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IntroductionIntroduction
HS&EHS&E
TimetableTimetable
Ground rulesGround rules
New Faces !!New Faces !!
StuartStuart -- http://http://peoplelink/ViewEmployee.asp?Idpeoplelink/ViewEmployee.asp?Id=6196=6196
How was yesterday for you ?How was yesterday for you ?
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Road MapRoad Map
Principles, then ToolsPrinciples, then Tools
Geology; then the Oil RigGeology; then the Oil Rig
Starting small then getting to the largerStarting small then getting to the largerpartsparts
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Turn off Mobile phonesTurn off Mobile phones Ask questions and share experiencesAsk questions and share experiences Return from breaks on timeReturn from breaks on time Have Fun!Have Fun!
Humor is good!Humor is good! RelaxRelax No side conversationsNo side conversations What is said here, stays hereWhat is said here, stays here
ParticipateParticipate House keepingHouse keeping Others.Others.
Ground RulesGround Rules
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Dont tell me, but which of the following areDont tell me, but which of the following are
you ? you ? Prisoner ?Prisoner ?
Passenger or HolidayPassenger or Holiday-- maker ?maker ?
Explorer ?Explorer ?
re you n e correc room
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Whilst youre here..Whilst youre here..
Learning..Learning..
PANIC ZONE
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Learning to LearnLearning to Learn
Things youknow
Things you needto find out
Things you
didnt know youknew
Things you findout unexpectedly
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IntroductionIntroduction
OKOK -- CLEAR THE DESKS !!CLEAR THE DESKS !!
Youll need notebook and aYoull need notebook and acalculatorcalculator
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Quick Quiz !Quick Quiz !
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Geology IntroductionGeology Introduction
Island arc
Ocean
spreading ridge
Subduction zone
Basin
Mountains
formed along a
collision zone
Terrain rafted
onto continent
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RouteRoute
Reservoir porosity & permeabilityReservoir porosity & permeability
Rock typesRock types
TrapsTraps
StructuresStructures Seeing structuresSeeing structures
Planning drillingPlanning drilling
Drilling with a rigDrilling with a rig
Th R iTh R i
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The ReservoirThe Reservoir
S lid SSolid Space
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Solid + SpaceSolid + Space
Matrix Hydrocarbons (?) Water
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Matrix + Hydrocarbons (?) + Water
ReservoirsReservoirs
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ReservoirsReservoirs
Critical characteristics of a petroleum reservoir rock :Critical characteristics of a petroleum reservoir rock :
Thickness andThickness and arealareal extentextent -- gross rock volumegross rock volume
Percentage of pore spacePercentage of pore space -- potential fluid volumepotential fluid volume
Fluid SaturationFluid Saturation -- percentage of water vpercentage of water v hydocarbonshydocarbons
PermeabilityPermeability -- ability to flow the contained fluidability to flow the contained fluid
PorosityPorosity
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PorosityPorosity
Porosity (%)Porosity (%) == Pore VolumePore Volume x 100x 100
Total Rock VolumeTotal Rock Volume
PrimaryPrimary - originates at the time of depositionoriginates at the time of deposition
egeg.. intergranularintergranular sandstone porositysandstone porosity
SecondarySecondary - postpost--depositional due to chemical or physicaldepositional due to chemical or physical
changeschanges egeg.. dolomitisationdolomitisation of limestones, fracturingof limestones, fracturing
Total PorosityTotal Porosity - Connected and nonConnected and non--connected pore spaceconnected pore space
Effective PorosityEffective Porosity -- Connected pore space onlyConnected pore space only
P it &P kiP it &P ki
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Porosity &PackingPorosity &Packing
CUBICCUBIC RHOMBOHEDRALRHOMBOHEDRAL
P it & P kiP it & P ki
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Porosity & PackingPorosity & Packing
Mix of Cubic ofMix of Cubic ofRhombohedralRhombohedral
packingpacking
Q: How could thisQ: How could this
occur in the field ?occur in the field ?
R i P ti lReservoir Practical
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Reservoir PracticalReservoir Practical
Exercise in measuring reservoir propertiesExercise in measuring reservoir properties --
PorosityPorosity
Contents of the exerciseContents of the exercise
Porosity to be measured (unknown)Porosity to be measured (unknown) Salt waterSalt water
ReservoirReservoir
Electric currentElectric current MeasurementMeasurement
Your ReservoirsYour Reservoirs
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Your ReservoirsYour Reservoirs
Your ReservoirsYour Reservoirs
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Your ReservoirsYour Reservoirs
Your Reservoir shapesYour Reservoir shapes
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Your Reservoir shapesYour Reservoir shapes
12.5 cm
12.5 cm
TerminologyTerminology
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TerminologyTerminology
R = ResistivityR = Resistivity
S = SaturationS = Saturation
s = shoulder beds = shoulder bed
i = invaded zonei = invaded zone
xo = Flushed Zonexo = Flushed Zone
mc = Mud cakemc = Mud cake
h = thicknessh = thickness
w = formation waterw = formation water
d = diameterd = diameter
z = mixed waterz = mixed water
o = 100% Watero = 100% Watersaturated nonsaturated non--
invaded zoneinvaded zone
TerminologyTerminology
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TerminologyTerminology
These are usually paired examples:These are usually paired examples:
RRxoxo = Resistivity of the flushed zone= Resistivity of the flushed zone
SSxoxo = Saturation of the flushed zone= Saturation of the flushed zone
R i ti it T i lR i ti it T i l
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Resistivity TerminologyResistivity Terminology
Practical MeasurementsPractical Measurements
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Practical MeasurementsPractical Measurements
In turn, take the Resistivity on each of the targets between theIn turn, take the Resistivity on each of the targets between the
contacts.contacts.
With the distance of 12.5cm between the contacts multiply theWith the distance of 12.5cm between the contacts multiply the
Resistivity by 8 ; this will generateResistivity by 8 ; this will generate OhmmOhmm
The measurement was taken in 100% water zone; what hasThe measurement was taken in 100% water zone; what has
been measured ?been measured ?
Measure the Resistivity in the control sample in the front of thMeasure the Resistivity in the control sample in the front of thee
class inclass in OhmmOhmm. What is this the equivalent of ?. What is this the equivalent of ?
Why is there a difference between the control sample of waterWhy is there a difference between the control sample of water
and the containers ?and the containers ?
Fluid SaturationFluid Saturation
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Fluid SaturationFluid Saturation
Resistivity of formation waterResistivity of formation water == RwRw
Resistivity of rock and waterResistivity of rock and water = Ro= Ro
Ro = F xRo = F x RwRwwherewhere F = formation factorF = formation factor
F = a /F = a /mm
wherewhere = porosity= porosity
a &a &mm = rock constants= rock constants (typically 1 & 2 respectively)(typically 1 & 2 respectively)
Resistivity of rock, water and HCResistivity of rock, water and HCs =s = RtRt
Water saturationWater saturation ((SwSw)) = Water Volume / Total Fluid Volume= Water Volume / Total Fluid Volume
SwSwnn = Ro /= Ro /RtRtwhere n = saturation exponentwhere n = saturation exponent (typically 2)(typically 2)
Hydrocarbon saturationHydrocarbon saturation ((ShcShc)) = Hydrocarbon volume / Total Fluid Volume= Hydrocarbon volume / Total Fluid Volume
ShcShc = (1= (1 -- SwSw))
ArchieArchie Clean SandClean Sand EquationEquation
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Hydrocarbon Sand, RtWater Sand, Ro
ArchieArchie Clean SandClean Sand EquationEquation
Rt
RoSw
n=
Ro=
m
Rwa
x
Rwax
m Rt
Swn=
From Your ResultsFrom Your Results
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From Your ResultsFrom Your Results
Resistivity of formation waterResistivity of formation water == RwRw (Control sample)(Control sample)
Resistivity of rock and waterResistivity of rock and water = Ro= Ro
Ro = F xRo = F x RwRw
wherewhere F = formation factorF = formation factor
F = a /F = a / FF mm
wherewhere FF = porosity= porosity
a &a & mm= rock constants= rock constants (typically 1 & 2 respectively)(typically 1 & 2 respectively)RESULTS ??RESULTS ??
Just checkJust check
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Just checkJust check
From all the canisters with glass beads carefully poor the wateFrom all the canisters with glass beads carefully poor the waterr
into the measuring jugs and read the volume.into the measuring jugs and read the volume.
The original round canisters contained 1.9 litres the smallerThe original round canisters contained 1.9 litres the smallercontainer holds 1.6 litrescontainer holds 1.6 litres
What percentage of fluids did you get back ? How good areWhat percentage of fluids did you get back ? How good are
your results ?your results ?
For the large container with large stones in it.For the large container with large stones in it.
Resistivity values on the bottom connection ?Resistivity values on the bottom connection ?
Resistivity value on the top connection ?Resistivity value on the top connection ?
In the container full with wet sand What is the approximateIn the container full with wet sand What is the approximate
porosity ?porosity ?
PermeabilityPermeability
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yy
Permeability (k) = measure of ease of fluid flow through the conPermeability (k) = measure of ease of fluid flow through the connecting porenecting pore
space of the reservoir rockspace of the reservoir rock
kk = Q.u / A (delta P / L)= Q.u / A (delta P / L)
QQ = flow rate (cm/s)= flow rate (cm/s)
uu = fluid viscosity (cp)= fluid viscosity (cp)
AA = cross sectional area of rock (cm2)= cross sectional area of rock (cm2)
LL = length of rock (cm)= length of rock (cm)delta Pdelta P = pressure drop= pressure drop
Unit of measure = DarcyUnit of measure = Darcy
One Darcy = when 1 cc fluid of 1 cp viscosity flows through 1 cmOne Darcy = when 1 cc fluid of 1 cp viscosity flows through 1 cm3 of3 of
rock in 1 sec, under a pressure gradient of 1 barrock in 1 sec, under a pressure gradient of 1 bar
Note : Viscosity of water at 20 C = 1 centipoise (cp)Note : Viscosity of water at 20 C = 1 centipoise (cp)
PermeabilityPermeability
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yy
Gamma ray logshale increasing
Rocktype
PorosityPermeability
in millidarcies
Tarbert
Ness
Etive
Rannoch
Broom
23-26%
16-27%
21-27%
23-28%
500-2000
50-2000
100-3000
10-1000
Note : Both porosity and permeability are adversely affected by compaction, cementation
and clay mineral content
Rock TypesRock Types
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ypyp
ChemicalChemical
CarbonateCarbonate
ClasticClastic
MetamorphicMetamorphic
VolcanicVolcanic
Chemical RocksChemical Rocks
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Evaporite Sedimentary RocksEvaporite Sedimentary Rocks
Sedimentary rocks can form from the deposition ofSedimentary rocks can form from the deposition ofinorganically precipitated salts, usually due to evaporation ofinorganically precipitated salts, usually due to evaporation oflake or seawater in arid environments.lake or seawater in arid environments.
Evaporite Minerals (in order of precipitation from seawater)Evaporite Minerals (in order of precipitation from seawater)
Calcium Carbonate (.3%)Calcium Carbonate (.3%) Calcium Sulphate (3.5%)Calcium Sulphate (3.5%) -- gypsum (saturated) and anhydritegypsum (saturated) and anhydrite
(dehydrated)(dehydrated)
Primary gypsum forms large, clear crystals of selenitePrimary gypsum forms large, clear crystals of selenite
ReRe--hydrated anhydrite forms fine crystals of alabasterhydrated anhydrite forms fine crystals of alabaster
Sodium Chlorite (78%)Sodium Chlorite (78%)
Potash salts (e.g..Potash salts (e.g.. KClKCl) (18%)) (18%)
Chemical RocksChemical Rocks
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ChertsCherts
Cherts are hard, aphanitic rocks made up of siltCherts are hard, aphanitic rocks made up of silt--sized quartzsized quartzcrystals (microcrystals (micro-- or cryptocrystalline quartz) and chalcedony, aor cryptocrystalline quartz) and chalcedony, aform of silica made up of radiating fibers tens to hundreds ofform of silica made up of radiating fibers tens to hundreds ofmicrons in length.microns in length.
Chert in sedimentary rock can be either diagenetic or primary.Chert in sedimentary rock can be either diagenetic or primary.
Diagenetic chert: generally occur as nodules or irregular beds,Diagenetic chert: generally occur as nodules or irregular beds,
usually in limestones or sometimes in mudstones. Chertusually in limestones or sometimes in mudstones. Chertnodules probably form by mineral replacement around nucleinodules probably form by mineral replacement around nucleiof crystallization, with additional dissolved silica arriving byof crystallization, with additional dissolved silica arriving bydiffusion.diffusion.
Primary (depositional) chert: Layers of siliceous ooze canPrimary (depositional) chert: Layers of siliceous ooze canaccumulate where the influx of siliceous particles (usually theaccumulate where the influx of siliceous particles (usually the
microscopic silica tests of radiolarians or diatoms) is muchmicroscopic silica tests of radiolarians or diatoms) is muchgreater than the influx of any other sedimentary particle. Mostgreater than the influx of any other sedimentary particle. Mostcommonly this occurs in deep ocean environments below thecommonly this occurs in deep ocean environments below thedepth at which calcium carbonate is insoluble (the carbonatedepth at which calcium carbonate is insoluble (the carbonatecompensation depth or CCD). Usually, primary chert occurs ascompensation depth or CCD). Usually, primary chert occurs asthin beds, interbedded with clay layers.thin beds, interbedded with clay layers.
Chemical RocksChemical Rocks
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Sedimentary IronstonesSedimentary Ironstones
Iron is a common element in the Earth' crust. SedimentaryIron is a common element in the Earth' crust. Sedimentary
rocks that contain more than 15% iron are called ironstones.rocks that contain more than 15% iron are called ironstones.
HaematiteHaematite -- GoethiteGoethite -- PyritePyrite --SideriteSiderite -- GlauconiteGlauconite
Chemical RocksChemical Rocks
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Carbonaceous (organic) depositsCarbonaceous (organic) deposits
Sedimentary layers rich in carbon (not to be confused withSedimentary layers rich in carbon (not to be confused with carbonatecarbonate--
rich deposits, which are calledrich deposits, which are called calcareouscalcareous).).
Peat.Peat.
CoalCoal -- The material making up the organic components of coal areThe material making up the organic components of coal arecalledcalled maceralsmacerals..
VitriniteVitrinite -- woody materialwoody material -- stems, leaves, branches, roots)stems, leaves, branches, roots)
ExiniteExinite -- spores, cuticles, resin, algaespores, cuticles, resin, algae InertiniteInertinite -- partially oxidized material, including charcoal (partially oxidized material, including charcoal (fusinitefusinite))
With burial,With burial, humichumic peatspeats (composed mainly of(composed mainly of vitrainvitrain) are) are
progressively altered duringprogressively altered during coalificationcoalification to produce a sequence ofto produce a sequence of
increasing carbon concentration and therefore energy value:increasing carbon concentration and therefore energy value:
PeatPeat -- lignite (brown coal)lignite (brown coal) subsub--bituminousbituminous -- bituminousbituminous -- anthraciteanthracite Oil shaleOil shale -- MudrocksMudrocks with a high proportion of organic material alteredwith a high proportion of organic material altered
to hydrocarbon. Also calledto hydrocarbon. Also called petroliferous shale.petroliferous shale.
Chemical RocksChemical Rocks
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Table discussion 5 minutes:Table discussion 5 minutes:
Where do we get chemical rocks formingWhere do we get chemical rocks forming
today ?today ?
Carbonate RocksCarbonate Rocks
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Carbonates (limestones and dolostones)Carbonates (limestones and dolostones)
rocks composed of particles of calcium carbonate or calciumrocks composed of particles of calcium carbonate or calcium
magnesium carbonatemagnesium carbonate second most abundant type of rock after clasticssecond most abundant type of rock after clastics
source of most carbonate material is biogenic, but some aresource of most carbonate material is biogenic, but some arechemical precipitateschemical precipitates
Carbonate mineralsCarbonate minerals
Calcite (trigonal crystal)Calcite (trigonal crystal)
high magnesium (11%high magnesium (11% -- 19% magnesium substitution)19% magnesium substitution) -- lesslessstablestable
low magnesium (0%low magnesium (0% -- 4% magnesium substitution)4% magnesium substitution) -- mostmoststablestable
Strontium also substitutes, but less than 1%Strontium also substitutes, but less than 1%
Aragonite (orthorhombic crystal)Aragonite (orthorhombic crystal) -- unstable, willunstable, will recrystallizerecrystallize totocalcitecalcite
DolomiteDolomite -- calcium magnesium carbonate, forms as acalcium magnesium carbonate, forms as a
replacement of calcite and aragonitereplacement of calcite and aragonite
Carbonate RocksCarbonate Rocks
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Carbonate Rock ClassificationCarbonate Rock Classification --
based on texture and grain typebased on texture and grain type
TextureTexture -- based on a classificationbased on a classificationdeveloped by Dunham in the earlydeveloped by Dunham in the early
'60s.'60s.
Dunham's classification isDunham's classification is
particularly useful for describingparticularly useful for describingcarbonate rocks in hand specimencarbonate rocks in hand specimen
and in outcrop. In addition to theand in outcrop. In addition to the
four main textures describingfour main textures describing
rocks with originally unboundrocks with originally unbound
sediments, there are a variety ofsediments, there are a variety oftextures used to describetextures used to describe
carbonate strata with large, organiccarbonate strata with large, organic
structures that trapped and boundstructures that trapped and bound
sediment during depositionsediment during deposition((boundstonesboundstones).).
CarbonatesCarbonates
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Carbonate Grain Types (Carbonate Grain Types (allochemsallochems))
Dunham's classification is primarily based on texture. It can beDunham's classification is primarily based on texture. It can beexpanded by incorporating description of the types of carbonateexpanded by incorporating description of the types of carbonate
grains present (see handout).grains present (see handout). Skeletal grainsSkeletal grains -- pieces of carbonate skeletal material (see below)pieces of carbonate skeletal material (see below)
NonNon--skeletal grains:skeletal grains:
OoidsOoids -- concentrically layered spheres of calcite less than 2mm in sizeconcentrically layered spheres of calcite less than 2mm in size
PisoidsPisoids -- ooidsooids larger than 2mmlarger than 2mm
PeloidsPeloids -- spherical to irregularly rounded pellets ofspherical to irregularly rounded pellets of micritemicrite withoutwithoutinternal structureinternal structure
OncoidsOncoids -- similar tosimilar to pisoidspisoids, but with an irregular internal structure, but with an irregular internal structure
IntraclastsIntraclasts -- fragments of reworked, partiallyfragments of reworked, partially lithifiedlithified carbonatecarbonate
MicriteMicrite -- lime mud; carbonate particles less than 4 mm in diameter.lime mud; carbonate particles less than 4 mm in diameter.
SparSpar -- a clear carbonate cement that precipitates between grains aftera clear carbonate cement that precipitates between grains after
deposition.deposition. CarbonateCarbonate intraformationalintraformational conglomeratesconglomerates -- these are calledthese are called floatstonefloatstone
oror rudstonerudstone in Dunham's classification, depending on the density ofin Dunham's classification, depending on the density oflargelarge intraclastsintraclasts..
CarbonatesCarbonates
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Important Biological Producers of Carbonate SedimentImportant Biological Producers of Carbonate Sediment
Animals (skeletal fragments)Animals (skeletal fragments)
MolluscsMolluscs (bivalves, gastropods, cephalopods, etc.)(bivalves, gastropods, cephalopods, etc.)
BrachiopodsBrachiopods
Echinoids and crinoids (echinoderms)Echinoids and crinoids (echinoderms)
CoralsCorals
ForaminiferaForaminifera
AlgaeAlgae Red algae (encrusting)Red algae (encrusting)
Green algae (benthic andGreen algae (benthic and planktonicplanktonic))
YellowYellow--green algae (green algae (coccolithophorescoccolithophores))
CyanobacteriaCyanobacteria -- these organisms are important because they formthese organisms are important because they form
mats that trap and bind carbonate mud, producingmats that trap and bind carbonate mud, producing stromatolitesstromatolites (a(a
type oftype of biohermbioherm oror biostromebiostrome structure). Also, some types ofstructure). Also, some types of
cyanobacteriacyanobacteria bore into skeletal debris and break down the shellbore into skeletal debris and break down the shell
material into tiny rods of calcite mud (material into tiny rods of calcite mud (micritizationmicritization).).
CarbonatesCarbonates
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Table discussionTable discussion 5 minutes5 minutes
Where do we get carbonate rocksWhere do we get carbonate rocks
forming today ?forming today ?
TERMS TO AVOIDTERMS TO AVOID
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CHALKCHALK
MARLMARL
CLASTIC ROCKSCLASTIC ROCKS
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Rocks made from broken fragments of other rocksRocks made from broken fragments of other rocks
Usually silicate mineral structures because theyUsually silicate mineral structures because theysurvivesurvive
Sometimes you hear the termSometimes you hear the term siliciclasticsiliciclastic in connection within connection with clasticclastic
rocks because their most common components, quartz & feldspar arrocks because their most common components, quartz & feldspar aree
silica (SiO2) containing minerals.silica (SiO2) containing minerals.
Argillaceous rock : microscopic grainsArgillaceous rock : microscopic grains 1/16mm1/16mm
Arenaceous rocks : 1/16mmArenaceous rocks : 1/16mm 2.0mm2.0mm
Rudaceous rocks : particle size greater than 2.0mmRudaceous rocks : particle size greater than 2.0mm
Clastic rocksClastic rocks
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Describe the rock sample given to youDescribe the rock sample given to you
Proper Order:
Rock type
Classification
Colour
Hardness or induration
Grain size
Grain shape
Sorting
Classification & ColourClassification & Colour
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ClassificationClassification
ClasticsClastics CarbonatesCarbonates
ChemicalChemical
ColourColour
Red and brownRed and brown
ferric ironferric iron
oxidizing environmentoxidizing environment
Green and greyGreen and grey
ferrous ironferrous iron reducing environmentreducing environment
Dark brownDark brown
organic materialorganic material
possible source rockpossible source rock
BlackBlack
anaerobic environmentanaerobic environment
Hardness andHardness and IndurationInduration
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Rudaceous & ArenaceousRudaceous & Arenaceous
UnconsolidatedUnconsolidated
FriableFriable
crumbles with light pressurecrumbles with light pressure
grains easy to separategrains easy to separate
Moderately hardModerately hard
grains detach with probegrains detach with probe cuttings break with pressurecuttings break with pressure
HardHard
grains difficult to detachgrains difficult to detach
Extremely hardExtremely hard
grains cannot detachgrains cannot detach
breakage through grainsbreakage through grains
ArgillaceousArgillaceous
SolubleSoluble
Readily dispersed by waterReadily dispersed by water SoftSoft
no shape or strengthno shape or strength
PlasticPlastic
easily molded & holdseasily molded & holds
shapeshape hard to wash through sievehard to wash through sieve
FirmFirm
definatedefinate shapeshape
easily penetrated by probeeasily penetrated by probe
HardHard sharp angular edgessharp angular edges
not easily penetratednot easily penetrated
More on Colour &More on Colour & IndurationInduration
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ColourColour Other terms in useOther terms in use
MulticolouredMulticoloured
IrridescentIrridescent
SpeckledSpeckled
SpottedSpotted
BandedBanded
ScatteredScattered
DisseminatedDisseminated
VariegatedVariegated
IndurationInduration
Other terms in useOther terms in use BrittleBrittle
DenseDense
CrumblyCrumbly
BlockyBlocky
LooseLoose
AmorphousAmorphous
Grain Size and ShapeGrain Size and Shape
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Grain SizeGrain Size
MeasureMeasure
size of individual grainssize of individual grains
mean size of grains inmean size of grains in
samplesample
ReportReport
weighted averageweighted average
range of sizesrange of sizes
Grain ShapeGrain Shape
AngularAngular
edges and corners sharpedges and corners sharp
SubangularSubangular
Edges and cornersEdges and corners
roundedrounded
SubroundedSubrounded
Edges and corners roundEdges and corners round
to smoothto smooth
RoundedRounded
Edges and cornersEdges and cornerssmoothsmooth
Well RoundedWell Rounded
No edges or cornersNo edges or corners
SortingSorting
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MonomodalMonomodal
extremely wellextremely wellsortedsorted
very well sortedvery well sorted
well sortedwell sorted PolymodalPolymodal
moderately sortedmoderately sorted
poorly sortedpoorly sorted very poorly sortedvery poorly sorted
LusterLuster
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Arenaceous RocksArenaceous Rocks
CoatedCoated
Vitreous/GlassyVitreous/Glassy Silky/PearlySilky/Pearly
Frosted/DullFrosted/Dull
PittedPitted
StriatedStriated
Argillaceous RocksArgillaceous Rocks
EarthyEarthy
SilkySilky WaxyWaxy
VelvetyVelvety
SoapySoapy
ResinousResinous
Cement and MatrixCement and Matrix
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CementCement
Results from secondaryResults from secondarycrystallization of silica,crystallization of silica,
carbonate or other solutescarbonate or other solutes
CalciteCalcite
SideriteSiderite SulphatesSulphates
Iron OxidesIron Oxides
SilicaSilica
DolomiteDolomite
PyritePyrite
MatrixMatrix The difference between matrixThe difference between matrix
and cement is one of degree butand cement is one of degree but
the following pointers can helpthe following pointers can help
with no interwith no inter--granulargranular
contact the fill is matrixcontact the fill is matrix
matrix is a primarymatrix is a primarysedimentary materialsedimentary material
Visual Structures & PorosityVisual Structures & Porosity
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StructuresStructures The following may be visibleThe following may be visible
beddingbedding
fracturesfractures
jointingjointing
bioturbationbioturbation
laminationlamination
slickensidesslickensides
metamorphismmetamorphism
PorosityPorosity
Cubic = 47.6%Cubic = 47.6% young sedimentsyoung sediments
Hexagonal = 39.5%Hexagonal = 39.5%
compacted sedimentscompacted sediments
Rhombohedral = 25.9%Rhombohedral = 25.9%
sedimentary rockssedimentary rocks
Accessories and InclusionsAccessories and Inclusions
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These include pretty much any minor amount ofThese include pretty much any minor amount of
mineral or fossil associated with the sample.mineral or fossil associated with the sample.
Some common accessories and inclusionsSome common accessories and inclusions
pyrite, mica, lignite,pyrite, mica, lignite, glauconiteglauconite,, chertchert
fossils of various typesfossils of various types
Clastic rocksClastic rocks
The rock you have has a depositional history dictatedThe rock you have has a depositional history dictated
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The rock you have has a depositional history, dictatedThe rock you have has a depositional history, dictated
by the environment in which it formed.by the environment in which it formed.
Think of energy required to move the materialThink of energy required to move the material
RudaceousRudaceous --> Arenaceous> Arenaceous --> Argillaceous> Argillaceous
Depositional EnvironmentsDepositional Environments
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DELTAIC GROUP INTERDELTAIC GROUP
CON
TINENTA
AEOLIAN AEOLIAN
ALLUVIAL ALLUVIAL
DELTAIC DELTAIC PLAIN
TRANSITIO
NAL
COSTAL INTERDELTAIC - MARINE
PRODELTAIC
PLAIN
MARINE
NORMAL MARINE SHELF
NORMAL MARINE SLOPE SLOPE
DEEP DEEP
Exaggerated
Schematic of Sedimentary EnvironmentsSchematic of Sedimentary Environments
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AlluvialFans
LakeDelta
Lake
Exaggeratedvertical scale
TurbiditeChannels
Continental
Slope
ContinentalShelf
Coastal
Continental
MeanderingStreamDelta
BraidedStream
DesertDunesBay
Beach
BarrierIsland
TidalShoals
DeepSeaFan
Bigelow et al.,1987
Feeder ChannelDebris D B Slumps
Walker model, 1978Walker model, 1978
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Slope into Basin
Lower Fan
DebrisFlows
D-BCGLS.
Slumps
Upper
Fan
Massive ssts.
Pebbly ssts.
Thin bedded turbiditeson levee
Thin bedded
Mid Fan
Classical turbidites
Graded-
stratified
Graded-bed
Conglomerates:Inverse-to normallly
graded Terrace
Proximal
New suprafan
lobe
Incisedchannel
Braided
Supra Fan Lobes
Basin
Plain No relative scale implied
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PermeabilityPermeability
G
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Gamma ray logshale increasing
Rocktype
PorosityPermeability
in millidarcies
Tarbert
Ness
Etive
Rannoch
Broom
23-26%
16-27%
21-27%
23-28%
500-2000
50-2000
100-3000
10-1000
Note : Both porosity and permeability are adversely affected by compaction, cementation
and clay mineral content
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as Basin Formation
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Gas Basin Rock
Geological StructuresGeological Structures
Sedimentary rocks are generally deposited in horizontal layersSedimentary rocks are generally deposited in horizontal layers
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y g y p yy g y p y
or shallow slopes called strata or beds.or shallow slopes called strata or beds.
Most rocks are unable to withstand the earthMost rocks are unable to withstand the earths geological forcess geological forces
and hence become deformed (scale can vary fromand hence become deformed (scale can vary from cmscms toto kmskms))
Folds :Folds : anticlinalanticlinal andand synclinalsynclinal
Faults : many rocks become fractured during earthFaults : many rocks become fractured during earth
movement (formingmovement (formingjointsjoints), but if the rock on one), but if the rock on one
side of aside of a fracturefracture has moved in relation to thehas moved in relation to the
other, the fracture is called aother, the fracture is called a faultfault
Geological StructuresGeological Structures
Unconformities :Unconformities :
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Unconformities :Unconformities :
Earth movement can allow erosion or prevent continued depositionEarth movement can allow erosion or prevent continued deposition of sedimentsof sediments
A buriedA buried erosion surfaceerosion surface is called an unconformityis called an unconformity
DisconformityDisconformity : beds above and below the surface of unconformity are parallel: beds above and below the surface of unconformity are parallel
Angular Unconformity : beds are nonAngular Unconformity : beds are non--parallel either side of the eroded surfaparallel either side of the eroded surfa
Origins of Oil and Gas : SourceOrigins of Oil and Gas : Source
Oil and gas are derived from plants bacteria and marine microOil and gas are derived from plants bacteria and marine micro--organismsorganisms
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Oil and gas are derived from plants, bacteria and marine microOil and gas are derived from plants, bacteria and marine micro-organismsorganisms
In areas such as swamps, flooded forests and sheltered lake or sIn areas such as swamps, flooded forests and sheltered lake or sea beds vastea beds vastamounts of plant material accumulate. Bacteria breaking down theamounts of plant material accumulate. Bacteria breaking down the materialmaterial
use up the available oxygen producing a stagnant environment preuse up the available oxygen producing a stagnant environment preventingventing
complete decomposition.complete decomposition.
The plants and bacteria become buried in silts andThe plants and bacteria become buried in silts and mudsmuds and are preserved.and are preserved.
Origins of Oil and Gas : MaturationOrigins of Oil and Gas : MaturationWith continued burial under more sediment the organic material iWith continued burial under more sediment the organic material is subject tos subject to
increasing temperature and pressure, which under the correct conincreasing temperature and pressure, which under the correct conditions will convertditions will convert
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c eas g te pe atu e a d p essu e, w c u de t e co ect cog p p , d t o s w co ve t
the organic material into hydrocarbonsthe organic material into hydrocarbons
Temperature range for Hydrocarbon generation :Temperature range for Hydrocarbon generation :
Minimum temperature requiredMinimum temperature required = approx 65 C= approx 65 C OptimumOptimum hydrocarbon windowhydrocarbon window = 107 C to 176 C= 107 C to 176 C Increasing temperaturesIncreasing temperatures = convert heavy to light HC= convert heavy to light HCs ands andultimately gasultimately gas
Maximum temperatureMaximum temperature = above 260 C all organic material= above 260 C all organic material carbonisedcarbonised
Kerogen
carbonisedno oil or gas
Oil and gas
Gas
Oil
No oil or gas yet
Oilfield Oilfield with gas
Gasfield
Depth
km
50
100
150
200
Temperature
degreescelcius
Source
rockmaturity
Origins of Oil and Gas : MaturationOrigins of Oil and Gas : Maturation
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Marine plankton and bacteria produce oil and gas :
eg Oil and most gas under the Central & Northern North Sea and West ofShetland formed from planktonic algae and bacteria that flourished in
tropical seas in the Jurassic Period (140 million years ago)
Land plants and bacteria produce coal and gas :
eg Gas from beneath the Southern North Sea and Irish Sea formed from
coals which were derived from the lush tropical rain forests that grew in
the Carboniferous Period (300 million years ago)
Hydrocarbon MigrationHydrocarbon Migration
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Compaction of the source rocks by the increasing weight of overburden
provides the driving force necessary to expel the hydrocarbons
Migration of the fluids progresses through porous and permeable beds or
along fractures and faults to regions of lower pressure (usually to a shallower
depth)
eg 1. Believer District, Venezuela : vertical migration via faults and fracturesleading to a large shallow accumulation
eg 2. Khurais Field, Saudi Arabia : migration over long distances up-dip in a
porous reservoir bed until a trap was encountered
Hydrocarbon MigrationHydrocarbon Migration
Oil and gas are less dense than rock or water and soOil and gas are less dense than rock or water and so
Seal destroyed Gas and tar seepages
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Oil and gas are less dense than rock or water and soOil and gas are less dense than rock or water and so
migrate upwardsmigrate upwards
Once migration is terminated by a trappingOnce migration is terminated by a trapping
mechanism the gas and oil displace water, and settlemechanism the gas and oil displace water, and settle
out in layers due to their different densities, with waterout in layers due to their different densities, with water
below.below.
Migration of oil and gas is a slow process, a fewMigration of oil and gas is a slow process, a few
kilometers over millions of years. Over geologic timekilometers over millions of years. Over geologic time
huge amounts have risen to sea floors and landhuge amounts have risen to sea floors and land
surfaces, escaping as gas and tar seepages.surfaces, escaping as gas and tar seepages.
Liquid oil seepages are rare since oil becomes viscousLiquid oil seepages are rare since oil becomes viscous
and tarry near the surface due to oxidation andand tarry near the surface due to oxidation and
bacterial action.bacterial action.
Permeable
Migration magnified
Permeable
Permeable
Impermeable
Impermeable
Impermeable
Seal broken
Trapped oiland gas
Oil and gas migratedthrough permeable rock
Water rock
4 km
Traps fall into two basic types :Traps fall into two basic types :
Trapping MechanismTrapping Mechanism
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StructuralStructural egeg.. AnticlinalAnticlinal folds, Faulting, Salt Domefolds, Faulting, Salt Dome PiercementPiercement
StratigraphicStratigraphic egeg. Differential thickness, Lithology change, Unconformity, Lens. Differential thickness, Lithology change, Unconformity, Lens
Trapping MechanismTrapping MechanismCommercial hydrocarbon accumulation requires migration to the suCommercial hydrocarbon accumulation requires migration to the surface to berface to be
halted by some kind ofhalted by some kind ofsealseal andand trapping mechanismtrapping mechanism
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halted by some kind ofy seal and trapping mechanismpp g
Typical impermeable sealing rocks are shales, cemented sandstoneTypical impermeable sealing rocks are shales, cemented sandstones or salts or salt
Accumulations will only form if the reservoir and seal are in thAccumulations will only form if the reservoir and seal are in the right shape ande right shape and
juxtaposition to form a trapjuxtaposition to form a trap
Gas dissolved in oil Spill point
Water
4 km
2 kmSeal or
cap-rock
Gas gap
Oil
Water
Permeable
reservoir
rock
SNIFFSNIFF Test !!Test !!
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Reservoir PressureReservoir PressureNormal reservoir pressure = hydrostatic pressure of column ofNormal reservoir pressure = hydrostatic pressure of column ofsaltwater tosaltwater to
reservoir depthreservoir depth
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pp
Hydrostatic pressure gradient depends on amount of dissolved salHydrostatic pressure gradient depends on amount of dissolved sal
ts in the water :ts in the water :
Fresh Water (300Fresh Water (300 ppmppm salts)salts) = 0.433= 0.433 psipsi/ft/ft Normal Marine water (35,000Normal Marine water (35,000 ppmppm salts)salts) = 0.446= 0.446 psipsi/ft/ft GOM marine water (80,000GOM marine water (80,000 ppmppm salts)salts) = 0.465= 0.465 psipsi/ft/ft
Abnormal pressure can develop in isolated reservoirs as a resultAbnormal pressure can develop in isolated reservoirs as a result of charging fromof charging fromsurrounding compacting shales. Such reservoirs can have reservoisurrounding compacting shales. Such reservoirs can have reservoir pressurer pressure
gradients up to 1.0gradients up to 1.0 psipsi/ft/ft
In this case, the overburden above the sandstone reservoir is suIn this case, the overburden above the sandstone reservoir is supported by anpported by an
abnormally high fluid pressure as well as the normal grainabnormally high fluid pressure as well as the normal grain--grain contact.grain contact.
Consequently, production will reduce the pressure and may allowConsequently, production will reduce the pressure and may allow furtherfurther
compaction, resulting in possible casing collapse or land subsidcompaction, resulting in possible casing collapse or land subsidenceence