305643433-Watddddddddddder-Flooding-M-tech.pdf

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1. T. SANTHOSHINI PRIYA
ENHANCED OIL RECOVERY
ANNA UNIVERISTY

2. SECONDARY RECOVERY PROCESS
Whenoilproductiondeclinesbecauseofthehydrocarbon
productionfromtheformation,thesecondaryoilrecovery
processisemployedtoincreasethepressurerequiredtodrive
theoiltoproductionwells.
Themechanismofsecondaryrecoveryoilissimilartothatof
theprimaryoilrecoveryexceptthatmorethanonewellboreis
involved,andthepressureofpetroleumreservoirisaugmented
ormaintainedartificiallytoforceoiltotheproductionwells.
Secondary Recovery Process 2

3. Secondary Recovery Process 3

4. SECONDARY RECOVERY PROCESS
Theprocessincludestheapplicationofavacuumtoawell,
theinjectionofgas,air,water,and/oraqueoussolutionsof
causticandpolymer.
Thedecreaseofpressureinthereservoirduringprimaryoil
recoverymayberestoredpartiallybyinjectingagasintothe
reservoirtoachieveahighpressure
Secondary Recovery Process 4

5. WHY WATERFLOODING?
Most widely used fluid injection process
It’s a “mature” technology
Water availability is generally good
Proven method to increase oil recovery
Secondary Recovery Process 5

6. WATER FLOODING
Water is injected for two reasons:
1) For pressure support of the reservoir (also known as void age
replacement).
2) To sweep or displace the oil from the reservoir, and push it
towards an oil production well.
Secondary Recovery Process 6

7. WHEN TO WATER FLOOD
Define your objectives
Maximum oil recovery
Highest investment efficiency
Maximize net present value
Minimize risk
Perform economics for various start up times, considering:
Revenue stream (oil & gas)
Injection requirements
Cost of fluid handling & treatment
Cost of facilities
Secondary Recovery Process 7

8. WATER FLOODING
Waterfloodingisutilizedprimarilyasasecondaryrecovery
technique,wheretheprimarydrivemechanismusedtoproduce
theoil(dissolvedgas)isdepleted.
Theinjectedwaterisdischargedintheaquiferthroughseveral
injectionwellssurroundingtheproductionwellandthe
injectedwatercreatesabottomwaterdriveontheoilzone
pushingtheoilupwards.Waterisrecoveredfromthewater
tableandinjectedintothereservoir,displacingtheoiltowards
thetargetproductionwells.
Becauseofthelimitedamountofdissolvedgasremainingin
solution,pumpsareusedtobringtheoiltosurface.8

9. WATER FLOODING
Theselectionofinjectionwatermethoddependsuponthe
mobilityratebetweenthedisplacingfluid(water)andthe
displacedfluid(oil).
Thewaterinjectionhowever,hassomedisadvantages:
 Reactionofinjectedwaterwiththeformationwatercan
causeformationdamage.
 Corrosionofsurfaceandsub-surfaceequipment.
Secondary Recovery Process 9

10. SELECTION OF FLOODING PATTERNS
The objective is to select the proper pattern that will provide
the injection fluid with the maximum possible contact with
the crude oil system.
This selection can be achieved by
1.Converting existing production wells into injectors.
2.Drilling infill injection wells.
Secondary Recovery Process 10

11. TYPES OF WELL ARRANGEMENTS
Essentially four types of well arrangements are used in
fluid injection projects:
Irregular injection patterns
Peripheral injection patterns
Regular injection patterns
Crestaland basal injection patterns
Secondary Recovery Process 11

12. DISPLACEMENT OF OIL THROUGH RESERVOIR
ROCKS BY WATER FLOODING (FIVE SPOT
PATTERN)
Forwaterfloodingthemostcommonpatternofinjectionand
productionwellsisafive-spotconfiguration
Secondary Recovery Process 12

13. IRREGULAR INJECTION PATTERNS
Surfaceorsubsurfacetopologyand/ortheuseofslant-hole
drillingtechniquesmayresultinproductionorinjectionwells
thatarenotuniformlylocated.
Somesmallreservoirsaredevelopedforprimaryproduction
withalimitednumberofwellsandwhentheeconomicsare
marginal,perhapsonlyfewproductionwellsareconvertedinto
injectorsinanonuniformpattern.
Faultingandlocalizedvariationsinporosityor
permeabilitymayalsoleadtoirregularpatterns.
Secondary Recovery Process 13

14. PERIPHERAL INJECTION PATTERNS
Secondary Recovery Process 14
Theinjectionwells
arelocatedatthe
externalboundaryof
thereservoirandthe
oilisdisplaced
towardtheinterior
ofthereservoir.

15. CRESTAL AND BASAL INJECTION PATTERNS
Increstalinjection,asthe
nameimplies,theinjection
isthroughwellslocatedat
thetopofthestructure.Gas
injectionprojectstypically
useacrestalinjection
pattern.
Inbasalinjection,thefluid
isinjectedatthebottomof
thestructure.Manywater-
injectionprojectsusebasal
injectionpatternswith
additionalbenefitsbeing
gainedfrom gravity
segregation.
Secondary Recovery Process 15

16. REGULAR INJECTION PATTERNS
Duetothefactthatoilleasesaredividedintosquaremilesand
quartersquaremiles,fieldsaredevelopedinaveryregular
pattern.
Themostcommonpatternsare:
Thepatternstermedinvertedhaveonlyoneinjectionwellper
pattern.Thisisthedifferencebetweennormalandinverted
wellarrangements.
(Note:Fourspotandinvertedsevenspotpatternsare
identical)
Secondary Recovery Process 16

17. DIRECT LINE DRIVE
Thelinesofinjectionand
productionaredirectly
opposedtoeachother
The pattern is
characterizedbytwo
parameters
a=distancebetweenwells
ofthesametype
d=distancebetweenlines
ofinjectorsandproducers
Secondary Recovery Process 17

18. STAGGERED LINE DRIVE
The wells are in lines as in
the direct line, but the
injectors and producers are
no longer directly opposed
but laterally displaced by a
distance of a/2
Secondary Recovery Process 18

19. FIVE SPOT
Special case of staggered
line, i.e., a=2d
Secondary Recovery Process 19

20. SEVEN SPOT
Theinjectionwellsarelocatedatthecornerofahexagonwith
aproductionwellatitscentre
Secondary Recovery Process 20

21. NINE SPOT
Similartofivespotbutwithanextrainjectionwelldrilledat
themiddleofeachsideofthesquare
Secondary Recovery Process 21

22. REGULAR
INJECTION
PATTERNS
Secondary Recovery Process 22

23. RECOVERY EFFICIENCY
Secondary Recovery Process 23

24. OVERALL RECOVERY EFFICIENCY
Theoverallrecoveryfactor(efficiency)RFofanysecondaryor
tertiaryoilrecoverymethodistheproductofacombinationofthree
individualefficiencyfactorsasgivenbythefollowinggeneralized
expression:
R
F=E
DE
AE
V N
P=N
SE
DE
AE
V
Where
RF=Overallrecoveryfactor
NS=Initialoilinplaceatthestartoftheflood,STB
NP=Cumulativeoilproduced,STB
ED=Displacementefficiency
EA=Arealsweepefficiency
EV=Verticalsweepefficiency
Secondary Recovery Process 24

25. OVERALL RECOVERY EFFICIENCY
ThearealsweepefficiencyEA
Isthefractionalareaofthe
patternthatissweptbythe
displacingfluid.
Themajorfactorsdetermining
arealsweepare:
Fluidmobility's
Patterntype
Arealheterogeneity
Totalvolumeoffluid
injected
TheverticalsweepefficiencyEV
Isthefractionofthevertical
sectionofthepayzonethatis
contactedbyinjectedfluids.
Theverticalsweepefficiency
isprimarilyafunctionof:
Verticalheterogeneity
Degree of gravity
segregation
Fluidmobility's
Totalvolumeinjection
Secondary Recovery Process 25

26. OVERALL RECOVERY EFFICIENCY-AREAL SWEEP
EFFICIENCY
Fluid mobilities
Pattern type
Areal heterogeneity
Total volume of fluid injected
Secondary Recovery Process 26

27. OVERALL RECOVERY EFFICIENCY-VERTICAL
SWEEP EFFICIENCY
Vertical heterogeneity
Degree of gravity segregation
Fluid mobilities
Total volume injection
Secondary Recovery Process 27

28. OVERALL RECOVERY EFFICIENCY-
DISPLACEMENTEFFICIENCY
ThedisplacementefficiencyEDisthefractionofmovableoil
thathasbeendisplacedfromthesweptzoneatanygiventime
orporevolumeinjected.Becauseanimmisciblegasinjection
orwaterfloodwillalwaysleavebehindsomeresidualoil,ED
willalwaysbelessthan1.0.
Allthreeefficiencyfactors(i.e.,ED,EA,andEV)arevariables
thatincreaseduringthefloodandreachmaximumvaluesat
theeconomiclimitoftheinjectionproject
Secondary Recovery Process 28

29. DISPLACEMENT EFFICIENCY
Mathematically,thedisplacementefficiencyisexpressedas:
Secondary Recovery Process 29

30. DISPLACEMENT EFFICIENCY
Secondary Recovery Process 30
Where,
Soi= Initial oil saturation at start of flood
Boi= Oil at start of flood, bbl/STB
Ŝo= Average oil saturation in the flood pattern at a
particular point during the flood

31. DISPLACEMENT EFFICIENCY
Assumingaconstantoilformationvolumefactorduringthe
floodlife.
Theaboveequationisreducedto
Wheretheinitialoilsaturationisgivenby
However,inthesweptarea,thegassaturationisconsidered
zero,thus
S
o=1−S
w
Secondary Recovery Process 31

32. DISPLACEMENT EFFICIENCY
ThedisplacementefficiencyEDcanbeexpressed
moreconvenientlyintermsofwatersaturationby
substitutingtheaboverelationshipsinto
Secondary Recovery Process 32

33. DISPLACEMENT EFFICIENCY
Where,
S
W=averagewatersaturationinthesweptarea
S
gi=initialgassaturationatthestartoftheflood
S
wi=initialwatersaturationatthestartoftheflood
Ifnoinitialgasispresentatthestartoftheflood,Equationis
reducedto
Secondary Recovery Process 33

34. DISPLACEMENT EFFICIENCY
ThedisplacementefficiencyEDwillcontinuallyincreaseat
differentstagesoftheflood,i.e.,withincreasingS
w.
Secondary Recovery Process 34

35. Secondary Recovery Process 35

36. FACTORS TO CONSIDER IN WATERFLOODING
1.Reservoir Geometry
2.Lithology, Porosity, Permeability
3.Reservoir Depth
4.Continuity of Rock Properties
5.Fluid Saturations & Distributions
6.Fluid Properties
7.Relative Permeability
8.Other Considerations
9.Primary Drive Mechanism(s)
Secondary Recovery Process 36

37. 1. RESERVOIR GEOMETRY
Thearealgeometryofthereservoirwillinfluencethelocationof
wellsand,ifoffshore,willinfluencethelocationandnumberof
platformsrequired.
Ifawater-drivereservoirisclassifiedasanactivewaterdrive,
injectionmaybeunnecessary.
Secondary Recovery Process 37

38. 2. LITHOLOGY AND ROCK PROPERTIES
Reservoir lithologyand rock properties that affect flood ability and
success are:
-Porosity -Permeability
-Clay content -Net thickness
The clay minerals present in some sands may clog the pores by
swelling and deflocculating when water flooding is used, no exact data are
available as to the extent to which this may occur.
Tight (low-permeability) reservoirs or reservoirs with thin net thickness
possess water-injection problems in terms of the desired water injection
rate or pressure.
Secondary Recovery Process 38

39. 3. RESERVOIR DEPTH
Reservoirdepthhasanimportantinfluenceonboththetechnical
andeconomicaspectsofasecondaryortertiaryrecoveryproject.
Maximuminjectionpressurewillincreasewithdepth.Thecostsof
liftingoilfromverydeepwellswilllimitthemaximumeconomic
water–oilratiosthatcanbetolerated,therebyreducingtheultimate
recoveryfactorandincreasingthetotalprojectoperatingcosts.
Inwaterfloodoperations,thereisacriticalpressure
(approximately1psi/ftofdepth)that,ifexceeded,permitsthe
injectingwatertoexpandopeningsalongfracturesortocreate
fractures
Secondary Recovery Process 39

40. 3. RESERVOIR DEPTH
Drilling costs a function of depth
Dual porosity systems
Temperature gradient
Oil viscosity Vs. temperature
If primary operations were extensive
Fracturing (max. injection pressure vs. depth)
Fracture type (vertical vs. horizontal)
Secondary Recovery Process 40

41. 4. RESERVOIR UNIFORMITY AND PAY
CONTINUITY
Substantialreservoiruniformityisoneofthemajorphysical
criterionsforsuccessfulwaterflooding.Forexample,ifthe
formationcontainsastratumoflimitedthicknesswithavery
highpermeabilityrapidchannelingandbypassingwill
develop.
Secondary Recovery Process 41

42. 5. FLUID SATURATIONS
Indeterminingthesuitabilityofareservoirforwaterflooding,
ahighoilsaturationthatprovidesasufficientsupplyof
recoverableoilistheprimarycriterionforsuccessfulflooding
operations.
Notethathigheroilsaturationatthebeginningofflood
operationsincreasestheoilmobilitythat,inturn,giveshigher
recoveryefficiency.
Secondary Recovery Process 42

43. 6. FLUID PROPERTIES
Thephysicalpropertiesofthereservoirfluidshavepronounced
effectsonthesuitabilityofagivenreservoirforfurther
developmentbywaterflooding.
Theoilviscosityhastheimportanteffectofdeterminingthe
mobilityratiothat,inturn,controlsthesweepefficiency.
Secondary Recovery Process 43

44. 7. RELATIVE PERMEABILITY
Shape of relative permeability curves impacts oil bank
formation
End point relative permeability to water may impact injectivity
Relative permeability from depletion doesn’t apply to water
flooding
Secondary Recovery Process 44

45. 8. OTHER CONSIDERATIONS

•Pressure.
•Keep average reservoir pressure high for improved well.
•Hydraulics equipment costs are higher for increasing pressures.
•Water floods should always be evaluated; while considering the
project life-cycle with other EOR methods in mind.
Secondary Recovery Process 45

46. 9.PRIMARY RESERVOIR DRIVING
MECHANISMS
Sixdrivingmechanismsbasicallyprovidethenaturalenergy
necessaryforoilrecovery:
1.Rockandliquidexpansion2.Solutiongasdrive3.Gas
capdrive.4.Waterdrive5.Gravitydrainagedrive6.
Combinationdrive
Theprimarydrivemechanismandanticipatedultimateoil
recoveryshouldbeconsideredwhenreviewingpossiblewater
floodprospects.
Secondary Recovery Process 46

47. 9. Primary Reservoir Driving Mechanisms cont.
The approximate oil recovery range is tabulated below for various
driving mechanisms.
Note that these calculations are approximate and, therefore, oil
recovery may fall outside these ranges.
Secondary Recovery Process 47

48. WATER FLOOD
At the scale of field, the main factors governing the efficiency
of a water flood are
The Mobility Ratio,
Reservoir heterogeneity,
Gravity.
Secondary Recovery Process 48

49. MOBILITY RATIO
Mobility,k/µ,isdefinedas
permeabilityofaporous
materialtoagivenphase
dividedbytheviscosityofthat
phase
Mobilityratio,M,isdefinedas
mobilityofthedisplacing
phasedividedbythemobility
ofthedisplacedphase.
Secondary Recovery Process 49

50. MOBILITY RATIO
Secondary Recovery Process 50

51. Secondary Recovery Process 51

52. MOBILITY
Ingeneral,themobilityofanyfluidλisdefinedastheratioof
theeffectivepermeabilityofthefluidtothefluidviscosity
Secondary Recovery Process 52
where,
λ
o,λ
w,λ
g=mobilityofoil,water,andgas,respectively
k
o,k
w,k
g=effectivepermeabilitytooil,water,andgas,
respectively
k
ro,k
rw=relativepermeabilitytooil,water,andgas,
respectively
k=absolutepermeability

53. MOBILITY RATIO
Secondary Recovery Process 53
Substituting for λ:

54. OPTIMUM TIME TO WATERFLOOD
The most common procedure for determining the optimum time to start
water flooding is to calculate:
Anticipated oil recovery
Fluid production rates
Monetary investment
Availability and quality of the water supply
Costs of water treatment and pumping equipment
Costs of maintenance and operation of the water installation facilities
Costs of drilling new injection wells or converting existing production
wells into injectors
Secondary Recovery Process 54

55. FACTORS TO DETERMINE THE RESERVOIR
PRESSURE (OR TIME) TO INITIATE A SECONDARY
RECOVERY PROJECT
Reservoiroilviscosity
Waterinjectionshouldbeinitiatedwhenthereservoir
pressurereachesitsbubble-pointpressuresincetheoil
viscosityreachesitsminimumvalueatthispressure.The
mobilityoftheoilwillincreasewithdecreasingoil
viscosity,whichinturnsimprovesthesweepingefficiency.
Secondary Recovery Process 55

56. FLOOD PATTERNS
Secondary Recovery Process 56

57. Stages of
water
flooding.
Secondary Recovery Process 57

58. OIL FIELD WATER
Petroleumformedfromtheorganicmatterdepositedwiththe
sediments,migratedfromwhatitisusuallycalledthesource
rockintomoreporousandpermeablesedimentaryrock
(reservoirrock).
Petroleum,i.e.,oilandgasislessdenserthanwater;therefore
ittendstofloattothetopofawaterbodyregardlesswhether
thewaterisonthesurfaceorinthesubsurface.
Waterassociatedwiththepetroleuminsubsurfacereservoiris
calledoilfieldwater.(i.e.,anywaterassociatedwitha
petroleumdeposit).
Secondary Recovery Process 58

59. CHEMICAL AND PHYSICAL PROPERTIES OF
OILFIELD WATER
Analyzed for various chemical and physical properties.
Most oilfield water contains organic and inorganic compounds.
Secondary Recovery Process 59
Inorganic
constituents
Cations
Anions
Physical
properties
Dissolved
gases
Stable
isotopes
Organic
constituents

60. OIL FIELD WATER
MustbeconsideredinallEnhancedOilRecoveryOperations
(EOR)
TherearesevenmajorEORtechniques
1.Steaminjection
2.In-situcombustion
3.Carbondioxideinjection
4.Surfactant-polymerinjection
5.Polymerinjection
6.Alkaline(caustic)injection
7.Injectionofpetroleummisciblehydrocarbons
Secondary Recovery Process 60

61. OIL FIELD WATER
ImportanceofwaterinEORtechnologybecomesobvious
whenoneconsiderstheamountofwaternecessarytorecover
onebarrelofoil.
Thewaterqualityrequiredmayvaryfromexcellenttopoor.
Secondary Recovery Process 61

62. SECONDARY RECOVERY PROCESS –
GASINJECTION
Gas injection methods can be subdivided into three categories:
1)Pressure restoration
2)Pressure maintenance
3)Gas drive
depending upon the way in which the gas is injected into the
reservoir.
Secondary Recovery Process 62

63. PRESSURE RESTORATION
Thegasisinjectedintoproductiveformationthroughonewell
whiletheotherwellsarecloseduntilthepressureisrestored
throughoutthereservoir.
Thismaytakeaslongasayearormore.
Whenthedesiredreservoirpressureisreached,gasinjectionis
stoppedandallofthewellsstartproducingoilunderthe
influenceoftheartificiallydevelopedpressure.
Secondary Recovery Process 63

64. PRESSURE MAINTENANCE METHOD
Inthismethod,gasfromproducingwellisrecompressedand
injectedintotheselectedwellsbeforethereservoirpressureis
totallyexhausted.
Inthismethod,somewellsareoperatedasinjectionwells,
whereasothersareoperatedasproductionwells.
Secondary Recovery Process 64

65. GAS DRIVE METHOD
Gasisinjectedintothereservoirunderpressureanda
continuousgasflowismaintainedfrominjectionwellsto
producingwells.
Themovinggasdrivestheoilintheformofafilm,orgas
bubblesaheadofthegas,towardtheproducingwells.
Secondary Recovery Process 65