001 course slides

8/8/2019 001 Course Slides

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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 Reservoir shapesYour Reservoir shapes


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Your Reservoir shapesYour Reservoir shapes

12.5 cm

12.5 cm

TerminologyTerminology


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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



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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)



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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%)



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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.



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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



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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.



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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..



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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).).



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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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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

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