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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Petroleum Geoscience, 2nd edition is a comprehensive introduction to the application of geology and geophysics to the search for and production of oil and gas. The aim this updated second edition remains the same - to provide a comprehensive grounding in the geological sciences as applied to exploration for and production of oil and gas.
Uniquely, this book is structured to reflect the sequential and cyclical processes of exploration, appraisal, development and production. Chapters dedicated to each of these aspects are further illustrated by new case histories drawn from the authors' experiences. Petroleum Geoscience, 2nd edition has a global and 'geo-temporal' backdrop, drawing examples and case histories from around the world and from petroleum systems ranging in age from late-Pre-Cambrian to Pliocene.
In order to show how geoscience is integrated at all levels within the industry, the authors stress throughout the links between geology and geophysics on the one hand, and drilling, reservoir engineering, petrophysics, petroleum engineering, facilities design, and health, safety and the environment on the other.
Discovery and production of petroleum underpinned global development throughout the twentieth century but times are changing. Combustion of fossil fuels and release of greenhouse gases, mainly carbon dioxide, is driving climate change. The skills and knowledge of the petroleum geoscientist also find application in carbon storage in and heat recovery (geothermal energy) from the Earth. This second edition addresses such technologies in the newly added Chapter 7.
The target readership is mainly final year undergraduates and postgraduates in the earth sciences together with little-experienced technical staff within the petroleum industry. The book draws on a large variety of examples from many basins around the world and as a consequence should appeal to those interested in petroleum geoscience, whether they be in Aberdeen or Abu Dhabi, Houston or Ho Chi Min.
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Veröffentlichungsjahr: 2021
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Table of Contents
Cover
Title Page
Copyright
Preface to Second Edition
Preface to First Edition
Acknowledgments
1 Introduction
1.1 The Aim and Format of the Book
1.2 Background
1.3 What Is in this Book
1.4 What Is Not in this Book
1.5 Key Terms and Concepts
1.6 The Chemistry of Petroleum
1.7 Geoscience and the Value Chain
1.8 Geoscience Activity
1.9 Oil, Gas, and Geoscientists – A Global Resource!
Further Reading
2 Tools
2.1 Introduction
2.2 Satellite Images and Other Remote Sensing Data
2.3 Seismic Data
2.4 Wireline Log Data
2.5 Core and Cuttings
2.6 Fluid Samples From Wells
2.7 Outcrop Data
2.8 Seepage of Petroleum
Further Reading
Notes
3 Frontier Exploration
3.1 Introduction
3.2 Acquisition of Acreage
3.3 Direct Petroleum Indicators
3.4 Basin Types
3.5 Basin Histories
3.6 Stratigraphy
3.7 Source Rock
3.8 Jubilee Field, Ghana, West Africa
3.9 Johan Sverdrup Oilfield, Norwegian North Sea
Further Reading
4 Exploration and Exploitation
4.1 Introduction
4.2 The Seal
4.3 The Reservoir
4.4 Migration
4.5 The Trap
4.6 Play and Play Fairway
4.7 Lead and Prospect
4.8 Yet to Find
4.9 Risk and Uncertainty
4.10 Thunder Horse Field, Gulf of Mexico, USA
4.11 Clyde Field, UK North Sea
Further Reading
5 Appraisal
5.1 Introduction
5.2 The Trap Envelope
5.3 Fluid Distribution and Contacts
5.4 Field Segmentation
5.5 Reservoir Property Distribution
5.6 Reservoir Quality
5.7 Reservoir Description from Seismic Data
5.8 Petroleum in Place, Reservoir Models, and Reserves
5.9 Kadanwari Field, Pakistan
5.10 Pedernales Field, Venezuela
Further Reading
6 Development and Production
6.1 Introduction
6.2 Well Planning and Execution
6.3 Reservoir Management
6.4 Reserves Revisions, Additions, and Field Reactivation
Case Histories
6.5 Thistle Field, North Sea – Improving Late Field Life Oil Production
6.6 Ardmore Field, UKCS
Further Reading
7 Unconventional Petroleum, Gas Storage, Carbon Storage, and Secondary Products
7.1 Introduction
7.2 Unconventional Gas
7.3 Unconventional Oil
7.4 Underground Coal Gasification
7.5 Gas Storage
7.6 Carbon Storage
7.7 Heat, Helium, and Other Secondary Products
7.8 Dunlin Field, UK North Sea, Opportunities for Power Generation from Unconventional Gas and/or Co-Produced Water
7.9 Clipper South Field, UK North Sea – Development of a Tight Gas Field
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Conversion factors for British/US units to metric units
Chapter 2
Table 2.1 Data used in petroleum exploration and production
Table 2.2 Rock densities
Table 2.3 Uses of vertical seismic profile (VSP) data
Chapter 3
Table 3.1 Examples of the resolution of fossil groups by age and by geography
Chapter 4
Table 4.1 Intrinsic properties and recovery factors for reservoirs within UK ...
Table 4.2 Fractured reservoirs
Table 4.3 Structural and stratigraphic traps
Chapter 5
Table 5.1 Order-of-magnitude diffusion rates for methane and molecules with 1...
Table 5.2 Aspect ratios for clastic sand bodies in fluvial, paralic, and shal...
Table 5.3 Sea level and climatic controls on near-surface carbonate sediment ...
Table 5.4 Contrasting recovery factors: North Sea and Trinidad
Table 5.5 Revised oil in place for the Pedernales Field, Eastern Venezuela ba...
Chapter 6
Table 6.1 New well, sidetrack, and perforation options for an Asian gasfield
Chapter 7
Table 7.1 Estimate of in-place shale gas resources EIA/ARI (2011)
Table 7.2 Products arising from UGC processes
Table 7.3 shows in the Upper Jurassic close to the Dunlin Field
Table 7.4 Anomaly properties and gas in place estimates
Table 7.5 Financial losses due to power supply issues on the Dunlin Platform
List of Illustrations
Chapter 1
Figure 1.1 A cartoon cross-section of part of a petroleum-bearing basin. Mos...
Figure 1.2 A stratigraphic time scale.
Figure 1.3 (a) Chemical formulas for alkanes and alkenes, plus examples. (b)...
Figure 1.4 Naphthene, or ring, compounds have the chemical formula C
n
H
2
n
. Th...
Figure 1.5 Aromatic compounds are unsaturated ring compounds with the chemic...
Figure 1.6 Geoscience and the value chain. The cartoon sections of the oilfi...
Figure 1.7 The rate of oil discovery (bars) and consumption (line). Discover...
Figure 1.8 Global sedimentary basins and petroleum production provinces.
Chapter 2
Figure 2.1 A Landsat satellite image of the Zagros Mountains, Iran. The cent...
Figure 2.2 The evolution of the structural interpretation of the Boqueron Fi...
Figure 2.3 A schematic diagram showing ray-paths during seismic acquisition....
Figure 2.4 Examples of various types of seismic trace display:
a
= amplitude...
Figure 2.5 Land seismic acquisition using Vibroseis™ as an energy source. Th...
Figure 2.6 Stratigraphic information derived from seismic: a lowstand system...
Figure 2.7 “Hot black shale” radioactivity. The spectral gamma log, from the...
Figure 2.8 A typical gamma log response in a mixed sandstone and mudstone se...
Figure 2.9 A comparison of gamma ray and spontaneous potential logs run at t...
Figure 2.10 (a) Dipmeter and core logs from the Blader Formation (Eocene) in...
Figure 2.11 Vertical seismic profile configurations. (a) Zero offset; (b) (l...
Figure 2.12 Zero-offset Vibroseis™ VSP data from the Devine Test Site, Texas...
Figure 2.13 Sonic log responses in a sandstone and mudstone sequence. In (a)...
Figure 2.14 Typical responses of a density log. The density log records bulk...
Figure 2.15 An annotated NMR log. Curves are commonly provided for porosity,...
Figure 2.16 Shallow (LLS) and deep (LLD) resistivity logs with an interprete...
Figure 2.17 The preparation of core plug samples from core.
Figure 2.18 Critical point drying allows drying of the sample while avoiding...
Figure 2.19 Permeability overburden corrections. Curves for conversion of (a...
Figure 2.20 A core log from Triassic reservoirs within the Gawain Field, UK ...
Figure 2.21 A thin-section photomicrograph of a fine-grained micaceous sands...
Figure 2.22 A scanning electron photomicrograph showing the same chlorite-co...
Figure 2.23 A gas chromatograph. The
x
-axis is the retention time in minutes...
Figure 2.24 A field map of the Mixon Anticline (North Staffordshire, England...
Figure 2.25 A van Krevelen plot, showing maturation pathways of the dominant...
Figure 2.26 A plot of vitrinite reflectance against depth from well David Ri...
Figure 2.27 Oil that has leaked from sea-floor vents to the sea surface, usu...
Chapter 3
Figure 3.1 Oil- and gasfields on the Atlantic margin west of the Shetland Is...
Figure 3.2 The quadrant system of license areas adopted by countries around ...
Figure 3.3 Seal failure, tertiary migration, and dissipation.
Figure 3.4 Capillary failure (a) and fracture failure (b) of a seal. Active ...
Figure 3.5 A mud volcano with a fresh mud flow, Azerbeijan. Seepage of both ...
Figure 3.6 A gas hydrate mound.
Figure 3.7 A
bottom-simulating reflector
(
BSR
), a seismic expression of shal...
Figure 3.8 Two-way time seismic and depth sections across the Bittern Field,...
Figure 3.9 A direct hydrocarbon indicator at a possible gas/water contact in...
Figure 3.10 The Earth's tectonic plates.
Figure 3.11 The main compositional and rheological boundaries of the Earth. ...
Figure 3.12 The geometry of the Michigan Basin, USA. (a) Structural contours...
Figure 3.13 The reconstructed paleogeography and a cross-section of the Nort...
Figure 3.14 (a) Uninterpreted and (b) Interpreted 2-D seismic time line sect...
Figure 3.15 Compressional and tensional areas created during convergent plat...
Figure 3.16 Piggyback basins (e.g. the Apennines) developed behind a forelan...
Figure 3.17 A strike-slip basin plan and cross-section, showing typical mega...
Figure 3.18 A basin developed on mantle plume. The map represents the concen...
Figure 3.19 A schematic burial history for a rift basin. The syn-rift burial...
Figure 3.20 The effect of repeated deformation in a foreland basin. With eac...
Figure 3.21 A flower structure, Burun Field, Turkmenistan. The flower struct...
Figure 3.22 (a) The burial history of the Miller Field, UK North Sea. (b) Th...
Figure 3.23 The reconstructed burial and thermal histories for a well In the...
Figure 3.24 Pressure-depth plot illustrating hydrostatic (normal) and lithos...
Figure 3.25 Pressure transition zones reflect fluid retention due to low sed...
Figure 3.26 Unconformities. (a) Schematic of an angular unconformity between...
Figure 3.27 A local-scale chronostratigraphic diagram and cross-section, Fri...
Figure 3.28 A biostratigraphic range diagram.
Figure 3.29 A tertiary planktonic foraminiferal zonal scheme developed in th...
Figure 3.30 A comparison of (a) chronostratigraphic correlation and (b) lith...
Figure 3.31 A cross-section through a rift basin. The geometry of such rift ...
Figure 3.32 A syn-rift wedge of Upper Jurassic deep-water sandstones and mud...
Figure 3.33 A geologic section across the Lianos Basin, Colombian Andes. The...
Figure 3.34 A sea-level curve for the Cenozoic of the eastern North Sea. The...
Figure 3.35 A classification of the types and hierarchy of stratigraphic cyc...
Figure 3.36 Components of the lowstand systems tract on a shelf/slope break ...
Figure 3.37 Stratal geometries in a Type 1 sequence on a shelf/slope break m...
Figure 3.38 Stratal geometries in a Type 2 sequence on a shelf/slope break m...
Figure 3.39 A carbonate lowstand systems tract (LST) on a humid escarpment-m...
Figure 3.40 The preservation of organic matter in (a) large anoxic lakes suc...
Figure 3.41 Microfacies of laminated sapropelic mudstone, Lower Liassic, Por...
Figure 3.42 Activation energies and product yield. (a) Green River shales (T...
Figure 3.43 The maturation of oil from source rock as a function of depth an...
Figure 3.44 Maturation from a gas-prone source rock (1 km
3
). The curve is ba...
Figure 3.45 Location map for Jubilee Field, within the Upper Tano Basin, off...
Figure 3.46 Cross section of the West African margin In the area of the Jubi...
Figure 3.47 The Jubilee Field is located across two offshore license blocks ...
Figure 3.48 Location map for the Johann Sverdrupp giant oilfield, offshore N...
Figure 3.49 The Johann Sverdrupp field Is the largest accumulation within a ...
Figure 3.50 Cross-section from west to east illustrating the migration route...
Chapter 4
Figure 4.1 A pressure versus depth plot illustrates a typical water gradient...
Figure 4.2 A schematic illustration of a pore throat between two grains. The...
Figure 4.3 The relative magnitudes of the three principal stresses – one ver...
Figure 4.4 A Mohr diagram, used to determine when and how rocks will fail un...
Figure 4.5 The vertical height of a petroleum column beneath a seal is deter...
Figure 4.6 A conceptual diagram to show “fill and spill” during successive f...
Figure 4.7 A pressure reversal (reduction of the amount of overpressure with...
Figure 4.8 (a) A scanning electron microscope photomicrograph of a porous (2...
Figure 4.9 The formation volume factor (
Bo
) is a measure of the volume diffe...
Figure 4.10 Net to gross is the ratio between reservoir rock capable of flow...
Figure 4.11 Porosity. (a) Intergranular porosity (X) between quartz grains w...
Figure 4.12 Average permeability for various producing fields on the UK and ...
Figure 4.13 The distribution of reservoir ages for giant (a) oilfields and (...
Figure 4.14 (a) Alluvial fan – Leh, Indian Kashmir (looking SW, photograph b...
Figure 4.15 (a) The margin of an aeolian dune field, showing the relationshi...
Figure 4.16 An outcrop panel for the Otter Sandstone (Sherwood Sandstone equ...
Figure 4.17 Three dimensional reservoir architecture of a meander system in ...
Figure 4.18 A delta ternary diagram, showing the distribution of modern delt...
Figure 4.19 The average size, shape, and location of sand bodies in wave-, t...
Figure 4.20 A schematic cross-section of Upper Cretaceous offshore sandstone...
Figure 4.21 The summarized paleogeography for the late Kimmeridgian of the S...
Figure 4.22 Block diagrams of (a) a rimmed carbonate shelf with a landward s...
Figure 4.23 About 90% of the Devonian oil reserves of western Canada occur i...
Figure 4.24 Tower karst within Paleozoic limestones, Zhaoqing, Guangdong Pro...
Figure 4.25 A schematic diagram showing the structural-stratigraphic interpr...
Figure 4.26 Upper Permian (Zechstein) dolomite, County Durham UK. These frac...
Figure 4.27 A sketch of the three stages of migration: primary migration out...
Figure 4.28 (a) The average hydrogen index (mg g
−1
TOC
[
total organic c
...
Figure 4.29 (a) The total soluble extract yield relative to TOC (mg g
−1
...
Figure 4.30 An outline of Pepper's (1991) hypothesis linking petroleum expul...
Figure 4.31 Average petroleum expulsion efficiency plotted against hydrogen ...
Figure 4.32 Buoyancy as a driving force for secondary migration. Buoyancy is...
Figure 4.33 The decrease of oil column height with depth (contrary to popula...
Figure 4.34 Reconstructed subsalt petroleum migration pathways from the Ewin...
Figure 4.35 Petroleum migration along high-permeability sandstone beds withi...
Figure 4.36 Structural traps. (a) Tilted fault blocks in an extensional regi...
Figure 4.37 Stratigraphic traps. (a) A “reef” trap. Oil is trapped in the co...
Figure 4.38 The hydrodynamic displacement of oil and gas accumulations throu...
Figure 4.39 Cross-sections of the Brent Province field. (a) A geologic inter...
Figure 4.40 A simplified map and cross-section of the Zagros orogenic belt (...
Figure 4.41 El Furrial, eastern Venezuela. The petroleum traps occur as larg...
Figure 4.42 Trinidadian trap geometries. The thrust-related anticlinal struc...
Figure 4.43 A NW–SE cross-section of the Painter Reservoir and East Painter ...
Figure 4.44 Anticlinal culminations along and adjacent to a major right-late...
Figure 4.45 A seismic cross-section of the Maui Field, New Zealand. The anti...
Figure 4.46 (a) Mud volcano, Trinidad; (b) live mud flow on mud volcano, Tri...
Figure 4.47 A sketch section showing the common types of petroleum traps ass...
Figure 4.48 Turtle-structure anticlines form from the inversion of sediments...
Figure 4.49 A structural cross-section and inset location map of the Machar ...
Figure 4.50 The Balmoral Field, UK North Sea. A north–south, seismic cross-s...
Figure 4.51 A seismic map on top reservoir of the East Brae Field, South Vik...
Figure 4.52 Growth fault patterns from the Tertiary of the US Gulf Coast. Th...
Figure 4.53 Paralic field shapes are commonly of a highly complex shape, bec...
Figure 4.54 The Oficina Field, eastern Venezuela. The isopach, structural co...
Figure 4.55 A NE–SW cross-section through the Scapa Field of the Witch Groun...
Figure 4.56 A map and cross-section of the Prudhoe Bay Field, Alaska. Petrol...
Figure 4.57 The crest of the giant, gas and oil Troll Field (Norwegian North...
Figure 4.58 The Frannie Field, Big Horn Basin, Wyoming. The oil/water contac...
Figure 4.59 The distribution of the four main plays in the northern and cent...
Figure 4.60 The petroleum source-rock maturity distribution and vertical mig...
Figure 4.61 A sketch of a prospect with four-way dip closure. The deepest cl...
Figure 4.62 A sketch of reservoir shale-out. There is no closure on the top ...
Figure 4.63 In the UK continental shelf 11th License Round, 16 companies app...
Figure 4.64 The field (reserves) size distribution for the Columbus (gas) Ba...
Figure 4.65 The pool size distribution for both oil and gas accumulations in...
Figure 4.66 The reserves size distribution for Iranian petroleum fields in t...
Figure 4.67 The creaming curve for oil and gas accumulations in the Norwegia...
Figure 4.68 The creaming curve for the Berkine Basin, Algeria (equivalent to...
Figure 4.69 Decision tree analysis for a simple development well problem. Th...
Figure 4.70 A probability distribution (exceedance curve) for a hypothetical...
Figure 4.71 A gallery of possible possibility distributions that can be used...
Figure 4.72 Sediment source and distribution patterns for the Lower Tertiary...
Figure 4.73 Geological setting of the Gulf of Mexico, (a) shaded bathymetry ...
Figure 4.74 Seismic cross sections of Thunder Horse; (a) time-depth plot 199...
Figure 4.75 Subsurface structure of the Thunder Horse Field and overlying sa...
Figure 4.76 Stratigraphic Well Log Section through THS Brown.
Figure 4.77 Production profile and history for the Thunder Horse Field 2009 ...
Figure 4.78 The Clyde cluster of fields before production start up Alpha = L...
Figure 4.79 The 2016 distribution of fields within the Fulmar-Clyde cluster....
Figure 4.80 Clyde area production profiles. Both Fulmar and Auk have much lo...
Chapter 5
Figure 5.1 The interrelationship between reserves, production rate, operatin...
Figure 5.2 Temporal changes in reserves estimation during field development ...
Figure 5.3 Time versus depth data for wells within the Inner Moray Firth, UK...
Figure 5.4 A synthetic sonic log for a well, showing three possible methods ...
Figure 5.5 The spacing of contour lines is a function of the shape and slope...
Figure 5.6 Contours on the underside of an overhanging structure (a) are sho...
Figure 5.7 A sketch of a mapped surface, showing anticlinal, and synclinal c...
Figure 5.8 Fault nomenclature. AB, strike-slip; BD, dip-slip; BE, oblique sl...
Figure 5.9 Fault heaves appear as gaps for normal faults. This example is fr...
Figure 5.10 (a) A block diagram showing folded and faulted reservoir interva...
Figure 5.11 Closing contour on Tertiary Structure Block 9/28 – South Viking ...
Figure 5.12 Spill points on four-way dip-closed and fault-closed structures....
Figure 5.13 Exploration well 1 failed to find an oil/water contact (OWC). Th...
Figure 5.14 (a) The oil/water contact penetrated by well 2 lies between the ...
Figure 5.15 The static water saturation distribution and definition of conta...
Figure 5.16 Capillary rise above free water level.
Figure 5.17 Repeat Formation Tester (RFT™) data from the Bruce Field, UK Nor...
Figure 5.18 Intra-field petroleum variations. (a) Inherited differences due ...
Figure 5.19 An example of gravitational segregation causing vertical changes...
Figure 5.20
Strontium residual salt analysis
(
SrRSA
) trends for two wells in...
Figure 5.21 Barriers to lateral flow. (a) A faulted sandstone bed. (b) Cemen...
Figure 5.22 Juxtaposition diagrams. (a) A 3D fault with varying displacement...
Figure 5.23 Barriers to vertical flow. (a) Cemented layers within the Jurass...
Figure 5.24 Heterogeneity at different scales, from basin to pore.
Figure 5.25 Thickness-to-width relationships (aspect ratios) for sandstones ...
Figure 5.26 Thickness-to-width relationships (aspect ratios) for shales/muds...
Figure 5.27 The Clyde Field, UK North Sea. Schematic cross-sections before (...
Figure 5.28 Idealized log trends, assuming saltwater-filled porosity.
Figure 5.29 A well log through the Late Jurassic reservoir of the Ula Field,...
Figure 5.30 A correlation panel through part of the Carboniferous of the App...
Figure 5.31 Relative permeability. The figure shows the dramatic decline in ...
Figure 5.32 An experimental sand compaction curve compared with data on the ...
Figure 5.33 The main cements in sandstones. The data are taken from a survey...
Figure 5.34 Diagenetic mineral habits in sandstones. (a) Quartz-cemented quart...
Figure 5.35 (a) A porosity (%) versus permeability (mD) cross-plot for Fonta...
Figure 5.36 A model for the preservation of porosity and permeability by ear...
Figure 5.37 The relationship between ice-house and greenhouse conditions, eu...
Figure 5.38 A comparison of porosity and permeability for dolomitized and un...
Figure 5.39 The mineralogy of marine inorganic carbonate precipitates throug...
Figure 5.40 The solubility of carbonate sediment grains in sea water as a fu...
Figure 5.41 P-wave velocities for various lithologies.
Figure 5.42 The Poisson's ratio for various lithologies.
Figure 5.43 (a) The relationship between porosity and interval velocity for ...
Figure 5.44 A dip–azimuth display for top Mandal Mudstone (a little above to...
Figure 5.45 A seismic line overlaid with wireline curves from wells, Pederna...
Figure 5.46 A petroleum column height map, generated from combining a struct...
Figure 5.47 An object model of a meandering system. The model comprises thre...
Figure 5.48 A numerical description of a meandering system.
Figure 5.49 (a) A grid-filled model using sequential indicator simulation fo...
Figure 5.50 The variogram is a measure of the spatial correlation of a varia...
Figure 5.51 A geocellular model for the Lennox Field, East Irish Sea Basin. ...
Figure 5.52 The recovery factor: the proportion of oil or gas that can be wo...
Figure 5.53 Location map of Kadanwari Field and adjacent gas fields.
Figure 5.54 Shrinking field, (a) mapped Kadanwari Field geometry at the end ...
Figure 5.55 Location and structure of the Pedernales Field Eastern Venezuela...
Figure 5.56 Stratigraphic column for the area around the Pedernales Field.
Figure 5.57 Production profile for Pedernales from 1935 to 1985.
Chapter 6
Figure 6.1 An idealized production profile for an oilfield. Production build...
Figure 6.2 Typical, time-dependent, fluid changes in an oilfield being produ...
Figure 6.3 Well patterns used for water drive, secondary recovery.
Figure 6.4 Vertical versus horizontal wells (contrasted development methods)...
Figure 6.5 Clustered wellheads and radiating wells beneath the two productio...
Figure 6.6 Multilateral wells in the Lennox Field, East Irish Sea Basin, UK....
Figure 6.7 A sketch showing the control of permeability profile in a well on...
Figure 6.8 Artificial fracturing of wells can stimulate production by increa...
Figure 6.9 A temperature log from a production logging suite. Below the perf...
Figure 6.10 A pressure drawdown test, showing the time ranges for which vari...
Figure 6.11 A summary of well/reservoir responses to testing in different re...
Figure 6.12 Field production data represented using a “bubble” plot. The dia...
Figure 6.13 Well logs and pressure data from a well in the Brent Field, UK c...
Figure 6.14 A 3D seismic data cube, showing two orthogonal cross-sections an...
Figure 6.15 An object model of a channel belt consisting of four channels....
Figure 6.16 Seismic data can be viewed and interpreted within a visionarium....
Figure 6.17 A walk in an outcrop, Miocene sandstones, Gulf of Suez (Egypt). ...
Figure 6.18 Results of time-lapse Bayesian fluid classification for the Stat...
Figure 6.19 Time-lapse images of the CO
2
plume at Sleipner (a) N-S inline th...
Figure 6.20 Production profiles for the Fulmar Fields.
Figure 6.21 Production profile NW Hutton Field.
Figure 6.22 Production profile for the Murchison Field annotated by field ow...
Figure 6.23 Production profile (rate vs cumulative) for the Argyll Field. m
3
Figure 6.24 Cumulative production vs water oil ratio (WOR) for the Argyll Fi...
Figure 6.25 Monthly and cumulative voidage profiles Fulmar Field.
Figure 6.26 Monthly and cumulative voidage profiles Thistle Field.
Figure 6.27 Cumulative production vs WOR for the Thistle Field. Note the red...
Figure 6.28 Oil rate rise, late field life Thistle Field.
Figure 6.29 Argyll/Ardmore location map.
Figure 6.30 SW-NE depth cross section across the Ardmore Field showing the s...
Figure 6.31 Correlation of the Rotliegend interval within Block 30/24 from S...
Figure 6.32 Well locations and trajectories for the Ardmore Field developmen...
Figure 6.33 Ardmore Field production history. (
See color plate section for c
...
Chapter 7
Figure 7.1 Oil price trend since 1960.
Figure 7.2 Growth of unconventional and decline of conventional gas in the U...
Figure 7.3 Tight gas and oil reservoirs in core and thin section (blue areas...
Figure 7.4 Hyde, Clipper, and Ensign gas fields, UK North Sea.
Figure 7.5 Partially open and partially cemented fractures, Lower Permian Ro...
Figure 7.6 USA natural gas production and consumption.
Figure 7.7 USA natural gas production by source.
Figure 7.8 Pore throat sized spectrum in petroleum reservoirs. Pore throat s...
Figure 7.9 Multifrack well at Siedenberg Z17 (Germany). The well targeted Pe...
Figure 7.10 Mineralogical composition of US shale gas reservoirs (black circ...
Figure 7.11 Correlation between total organic carbon (TOC) and gas content....
Figure 7.12 Distribution of water and trapped gas in a low-saturation gas re...
Figure 7.13 Water molecules (1 gray oxygen and 2 white hydrogens) form a pen...
Figure 7.14 Phase diagrams showing the stability of gas hydrate in shallow s...
Figure 7.15 (a) The skyline to the west of Edinburgh, around Livingston, Bat...
Figure 7.16 Schematic illustration showing a possible development scheme for...
Figure 7.17 Distribution of the main halite-bearing basins in Britain and th...
Figure 7.18 Potential power output of organic Rankine cycle fueled by coprod...
Figure 7.19 Dunlin location map showing adjacent oilfields. Oil export pipel...
Figure 7.20 Mapped seismic amplitude anomalies each of which could represent...
Figure 7.21 (a) Seismic amplitude map and section across Event A. (b) The ma...
Figure 7.22 Comparison of projected production from Dunlin and satellites ba...
Figure 7.23 Lost production for the Dunlin and satellite fields due to power...
Figure 7.24 Distribution of gas fields in the UK and Dutch sectors of the So...
Figure 7.25 Cross-laminated eolian dune sandstones, well 48/19a-3 Clipper So...
Figure 7.26 Well test results from Clipper South and Clipper.
Guide
Cover
Table of Contents
Begin Reading
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Petroleum Geoscience
Jon G. Gluyas
Durham UniversityDurhamUK, DH1 3LE
Richard E. Swarbrick
Department of Earth Sciences (emeritus)Durham UniversityUK, DH1 3LE
Second Edition
This second edition first published 2021
© 2021 John Wiley & Sons Ltd
Edition History
Blackwell Publishing (1e, 2004)
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Library of Congress Cataloging-in-Publication Data
Names: Gluyas, J. G. (Jon G.), author. | Swarbrick, Richard E. Swarbrick, author.
Title: Petroleum geoscience / Jon G. Gluyas, Durham University, UK, Richard E. Swarbrick, Durham University, UK.
Description: Second edition. | Hoboken, NJ : Wiley-Blackwell, 2021. | Includes bibliographical references and index.
Identifiers: LCCN 2020025465 (print) | LCCN 2020025466 (ebook) | ISBN 9781405199605 (paperback) | ISBN 9781119232339 (adobe pdf) | ISBN 9781119232346 (epub)
Subjects: LCSH: Petroleum–Geology.
Classification: LCC TN870.5 .G58 2021 (print) | LCC TN870.5 (ebook) | DDC 553.2/8–dc23
LC record available at https://lccn.loc.gov/2020025465
LC ebook record available at https://lccn.loc.gov/2020025466
Cover Design: Wiley
Cover Image: © Jon Gluyas
Preface to Second Edition
The first edition of Petroleum Geoscience was published in 2004 having taken 10 years to write. This second edition was requested by the publishers in 2009 and again it has taken 10 years to update and write. During the time we took to write the first edition there were incremental changes to the petroleum industry, many of which we incorporated into the text as they happened. However, since 2004 the petroleum industry has undergone two radical changes as well as the incremental changes associated with improvements in technology.
The production of shale-oil and shale-gas (sometimes referred to as “unconventional” hydrocarbons) has changed the world in terms of the relationship between supply and demand for petroleum and in turn this has influenced global energy politics.
The production and combustion of petroleum and coal has changed the world in terms of the concentration of carbon dioxide in the atmosphere – now almost double pre-industrial levels. As a consequence our climate is changing. We must use less petroleum and mitigate the effects of that which is used if we are to maintain a habitable planet for all of humanity.
We will address both climate change and shale-oil/shale-gas in this preface but first let us reflect on some profound changes in our own employment circumstances in these past 10 years.
JG was in 2004 a director of Acorn Oil and Gas, a company he helped found. By late 2005 Acorn had been sold and a new company, Fairfield Energy formed. Fairfield inherited from Acorn the abandoned Maureen Field in the Central North Sea, a field of interest to a start-up company wishing to use Maureen for the geo-storage of carbon dioxide (carbon capture and storage, CCS) from a planned new power station on Teesside, north east England. The power plant was not built but industrial support for a new post at Durham University, the chair in Geoenergy and CCS, led JG to switch from industry to academia in 2009 and join the Earth Sciences Department at Durham University where he has since served as Head of Department, Dean of Knowledge Exchange, and Executive Director of the Durham Energy Institute.
RS was Reader in Petroleum Geology at Durham University in 2004, but also Founder and Managing Director of a small university start-up company, GeoPressure Technology. In 2005 he moved to work full-time with GeoPressure Technology located on the university Science site. Later GeoPressure Technology merged with Ikon Science and from 2010–2013 RS was the Global Director of GeoPressure & Geomechanics at Ikon Science. In 2013 RS left to set up his own consultancy and training company, but he is planning to retire from paid employment soon!
In the 16 years, since the first edition of this book was published, the USA has switched from being the world's largest importer of petroleum and derivative products to a modest exporter of petroleum liquids and liquified gas. This in turn led to a collapse in oil prices between 2014 and 2016 (and collateral fall in the value of coal) as competition for global market share led OPEC to try to regain the upper hand. The switch of the USA from importer to exporter of petroleum is also mirrored by the USA's foreign policy from expansive and global to introverted – it no longer needs to buy the petroleum produced by other countries.
The turnaround in petroleum production in the USA comes from the development of shale-gas and shale oil, principally facilitated by development of hydrofracturing along horizontal wells. Gas and oil are now produced from rocks, mainly hydrocarbon source rocks, once considered too impermeable to flow. Advances in drilling and completion technology have opened up vast areas of the USA (and Canada) for exploitation of this hard-to-produce resource. Other countries such as Argentina and China are beginning to exploit their resources too, but all are around 20 years behind the USA. Given the vast areas yet to be exploited in the USA and other countries it would seem the shale-gas and shale-oil revolution is a long way from being finished.
While much of the world still craves petroleum and other energy-dense fuels such as coal, the damage to the Earth's atmosphere from burning fossils fuels has become only too apparent. Carbon dioxide released to the atmosphere from burning coal, oil, and gas has led to a near doubling of the concentration of CO2 in the atmosphere (now at >400 ppm) since the beginning of the industrial revolution. The increase in CO2 and other greenhouse gases such as methane (vented and accidental leakage) is driving climate change and in particular global warming and ocean acidification. In the most recent report form the Intergovernmental Panel on Climate Change (2018) we are faced with the stark reality that humanity has little more than a decade to decarbonize its energy industry or face the irreversible consequences of increased temperatures, rising sea-levels, and significant losses of biodiversity.
And so, the largest change to occur for the petroleum industry is one of perception. To many, especially in the developed parts of the world, fossil fuels (oil, coal, and gas) are seen as bad – enemies of the environment. Greenpeace, Friends of the Earth, and other environmental lobby and projection groups have gone mainstream and in 2019 Extinction Rebellion emerged as a new force in the quest to minimize climate change. The response of many multinational oil giants as well as some of the even larger national petroleum companies has been enlightening. Business models are changing, such companies are describing themselves as “energy companies” rather than oil companies and while this may be regarded as superficial given that most expenditure still goes into finding and producing petroleum, new business streams are emerging, not least the Oil and Gas Climate Initiative (OGCI). Formed from oil majors, OGCI will begin to capture and bury carbon dioxide in industrial quantities, something that most national governments have failed to do. It seems unlikely that enough will be done to prevent major impacts from climate change – time will tell.
The problem with lessening humanity's dependence on petroleum consumption is that it has underpinned almost everything we do as a modern society. The energy density of oil and gas and the ease with which it is transported make it the energy product of choice for most applications, including transport and heating/cooling. In energy terms, petroleum is energy dense, much more so than geothermal fluids, a windy day, a lithium battery, or the sun shining upon our PV panels: it is difficult not to choose petroleum for one's energy needs. That said, and driven by real concerns about the impacts climate change will bring, carbon capture and storage, solar and geothermal energy will emerge as important energy vectors in a rapidly changing market. We have included geothermal energy and CCS sections within our new final chapter. Beyond petroleum, former petroleum geoscientists will be in demand to help realize the worth of hot water, develop storage space for CO2, and deliver the basic materials for a cleaner world.
Preface to First Edition
Wemet at AAPG London 1992 and, unknown to each other at the time, we were both facing similar problems with respect to teaching petroleum geoscience within the industry (J.G.) and academia (R.S.). The main problem was the paucity of published information on the basics of the applied science—how the geoscientist working in industry does his or her job, and with which other disciplines the geoscientist interacts. R.S. had already taken steps to remedythis with a proposal for a book on petroleum geoscience sent to Blackwell. The proposal was well received by reviewers and the then editor Simon Rallison. Simon sought an industry-based coauthor and found one in J.G. At that time, J.G. was teaching internal courses at BP to drillers, reservoir engineers, petroleum engineers, and budding geophysicists with a physics background. Simon's invitation was accepted and by early 1994 work had begun. It seemed like a good idea at the time, but the petroleum industry was changing fast, nowhere more so than in the application of geophysics, stratigraphicgeology, and reservoir modeling. The use of 3D seismic surveys was changing from being rare to commonplace, 4D time-lapse seismic was being introduced, and multi-component seismic data was also beginning to find common use. Derivativeseismic data were also coming to the fore, with the use of acoustic impedance, amplitude versus offset, and the like. The application of sequencestratigraphic principles was becoming the norm. Reservoir models were increasing in complexity manifold, and they were beginning to incorporate much more geologic information than had hitherto been possible. Along side the technological changes, there were also changes in the business as a whole. Frontier exploration was becoming less dominant, and many geoscientists were finding themselves involved in the rehabilitation of old oilfields as new geographies opened in the former Soviet Union and South America. It was tough to keep pace with these changes in respect of writing this book, but as the writing progressed it became even clearer that information on the above changes was not available in textbooks. We hope to have captured it for you! This book is written for final-year undergraduates, postgraduate M.Sc. and Ph.D. students, and non-geologic technical staff within the petroleum industry.
Jon G. Gluyas
Department of Earth Sciences
Durham University
UK
Richard E. Swarbrick
Department of Earth Sciences (emeritus)
Durham University
UK
Acknowledgments
Producing a second edition of Petroleum Geoscience has been a long, arduous and at times thankless journey, unassisted by numerous changes in computer hardware and software since the first edition was produced. With help from Wiley we eventually managed to track down image files of the original figures but for many they were originally constructed using software that no longer exists, or at least was not accessible to us. Editing was not an option. We had to start from scratch. We thank Antony Sami and a string of earlier editors at Wiley for digging deep into archives inherited from Blackwell to find most of the original material.
Mike Bowman (long-term BP employee and now retired) was a huge help with the first edition and he was on hand to supply most of the material we needed for the new Thunder Horse case history in Chapter 4. We also need to thank senior staff at Lundin for verifying the material used in the Johan Sverdrup case history (Chapter 3) and at Tullow for the review of the information used in the Jubilee case history (Chapter 3).
The biggest thanks though go to Theresa Gluyas and Alison Swarbrick, our wives. That we have now completed the second edition is down to their support, encouragement, and at times well-directed instructions to, “get on with it,” thank you!
1Introduction
1.1 The Aim and Format of the Book
The aim of this book is to introduce petroleum geoscience to geologists, be they senior undergraduates or postgraduates, and to non-geologists (petrophysicists, reservoir engineers, petroleum engineers, drilling engineers, and environmental scientists) working in the petroleum industry. We define petroleum geoscience as the disciplines of geology and geophysics applied to understanding the origin and distribution and properties of petroleum and petroleum-bearing rocks. The book will deliver the fundamentals of petroleum geoscience and allow the reader to put such information into practice.
The format of the book follows the path known within the oil industry as the “value chain.” This value chain leads the reader from frontier exploration through discovery to petroleum production. Such an approach is true to the way in which industry works; it allows the science to evolve naturally from a start point of few data to an end point of many data. It also allows us to work from the larger basin scale to the smaller pore scale, and from the initial superficial analysis of a petroleum-bearing basin to the detailed reservoir description.
Case histories are used to support the concepts and methods described in the chapters. Each case history is a complete story in itself. However, the case histories also form part of the value chain theme. Specific emphasis is placed upon the problems presented by exploration for and production of petroleum. The importance and value of data are examined, as are the costs, both in time and money, of obtaining data.
1.2 Background
Petroleum geoscience is intimately linked with making money, indeed profit. The role of the petroleum geoscientist, whether in a state oil company, a massive multinational company, or a small independent company, is to find petroleum (oil and hydrocarbon gas) and help produce it so that it can be sold.
In years past, geoscientists overwhelmingly dominated the bit of the industry that explores for petroleum – they have boldly gone to impenetrable jungles, to scorching deserts, and to hostile seas in the search for petroleum. Getting the oil and gas out of the ground – that is, production – was left largely to engineers.
Today, the situation is different. Geoscience is still a key part of the exploration process, but finding oil and gas is more difficult than it used to be. There are many fewer giant oilfields to be discovered. The geoscientists now need to work with drilling engineers, reservoir engineers, petroleum engineers, commercial experts, and facilities engineers to determine whether the petroleum that might be discovered is likely to be economical to produce as crude oil for market.
Geoscientists now also play an important role in the production of petroleum. Oilfields and gasfields are not simply tanks waiting to be emptied. They are complex three-dimensional (3D) shapes with internal structures that will make petroleum extraction anything but simple. The geoscientist will help describe the reservoir and the trapped fluids. Geoscientists will also help determine future drilling locations and use information from petroleum production to help the interpretation of reservoir architecture.
1.3 What Is in this Book
This book is aimed at satisfying the needs of undergraduates who wish to learn about the application of geoscience in the petroleum industry. It is also aimed at nongeoscientists (petrophysicists, reservoir engineers, and drilling engineers) who, on account of their role in the old industry, need to find out more about how geologists and geophysicists ply their trade.
The book is divided into seven chapters. The first chapter introduces both the book and the role of petroleum geoscience and geoscientists in industry. It also includes a section on the chemistry of oil. Chapter 2 examines the tools used by petroleum geoscientists. It is brief, since we intend only to introduce the “tools of the trade.” More detail will be given in the body of the later chapters and in the case histories as needed.
Chapters 3 through 7 comprise the main part of the book. Chapters 3 and 4 cover exploration. We have chosen to divide exploration into two chapters for two reasons. To include all of the petroleum geoscience associated with exploration in one chapter would have been to create a massive tome. Moreover, it is possible to divide the exploration geoscience activity into basin description and petroleum exploration. Chapter 3 contains the basin description, with the addition of material on acreage acquisition and a section on possible shortcuts to finding petroleum. The final section of Chapter 3 is about petroleum source rocks, where they occur, and why they occur. Chapter 4 opens with sections on the other key components of petroleum geoscience; that is, the petroleum seal, the petroleum reservoir, and the petroleum trap. The second half of Chapter 4 examines the spatial and temporal relationships between reservoir and seal geometries and migrating petroleum. Risk (the likelihood of a particular outcome) and uncertainty (the range of values for a particular outcome) are both intrinsic parts of any exploration, or indeed appraisal, program. These too are examined.
Once a discovery of petroleum has been made, it is necessary to find out how much petroleum has been found and how easily oil or gas will flow from the field. This is appraisal, which is treated in Chapter 5. During appraisal, a decision will be made on whether to develop and produce the field under investigation. The geoscience activity associated with development and production is covered in Chapter 6. Since publication of the first edition in 2003, the term unconventional petroleum has come into common usage within the industry and particularly within the news media and we have recognized this by extracting material on unconventional petroleum from Chapter 6 and adding new material to produce Chapter 7.
1.4 What Is Not in this Book
The book introduces petroleum geoscience, a discipline of geoscience that embraces many individual and specialist strands of earth science. We deal with aspects of all these strands, but these important topics – such as basin analysis, stratigraphy, sedimentology, diagenesis, petrophysics, reservoir simulation, and others – are not covered in great detail. Where appropriate, the reader is guided to the main texts in these sub-disciplines and there are also suggestions for further reading.
1.5 Key Terms and Concepts
The source, seal, trap, reservoir, and timing (of petroleum migration) are sometimes known as the “magic five ingredients” without which a basin cannot become a petroleum province (Figure 1.1). Here, we introduce these and other essential properties, before examining each aspect in more detail in the chapters that follow.
1.5.1 Petroleum
Petroleum is a mixture of hydrocarbon molecules and lesser quantities of other organic molecules containing sulfur, oxygen, nitrogen, and some metals. The term includes both oil and hydrocarbon gas. The density of liquid petroleum (oil) is commonly less than that of water and the oil is naturally buoyant. So-called heavy (high specific gravity) oils and tars may be denser than water. Some light (low specific gravity) oils are less viscous than water, while most oils are more viscous than water. The composition of petroleum and its properties are given in Section 1.6.
1.5.2 The Source
A source rock is a sedimentary rock that contains sufficient organic matter such that when it is buried and heated it will produce petroleum (oil and gas). High concentrations of organic matter tend to occur in sediments that accumulate in areas of high organic matter productivity and stagnant water. Environments of high productivity can include nutrient rich coastal upwellings, swamps, shallow seas, and lakes. However, much of the dead organic matter generated in such systems is scavenged and recycled within the biological cycle. To preserve organic matter, the oxygen contents of the bottom waters and interstitial waters of the sediment need to be very low or zero. Such conditions can be created by overproduction of organic matter, or in environments where poor water circulation leads to stagnation.
Different sorts of organic matter yield different sorts of petroleum. Organic matter rich in soft and waxy tissues, such as that found in algae, commonly yields oil with associated gas on maturation (heating), while gas alone tends to be derived from the maturation of woody tissues. Even oil-prone source rocks yield gas when elevated to high temperatures during burial. A detailed description of source rocks and source rock development can be found in Section 3.7. Most source rocks expel petroleum as it is generated. However, all source rocks retain at least some of the petroleum generated and it is typically these which may be exploited as the so-called unconventional shale-gas and shale-oil deposits.
Figure 1.1 A cartoon cross-section of part of a petroleum-bearing basin. Most of the “key terms” described in the text are shown pictorially.
1.5.3 The Seal
Oil and gas are less dense than water and, as such, once they migrate from the source rock they tend to rise within the sedimentary rock column. The petroleum fluids will continue to rise under buoyancy until they reach a seal. Seals tend to be fine-grained or crystalline, low-permeability rocks. Typical examples include mudstone/shale, cemented limestones, cherts, anhydrite, and salt (halite). As such, many source rocks may also be high-quality seals. Seals to fluid flow can also develop along fault planes, faulted zones, and fractures.
The presence of a seal or seals is critical for the development of accumulations of petroleum in the subsurface. In the absence of seals, petroleum will continue to rise until it reaches the Earth's surface. Here, surface chemical processes including bacterial activity will destroy the petroleum. Although seals are critical for the development of petroleum pools, none are perfect. All leak. This natural phenomenon of petroleum seepage through seals can provide a shortcut to discovering petroleum. Seals and seal mechanisms are described in Section 4.2.
1.5.4 The Trap
The term “trap” is simply a description of the geometry of the sealed petroleum-bearing container (Section 4.5). Buoyant petroleum rising through a pile of sedimentary rocks will not be trapped even in the presence of seals if the seals are, in gross geometric terms, concave-up. Petroleum will simply flow along the base of the seal until the edge of the seal is reached, and then it will continue upwards toward the surface. A trivial analogy, albeit inverted, is to pour coffee onto an upturned cup. The coffee will flow over but not into the cup. However, if the seal is concave-down it will capture any petroleum that migrates into it.
The simplest trapping configurations are domes (four-way dip-closed anticlines) and fault blocks. However, if the distribution of seals is complex, it follows that the trap geometry will also be complex. The mapping and remapping of trap geometry is a fundamental part of petroleum geoscience at the exploration, appraisal, and even production phases of petroleum exploration.
1.5.5 The Reservoir
A reservoir is the rock plus void space contained in a trap. Traps rarely enclose large voids filled with petroleum; oil-filled caves, for example, are uncommon. Instead, the trap contains a porous and permeable reservoir rock. The petroleum together with some water occurs in the pore spaces between the grains (or crystals) in the rock. Reservoir rocks are most commonly sandstones or carbonates, although source rocks themselves can act as reservoirs as can more exotic lithologies such as fractured granites and gneiss. Viable reservoirs occur in many different shapes and sizes, and their internal properties (porosity and permeability) also vary enormously (Section 4.3).
1.5.6 The Timing of Petroleum Migration
We have already introduced the concept of buoyant petroleum migrating upward from the source rock toward the Earth's surface. Seals in suitable trapping geometries will arrest migration of the petroleum. When exploring for petroleum it is important to consider the timing of petroleum migration relative to the time of deposition of the reservoir/seal combinations and the creation of structure within the basin. If migration of petroleum occurs before deposition of a suitable reservoir/seal combination, then the petroleum will not be trapped. If petroleum migrates before structuring in the basin creates suitable trap geometries, then the petroleum will not be trapped. In order to determine whether the reservoir, seal, and trap are available to arrest migrating petroleum, it is necessary to reconstruct the geologic history of the area under investigation. Petroleum migration is examined in Section 4.4.
1.5.7 Porous Rock and Porosity
A porous rock has the capacity to hold fluid. By definition, reservoirs must be porous. Porosity is the void space in the rock, reported either as a fraction of one or as a percentage. Most reservoirs contain >0% to <40% porosity.
1.5.8 Permeable Rock and Permeability
A permeable rock has the capacity to transmit fluid. A viable reservoir needs to be permeable or the petroleum will not be extracted. By definition, a seal needs to be largely impermeable to petroleum. Permeability is a measure of the degree to which fluid can be transmitted. The unit for permeability used in the petroleum industry is the darcy (D), although the permeability of many reservoirs is measured in millidarcies (mD). Typically, the permeability of reservoirs is 10 D or less. At the lower end, gas may be produced from reservoirs of 0.1 mD, while oil reservoirs need to be 10× or 100× more permeable. The darcy is not an SI unit but like other measures of permeability its units are the same as area and it is equivalent to 9.689 233 × 10−13 m2.
1.5.9 Relative Permeability
Most reservoirs contain both oil and water in an intimate mixture. A consequence of there being more than one fluid in the pore system is that neither water nor oil will flow as readily as if there were only one phase. Such relative permeability varies as a function of fluid phase abundance.
1.5.10 Net to Gross and Net Pay
A reservoir commonly contains a mixture of nonreservoir lithologies (rocks) such as mudstone or evaporite minerals interbedded with the reservoir lithology, commonly sandstone or limestone. The ratio of the porous and permeable interval to the nonporous and/or nonpermeable interval is called the “net to gross.” Net pay is the portion of the net reservoir containing petroleum and from which petroleum will flow.
1.5.11 Water Saturation
A petroleum-bearing reservoir always contains some water. The quantity of water is commonly expressed as a fraction or percentage of the pore space. There are, of course, comparable terms for oil and gas.
1.5.12 Formation Volume Factor
The formation volume factor is the volume of the petroleum in the trap divided by the volume of the same mass of petroleum at the Earth's surface under conditions of standard temperature and pressure (25 °C and 1 atm). The increase in pressure at depth means that gas occupies less volume in the subsurface. However, the situation differs for most oils which shrink when raised from the trap to the surface. This is because most oils contain dissolved gas and as the pressure is lowered there comes a pressure known as the bubble point when gas starts to exsolve. The gas expands and in consequence the oil shrinks.
Most oils have formation volume factors of between 1 and 2. Gases typically have formation volume factors of 0.003–0.01. The inverse of these figures for gas are commonly quoted and called the gas expansion factor.
