Petroleum Geology of the South Caspian Basin

The South Caspian Basin, which comprises the SouthCaspian Sea, Eastern Azerbaijan, and Western Turkmenistan, with ahigh density of confirmed structures, was studied in greatest detail.Hy

Petroleum Geology

of the South Caspian Basin

Petroleum Geology

of the South Caspian Basin

Leonid A Buryakovsky George V Chilingar Fred Aminzadeh

Boston Oxford Johannesburg Melbourne New Delhi Singapore

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demon-Special Acknowledgment

We especially wish to acknowledge the outstanding help

of academician John O Robertson Jr., Ph.D., in tion of the illustrations The help extended by Michael V.Garfunkel, Essam Al-Ajeel, and Khaled Ben-Ameirah is alsogreatly appreciated

prepara-CHAPTER 1

CH

Contribution No 10, Rudolf W Gunnerman

Energy and Environment Laboratory,

University of Southern California, Los Angeles, California

Geology of Azerbaijan and the

South Caspian Basin 111

General Overview, 1 Geologic Setting of Super-Deep

Deposits, 5 Saatly Super Deep Well, SD-1, 9

Onshore Oil and Gas Fields 132

Region I: Apsheron Peninsula, 32 Region II:

Pre-Caspian–Kuba Monocline, 43 Region III: Lower

Kura Lowland, 44 Region IV: Yevlakh-Agdzhabedi Area, 44

CHAPTER 6

Offshore Oil and Gas Fields 52

Caspian Sea Overview, 52 Zone I: Western Portion

of Apsheron–Pre-Balkhan Anticlinal Trend, 57 Zone II:

South Apsheron Offshore Area, 91 Zone III: Baku

Archipelago, 101

CHAPTER 7

General Regularities in Oil and

Gas Distribution 113

I Azerbaijan Portion of the South Caspian Basin, 113

II Turkmenistan Portion of the South Caspian Basin, 199.III Regions Adjacent to the South Caspian Basin, 212

CHAPTER 8

Conclusions (Chapters 1–7) 239

CHAPTER 9

Mathematical Models in Petroleum Geology 243

Introduction, 243 Mathematical Simulation of Geologic

Systems, 244

CHAPTER 10

Mathematical Models in Oil and Gas Exploration and Production (Static Geologic Systems) 248

Mapping of Structures within the Apsheron–Pre-Balkhan

Anticline Trend, 248 Reservoir Characterization Using

viii

on Well-Logging Data, 284 Entropy as Criterion of

Heterogeneity of Rocks, 290 Anisotropy of Stratified Rocks,

297 Permeability of Reservoir Rocks, 302 Surface Activity ofRocks, 313 Models of Oil Composition and Properties, 324

CHAPTER 11

Mathematical Modeling of Geological Processes

(Dynamic Geological Systems) 347

Methodology of Simulation of Dynamic Systems, 347

Mathematical Simulation of Sediment Compaction, 355

Numerical Simulation of Oil- and Gas-Bearing Rock

Properties, 365

CHAPTER 12

Other Applications of Numerical Simulation

Methodology 384

Basic Principles and Calculation Techniques, 384

Simulation of Reservoir-Rock Properties, 386 Simulation

of Petrophysical Properties of Rocks, 390 Simulation of

Water Invasion into Oil-Saturated Rocks, 398 Simulation

of Pore-Fluid (Formation) Pressure, 400 Simulation of

Hydrocarbon Resources and Evaluation of Oil and Gas

If the end of cold war is the biggest news of the century in terms ofworld politics, the unleashing of the wealth in terms of untapped oil andgas reservoirs in the Caspian Sea region is probably the biggest economicnews of the same century Addressing the petroleum geology of SouthCaspian Basin at this crucial time of energy awareness shows unparalleledwisdom, experience, and maturity of the authors The timing for such auseful book on a region that is considered to be the next Persian Gulfcould not be more appropriate

The news of petroleum discoveries in the Caspian Sea region continue

to pour in Only a few months ago, the news broke about the possibility

of discovering 50 billion barrel in the Kashagan offshore structure If this

is true, as all indications are, this latest discovery will put Kashaganstructure second to only Saudi Arabia’s onshore Ghawar field, withremaining reserve of 70 billion barrels Incidentally, Saudi offshore,Safaniya, the world’s currently known largest offshore deposit contains

19 billion barrels The book provides one with a treasure of information

on the most studied section of the Caspian Sea region The book is writtenwith a comprehensive approach that includes the development of scientificbases, simulation techniques, and mathematical models of both static anddynamic geological systems This approach is necessary if one is interested

in exploration, development, and production of a petroleum reservoir Thecombination of science and engineering has been sought for a long time,and the book provides one with a fine example of how one shouldapproach in developing oil and gas fields in the 21st century

As the world order is moving from the Modern to the Knowledge Era,the petroleum industry is creating a culture that requires combining cuttingedge science with engineering into the core of decision making structure.This, in petroleum vocabulary, means that the petroleum industry mustcombine geological and geophysical skills with petroleum productionengineering This book collects this information from the anal of 150 years

x

presents them in a format that is useful for both scientists and engineers.The book is helpful for determining oil and gas potential as well asoptimum production strategies in the region.

The book takes the reader through some of the most fundamentaldescription of geological history in the region, and embarks into theapplication of advanced mathematical models and engineering techniques.The authors do this with impeccable dexterity and provides the reader with

a powerful interdisciplinary tool for exploration, reserve evaluation, andproduction optimization The authors take a bold approach to educatingengineers on some of the essential aspects of geology and geophysics I

am not aware of another book that amalgamates geology, geophysics, andpetroleum engineering with such a seamless approach I recommend thisbook to every geologist, geophysicists, practicing engineer, graduatestudent, and academic who is engaged in petroleum studies

Rafiq Islam Killam Chair in Oil and Gas Dalhousie University

Canada

xi

788 m/2,584 ft and in the southern part, up to 1,025 m/3,361 ft.The Caspian Sea has no outlet, and although the surface level fluc-tuates, it averages about 25 m/82 ft below ocean level according torecent measurements.

Geological studies in the Caspian Sea began in the second half ofthe 19th century The South Caspian Basin, which comprises the SouthCaspian Sea, Eastern Azerbaijan, and Western Turkmenistan, with ahigh density of confirmed structures, was studied in greatest detail.Hydrocarbon accumulations have been discovered, explored and produced

in areas with water depth up to 60 m/200 ft, and several oil and gasfields have been discovered in water depth up to 200 m/655 ft.Azerbaijan is one of the independent countries in western Asia,bounded on the south by Iran (Province of Iranian Azerbaijan), on thenorth by Russia, on the west by Georgia and Armenia, and on the east

by the Caspian Sea The country consists mainly of lowlands rounded by the Kura River and its tributary, the Araks, which formsthe border with Iranian Azerbaijan The landscape ranges from semi-desert to mountains of the Greater and Lesser Caucasus Azerbaijancovers an area of about 86,600 km2 or 33,400 mi2

sur-Azerbaijan is one of the oldest oil- and gas-producing provinces inthe world For example, the oldest oil-field, the Kirmaku, has beenknown from ancient times as a place of primitive production of oil

xii

1834 The first deep oil well in Azerbaijan was drilled in the Bibieibatoilfield in 1848.

Recoverable reserves of this unique oil- and gas-bearing provinceinclude about 1,700 MMtons/12 Bbbl of oil and 1 Tm3/35 Tft3 ofnatural gas The main oil- and gas-bearing section in Azerbaijan is theso-called clastic Productive Series of Middle Pliocene age It includesabout 90% of all the identified hydrocarbon reserves of Azerbaijan andadjacent offshore area of the South Caspian Basin During the last 20years, a new type of reservoir rocks has been discovered in theterritory of central and western Azerbaijan, mainly in the centralportion of the Kura Depression Commercial oil and gas reserves arepresent in the fractured Upper Cretaceous volcanic rocks

Extensive offshore development in Azerbaijan began in 1949 Sincethen, numerous oil and natural gas fields have produced about halftheir recoverable reserves All fields are multi-bedded with as many

as 30 producing zones in the Middle Pliocene sandstones and stones Exploratory and production drilling is carried out from indi-vidual platforms and piers Also, floating and semi-submersible drillingrigs are used for exploration At present, exploration drilling in theCaspian Sea is carried out in water depth of 200 m/655 ft; the deepestwell was drilled to a depth of 6,500 m/21,311 ft Azerbaijan’s ApsheronPeninsula and adjacent offshore area is now being developed undermulti-billion dollar contract with Western oil companies

silt-Turkmenistan is located in Central Asia and is the southernmost ofthe CIS countries The Turkmenistan Republic is bordered by theCaspian Sea to the west, Iran and Afghanistan to the south, Kazakhstan

to the north, and Uzbekistan to the northeast and east Its territoryextends 1,100 km east-west and 650 km north-south and covers anarea of approximately 488,000 km2 or 188,200 mi2 The climate ofthe country is dry and 80% of its territory is desert Water resourcesare distributed by canal and irrigation systems The petroliferous areasinclude the eastern portion of South Caspian Basin and the Amu-Daryaoil- and gas-bearing provinces

The presence of seeps and mud volcanoes first attracted attention

to the eastern part of South Caspian Basin at an early date Oil wasbeing produced from 3500 hand-dug wells and seeps on ChelekenIsland by 1938 About 28 fields have been discovered to date inwestern Turkmenistan (onshore and offshore) More than 48 fields have

xiii

Amu-Darya area in 1929.

After Russia, Turkmenistan is the second largest gas-producingrepublic In 1990, the gas production was 3,100 Bft3 Oil productiondecreased 30% after 1980, but was stable (50 Mbbl/yr) during the lastfive years of 1980s

In Western Turkmenistan, the most promising area is probably theshallow offshore With water depths of 50 m/164 ft or less, explorationand production techniques developed in the Gulf Coast area of U.S.could be applied here, i.e., using drilling barges and dredges in veryshallow water and jack-up rigs in deeper water

Progress in the oil- and gas-producing industry is related closely tothe improvement in exploration techniques and increase in discoveryrates Exploration and production of hydrocarbon resources must bebased on reliable scientific information During more than 150 years

of oil and natural gas exploration and production in Azerbaijan, a greatamount of geological, geophysical, petrophysical, geochemical, andengineering information has been gathered This information will aid

in estimating oil and gas reserves as well as improving field ment technology We used advanced mathematical methods to processthe geological, geophysical, and engineering data, and our investigationincluded development of simulation techniques and construction ofmathematical models of both static and dynamic geologic systems(geologic processes)

develop-Leonid A Buryakovsky George V Chilingar Fred Aminzadeh

xiv

A da diffusion-adsorption factor

A t absolute geological age

B “benzine” (gasoline) content

C carb carbonate cement content

C cl clay cement content

C sh shale cement content

d w wellbore diameter

dact actual wellbore diameter

dnom nominal wellbore diameter

d ch pore-channel diameter

d p,ave average pore diameter

d p,Me median pore diameter

F formation resistivity factor

F p,t formation resistivity factor at reservoir conditions

∆Iγ relative GR factor

∆I nγ relative NGR factor

xv

Ka pressure-abnormality factor

k permeability

k|| permeability parallel to bedding

k⊥ permeability perpendicular to bedding

N number of measurements, tests or observations

n number of objects in the data matrix

n saturation exponent

p i probability

p pressure

p e external pressure, total overburden pressure

p i internal pressure, pore-fluid pressure

p eff effective (grain-to-grain) pressure

qliq liquid production rate

qoil oil production rate

R resins plus asphaltenes content

R d rate of sedimentation

R electric resistivity

R a apparent resistivity

R a(AO) apparent resistivity from lateral sonde of AO size

R cr oil-saturated reservoir rock cut-off (critical) resistivity

R g,r gas-saturated reservoir rock resistivity

R oil oil resistivity

R o,r oil-saturated reservoir rock resistivity

R sh shale resistivity

R t true resistivity

R t,min minimum true resistivity

xvi

Ro water-saturated reservoir rock resistivity

S o/g oil/gas saturation

S o,r residual oil saturation

S w water saturation

S w,r residual water saturation

S carb homogeneity of carbonates

S sort sorting factor

S sh sorting of shales

S ss sorting of sandstones

s b specific surface area of pore space per unit of bulk volume

s g specific surface area of pore space per unit of grain volume

s p specific surface area of pore space per unit of pore volume

s hf shape factor for pores

T temperature

∆t interval transit time

tα probability index @ α confidence level

U relative change in volume of sediments

∆USP relative SP factor

ηr formation-pressure gradient in reservoir rocks

λ anisotropy coefficient

µ dynamic viscosity

ν kinematic viscosity

σ stress

σ standard deviation, or mean square error

σR standard deviation of resistivity

σr standard deviation of correlation coefficient

τ electrical tortuosity of pore channels

τw thickness of pore-water film

Σω cumulative frequency or probability

Σ macroscopic cross-section of thermal neutron capture (absorption)

xviii

AHFP abnormally high formation pressure

Bbbl billion barrels of oil

Bcfg billion cubic feet of gas

bpd barrels per day

bopd barrels of oil per day

cfd cubic feet per day

cmd cubic meters per day

FSU Former Soviet Union

GKZ State Committee on Reserves (in FSU)GOC gas-oil contact

GOR gas/oil ratio

GWC gas-water contact

HC hydrocarbons

Mbpd thousand barrels per day

Mcfd thousand cubic feet per day

Mcmd thousand cubic meters per day

MD measured depth

MMcfd million cubic feet per day

MMcmd million cubic meters per day

MMt million tons

MSE mean square error

Mtd thousand tons per day

OWC oil-water contact

PTD proposed total depth

SEM scanning electron microscope

Tcf trillion cubic feet

Tcfg trillion cubic feet of gas

tpd tons per day

TD total depth

TOC total organic carbon

TVD true vertical depth

xix

Structures of Azerbaijan Part of the South Caspian Basin

After declaring independence in 1991, many structures, oil and gasfields, and prospects in Azerbaijan were renamed For reference, a list

of old and new names of most oil and gas fields and prospects located

in the Azerbaijan part of the South Caspian Basin is provided below

In this book, only new names are used

26th Baku Commissars Azeri

28th of April Gyuneshli

40th Anniversary of Azerbaijan Ashrafi

Andreyev Bank Umid

Andriyevski Bank Gilavar

East Andriyevski Bank Khazri

Artyom Island Pirallaghi Adasi

Bulla Island Khara Zyrya

Bulla-moré Bulla Deniz

Byandovan-moré Byandovan Deniz

Darvin Bank Darvin Bank

Duvanny Island Zenbil

xx

East Apsheron Shargi Absheron

Golovachev Bank Atashkyakh

Gryazevaya Sopka Palchygh Pilpilasi

Gyurgyany-moré Gyurgyan DenizKalmychkov Bank Shirvan DenizKamen’ Ignatiya Dashli

Kamen’ Persiyanina Aran Deniz

Kamni Dva Brata Goshadash

Kamni Grigorenko Khali

Karadag-moré Karadag DenizKaragedov Bank Mugan Deniz

Kurinskiy Kamen’—2 Araz Deniz

Kyurdakhany-moré Kyurdakhany DenizKyzylburun-moré Kyzylburun DenizLenkoran’-moré Lenkoran Deniz

Mekhdi Gusein-zadeh Ufug

Nakhichevanskiy NakhchevaniNardaran-moré Nardaran DenizNeftechala-moré Neftechala DenizNeftyanyye Kamni Neft DashlaryNeftyanyye Kamni—2 Oguz

North Apsheron Shimali AbsheronPeschany Island Gum Adasi

Peschany-moré Gum Deniz

Pogorelaya Plita Yanan Tava

Promezhutochnaya Kyapaz

xxi

Samed Vurgun Vurgun

Sangachaly-Duvanny-Bulla Sangachal-Duvanny Deniz-Khara

South Kurinskaya Talysh Deniz

South Shirvanskaya Lerik Deniz

Sovetabad-moré Shorabad Deniz

Tsyurupa Bank Agburun Deniz

Tyurkyany-moré Tyurkyan Deniz

Uzeir Gadzhibayev Peik

West Apsheron Garbi Absheron

Yalama Khudat Shollar Deniz

Yashma-moré Yashma Deniz

Zhiloi Island Chalov Adasi

Zorat-moré Dzhorat Deniz

xxii

Geology of Azerbaijan and the South Caspian Basin

GENERAL OVERVIEW

The territory of Azerbaijan (Figure 1-1) is part of the Alpine foldbelt and consists of folded systems, embracing the eastern parts ofthe Greater and Lesser Caucasus Mountains, the Kura IntermontaneDepression (Kura Lowland) separating them, and also the Middle andSouth Caspian basins (Figure 1-2) Thickness of the Earth’s crust hereranges from 38 to 55 km The greater thickness occurs within theGreater Caucasus, the lesser in the Talysh foothills In the submontanebelt of the Lesser Caucasus crustal thickness reaches 40 to 45 km, and

50 km in the Kura Intermontane Depression

Peculiarities of the folded system of the Greater Caucasus include

a flysch-filled trough at the southern slope of the Greater Caucasuswith an extensive development of overlying structures Where isolated,Early Jurassic, shaly copper-pyrite deposits occur Within the Kura Inter-montane Depression, Mesozoic-Early Paleogene and Late Paleogene-Quaternary structures are clearly distinguished The first stage ofMesozoic volcanogenic-sedimentary rocks forms a single unit withinthe folded system of the Lesser Caucasus in the south and the Vandamzone in the north Within the depression, a thick sequence of LatePaleogene-Quaternary deposits is widespread, unconformably overlyingthe lower structures The Lesser Caucasus was a zone of volcanismduring the Mesozoic, Paleogene, Miocene-Pliocene and Quaternary,and is characterized, in the central part, by an extensive ophioliticbelt—the eastern portion of the North Anatolia Belt

Jurassic and Cretaceous deposits are widespread in Azerbaijan.Lower Jurassic deposits (thickness of 2,000 m and more) are widelydistributed in the Greater Caucasus and are represented by slate andsometimes by sandstone, with intrusive sheets of diabase and gabbro-diabase In its analogous terrigenous facies, the Lower Jurassic is moresparsely represented in the Lesser Caucasus and the Nakhichevanregion Apparently, within the Kura Depression, the Lower Jurassicdeposits occur as equivalent, thin terrigenous facies.

The lowermost Middle Jurassic strata of the Greater Caucasus arecomposed of argillaceous slates with rare partings of sandstone,

Figure 1-1. Caspian Sea Region (Modified after National Geographic Society map, Washington, D.C., 1999).

whereas the uppermost section (2,500 to 4,000 m thick) is dominated

by thick strata and beds of quartz sandstones with rare partings ofshales In the Lesser Caucasus, terrigenous rocks (thickness of 120 m)

of the lowermost Middle Jurassic [the main part of the section (2,000–3,000 m thick)] consists of lava sheets and diabasic volcanics Quartzplagio-porphyrites with their volcaniclastic and sedimentary-volcanogenicsequences occur in the uppermost strata In the Kura Depression thesedeposits are represented by similar facies

The Upper Jurassic deposits in the northern slope of the GreaterCaucasus are composed of calcarenites and reef limestones (thickness

Figure 1-2. Structural pattern of Azerbaijan (Modified after the Excursion Guide-Book for Azerbaijan SSR, Vol II, 1984) A—Greater Caucasus Anti- clinorium; B—Kura Intermontane Depression; C—Lesser Caucasus Anti- clinorium; D—South Caspian Basin; I—Gobustan-Apsheron Trough; II—Lower Kura Trough; III—Geokchai-Saatly Anticlinal Trend; IV—Yevlakh-Agdzhabedy Trough; V—Iori-Adzhinour Trough 1—Quaternary, 2—Miocene–Paleogene, 3—Mesozoic, and 4—consolidated crust.

of 300 m), and in the southern slope by flysch-like variegated, fied, and carbonaceous shales (thickness of 500 m) These deposits inthe Lesser Caucasus and in the Kura Depression consist of reeflimestone and volcanogenic-clastic intervals (500–1,500 m).

silici-Lower Cretaceous deposits of the Greater Caucasus consist ofcarbonaceous-terrigenous flysch (thickness of 500–2,000 m), whereas

in the Lesser Caucasus and Kura Depression they are represented bytuffaceous-terrigenous and carbonaceous intervals

Upper Cretaceous deposits of the Greater Caucasus (thickness of2,000 m) consist of terrigenous-carbonaceous flysch facies Within theLesser Caucasus their content is decreased and within the Kura Depres-sion it greatly increased

The Paleogene, Neogene and Quaternary deposits are widespreadwithin the Kura and Araks depressions, Kusary sloping plain, Gobustanarea, Apsheron peninsula, Talysh foothills and in a number of residualand superimposed depressions of the Greater and Lesser Caucasus.These deposits of considerable thickness in depressions constitute themain reservoir rocks for oil and gas accumulations in Azerbaijan.Paleogene deposits in the depressions consist of green-gray, blockyshales with partings of sandstones and marls The thickness of deposits

is 300–400 m in the Pre-Caspian region, 1,700 m in the Apsheronpeninsula, and 2,800 m in the Shemakha-Gobustan region Within theKura Depression, a thicker accumulation of more than 3,000 m ischaracteristic of the Paleogene deposits

Neogene deposits in regions adjacent to the Greater Caucasus consist

of sandy shale in the lowermost strata and of more shallow, thicksandstones and coquina in the uppermost strata Thickness ranges from1,700 m (Pre-Caspian region) and 4,500 m (Apsheron peninsula) to5,500 m (Gobustan area)

Quaternary deposits consist of marine, continental, and volcanogenicfacies The thickest accumulation is observed within the Lower Kurasubdepression (more than 1,500 m), where, in the lowermost strata,they are represented by shallow marine deposits, whereas the upper-most strata consist of alluvial and delluvial deposits

The above Phanerozoic deposits are submerged within Middle andSouth Caspian basins located to the east and the southeast of theAzerbaijan land area Within the South Caspian Basin these depositsare buried at great depth, and thickness of the Paleogene-Quaternaryinterval increases According to geophysical data in the South Caspian

Basin adjacent to the Lower Kura subdepression, thickness of thePaleogene-Quaternary interval reaches 20 km.

The modern structure of Azerbaijan and the South Caspian Basinoriginated during the last stage of Alpine folding This explains whystructures are parallel to ancient structural elements that predate thelatest movement Currently, this is a region of active folding, diapir-ism, fracturing, seismicity, mud volcanism, geysers, and thermal springs.The presence of Middle Pliocene terrigenous strata 2,500–3,500 mthick (the Productive Series) with oil and gas fields, and the wide-spread distribution of mud volcanism in the south-eastern Caucasusand in the offshore area of the South Caspian Basin, are distinctivefeatures of Azerbaijan geology

GEOLOGICAL SETTING OF SUPER-DEEP DEPOSITS

The deepest deposits occur within the Kura Intermontane sion, which is located between mountainous uplifts of Greaterand Lesser Caucasus mega-anticlinoria Structurally, it is a mega-synclinorium that originated during the orogenic stage of Caucasusdevelopment By its abyssal structure, the Kura Depression is dividedinto Upper, Middle, and Lower Kura troughs or subdepressions whichdemonstrate different mobility The Middle Kura Trough with an extent

Depres-of 300 km embraces the area from Tbilisi, Georgia, to the meridian

of Kyurdamir, Azerbaijan A wide, buried uplift extends toward Vandamfrom the region of Talysh foothills to the north The Lower KuraTrough extends from the western Caspian abyssal fracture, locatedalong the eastern slope of Talysh-Vandam uplift, to the western shore

of the Caspian Sea These geological features are separated by faults

of the northwest extension (Figure 1-2)

The surface of the Middle Kura intermontane area is named the Mugan steppe and is composed of the Quaternary alluvial-deluvialdeposits 800-m thick The first indication of abyssal structure wasrevealed as a gravity maximum by a survey conducted in 1929–1931.The first investigator, V V Fedynskiy, named this gravity maximum

Mil-as Talysh-Vandam Detailed investigations of Talysh-Vandam gravitymaximum were conducted by geologists and geophysicists of Azerbaijanwho noted that the Saatly uplift region in latitudinal section is a block

of shallow (about 8 km) “basalt” rocks with a velocity discontinuity

of 6.7–6.8 km/sec Different tectonic regimes caused a change in

folding characteristics of the Middle Kura Trough During Hercynic stages the trough was a part of the Transcaucasus anticline(the Median Masiff) Within this trough, the uplift, erosion, andformation of separate basement fault blocks predominate The mainstructural elements of the Middle Kura subdepression originated duringthe earliest Alpine stage These are the Geokchai-Saatly (or Kyurdamir-Saatly) uplift, Iori-Adzhinour, and Yevlakh-Agdzhabedy troughs (Fig-ure 1-2) During the Liassic time, the region of the modern KuraDepression was occupied by a shallow sea where terrigenous sedimentsaccumulated During Middle and Late Jurassic, a 5,000-m volcanogenicsequence accumulated as a result of intensive volcanic activity Carbo-nate reefs grew in the Late Jurassic–Early Cretaceous time A secondstage of volcanic activity occurred during the Late Cretaceous timewhen volcanogenic sequence accumulated in separate parts of theTalysh-Vandam gravity maximum The end of Late Cretaceous ismarked by the accumulation of Campanian-Maastrichtian carbonatesediments Sedimentation occurred in the Iori-Adzhinour, Yevlakh-Agdzhabedy, and Lower Kura troughs.

Caledonian-The beginning of Oligocene-Miocene orogenesis altered the pre-existinggeotectonic regime in the Kura Depression, and was dominated bywarping with molasse accumulation The Geokchai-Saatly zone of theburied uplifts is characterized by an elevated basement surface inthe eastern part of Middle Kura Trough The Saatly-Kyurdamir andMil-Khaldan subzones (blocks) occur within the Geokchai-Saatly zone.The Saatly-Kyurdamir subzone includes Karadzhaly, Sor-Sor, Dzharly,and Saatly local uplifts, whereas the Mil-Khaldan subzone experiencedMuradkhanly, Zardob, and Mil uplifts

It is hard to investigate Saatly-Kyurdamir buried uplift because thereare no natural outcrops, and Cenozoic molasse deposits, overlappingMesozoic sedimentary-volcanogenic strata, are very thick Drilling

on various parts of the uplift, however, has produced new data onMesozoic magmatism It was ascertained that the Mesozoic stage ofuplift involved volcanogenic-sedimentary deposition with a volcanogenic-plutonic association

Seismic, gravity and magnetic investigations of the Earth’s crustalong profile, which crosses the uplift in a latitudinal direction, showthat a velocity model of the crust based on reflected waves is ratherinformative Seismic observations were conducted by vertical seismicsounding by reflected waves Observations were conducted only along

the sublatitudinal profile that crosses the uplift area As a result, a moredetailed velocity model was obtained (Figure 1-3) According to thesedata, a high-velocity layer [V > (6.7–6.8) km/sec] is expected at adepth of 9 km.

It became evident that the Saatly-Kyurdamir gravity maximum isexpressed as a nose of the most ancient (Pre-Baikal) complex (Figure1-4) The nose is overlapped by a magmatic sequence of basic andintermediate composition, mainly of Mesozoic age Its roots penetratedeep into the mantle to the west where the Zardob magnetic maximum

is present

These investigations show the development of Mesozoic magmatites

as thick, highly-magnetic strata To confirm these data, it was decided

Figure 1-3. Seismic density model along the line of deep seismic sounding (Modified after the Excursion Guide-Book for Azerbaijan SSR, Vol II, 1984) (a) Observed and calculated plots of gravity field for section; (b) Seismic density model; Curves: 1—observed, 2—calculated, 3—Cenozoic sequence, 4—Mesozoic sequence, 5—sequence G (velocity analogous to that in “granitic” layer), 6—sequence B (velocity analogous to that in “basalt” layer), divided into two sub-sequences: Bu and Bl, 7—sequence B1 (supposed peridotite content), 8—boundary of velocity (density), 9—unconformities, 10—deep wells.

to drill a super-deep well It was expected that on reaching a depth

of 9 km, the super-deep well would penetrate a volcanogenic section.Disturbed deposits, which are the source of the regional Talysh-Vandam gravity maximum, are expected lower The authors supposethat as a whole, these are primarily sedimentary, metamorphosed, andconsolidated deposits of the Upper Archean-Lower Proterozoic age

Figure 1-4. Geologic and geophysical model of Saatly-Kyurdamir anticlinal trend (Modified after the Excursion Guide-Book for Azerbaijan SSR, Vol II, 1984) 1—Cenozoic sequence-terrigenous deposits; 2—Mesozoic sequence:

a terrigenous-carbonate deposits, b extrusive formations of basic and intermediate composition; 3—Baikal sequence, metamorphozed primary terri- genous formations; 4—Pre-Baikal sequence, gneiss and marl; 5—the oldest interval, gneiss and amphibolite; 6—intrusive formations of basic and inter- mediate composition; 7—undivided extrusive-intrusive interval; 8—low density rocks, serpentinites; 9—rocks of intermediate composition between crust and mantle; 10—position of upper mantle top; 11—zones of large faults; 12— deep wells.

It is possible that between the Mesozoic magmatic strata and the Baikal basement, there may occur somewhat thin intermediate deposits,which cannot be identified by common techniques.

Pre-SAATLY SUPER DEEP WELL SD-1

The Saatly Super Deep well SD-1, with a proposed depth of 15,000m/49,212 ft, was located within the Middle Kura Intermontane Depres-sion (Kura Lowland), where the Kura and Araks rivers convergeand the Mil and Mugan steppes join (Figure 1-5) It is a region ofwarm semi-desert and dry steppes with an arid climate The averageannual temperature is +10°C Annual precipitation does not exceed200–300 mm

From December 1971 to August 1974, a preliminary well was drilled

to 6,240 m/20,472 ft The well penetrated Cenozoic molasse, MesozoicCarboniferous deposits, and from 3,550 m/11,647 ft to bottom of thewell, volcanogenic strata

The Saatly Super Deep well was designed in accordance with a “Study

of the Earth’s mineral resources and super-deep drilling” conducted

by the State Committee on Science and Engineering The main goal

of this program was to study the Earth’s crust in the MediterraneanAlpine geosynclinal belt, including the following investigations:

1 A detailed study of solid, fluid and gaseous phases of the Earth’scrust and their changes with depth

2 The study of the geologic nature of seismic boundaries and theestablishment of the reasons for crustal foliation by geophysicalparameters

3 The study of peculiarities of endogenic geologic processes fested in deep parts of the Earth’s crust, including the process

mani-of ore generation

During the first stage of the investigations, while drilling the Saatlywell to 8,000 m/26,247 ft, the main goal was to penetrate the sedi-mentary and volcanogenic section at a site of minimum thickness,according to geophysical study conducted in the area of Saatly localuplift This was done (a) to study its composition, structure, occur-rence, and oil content; (b) to study the conditions of generation anddistribution of ores in the lower part of sedimentary-volcanogenicstrata; (c) to penetrate granitic rocks, to study their interrelation with

sedimentary-volcanogenic formations; and (d) to develop and improvethe drilling technology and methods of geological and geophysicalinvestigations at great depth.

In this section the following stratigraphic units were penetrated(Figure 1-6):

Post-Pliocene (Quaternary) deposits (0–860 m) are represented by the

irregular alternation of gray, thick-bedded clay; gray, unconsolidatedsiltstone; medium-grained and coarse-grained sandstone with gritinclusions; thin-bedded intervals with grit inclusions; and thin-bedded intervals of continental origin

Apsheronian Stage (860–1,930 m) is represented lithologically by

alternation of sandy, silty and clayey rocks in the upper portion of

Figure 1-5. Location of Saatly Super Deep Well SD-1 Distances: Baku to Saatly: 180 km (112 mi); Baku to Alyat: 72 km (45 mi); Alyat to Kazi- Magomed: 46 km (28 mi); Kazi-Magomed to Ali-Bairamly: 13 km (8 mi); Ali- Bairamly to Sabirabad: 38 km (24 mi); Sabirabad to Saatly: 12 km (7.5 mi).

the section and with gray clay separated by silty, sandy and limyinterlayers in the lower portion.

Akchagylian Stage (1,930–2,250 m) is composed of gray silty clay

with rare and thin partings of polymictic siltstone

Middle Pliocene (2,250–2,780 m) is represented by brown-gray silty

clay alternating with polymictic sandstone

Figure 1-6. Stratigraphic section (from cores and logs) of Saatly Super Deep Well SD-1 (Modified after the Excursion Guide-Book for Azerbaijan SSR, Vol I, 1984) Aleurites = siltstones.

Sarmatian Stage (2,780–2,830 m) is represented by alternation of

thin-bedded sandy argillaceous rocks and carboniferous rocks, overlyingMesozoic carbonate

Cretaceous—Late Jurassic (2,830–3,529 m) is represented by the

alternation of thick (200 m), fractured, pelitomorphic, siliceousmetamorphosed limestone and volcanogenic intervals (5 and 54 m,respectively)

Jurassic (3,529–8,230 m) is represented by thick volcanogenic strata.

The main attention was paid to the composition, structure, physicalproperties, and geochemical attributes of volcanogenic rocks Coresamples from volcanogenic strata, studied petrographically in detail,give an idea of structure, composition, facies, and rock deformation

of volcanic matter masks sedimentation

According to petrographic data, volcanogenic strata changed frombasalt to rhyolite Most rocks belong to the porphyritic facies, and only

a small group (dikes and sills) consists of aphyric basalt In porphyriticrocks, plagioclase and magnetite are the main minerals They arejoined by dark-colored minerals, i.e., pyroxene, amphibole, and olivine.The contents of plagioclase, monoclinic pyroxene, amphibole, andmagnetite in the main petrographic groups of rocks have been studied.Porphyritic basalts and andesite-basalts are very similar to each other

in the content of all rock-forming minerals Plagioclase is present inboth and its content is approximately equal to that of bytownite-

anorthite Clinopyroxenes are represented by subcalcic ferrous augites,characteristic of geosynclinal sequences of normal alkalinity It issupposed that hyperalkalinity, sometimes noted in these rocks, isallogenic The presence of amphiboles in hornblende-andesite andzeolitic metasomatites shows the volcanic origin of replaced rocks.The data obtained from chemical analyses prove the association ofvolcanics with basalts, andesite-basalts, andesites, andesite-dacites,dacites and rhyodacites According to silica and alkaline oxide ratios(Na2O/K2O), basalts, andesite-basalts, andesites, and dacites belong tothe limestone-alkaline gradation Basalts and andesite-basalts arecharacterized by a high content of aluminia and low content of silica.

In general, the composition of basic rocks of volcanogenic stratacorresponds to that of the high-aluminiferous basalts of the andesite-basalt series

Acid and intermediate rocks are characterized by a low alkalicontent Na2O predominates over K2O High content of Na2O both inthe basic and acidic volcanics is due to autometamorphism Lowcontent of TiO2 and low content of Fe2O3+FeO point to thegeosynclinal nature of basalts Analyzed rocks, on the whole, arecharacterized by the low content of SiO2, Fe2O3+FeO, MgO, TiO2, and

K2O, and high content of Al2O3 and Na2O

Volcanogenic rocks can be differentiated on the basis of certainstructural features Rocks of the upper and middle parts of volcanogenicstrata are of geosynclinal andesite-basaltic type, analogous to the MiddleJurassic (Bathonian) sequence, occurring within the Lesser Caucasus.Rocks of the lower part of the section cannot be determined before-hand because their lower boundary was not penetrated As acidicvolcanics predominate in the section, the rocks can be identified assodic rhyolites It is possible that at deeper horizons the volcanics ofbasic composition are present; then, the sequence can be identified asbasalt-andesite-rhyolitic, analogous to the Lower and Middle Jurassicsequence of the Lesser Caucasus

All the rocks of volcanogenic strata are metamorphosed Secondaryminerals replace volcanic glass and primary minerals, and also infillcavities and fractures Metamorphic minerals form varied mineralassociations, among which are clay minerals, chlorite, calcite, chalce-dony, quartz, albite, zeolite (laumonite), hematite, leucoxene, sphene,prehnite, epidote, pumpellyite, and sulphides Acidic rocks, whichcompose the lower part of the strata, are silicified and calcitized

In the lower part of the section some secondary minerals as quartz,chalcedony, sericite, and epidote are added to chlorite and calcite Withincrease in depth, the low-temperature zeolites are replaced by morehigh-temperature epidote and then by prehnite-pumpellyite (greenschiststage of metamorphism) A low-temperature calcite-chlorite is alsodeveloped A geochemical trend of main chalco-lithophylic elements

in volcanics coincides with that in calcic-alkaline extrusive series ofisland arcs

Geochemical regularities in distribution of rare elements in rocks

of volcanogenic strata correspond to those in volcanics, originated inzones of island arcs In the SD-1 well section, the degree of heliumpreservation in volcanics is lower than in terrigenous deposits of the sedi-mentary sequence Geochemical analyses of gases dissolved in interstitialsolutions and/or adsorbed in the rocks, showed that the main components

of gases emanating from volcanic rocks are carbonic-acid, acid, and hydrocarbons The main hydrocarbon gas is methane

nitric-carbonic-According to the results of gravity and magnetic surveys, the region

of the Talysh-Vandam gravity maximum is structurally heterogeneous.Different areas of maxima (anomalies of the second order) are ofdifferent origin in the Earth’s crust In the subsurface structure of theSaatly-Kyurdamir maximum, the projection of Pre-Alpine basement isinterpreted as the complex of Upper Archean and Lower Acheansequences with allochtonous features In the Alpine complex over-lapping basement, products of Mesozoic magmatism of basic andintermediate composition are developed

During the second stage of drilling (below 8,000 m), it is expectedthat the SD-1 well will penetrate magmatic rocks of Mesozoic or olderage; below 10,000 m, the older basement metamorphic rocks areexpected Saatly SD-1 well is one of the first wells which will pene-trate rocks of great depth and answer many questions

Scientific and practical findings from the first stage of drilling theSD-1 well are the following:

1 The Earth’s crust section 8-km thick has been penetrated Thissection is a standard not only for Saatly-Kyurdamir buried uplift,where commercial oil is produced from the volcanogenic strata,but also for the whole Alpine zone of the southern part of theTranscaucasus, where deposits of the most important commercialminerals are located

2 The volcanogenic section penetrated by the well is 5,000-m thick,which contradicts the existing opinion that the sedimentary-volcanogenic section overlying the Saatly local uplift is thin.

3 Microfauna (radiolaria) present at a depth of 6,560 m in siliceoustuff siltstones point to the deep accumulation of volcanogenicmaterial of Jurassic age This changes the existing opinion on thetectonic-magmatic evolution of the region reflecting the geosynclinalregime of the Transcaucasus Median Masiff development

4 The results of petrochemical and geochemical study of thevolcanics and the distribution of rare elements in the depositsshow that they have been derived from calcic-alkali magma ofthe same source formed in island arc zones

5 According to the prognosis, within the Kura Depre ssion thetemperature must rise by 2–2.5°C per hundred meters of depth.This prognosis was not confirmed At a depth of 8 km, thetemperature reaches only 140°C Such a low temperature at greatdepth is caused by low heat flow from the interior of the Earth’scrust due to tectonic-magmatic evolution of the region

tec-of volcanic activity are responsible for the transfer tec-of huge masses tec-ofnot only fluids but also breccia-plastic rocks Thus, mud volcanism is

an indicator of, and powerful factor for, transfer, dispersion, andconcentration of rocks, liquids and gases, including oil and natural gas.Eastern Azerbaijan and Western Turkmenistan with adjacent sub-merged areas of the Caspian Sea are classic regions of mud volcanoes

of different morphological types which eject solid, liquid and gaseousproducts at the surface Roots of mud volcanoes reach to depths of10–15 km and more (Mesozoic) in the Apsheron Peninsula, in theGobustan area, Kura lowland, offshore areas of Apsheron and Bakuarchipelagoes and Apsheron Threshold, which are important oil- andgas-producing regions

The total area of mud volcanism in Eastern Azerbaijan is 16,000

km2, including more than 200 mud volcanoes (Figure 2-1) Scientistsbelieve that there are 150 underwater mud volcanoes in the SouthernCaspian Sea and 9 mud-volcanic islands It is ascertained that mudvolcanoes are confined to the most deformed portions of late geo-synclinal trend (i.e., to molasse troughs), to the periphery of foldedsystems (i.e., to foredeeps), periclinal troughs of active geosynclinalfolded regions, where thickness of sedimentary fill exceeds 10 km Thefollowing factors are prerequisites for generation of mud volcanoes:anticlinal structure, dislocations with breaks of continuity, plasticclays, buried formation water, accumulation of hydrocarbon gases andabnormally-high formation pressure

Figure 2-1. Locations of mud volcanoes in the eastern Azerbaijan (Modified after the Excursion Guide-Book for Azerbaijan SSR, Vol I, 1984) a— Anticlines, b—mud volcanoes, c—areas with mud cones, d—boundaries between regions The main structural areas: I—Pre-Caspian monocline, II—Shemakha-Gobustan area, III—Lower Kura Depression, IV—Apsheron Peninsula, V—Baku Archipelago.

Mud-volcano gases consist of saturated and unsaturated carbons (99% of which is CH4), a small amount of heavy hydro-carbons, CO2, N2, and other inert components (helium, argon) Thechemical composition of gases varies between different regions.Isotopic analyses show that these gases originated mainly in sedi-mentary strata.

hydro-Salinity and trace elements (I, B, Br) indicate that water from mudvolcanoes is similar to the formation water of oil and gas fields.Alkaline water of sodium bicarbonate type predominates

Oligocene-Miocene and Pliocene deposits are dominated by mental products of mud volcanoes eruptions About 90 minerals andmore than 30 trace elements are present in mud-volcanic breccia.These include: boron, mercury, manganese, barium, strontium, rubi-dium, and copper Volcanic mud is used widely for medicinal purposesincluding treatment of arthrithis and rheumatism

frag-YASAMALY VALLEY

The offshore portion of the Dzheirankechmes Depression inthe Central Gobustan area is located south of Baku Trough It wasfilled with sediments of the Productive Series, and Akchagylian andApsheronian deposits A number of narrow and wide anticlinal trendsare revealed within this depression Anticlines are faulted; the faultsare associated with wide zones of breccia, to which centers of mudvolcanoes are confined Mud volcanoes are widely distributed withinthe Dzheirankechmes Depression, where they reach large size: Lokbatan,Akhtarma, Kushkhana, Kyzyltepe, Shongar, Sarynja, Gyulbakht, Pilpilya,Otmanbozdag, Greater Kyanizadag, Tourogai, etc

The Lokbatan-Otmanbozdag group of volcanoes (Figure 2-2) islocated in the northwestern portion of the Dzheirankechmes Depres-sion, whereas Greater Kyanizadag and Tourogai are situated in thesouthwestern part of this depression, south of the DzheirankechmesRiver There are two anticlinal uplifts: dome-shaped Tourogai andbrachyform Kyanizadag, which are composed of deposits of ProductiveSeries in the crestal areas These anticlines are faulted, and mudvolcanoes are confined to faults

Lokbatan Mud Volcano is situated within the southern part of

Yasamaly Valley and coincides with the Lokbatan oil field (Figure2-3) Here, Pleistocene terraces are widespread, as well as limestones