.2 C2 (See, Table (3))
3.3.1.7.3 RS (Red Shale) (See, Table (4))
3.3.1.7.4 C3 (See, Table (5))
Table (2): Qishn Carbonate (C1) of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Qishn Carbonate (C1)
Name C1 Max. C1 Min. C1 Ave.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 133 (S-11) 82 (S-3) 93.7
NE Sunah 129 (NES-2) 114 (NES-1) 121.5
Heijah 86 (HJ-2) 62 (HJ-5) 73.7
Camaal 117 (C-14) 91 (C-19) 88
North Camaal 105 (NC-2) 98 (NC-1) 101.5
Hemiar 123 (HR-5) 100 (HR-2) 113.3
S.Hemiar 118 (S.HR-1) 117 (S.HR-2) 78.3
W.Hemiar 111 (W.HR-3) 109 (W.HR- 2) 73.3
Tawila 94 (T-2) 87 (T-8) 65.9
Masila Block (Thickness Max.) 133 (S-11) 117 (S.HR-2) 121.5
Masila Block (Thickness Min.) 86 (HJ-2) 62 (HJ-5) 65.9
Masila Block (Thickness Ave.) 112.9 95.6 89.9
14
27. Table (5) Qishn Carbonate (C3) of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Qishn Carbonate (C3)
Name C3 Max. C3 Min. C3 Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 87 (S-1) 75(S-9) 82.5
NE Sunah 79 (NES-1) 74 (NES-2) 76.5
Heijah 80 (HJ-11) 58 (HJ-12) 71.2
Camaal 80 (C-10) 12 (C-20) 66.7
North Camaal 82 (NC-2) 77 (NC-1) 79.5
Hemiar 71 (HR-1) 65 (HR-5 & 6) 67.9
S.Hemiar 64 (S.HR-2) 61 (S.HR-3) 62.3
W.Hemiar 73 (W.HR-3) 60 (W.HR-1) 64.7
Tawila 90 (T-8) 31 (T-11) 69.5
Masila Block (Thickness Max.) 90 (T-8) 77 (NC-1) 82.5
Masila Block (Thickness Min.) 64 (S.HR-2) 12 (C-20) 62.3
Masila Block (Thickness Ave.) 78.4 57 71.2
3.3.2 Qishn Clastic Member: (See, Figs. (11), (12) and Table (6))
3.3.2.1 Qishn Clastic Member – Age: (Generally Hauterivian – Early Barremian,
especially in the eastern province, to Barremian - Early Aptian in the west (?))
3.3.2.2 Qishn Clastic Member - Lithology in General: Principally clastics as the
name implies, includes coarse clastics in some sections as well as fine sands, silts and
mudstones, shales, as well as marls.
3.3.2.3 Qishn Clastic Member - Lithological Description: In my study area, Qishn
Clastic Member is mainly of Sandstone with Claystone streaks and traces of
Anhydrite. A trace of Coal was logged also.
Sandstone: Quartz, colourless, grayish white, brownish grey, medium grained,
moderately sorted to well sorted in places, subrounded to subangular, poor to
moderate intergranular porosity, with calcareous cement.
Claystone: Light grayish green, reddish brown, soft to firm, blocky, slightly silty,
subfissile in places graded to Shale. Towards the base Claystone was replaced by
Clay, which was highly washable.
Traces Anhydrite: Off white to white, colourless, amorphous, occasionally
crystalline, soft, locally hard, calcareous in places.
Coal: Black, firm to moderately hard, laminated, vitreous luster, earthy and pyretic.
16
28. 2 .0 0
1 .8 0
45
1 .6 0
1 .4 0
40 1 .2 0
1 .0 0
0 .8 0
35
0 .6 0
0 .4 0
30
0 .2 0
0 .0 0
25 -0 .2 0
35 40 45 50 55 60 65 70 75
Fig. (11) Qishn Clastics Member, Thickness Map
(Taking in account the whole eastern part of the Republic of Yemen, the western part
of Sultanate of Oman border and the Kingdom of Saudi Arabia border with the
Yemeni sector of Rub al-Khali Basin; Done by: Dr. Mohammed Darsi)
17
29. 2 .0 0
1 .8 0
1 .6 0
1 .4 0
1 .2 0
1 .0 0
0 .8 0
0 .6 0
0 .4 0
0 .2 0
0 .0 0
-0 .2 0
Fig. (12) Qishn Clastics Member, Three Dimension Model
(Taking in account the whole eastern part of the Republic of Yemen, the western part
of Sultanate of Oman border and the Kingdom of Saudi Arabia border with the
Yemeni sector of Rub al-Khali Basin; Done by: Dr. Mohammed Darsi)
18
Table (6) Qishn Clastics of Masila, Block 14 Thicknesses
30. (Done by: Dr. Mohammed Darsi)
Field Qishn Qishn Qishn
Name Clastics Clastics Clastics
(Max. (ft (Min. (ft (Aver. (ft
Sunah 816 (S-6) 232 (S-8 D2) 713.6
NE Sunah 741 (NES-1) 719 (NES-2) 730
Heijah 598 (HJ-11) 396 (HJ-12) 524.8
Camaal 690 (C-22) 78 (C-14) 593.9
North Camaal 741 (NC-2) 654 (NC-1) 697.5
Hemiar 666 (HR-1) 80 (HR-8) 372.3
S.Hemiar 658 (S.HR-1) 229(S.HR-3) 512
W.Hemiar 627 (W.HR-1) 608 (W.HR-3) 615
Tawila 506 (T-5) 0 (T-15) 427.5
Masila Block (Thickness Max.) 816 (S-6) 719 (NES-2) 730
Masila Block (Thickness Min.) 506 (T-5) 0 (T-15) 372.3
Masila Block (Thickness Ave.) 671.4 332.9 576.3
3.3.2.4 Rate of Penetrations for Qishn Clastic Member:
Average ROP in Sandstone 15 Min/M, with maximum of 7 Min/M.
Average ROP in Claystone 20 Min/M.
Average ROP in Anhydrite 25 Min/M.
3.3.2.5 Gases in Qishn Clastic Member:
Background gas levels slightly increased through some sections ranging from 0.5 to
1.0 API units. A gas peak was recorded at some wells with a maximum of 14.1 unit.
The chromatographic analysis of which broke down in some wells as follows:
C1= 0.77U; C2= 0.11U; C3= 0.98U; C4= 0.2 U
3.3.2.6 Oil Shows in Qishn Clastic Member:
A good oil shows was observed through the sandstones of the Qishn Clastics Member
of the Qishn Formation. Light brown oil stain, bluish white and bright fluorescence,
and straw yellow chloroethane cut of dull to bright intensity.
3.3.2.7 Drilling Parameters for Qishn Clastic Member:
WOB 23 klbs; RPM 93; SPM 698 gpm; SPP 2350 psi
MW 9.3-9,4 PPG; FW 43-48
3.3.2.8 Qishn Clastic Member – Subdivision:
The Qishn Clastic Member is subdivided into two sub members:
3.3.2.8.1 Upper Qishn Clastic Sub Member
3.3.2.8.2 Lower Qishn Clastic Sub Member
19
3.3.2.8.1 Upper Qishn Clastic Sub Member: (See, Table (7))
31. Production is mainly from the Lower Cretaceous of the Upper Qishn Clastic Sub
Member, a sandstone-dominated sequence that reflects deposition during an overall
transgression.
Table (7) Upper Qishn Clastics of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field U. Qishn U. Qishn U. Qishn
Name Clastics Clastics Clastics
(Max. (ft (Min. (ft (Aver. (ft
Sunah 260 (S-6) 221 (S-3) 240
NE Sunah 327 (NES-2) 321 (NES-1) 324
Heijah 216 (HJ-7) 177 (HJ-5) 196.4
Camaal 289 (C-15) 78 (C-14) 244.1
North Camaal 237 (NC-2) 215 (NC-1) 226
Hemiar 266 (HR-1 & 4) 80 (HR-8) 171.5
S.Hemiar 235 (S.HR-1 & 2) 229 (S.HR-3) 233
W.Hemiar 212 (W.HR-3) 208 (W.HR-2) 210.3
Tawila 218 (T-6) 169 (T-12) 178.3
Masila Block (Thickness Max.) 327 (NES-2) 321 (NES-1) 324
Masila Block (Thickness Min.) 212 (W.HR-3) 78 (C-14) 171.5
Masila Block (Thickness Ave.) 251.1 188.7 224.8
Upper Qishn Clastic Sub Member subdivided into three units:
3.3.2.8.1.1 S1
3.3.2.8.1 .2 S2
3.3.2.8.1.3 S3
3.3.2.8.1.1 S1
Important Notice: The base of S1, which it is the top of S2 is marked by the
correlative lowest bed of S1 sequence, a thin basal conglomeratic, muddy, calcareous
sandstones, with abundant shale clasts and shells.
3.3.2.8.1 .2 S2
Important Notice: The base of S2 is marked by the correlative shales of S2-D, which
directly overly the thick sand S3.
3.3.2.8.1.3 S3
Important Notice: S3 abruptly overlies the Lower Qishn Clastics section of shales
and sands.
20
3.3.2.8.1.1 S1
32. The S1 sequence is composed of upper porous quartzose sand and lower, tight,
muddy, calcareous sand. The upper quartzose sand marks the top of the Upper Qishn
Clastics and its oil-bearing sand, which ranges in pay thickness from 2.8 m in
Camaal-2 to 9.1 m in Sunah-2. The S1 sequence is widespread and thicking of the S1
sand occurs off the crest of the structures. (My pervious studies to Camaal fields
prove this fact)
The S1 sand is a fine to medium grained, moderately to well sorted and poorly
cemented quartzose sand interbedded with thin calcite cemented sands. The
Mineralog shows 10% of clay potassium feldspar. Based on the presence of low angle
planner cross-bedding with rippled tops, shell lags at the base of cross-bedded units
and glauconite company researchers suggest deposition in a shallow marine
environment.
S1 is subdivided into three sub-units:
3.3.2.8.1.1.1 S1A: (See, Table (8))
It is marine sandstone, forms at the top of this regional open marine shale, and is
characterized by an overall coarsening-upward sequence. The top of the S1A is
marked by another thin,regional, open marine shale.
Table (8) Upper Qishn Clastics (S1A) of Masila Fields Thiknesses
(Done by: Dr. Mohammed Darsi)
Field Upper Qishn Clastics
Name S1A Max. S1A Min. S1A Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 42 (S-2) 27 (S-3) 33.3
NE Sunah 41 (NES-1) 39 (NES-2) 40
Heijah 30 (HJ-1) 20 (HJ-2 & 11) 23.6
Camaal 39 (C-9) 18 (C-10) 31.7
North Camaal 28 (NC-2) 26 (NC-1) 27
Hemiar 12 (HR-5) 7 (HR-8) 9.6
S.Hemiar 24 (S.HR-2) 19 (S.HR-3) 21.3
W.Hemiar 29 (W.HR-1) 11 (W.HR-3) 22.3
Tawila 18 (T-5 & 10) 10 (T-8 & 9) 12.8
Masila Block (Thickness Max.) 42 (S-2) 39 (NES-2) 40
Masila Block (Thickness Min.) 12 (HR-5) 7 (HR-8) 9.6
Masila Block (Thickness Ave.) 29.2 19.7 24.6
3.3.2.8.1.1.2 S1B: (See, Table (9))
It is marine sandstone. The top of the S1B is marked by a regional, open-marine
-shale.
21
Table (9) Upper Qishn Clastics (S1B) of Masila, Block 14 Thicknesses
33. (Done by: Dr. Mohammed Darsi)
Field Upper Qishn Clastics
Name S1B Max. S1B Min. S1B Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 38(S-1) 21 (S-7) 27.6
NE Sunah 33 (NES-1) 29 (NES-2) 31
Heijah 30 (HJ-5) 23 (HJ-6) 25.6
Camaal 39 (C-8) 20 (C-4) 28.3
North Camaal 28 (NC) 28 (NC) 28
Hemiar 35 (HR-3 & 5) 29 (HR-6) 32.6
S.Hemiar 31 (S.HR-1) 23 (S.HR-2) 27.3
W.Hemiar 22 (W.HR-3) 18 (W.HR-2) 20.3
Tawila 44 (T-14) 27 (T-8) 31.5
Masila Block (Thickness Max.) 44 (T-14) 29 (NES-2) 32.6
Masila Block (Thickness Min.) 22 (W.HR-3) 18 (W.HR-2) 20.3
Masila Block (Thickness Ave.) 33.3 24.2 28
Important Notice: The proximal clastic-dominated followed by carbonate-dominated
(coquinas) shelf deposits of the S1B and finally subtidal sandstone bars of the S1A are
produced as a result of continued transgression.
3.3.2.8.1.1.3 S1C: (See, Table (10))
It is deposit of tidal flats; tidal channels and fine-grained bay fill deposits.
Table (10) Upper Qishn Clastics (S1C) of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Upper Qishn Clastics
Name S1C Max. S1C Min. S1C Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 40 (S-5) 17 (S-6) 29.3
NE Sunah 29 (NES-2) 27 (NES-1) 28
Heijah 27 (HJ-2) 12 (HJ-1) 17.9
Camaal 34 (C-19) 15 (C-4) 23.9
North Camaal 44 (NC-2) 36 (NC-1) 40
Hemiar 13 (HR-2) 10 (HR-3,4 & 7) 11.3
S.Hemiar 8 (S.HR-1 & 3) 7 (S.HR-2) 7.6
W.Hemiar 16 (W.HR-3) 12 (W.HR-2) 14
Tawila
Masila Block (Thickness Max.) 44 (NC-2) 36 (NC-1) 40
Masila Block (Thickness Min.) 8 (S.HR-1 & 3) 7 (S.HR-2) 7.6
Masila Block (Thickness Ave.) 26.4 17 21.5
22
Important Notice: The two sub-units, the tidal S1C and the marine S1B, overlie the S2
sub-unit.
34. 3.3.2.8.1.2 S2:
S2 is a thick muddy paleosols unit that can form a vertical flow barrier, which is
interpreted to be a non-marine expression of a relative rise of sea level. It is a fluvial
to marginal marine, characterized by tidally influenced channels and tidal deposits.
The S2 is normally about 25 m thick, and arranged in an overall fining upward
sequence.
The S2 sequence of interbedded sands and shales is further subdivided into for
sequences, which in descending order are S2A, S2B, S2C and S2D. Each sub-
sequence contains reservoir quality sands over different parts of the study area. In
contrast to S1, the S2 reservoir sands show less continuity, and S2A and S2B show
the lowest continuity.
Lithofacies in S2 include tidal channel reservoir sandstones, crevasse splay reservoir
sandstones and tidal flat non-reservoirs of interbedded silty mudstones and muddy
sandstones.
S2 is subdivided into four sub units:
3.3.2.8.1.2.1 S2A: (See, Table (11))
Table (11) Upper Qishn Clastics (S2A) of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Upper Qishn Clastics
Name S2A Max. S2A Min. S2A Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 89 (S-6) 60 (S-8) 71.5
NE Sunah 84 (NES-2) 74 (NES-1) 79
Heijah 92 (HJ-7) 68 (HJ-12) 80.5
Camaal 43 (C-21) 15 (C-17) 23.7
North Camaal 24 (NC) 24 (NC) 24
Hemiar 161 (HR-4) 27(HR-8) 93.9
S.Hemiar 83 (S.HR-2) 80 (S.HR-3) 81.3
W.Hemiar 84 (W.HR-3) 72 (W.HR-2) 76.7
Tawila 98 (T-5) 64 (T-13) 74.7
Masila Block (Thickness Max.) 161 (HR-4) 80 (S.HR-3) 93.9
Masila Block (Thickness Min.) 24 (NC) 15 (C-17) 23.7
Masila Block (Thickness Ave.) 84.2 53.8 67.3
23
3.3.2.8.1.2.2 S2B: (See, Table (12))
Table (12) Upper Qishn Clastics (S2B) of Masila, Block 14 Thicknesses
36. Field Upper Qishn Clastics
Name S2D Max. S2D Min. S2D Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah
NE Sunah
Heijah
Camaal 10 (C-9) 1 (C-10 & 15) 5.5
North Camaal 5 (NC-2) 4 (NC-1) 4.5
Hemiar
S.Hemiar
W.Hemiar
Tawila
Masila Block (Thickness Max.) 10 (C-9) 4 (NC-1) 5.5
Masila Block (Thickness Min.) 5 (NC-2) 1 (C-10 & 15) 4.5
Masila Block (Thickness Ave.) 7.5 2.5 2.3
3.3.2.8.1.3 S3: (See, Table (15))
The S3 sequence is massive sand section about 15 m thick, marking the base of the
Upper Qishn Clastics section. Lithofacies in S3 are the same as S2, except that the
meandering tidal channel facies is dominant. The sand grains are subrounded, weakly
to moderately consolidated with minor calcareous and silica cement. The Mineralog
shows about 10% clay content and less than 5% potassium-feldspare. Clays are
primarily illite/smecitite with lesser kaolinite.
Table (15) Upper Qishn Clastics (S3) of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Upper Qishn Clastics
Name S3 Max. S3 Min. S3 Ava.
(Thickness (ft (Thickness (ft (Thickness (ft
Sunah 88 (S-8) 67 (S-3) 78.3
NE Sunah 146 (NES) 146 (NES) 146
Heijah 64 (HJ-2) 34 (HJ-5) 48.8
Camaal 89 (C-15) 52 (C-2) 65.8
North Camaal 47 (NC-2) 36 (NC-1) 41.5
Hemiar 56 (HR-1) 32 (HR-2) 24.1
S.Hemiar 68 (S.HR-2) 63 (S.HR-1) 65.3
W.Hemiar 73 (W.HR-3) 53 (W.HR-1) 62.7
Tawila 84 (T-13) 43 (T-12) 59.4
Masila Block (Thickness Max.) 146 (NES) 146 (NES) 146
Masila Block (Thickness Min.) 47 (NC-2) 32 (HR-2) 24.1
Masila Block (Thickness Ave.) 79.4 58.4 65.8
25
3.3.2.8.2 Lower Qishn Clastic Sub Member: (See, Table (16))
The Lower Qishn Clastics are the shales and sands found between the Upper Qishn
Clastics and the Saar Formation. The sands are tidal channel in origin and have
limited areal extent. The sands are fine to medium grained and quartzose.
Table (16) Lower Qishn Clastics of Masila, Block 14 Thicknesses
38. NE Sunah 153 (NES-1) 134 (NES-2) 143.5
Heijah 164 (HJ-1) 136 (HJ-10) 136.7
Camaal 244 (C-1) 130 (C-2) 160.7
North Camaal 225 (NC-2) 197 (NC-1) 211
Hemiar 151 (HR-4) 131 (HR-3) 72.3
S.Hemiar 161 (S.HR-1) 153 (S.HR-2) 104.7
W.Hemiar 177 (W.HR-3) 133 (W.HR-1) 156.7
Tawila 168 (T-12) 117 (T-11) 112.8
Masila Block (Thickness Max.) 287 (S-7) 197 (S-9) 211
Masila Block (Thickness Min.) 151 (HR-4) 117 (T-11) 72.3
Masila Block (Ava. Thickness) 192.2 147.6 144.4
3.3.2.8.2.3 LQ3
3.3.2.8.2.4 LQ4
Important Notice:
It must be known that above mentioned fields majorities occupy separate normal
fault-bounded structures, aligned along a NE-SW oriented structural high trend (called
the Masila High). These faults were formed by late stage reactivation of faults initially
created during Late Jurassic to Early Cretaceous active rifting. On the highs a
relatively thin veneer of Lower Cretaceous sandstones and carbonates rest
unconformably upon granitic or metamorphic basement. In the adjacent paleo-lows, a
significantly thicker stratigraphic section exists in which carbonates predominate.
(See, Table (19), Figs. (13) and (14)) as a conclusions.
Table (19) Qishn Formation of Masila, Block 14 Thicknesses
(Done by: Dr. Mohammed Darsi)
Field Qishn Qishn Qishn 1 .8 0
Name Formation Formation Formation
(Max. (ft (Min. (ft (Aver. (ft 1 .7 0
Sunah
40 1227 (S-6) 376 (S-8 D2) 1081.2 1 .6 0
NE Sunah 1165 (NES-1) 1137(NES-2) 1151
Heijah 975 (HJ-11) 750 (HJ-12) 881.1
1 .5 0
Camaal 1071 (C-1) 480 (C-14) 937 1 .4 0
North Camaal 1160 (NC-2) 1046 (NC-1) 1103
Hemiar 1088 (HR- 1) 494 (HR-8) 786.1
1 .3 0
S.Hemiar 1204 (S.HR-1) 346 (S.HR-3) 872.3 1 .2 0
W.Hemiar 1023 (W.HR-3) 744 (W.HR-1) 923
30
Tawila 871 (T-12) 0 (T-15) 712.9
1 .1 0
Masila Block (Thickness Max.) 1227 (S-6) 1137 1151 1 .0 0
Masila Block (Thickness Min.) 871 (T-12) 0 (T-15) 712.9
Masila Block (Thickness Ave.) 1087.1 597 938.6
0 .9 0
27 0 .8 0
0 .7 0
20 0 .6 0
0 .5 0
0 .4 0
0 .3 0
0 .2 0
10 0 .1 0
0 .0 0
-0 . 1 0
20 30 40 50 60 70
39. Fig. (13) Qishn Formation, Thickness Map
(Taking in account the whole eastern part of the Republic of Yemen, the western part
of Sultanate of Oman border and the Kingdom of Saudi Arabia border with the
Yemeni sector of Rub al-Khali Basin; Done by: Dr. Mohammed Darsi)
1 .8 0
1 .7 0
1 .6 0
1 .5 0
1 .4 0
1 .3 0
1 .2 0
1 .1 0
28
1 .0 0
0 .9 0
0 .8 0
0 .7 0
0 .6 0
0 .5 0
0 .4 0
0 .3 0
0 .2 0
0 .1 0
0 .0 0
-0 .1 0
40. Fig. (14) Qishn Formation, Three Dimension Model
(Taking in account the whole eastern part of the Republic of Yemen, the western part
of Sultanate of Oman border and the Kingdom of Saudi Arabia border with the
Yemeni sector of Rub al-Khali Basin; Done by: Dr. Mohammed Darsi)
29
CHAPTER 4
QISHN FORMATION PETROLEUM SYSTEM
4.1 INTRODUCTION
The petroleum system of the Masila Block (14) is related to an Upper Jurassic source
rock sequence essentially deposited as deep marine deposits in a synrift setting (in
41. some areas prerift sag). Qishn Clastic Member as a primary reservoir and the main
subject of our study to the reservoir rocks of Qishn Formation, is a postrift reservoir.
In detail, the petroleum system of our studied area is related to the presence of the
following factors:
4.2 SOURCE ROCKS
The Upper Jurassic (Kimmeridgian) source rock of the Madbi Formation is organic-
rich black shales deposited in the deeper portions of rifts in the Late Jurassic. Madbi
Formation is the main potential source rocks for the reservoir rocks of Qishn
Formation.
4.3 MATURATION
Source rocks began generating in the central rift basin in latest Cretaceous to
earliest Paleogene time and the process were largely completed by the end of
Paleogene time. Degree of maturation: (Oil Window) 0.6. Type of kerogen: 1 and 2
type of organic mater types.
4.4 MIGRATION
In the Masila Basin, oil and gas migrated along faults to horst blocks. Numerous horst
uplifts occur; however migration resulted in hydrocarbon accumulations, where sealed
by Early Cretaceous carbonate (Qishn Carbonate Member). Heavy oil is known to
occur marginal to the accumulation sites.
4.5 RESERVOIR ROCKS
In the Masila Basin, the Early Cretaceous estuarine sandstones of the Qishn
Formation (Berremian/Aptian), mainly the Upper and Lower Qishn Clastics Members
are the primary reservoir. Porosity average: 18 % – 21 %. Permeability average: 140 –
2000 mD
4.6 TRAPS AND SEALS
The Qishn Carbonate Member (Aptian) provides the seal for the underlying Qishn
Clastic Member in the Masila Basin.
30
CHAPTER 5
DISSCUSION POINTS, RECOMMENDATIONS AND
CONCLUSIONS
5.1 DISSCUSION POINTS
42. 1. Masila Block’s Fields are located within the Sirr-Sayun Rift Basin that formed
during the Upper Jurassic when the Africa-Arabian Plate separated from the India-
Madagascar Plate. The Sirr-Sayun Basin is a few hundred kilometres wide and
several hundred kilometres long, and is oriented northwest southeast. The basin is
bounded on the west by Jahi - Mukalla High, to the south by the South Hadramaut
Arch, to the east by the Ras Fartak High and partially interrupted to the northwest
by the Sayun High. The Masila Block is situated on an intragraben terrace, and is
ideally located to access migrating hydrocarbons from mature deeper buried
Jurassic Madbi source rocks.
2. I found that one of the most famous, more complex and interesting topic
problems, which faces any researcher who would like to make any kind of
academic works. Such as any kind of geological studies on Masila Block 14
reservoir rocks of Qishn formation or any other geological research studies on the
whole area, is that:
a. We have a huge material in the Database Center of the Petroleum
Exploration and Production Authority (P.E.P.A) and its offices around the
country.
b. We till now don’t have any full-blooded Geo-Scientific Research
Centers and the suitable laboratories, where we can make new restudies on
all data and materials located now in our Databases Centers.
What we can do now? … In my opinion the first step we should take it, as a right
step in the right direction, is that P.E.P.A. ’s Database Center must be open for all
Yemeni nationality scientific researchers 24 hour per day. Because this step will
encourage young Yemeni scientists and researchers to make a lot of studies used the
above mentioned materials. I am sure, GOD and then History will keep the names of
those Yemeni peoples, who work as decision-makers and give their time and life for
their country and its young generation.
Important Notice:
I would like to drew the reader of this study attention on the following most important
mater, that one of the most important problem which make it so difficult to write on
the Yemeni Geology as a whole or partly is that the whole Yemen was divided to
blocks. In my opinion dividing Yemen, as a whole to blocks is the real reason, which
lead to the development of company-centered informal stratigraphic nomenclature
schemes. Companies’ main principal objective was to facilitate operations within the
individual company’s concession area rather than facilitating scientific research and
any ultimate communication in journals. So to solve this question, we must
scientifically divide just the sedimentary basins in Yemen to blocks in accordance to
their categorisation. (No, for dividing Yemen as a whole to blocks. I said it in the
past, say it now and will say it).
31
5.2 RECOMMENDATIONS
1. In the absence of the more detailed and accurate studies on the reservoir rocks of
Qishn Formation, I suggest the following known steps as an emergency solution to
our case of study:
43. a. Modelling of the Qishn Formation as whole and
specially the Qishn Clastic Member and its related
subdivision in detail. This must included:
• The gross thickness
• Facies proportions and distribution (vertically and laterally)
• Porosity modelling (vertically and laterally for each facies)
• Permeability (vertically and laterally for each facies).
b. To model each of above-mentioned parameters, modelling steps must
included the following:
• Declustering the well data
• Examine data and clean up if necessary
• Identify and mathematically describe trends that exist
• Remove trends from the data
• Perform variogram analysis and determine variogram model
• Simulate the parameter in 3-D space
• Re-introduce the trends that were removed earlier
c. The geostatistical surfaces resieved as results of our pervious steps must be
compared to maps generated by conventional geologic mapping methods in
order to highlight the differences between the two techniques.
2. We are highly in need to make a restudy on all Upper Qishn Clastics samples cored
in productive structures. Through standard core analysis and special core analysis and
petrographic analysis, we can give a full more detailed restudy on the Upper Qishn
Clastics reservoir geology and petrophysics.
3. NOW, It is recommended that a very highly qualified team must lead local and
regional studies on the Yemeni Sedimentary Basin by keeping contacts with all
International Geoscientific Centers in and out side Yemen.
Important Notice:
We in the Republic of Yemen must give a high attention to the Environmental Geo-
sciences. It is known that the global warming issue poses a number of potential
challenges and opportunities for the oil industry. Ongoing negotiations are defining
not only targets for greenhouse gas reduction but also mechanisms to enable countries
and companies to respond. A broad range of options exists to reduce or sequester
emissions. So it is recommended to discuss some of the important technical,
economic, and political questions that surround the ultimate viability of this option.
32
5.3 CONCLUSIONS
1. One of the main conclusions of this study is that Qishn Formation as a whole and
also its subdivision mostly thin to the south and to the east. This important
44. conclusion, I received it as a result of my geostatistical and mathematical analysis
study on every Qishn Formation ’s subdivision in detail.
2. As a result of this study, it is easy now to understand the great importance of
studying:
a. The Masila Block (14) as a part of Say’un Al-
Masila basin.
b. The pervious and present geological activities of
the whole eastern part of the Republic of
Yemen.
c. The Qishn formation in the outcrop, the
reservoir rocks of Qishn formation in the
subsurface and the upper Qishn stratigraphy.
d. The Qishn formation sequence stratigraphy.
e. The Qishn formation (Masila, Block 14)
petroleum system.
3. If we really want to be Excellent and long vision decision makers, we must
identify the best mechanism or trend, that could be used to study the reservoir
rocks of Qishn Formation and by the way to predict the better-developed methods.
4. In my opinion, the best mechanism or trend is that we must use the latest multi
functional geological soft ware application which can gave the more accurate
scientific solutions to our geological problems saving time and money.
5. We in the Petroleum Exploration and Production Authority, as a main part of the
Ministry of Oil and Mineral Resources, must build a strong long vision strategy on
studying the oil exploration and production future prospect. Because the first
lesson I learned from this study, is that we must take in account our great Yemeni
grandchildren interests, by making long-term studies on our sedimentary basins.
6. I believe in that Yemeni Geology, which took some care in the past and attracts
many experts in the present time, is not going just to surprise all with its oil and
gas discoveries, but also with its rich and useful data in the near future.
Important Notice:
Here, I would like to inform interested readers of this study, that I planned to continue
this work by publishing a paper on my mathematical description to the reservoir rocks
of Qishn Formations and its subdivision, based on its geostatistical data.
33
ACKNOWLEDGEMENTS
45. In this respect, I would like to extend my thanks to the Petroleum Exploration and
Production Authority – (San’a), for their great trust on asking me to work on this
study, especially Mr. Nabeel Al-Kaosi, Dr. Ahmed Ali Abdellah and Dr. Mohammed
Ahmed Al-Zubairi (P.E.P.A – San’a). Mr. Abdullah Salem Ta’lab and Mr. Nagib
Saeed Tabet (P.E.P.A – ADEN). Mr. Tawfik Ahmed Ismail and Mr. Mohammed
Mahyoub (P.E.P.A ’s Office in CPF – Masila Block 14).
I would like to express my deep gratitude and sincere thanks to Mr. Victor W. Dudus
(The Operation Geologist), Mr. L. A. Len Flexhaug (The Petrophysicist) and Al Jones
(The Construction Superintendent) Canadian Nexen (CPF, Masila Block 14), for their
help and support on fulfilling this study.
I have to thank Miss. Wafa and Miss. Fatimah Salem Khamis, for help and support.
Special thanks go to that kind of people, who work hard and in silence on building a
bright future for our lovely Yemen, from both sides, the Yemeni Ministry of Oil &
Mineral Resources (The Petroleum Exploration and Production Authority) side,
the Nexen Inc. (Canadian Nexen Petroleum Yemen) side.
Someone said that "many people will walk in & out of your life, but only true friends
will leave footprints in your heart." I'm so glad that all above mentioned people lift
theirs in mine. Hope it is the right step in the right direction!
34
REFERENCES
46. 1. Beydoun, Z.R., Bamahmoud, M.O., and Nani, A.S.O., 1993. The Qishn Formation,
Yemen: lithofacies and hydrocarbon habitat. Marine and Petroleum Geology, 10 (4):
364-372.
2. Beydoun, Z.R., and others, 1998, International lexicon of stratigraphy, v. III,
Republic of Yemen, (2nd ed.): International Union of Geological Sciences and
Ministry of Oil and Mineral Resources, Republic of Yemen Publication no. 34, 245 p.
3. Bosence, D.W.J., ed., 1997, Special issue on Mesozoic rift basins of Yemen:
Marine and Petroleum Geology, v. 14, no. 6, p. 611-730.
4. Brannin, Joe, and others, 1999, Geological evolution of the central Marib-Shabwa
basin, Yemen: GeoArabia, v. 4, no. 1, p. 9-34.
5. Nedham, M. Darsi, 2000. The Geological Research History Work in the Republic
of Yemen during the period from 1852 until Today (Three papers). Yemen Times
newspaper. Issue 2-January 10th through January 16 2000, Vol. IX, Culture Page,
Issue 10 - March 6 through March 12 2000, Vol. X, Culture Page and Issue 15 - April
10 through April 16 2000, Vol. X, Culture Page.
6. Productivity Prediction from Well Logs in Variable Grain Size Reservoirs
Cretaceous Qishn Formation, Republic of Yemen, Michael L. Cheng and Marco A.
Leal: Canadian Petroleum Ltd., Calgary, Canada David McNaughton: Mincom Inc.,
Houston, Texas U.S.A.
7. Putnam, P.E., 1997, Upper Qishn (Lower Cretaceous) reservoirs at Masila, Yemen,
CSPG-SEPM Joint Convention Core Conference, J. Wood and B. Martindale
(compilers), p. 429-448.
8. Putnam, P.E., Kendall, G.A., and Winter, D. A. 1997, Estuarine deposits of the
upper Qishn Formation (Lower Cretaceous) in the Masila region of Yemen, American
Association of Petroleum Geologists Bulletin, v.81, p. 1306-1329.
9. The Masila Fields, Republic of Yemen, W.A. King1, B.R. Mills1, Scott Gardiner2,
and A.A. Abdellah3. (1) Nexen Inc. (Formerly Canadian Occidental Petroleum Ltd.),
Calgary, AB T2P 3Z1, Canada, (2) Nexen Inc. (formerly Canadian Occidental
Petroleum Ltd.), 1801 - 635 8th Avenue S.W, Calgary, AB T2P 3Z1, Canada, (3)
Petroleum Exploration and Production Authority (PEPA), Yemen Ministry of Oil and
Mineral Resources (MOMR), Yemen
10. Tide-Dominated Sedimentation in an Arid Rift Basin - Cretaceous Qishn Clastics,
Masila Block, Republic of Yemen, Dale A Leckie and Tom Rumpel. Nexen Inc,
Calgary, AB T2P 3P7, Canada, and phone: 403699-5902, Dale_leckie@nexeninc.com
11. Local, Regional, International and Global ’s World Web Site Internet Resources
35
ABOUT THE AUTHOR
47. * Dr. Eng. Mohammed Darsi Abdulrahman Nedham, born on November 17, 1963,
Crater (Aden). 5 Languages (Arabic, English, Russian, Chinese and German
Languages). Petroleum Engineer, Geologist; Married have 2 sons. Education:
Graduated from the Earth Science College of Jilin University as a Doctor of Science
in Mineralogy, Petrology and Ore Deposit on May 29 2002 and also graduated from
the Russian among People Friendship University in 1991 as a Petroleum Engineer,
Geologist (M.S. degree) on June 29 1991. Appointments: Petroleum Exploration and
Production Board, Aden Branch, Ministry of Oil and Mineral Resources; Petroleum
Engineer; Senior Geologist; Representative; Coordinator. Publications: 10 scientific
papers, 6 published in the Yemen Times Newspaper, 3 in China (2 in World Geology
and 1 in the Journal of Geoscientific Research of Northeast Asia) and the last one in
Russia. Two registered Patents. 18 Certificate from different institutes, centers,
organizations and clubs. Membership: Fellow, Geological Association of Canada,
American Association of Petroleum Engineers and other memberships. Dr. Eng.
Mohammed Darsi Abdulrahman Nedham began his professional career by working as
petroleum engineer, geologist in the Petroleum Exploration and Production Board
(Aden Branch). His scientific interest is concentrated on the Geological Research
History Work, Earth science software application and basin-modeling problems. The
most important thing, Dr. Darsi is ONE of the Who is Who in the 21st Century for
2001 and 2002 (First and Second Publication), choosed by the International
Geographical Centre, Cambridge, England.
36