shaker! Logging!While!Drilling!(LWD)!or! Measuremnt!While!Drilling!(MWD)! used!to!steer!deviated!wells! Mudlogging' cu8ngs! mud5loggers!!

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1 shaker! cu8ngs! mud5loggers!! Mudlogging' Logging!While!Drilling!(LWD)!or! Measuremnt!While!Drilling!(MWD)! used!to!steer!deviated!wells!

2 Drill'stem'tests' Requires! tripping!out! A!hydrocarbon5bearing!horizon!can!be!tested!while!drilling!the!well,!by!isola,ng! it,!allowing!fluids!to!flow!up!the!well5bore,!and!measuring!the!rate.!drilling!may! then!be!con,nued.!

3 Wireline'logging' Requires! tripping!out! Typical!wireline!logging!tool! assembly!or! sonde!

4 Tool' What'it'measures' How'it'does'this' Value' Caliper! Width!of!borehole! Presses!pads!against! side!of!borehole! Gamma!ray! Natural!γ!emissions!by! K,!U!and!Th! Spontaneous!poten,al! Permeability! Scin,lla,on!counter! Measures!voltage! between!electrodes! Resis,vity! Electrical!resis,vity!! Measures!current! between!electrodes! Sonic! Sonic!velocity! Sounds!source!and! detector! Density! Density!of!electrons,! thus!of!forma,ons! γ ray!source!and! detector! Indicator!of!caving! Lithology!(dis,nguish! shale!from!others)! Recogni,on!of! permeable!strata! Determina,on!of! nature!of!fluids' Determina,on!of! porosity' Determina,on!of! porosity' Neutron!porosity! Concentra,on!of!H! Source!emits!neutrons! Determina,on!of! porosity' Photoelectric! Nuclear!magne,c! resonance! Wireline'logging'tools' Weighted!average!of! atomic!numbers! Relaxa,on!,me!of!H! atoms!in!fluids! γ ray!source!and! detector! Magne,c!field! polarizes!h! Determina,on!of! lithology' Determina,on!of!of! pore'size'

5 Coring'and'core'analysis'Requires! tripping!out! Conven,onal!coring!requires!! Diamond!coring!bit! Core!barrel!(~10m!long)!! Preserved!samples!of!forma,on!fluids! Core!plugs!for!! porosity5permeability!measurements! biostra,graphy!! petrography!

6 Es?ma?on'of'recoverable'hydrocarbons'

7 Es?ma?on'of'hydrocarbon<filled'volume' 1:'trap'area' We'use'maps'to:' 1.!Define!spill!points! 2.!Measure!area!

8 Es?ma?on'of'hydrocarbon<filled'volume' 2:''reservoir'thickness'

9 Gross'rock'volume'uses'input'factors'1'&'2' Gross'Rock/Reservoir'Volume'(GRV)'or'Bulk'Rock'Volume'(BRV):'!!! The!three!dimensional!volume!of!reservoir!as!taken! from!the!crest!of!the!feature!down!to!the!hydrocarbon/water! contact!!!!accurate!mapping!and!depth/area!measurements!!!!required!!!!gross!reservoir!thickness!and!ver,cal!closure!are!!!!important!factors!!!!expressed!in!cubic!meters!(or"acre"feet)! '

10 Es?ma?on'of'hydrocarbon<filled'volume' 3:'net<to<gross'ra?o' Net<To<Gross'='(Net%reservoir% thickness)%/%(gross%thickness%of% reservoir%interval)%! Calculated%using%cut9 off%parameters%from% well%logs%and%core% calibra?on,%expressed% in%decimal%form% Sandstone % Recognises%that%not%all% the%volume%of%the% Mudstone reservoir%is% useful!

11 Net-To-Gross = (Net reservoir thickness) / (Total reservoir interval thickness) Calculated using cutoff parameters from well logs and core calibration, expressed in decimal form

12 Es?ma?on'of'recoverable'reserves' 5.'water'satura?on' Calculated'from'logs'using!the!Archie!Equa,on:!! S w '='['(a'/'φ! m )*(R w '/'R t )'] (1/n)' ' % Where:% S w :!water!satura,on!! Φ!:!porosity!! R w :!forma,on!water!resis,vity!! R t :!observed!bulk!resis,vity!! a:!a!constant!(o[en!taken!to!be!1)!! m:!cementa,on!factor!(varies!around!2)!! n:!satura,on!exponent!(generally!2)!!!

13 Es?ma?on'of'recoverable'reserves' 6.'Conversion'of'subsurface'to'surface'volumes' Fluid'proper?es'used'to'calculate'hydrocarbon'volumes'at'surface'condi?ons'! Forma?on'Volume'Factor'(B o ):'also!known!as!the!oil!shrinkage!factor;!used!to!convert! calculated!subsurface!volumes!to!surface!volumes!(stock!tank!barrels)!at!standard! temperature!(60 F/15.6!C)!and!pressure!(1!bar).!Commonly!expressed!as!1/B o.!! Gas'Expansion'Factor'(B g ):!used!to!convert!calculated!subsurface!volumes!to!surface! volumes!(cubic!meters)!at!standard!temperature!(60 F)!and!pressure!(1!bar).!!!

14 Puing'it'all'together' Standard Formula for calculating Hydrocarbons Initially In Place: HIIP = GRV x NTG x Φ x S h HIIP = Area x thickness x NTG x Φ x (1-S w ) The difference between this and reserves in place is the RECOVERY FACTOR Standard Formula for calculating Stock Tank Oil Initially In Place: STOIIP = GRV x NTG x Φ x S h x (1/Bo) Expressed in cubic metres or acre feet Conversion factor for oil to barrels = 6.29 Recoverable hydrocarbon reserves = STOIIP x recovery factor Recovery factor depends on trap and reservoir characteristics, drive mechanism, development system used, well spacing, artificial lift, pressure support, enhanced

15 Sta,c!reservoir! models!describe! distribu,on!of!rock! proper,es!and! hydrocarbons!within! the!reservoir! Modelling'the'reservoir'

16 Dynamic!reservoir! models!simulate!the! flow!of!fluids!through! the!reservoir;!they! may!contain!millions! of!grid!cells!and!take!a! long!,me!to!run!on! very!powerful! computer!clusters! Modelling'the'reservoir'

17 Produc?on:'what'makes'the'oil'come'out?' drive'mechanisms' Water!drive!(aquifer!support)! Gas!expansion! Solu,on!gas! Rock!or!compac,on!drive! Gravity!drainage! Water!or!gas!injec,on!

18 Aquifer'support'(water'drive)' Provides!very!good!pressure!support! with!minimal!pressure!drop!at!the! wellbore.!! Aquifer!water!expands!slightly,! displacing!oil!or!gas!toward!the! borehole!! Only!where!the!aquifer!is!of!equal!or! bezer!quality!than!the!reservoir!and:! Has!a!much!larger!volume!than!the! reservoir!(about!10!,mes)!or!is!in! communica,on!with!surface! recharge! Par,al!water!drive,!where!aquifer!is! poorer,!results!in!more!rapid!drop!in! produc,on!rate,!and!recovery!is! reduced!

19 Gas'expansion' Where!aquifer!is!limited!or!poor.! Free!gas!in!a!gas!reservoir!or!in!the!gas!cap!of!an! oil!reservoir!expands!to!replace!produced! hydrocarbons.!! In!oil!reservoir,!this!slows!rate!of!pressure!drop!in! the!reservoir!and!supports!hydrocarbon! produc,on.!! Pressure!drops!in!propor,on!to!the!volume!of! hydrocarbon!removed!from!the!reservoir!and!the! quality!of!the!reservoir.!!

20 Solu?on'gas'(deple?on'drive)' reservoir!energy!to!drive!the!oil!toward!the!wellbore! can!be!supplied!by!expansion!of!the!oil!due!to!gas! expanding!in!solu,on.!! When!pressure!drops!below!the!bubble!point!for! dissolved!gas,!small,!disconnected!gas!bubbles!form!in! pores,!pushing!the!oil!toward!the!wellbore.!! At!about!5 10%!free!gas!in!the!reservoir,!bubbles! coalesce!and!the!gas!moves!toward!the!wellbore!as!a! separate!flowing!phase,!and!oil!produc,on!drops! because!of!the!increased!rela,ve!permeability!to!gas.!

21 Rock'drive' Pressure!on!the!solids!increases!as!reservoir!fluid! pressure!declines!(because!pore!fluid!pressure! carries!less!of!the!weight!of!the!overburden).!! Some!reservoirs!respond!by!the!collapse!of!the! pore!space.!! Can!be!an!efficient!way!to!expel!hydrocarbons.!! Common!in!shallow!or!unconsolidated!reservoirs! or!where!porosity!has!been!held!open!by!high! fluid!pressures.!!

22 Gravity'drive' Oil!flows!out!under!gravity,!especially!where! replaced!by!exsolved!gas.!

23 Water'injec?on' To!support!pressure!of!the!reservoir!(also!known!as! voidage!replacement),!and!! to!sweep!or!displace!oil!from!the!reservoir,!and!push! it!towards!a!well.!