fj6242

7/21/2019 fj6242

http://slidepdf.com/reader/full/fj6242 1/116

INTRODUCTION TO RESERVOIR

ENGINEERING

LECTURE 1

7/21/2019 fj6242


7/21/2019 fj6242


Pressure-Temperature Diagram

!igure "#" shows a typical pressure#temperaturediagram o a multicomponent system with a specifcoverall composition. $lthough a dierenthydrocarbon system would have a dierent phasediagram% the general confguration is similar.

These multicomponent pressure#temperature diagramsare essentially

used to:

• &lassiy reservoirs

• &lassiy the naturally occurring hydrocarbon systems• 'escribe the phase behavior o the reservoir (uid

7/21/2019 fj6242


7/21/2019 fj6242


Petroleum Geology

LECTURE 2

7/21/2019 fj6242


1 How is petroleum formed?

Petroleum is result of the deposition of plant or animal

matter in areas whih are slowly su!siding"These areas are

usually in the sea or along its margins in oastal lagoons or

marshes#oasionally in la$es or inland swamps"%ediments

are deposited along with that at least part of the organimatter is preser&ed !y !urial !efore !eing destroyed !y

deay"'s time goes on and the areas ontinue to sin$

slowly#the organi material is !uried deeper an hene is

e(posed to higher temperatures and pressures"E&entually

hemial hanges result in the generation of petroleum#a

omple(#highly &aria!le mi(ture lf hydroar!ons"

7/21/2019 fj6242


2 what is )trap* ?

The term )trap* was first applied to a hydroar!on

aumulation !y +rton, )-sto$s of oil and gas might !e

reapped in the summits of folds or arhes found along

their wat to higher ground "*' detailed historial aount of

the su!se.uent e&olution of the onept and etymology of

the term trap is found in /ott and Reyonlds013"

7/21/2019 fj6242


7/21/2019 fj6242


6asi Conepts of +rigin# 'umulation and

Reo&ery of Hydroar!ons

LECTURE 4

7/21/2019 fj6242


型

游

梁

式

抽

油

机

异

型

游

梁

式

抽

油

机

旋

转

驴

头

游

梁

式

抽

油

机

调

径

变

矩

游

梁

式

抽

油

机

7/21/2019 fj6242


链传式抽油机天轮式抽油机直线往复式抽油机

7/21/2019 fj6242


链条式抽油机皮带式抽油机

7/21/2019 fj6242


Elements of Petroleum Reser&oir

777fluid ontent of the reser&oir

LECTURE 8

7/21/2019 fj6242


Porosity and Effeti&e Porosity

LECTURE 9

7/21/2019 fj6242


P+R+%:T;

< =or ro$ to ontain petroleum and later allow petroleum toflow#it must ha&e ertain physial harateristis" +!&ilusly#

there must !e some spaes in the ro$ in whih the

petroleum an !e stored"

< :f ro$ has openings#&oids#and spaes in whih li.uid and

gas may !e stored#it is said to !e porous "=or a gi&en

&olume of ro$# the ratio of the open spae to the total

&olume of the ro$ is alled porosity#the porosity may !e

e(pressed a deimal fration !ut is most often e(pressed

as a perentage"=or e(ample#if 1>> u!i feet of ro$

ontains many tiny pores and spaes whih together ha&e

a &olume of 1> u!i feet# the porosity of the ro$ is 1>"

7/21/2019 fj6242


P+R+%:T; The porosity o a roc) is a measure o the storage capacity

*pore volume+that is capable o holding (uids.

,uantitatively% the porosity is the ratio o the porevolume to the total volume *bul) volume+. Thisimportant roc) property is determined mathematicallyby the ollowing generali-ed

relationship:

where φ = porosity

7/21/2019 fj6242


$s the sediments were deposited and the roc)swere being ormed during past geological times%some void spaces that developed becameisolated rom the other void spaces by excessive

cementation. Thus% many o the void spaces areinterconnected while some o the pore spacesarecompletely isolated. This leads to two distincttypes o porosity% namely:

• $bsolute porosity• ective porosity

P+R+%:T;

7/21/2019 fj6242


Absolute porosity

The absolute porosity is defned as the ratio o the total porespace in

the roc) to that o the bul) volume. $ roc) may haveconsiderable

absolute porosity and yet have no conductivity to (uid or lac) opore

interconnection. The absolute porosity is generally expressed

mathematically by the ollowing relationships:

or

where φa = absolute porosity.

7/21/2019 fj6242


Ee!ti"e porosity

The eective porosity is the percentage o

interconnected pore space with respect to thebul) volume% or

where φ = eective porosity.

7/21/2019 fj6242


ne important application o the eective porosityis its use in determining the original hydrocarbonvolume in place. &onsider a reservoir with an arealextent o $ acres and an average thic)ness o heet. The total bul) volume o the reservoir can bedetermined rom the ollowing expressions:

/ul) volume = 01%234 $h% t1

or

/ul) volume = 5%526 $h% bblwhere $ = areal extent% acres

h = average thic)ness

7/21/2019 fj6242


Permea!ility and /ary@s Law

LECTURE

7/21/2019 fj6242


PER#EA$ILIT%

Permeability is a property o the porous medium that

measures the capacity and ability o the ormation totransmit (uids. The roc) permeability% )% is a very importantroc) property because it controls the directional movement

and the (ow rate o the reservoir (uids in the ormation. This roc) characteri-ation was frst defned mathematicallyby 7enry 'arcy in "623. In act% the e8uation that defnes

permeability in terms o measurable 8uantities is calledDar!y&s La'(

'arcy developed a (uid (ow e8uation that has since becomeone o

the standard mathematical tools o the petroleum engineer. Ia hori-ontal linear (ow o an incompressible (uid isestablished through a core sample o length 9 and a cross#section o area $% then the governing (uid(ow e8uation is

defned as

7/21/2019 fj6242


where ν = apparent (uid (owing velocity% cmsec) = proportionality constant% or permeability% 'arcys

µ = viscosity o the (owing (uid% cp

dpd9 = pressure drop per unit length% atmcm

The apparent velocity determined by dividing the (ow rateby the cross#sectional area across which (uid is (owing.;ubstituting the relationship% 8$% in place o ν in8uation 1#<" and solving or 8 results in

where 8 = (ow rate through the porous medium% cm1sec

$ = cross#sectional area across which (ow occurs% cm<

7/21/2019 fj6242


ne 'arcy is a relatively high permeability as thepermeabilities o

most reservoir roc)s are less than one 'arcy. In order toavoid the use o ractions in describing permeabilities%

the term millidarcy is used. $s the term indicates% onemillidarcy% i.e.% " md% is e8ual to one#thousandth o one'arcy or%

" 'arcy = "444 md

The negative sign in 8uation is necessary as the pressure

increases in one direction while the length increases inthe opposite direction.

Integrate the above e8uation

7/21/2019 fj6242


Linear flow model

7/21/2019 fj6242


where 9 = length o core% cm

$ = cross#sectional area% cm<

The ollowing conditions must exist during themeasurement o permeability:

• 9aminar *viscous+ (ow• =o reaction between (uid and roc)

• nly single phase present at "44> pore spacesaturation

This measured permeability at "44> saturation oa single phase is

called the absolute permeability o the roc).

7/21/2019 fj6242


!or a radial (ow% 'arcy?s e8uation in a dierential orm canbe written as:

7/21/2019 fj6242


:ntergrating /ary’s e.uation gi&es,

The term d9 has been replaced by dr as the length term

has now become a radius term.

7/21/2019 fj6242


%aturation

LECTURE A

7/21/2019 fj6242


SATURATION

;aturation is defned as that raction% or percent% o the pore

volume

occupied by a particular (uid *oil% gas% or water+. This property is

expressed mathematically by the ollowing relationship:

$pplying the above mathematical concept o saturation to eachreservoir

(uid gives

7/21/2019 fj6242


where

;o = oil saturation

;g = gas saturation;w = water saturation

;g + ;o + ;w = ".4

Criti!al oil saturatio)* So!

!or the oil phase to (ow% the saturation o the

oil must exceed a certain value which is

termed critical oil saturation. $t this particular

saturation% the oil remains in the pores and%

or all practical purposes% will not (ow.

7/21/2019 fj6242


Residual oil saturation, Sor

/uring the displaing proess of the rude oil system

from the porous media !y water or gas inBetion 0or

enroahment3 there will !e some remaining oil left that

is .uantitati&ely harateried !y a saturation &alue

that is larger than the critical oil saturation. This

saturation &alue is alled the residual oil saturation, Sor.

The term residual saturation is usually assoiated with

the nonwetting phase when it is !eing displaed !y a

wetting phase"

7/21/2019 fj6242


#o"able oil saturatio)* Som

@ovable oil saturation ;om is another saturation o

interest and is defned as the raction o pore

volume occupied by movable oil as expressed by

the ollowing e8uation:

;om = " − ;wc − ;oc

where

;wc = connate water saturation

;oc = critical oil saturation

7/21/2019 fj6242


Criti!al gas saturatio)* Sg!

$s the reservoir pressure declines below the bubble#point

pressure% gas evolves rom the oil phase and

conse8uently the saturation o the gas increases as the

reservoir pressure declines. The gas phase remains

immobile until its saturation exceeds a certain saturation%

called critical gas saturation, above which gas begins to

move.

Criti!al 'ater saturatio)* S'!

The critical water saturation% connate water saturation% and

irreducible water saturation are extensively used

interchangeably to defne the maximum water saturation

at which the water phase will remain immobile.

7/21/2019 fj6242


Capillary Pressure and :ts Cur&e

LECTURE D

7/21/2019 fj6242


&apillary pressureI a glass capillary tube is placed in a large open vessel

containing

water% the combination o surace tension and wettabilityo tube to water will cause water to rise in the tubeabove the water level in the container outside the tubeas shown in !igure 1.

The water will rise in the tube until the total orce acting to

pull theli8uid upward is balanced by the weight o the column o

li8uid being supported in the tube.

!igure 1

7/21/2019 fj6242


CAPILLAR% PRESSURE

The capillary orces in a petroleum reservoir are the result o thecombined eect o the surace and interacial tensions o the roc)and (uids% the pore si-e and geometry% and the wetting

characteristics o the system.$ny curved surace between two immiscible (uids has the tendency

to

contract into the smallest possible area per unit volume. This is true

whether the (uids are oil and water% water and gas *even air+% or oiland gas. Ahen two immiscible (uids are in contact% a discontinuity

in pressure exists between the two (uids% which depends uponthe curvature o the interace separating the (uids. Ae call thispressure dierence the capillary pressure and it is reerred to bypc.

&apillary pressure = *pressure o the nonwetting phase+ − *pressure o the wetting phase+

pc = pnw − pw

7/21/2019 fj6242


=igure8

7/21/2019 fj6242


Tra)sitio) +o)e

The fgure indicates that the saturations are graduallychanging rom "44> water in the water -one to

irreducible water saturation some vertical distance

above the water -one. This vertical area is reerred

to as the transition zone, which must exist in any

reservoir where there is a bottom water table. The

transition -one is then defned as the vertical

thic)ness over which the water saturation ranges

rom "44> saturation to irreducible water saturation

;wc.

7/21/2019 fj6242


,ater Oil Co)ta!t The A& is defned as the Buppermost depth in the

reservoir where a "44> water saturation exists.C

as Oil Co)ta!t The D& is defned as the Bminimum depth at

which a "44> li8uid% i.e.% oil + water% saturation

exists in the reservoir.C

7/21/2019 fj6242


=igure 9

7/21/2019 fj6242


It should be noted that there is a dierence

between the ree water level *!A9+ and the depth

at which "44> water saturation exists. !rom a

reservoir engineering standpoint% the ree water

level is defned by zero capillary pressure.

bviously% i the largest pore is so large thatthere is no capillary rise in this si-e pore% then

the ree water level and "44> water saturation

level% i.e.% A&% will be the same.

7/21/2019 fj6242


etta!iloity and /istri!ution of Reser&oir

=luids

LECTURE

7/21/2019 fj6242


,ETTA$ILIT%

Aettability is defned as the tendency o one (uid to

spread on or adhere to a solid surace in the

presence o other immiscible (uids. The concept o

wettability is illustrated in !igure". ;mall drops o

three li8uids#mercury% oil% and waterEare placed on

a clean glass plate.

7/21/2019 fj6242


The three droplets are then observed rom one sideas illustrated in !igure 1#". It is noted that the mercuryretains a spherical shape% the oil droplet develops anapproximately hemispherical shape% but the watertends to spread over the glass surace.

7/21/2019 fj6242


The tendency o a li8uid to spread over the surace

o a solid is an indication o the wettingcharacteristics o the li8uid or the solid. This

spreading tendency can be expressed more

conveniently by measuring the angle o contact

at the liquid-solid surace. This angle% which is

always measured through the li8uid to the solid%

is called the contact angle θ.

The contact angle θ has achieved signifcance as a

measure o wettability.

7/21/2019 fj6242


$s shown in !igure "% as the contact angle decreases% the wetting

characteristics o the li8uid increase. &omplete wettability would be

evidenced by a -ero contact angle% and complete nonwetting would beevidenced by a contact angle o "64F. There have been various

defnitions o intermediate wettability but% in much o the published

literature% contact angles o 34F to G4F will tend to repel the li8uid.

The wettability o reservoir roc)s to the (uids is important in that the

distribution o the (uids in the porous media is a unction o wettability.

/ecause o the attractive orces% the wetting phase tends to occupy the

smaller pores o the roc) and the nonwetting phase occupies the more

open channels.

7/21/2019 fj6242


Properties of Fatural Gas

LECTURE 1>

7/21/2019 fj6242


PT 6eha&iour

LECTURE 11

7/21/2019 fj6242


Classifiation of Hydroar!on

Reser&oir

LECTURE 12

7/21/2019 fj6242


CLASSIFICATION OF RESERVOIRSAND RESERVOIR FLUIDS

Petroleum reservoirs are broadly classifed as oilor gas reservoirs.

• The composition o the reservoir hydrocarbonmixture

• Initial reservoir pressure and temperature

pressure-temperature diagram

7/21/2019 fj6242


7/21/2019 fj6242



!igure "#" shows a typical pressure#temperature diagram o amulticomponent system with a specifc overall composition.$lthough a dierent hydrocarbon system would have adierent phase diagram% the general confguration issimilar.

These multicomponent pressure#temperature diagrams areessentially used to:

• &lassiy reservoirs

• &lassiy the naturally occurring hydrocarbon systems• 'escribe the phase behavior o the reservoir (uid

7/21/2019 fj6242


. Criti!al poi)t/ The critical point or a multicomponentmixture is reerred to as the state o pressure and

temperature at which all intensive properties o the gas andli8uid phases are e8ual *point &+. $t the critical point% thecorresponding pressure and temperature are called thecritical pressure pc and critical temperature Tc o themixture.


7/21/2019 fj6242


. $ubble-poi)t !ur"e/ The bubble#point curve *line /&+

is defned as the line separating the li8uid#phase regionrom the two#phase region.

. De'-poi)t !ur"e/ The dew#point curve *line $&+ isdefned as the line separating the vapor#phase regionrom the two#phase region.


7/21/2019 fj6242


• Oil reser"oirs/I the reservoir temperature Tis less than the critical temperature Tc o thereservoir (uid% the reservoir is classifed as an oilreservoir.

. as reser"oirs/I the reservoir temperature isgreater than the critical temperature o the

hydrocarbon (uid% the reservoir is considered agas reservoir.

Pressure7Temperature /iagram

7/21/2019 fj6242


Lo'-s0ri)1age oil

• il ormation volumeactor less than ".<bbl;T/

• Das#oil ratio less than <44sc;T/

• il gravity less than 12F$PI

• /lac) or deeply colored

Types of Crude Oil

7/21/2019 fj6242


Gas Reservoirs

In general% i the reservoir temperature is abovethe critical temperature o the hydrocarbonsystem% the reservoir is classifed as a natural

gas reservoir. n the basis o their phasediagrams and the prevailing reservoirconditions% natural gases can be classifed into1 categories:

• Hetrograde gas#condensate

• Aet gas• 'ry gas

7/21/2019 fj6242


I the reservoir temperature T liesbetween the critical temperature

Tc and cricondentherm Tct o the

reservoir (uid% the reservoir isclassifed as a retrograde gas#

condensate reservoir.

• the gas#oil ratio or a condensatesystem increases with time due to

the li8uid dropout and the loss oheavy components in the li8uid.

• &ondensate gravity above 24F $PI

• ;toc)#tan) li8uid is usually water#white or slightly colored.

Retrogra2e gas-!o)2e)sate reser"oi

7/21/2019 fj6242


Temperature o wet#gas reservoir

is above the cricondentherm o

the hydrocarbon mixture.

/ecause the reservoir

temperature exceeds the

cricondentherm o the

hydrocarbon system% the

reservoir (uid will always remain

in the vapor phase region as the

reservoir is depleted

isothermally% along the vertical

line $#/.

,et-gas reser"oir

7/21/2019 fj6242


Aet#gas reservoirs are characteri-ed by the ollowing

properties:

• Das oil ratios between 34%444 to "44%444 sc;T/

• ;toc)#tan) oil gravity above 34F $PI

• 9i8uid is water#white in color

• ;eparator conditions% i.e.% separator pressure and

temperature% lie within the two#phase region

,et-gas reser"oir

7/21/2019 fj6242


The hydrocarbon mixture

exists as a gas both in

the reservoir and in thesurace acilities.

sually a system having a

gas#oil ratio greater

than "44%444 sc;T/ isconsidered to be a dry

gas.

Dry-gas reser"oir

7/21/2019 fj6242


/ri&es in the Reser&oir0water dri&e and

ompation dri&e3

LECTURE 18

7/21/2019 fj6242


The Aater#'rive @echanism

@any reservoirs are bounded on a portion or all o theirperipheries by water bearing roc)s called a8uiers. Thea8uiers may be so large compared to the reservoir they adJoinas to appear infnite or all practical purposes% and they mayrange down to those so small as to be negligible in theireects on the reservoir perormance.

Heservoir havea water drive

Charateristis Trend

7/21/2019 fj6242


Reser&oir pressure /elines &ery slowly 0remains

&ery high3

Gas oil ratio Little hange during the life ofthe reser&oir 0remains low3

ater prodution Early e(ess water prodution

ell !eha&ior !low until water productiongets excessive.

+il reo&ery 49 to A9

7/21/2019 fj6242


Ro!1 a)2 Li3ui2 E4pa)sio)

Ahen an oil reservoir initially exists at a pressurehigher than its bubble#point pressure% the reservoir iscalled an undersaturated oil reservoir.

$t pressures above the bubble#point pressure% crudeoil% connate water% and roc) are the only materials

present. $s the reservoir pressure declines% the roc) and(uids expand due to their individual compressibilities.

The reservoir roc) compressibility is the result o twoactors:

• xpansion o the individual roc) grains

• !ormation compaction

7/21/2019 fj6242


Hoc) and 9i8uid xpansion

6oth of the a!o&e two fators are the results of a

derease of fluid pressure within the pore spaes#

and !oth tend to redue the pore &olume through

the redution of the porosity"

This dri&ing mehanism is onsidered the least

effiient dri&ing fore and usually results in the

reo&ery of only a small perentage of the total

oil in plae"

7/21/2019 fj6242


%olution7gas /ri&e#Gas7ap

/ri&e#Gra&ity /ri&e

LECTURE 19

7/21/2019 fj6242


The 'epletion 'rive @echanism

This driving orm may also be reerred to by the ollowing various

terms:

• ;olution gas drive

• 'issolved gas drive

• Internal gas drive

In this type o reservoir% the principal source o energy is a result

o gas liberation rom the crude oil and the subse8uent

expansion o the solution gas as the reservoir pressure is

reduced. $s pressure alls below the bubble#point pressure%

gas bubbles are liberated within the microscopic pore spaces.

These bubbles expand and orce the crude oil out o the pore

space as shown conceptually in !igure "

=igure 1 %olution gas dri&e reser&oir

7/21/2019 fj6242


g g

7/21/2019 fj6242


as Cap Dri"e

Das#cap#drive reservoirs can be identifed by the

presence o a gas cap with little or no water driveas shown in !igure <.

'ue to the ability o the gas cap to expand% thesereservoirs are

characteri-ed by a slow decline in the reservoir

pressure. The natural energy available to producethe crude oil comes rom the ollowing two sources:

• xpansion o the gas#cap gas

• xpansion o the solution gas as it is liberated

=igure 2 Gas7ap dri&e reser&oir

7/21/2019 fj6242


7/21/2019 fj6242


T0e ra"ity-Drai)age-Dri"e #e!0a)ism

The mechanism o gravity drainage occurs in

petroleum reservoirs as a result o dierences in

densities o the reservoir (uids. The eects o

gravitational orces can be simply illustrated by

placing a 8uantity o crude oil and a 8uantity o

water in a Jar and agitating the contents. $ter

agitation% the Jar is placed at rest% and the more

denser (uid *normally water+ will settle to the

bottom o the Jar% while the less dense (uid

*normally oil+ will rest on top o the denser (uid.

The (uids have separated as a result o thegravitational orces acting on them.

7/21/2019 fj6242


Charateristis Trend

Reser&oir pressure Kariable rates o pressuredecline% dependingprincipally upon the amounto gas conservation.

Gas oil ratio 9ow gas#oil ratio

ater prodution 9ittle or no waterproduction.

ell !eha&ior

+il reo&ery Fear to D>

7/21/2019 fj6242


T0e Combi)atio)-Dri"e #e!0a)ism

The driving mechanism most commonly encountered is one in

which both water and ree gas are available in some degreeto displace the oil toward the producing wells. The most

common type o drive encountered%

thereore% is a combination#drive mechanism as illustrated in

!igure

0. Two combinations o driving orces can be present incombinationdrive reservoirs. These are *"+ depletion drive

and a wea) water drive andL *<+ depletion drive with a small

gas cap and a wea) water drive.

Then% o course% gravity segregation can play an important

role in any o the aorementioned drives.

=igure 8 Com!ination dri&e reser&oir

7/21/2019 fj6242


7/21/2019 fj6242


/eri&ation of aterial 6alane E.uation

LECTURE 1

7/21/2019 fj6242


< hen an oil and gas reser&oir is trapped with wells#

oil and gas# and fre.uently some water# areprodued# there!y reduing the reser&oir pressureand ausing the remaining oil and gas to e(pand tofill the spae &a&ated !y the fluids remo&ed" henthe oil7and gas7!earing strata are hydraulially

onneted with water7!earing strata# or a.uifers#water enroahes into the reser&oir as the pressuredrops owing to prodution "This water enroahmentdereases the e(tent to whih the remaining oil andgas e(pand and aordingly retards the deline in

reser&oir pressure"

7/21/2019 fj6242


< :n as muh as the temperature in oil and gas

reser&oir remains su!stantially onstant duringthe ourse of prodution# the degree to whihthe remaining oil and gas e(pand depends onlyon the pressure "6y ta$ing !ottom7hole samples

of the reser&oir fluids under pressure andmeasuring their relati&e &olumes in thela!oratory at reser&oir temperature and under&arious pressures #it is possi!le to predit how

these fluids !eha&e in the reser&oir as reser&oirpressure delines"

7/21/2019 fj6242


< The general material !alane e.uation is simply

a &olumetri !alane# hih states that sine the

&olume of a reser&oir 0as defined !y its initial

limits3is a onstant # the alge!rai sum of the

&olume hanges of the oil # free gas # water # and

ro$ &olumes in the reser&oir &olumes dereases

# the sum of these two dereases must !e!alaned !y hanges of e.ual magnitude in the

water and ro$ &olumes "

7/21/2019 fj6242


< :f the assumption is made that omplete

e.uili!rium is attained at all times in thereser&oir !etween the oil and its solution gas #it is possi!le to write a generalied material!alane e(pression relating the .uantities of

oil # gas and water produed # the a&eragereser&oir pressure # the .uantity of water thatmay ha&e enroahed from the a.uifer # andfinally the initial oil and gas ontent of the

reser&oir"

7/21/2019 fj6242


%teady7state and Pseudo %teady7state

=low

LECTURE 1A

7/21/2019 fj6242


The area o concern in this lectureincludes:

• Types o (uids in the reservoir

• !low regimes

• Heservoir geometry

• =umber o (owing (uids in thereservoir

T;PE% += =LU:/%

7/21/2019 fj6242


In general% reservoir (uids are classifed intothree groups:

• Incompressible (uids• ;lightly compressible (uids

• &ompressible (uids

Incompressible (uids

$n incompressible (uid is defned as the (uidwhose volume *or density+ does not changewith pressure. Incompressible (uids do notexistL this behavior% however% may be assumed

in some cases to simpliy the derivation andthe fnal orm o many (ow e8uations.

7/21/2019 fj6242


;lightly compressible (uids

These BslightlyC compressible (uids exhibit smallchanges in volumeor density% with changes in pressure.

It should be pointed out that crude oil and water systemsft into this category.

&ompressible !luids

These are (uids that experience large changes in volumeas a unction o pressure. $ll gases are consideredcompressible (uids.

=L+ REG:E%

7/21/2019 fj6242


There are three (ow regimes:

• ;teady#state (ow

• nsteady#state (ow

• Pseudosteady#state (ow

;teady#;tate !low

The (ow regime is identifed as a steady#state(ow i the pressure at every location in thereservoir remains constant% i.e.% does notchange with time. @athematically% thiscondition is expressed as:

*0#"+

The above e8uation states that the rate o change opressure p with respect to time t at any location i is

7/21/2019 fj6242


pressure p with respect to time t at any location i is-ero. In reservoirs% the steady#state (ow condition canonly occur when the reservoir is completely rechargedand supported by strong a8uier or pressuremaintenance operations.

nsteady#;tate !low

The unsteady#state (ow *re8uently called transient fow+is defned as the (uid (owing condition at which therate o change o pressure with respect to time at anyposition in the reservoir is not -ero or constant.

This defnition suggests that the pressure derivative withrespect to time is essentially a unction o both position iand time t% thus

*0#<+

Pseu2ostea2y-State Flo'

Ahen the pressure at dierent locations in the reservoir is

7/21/2019 fj6242


Ahen the pressure at dierent locations in the reservoir isdeclining

linearly as a unction o time% i.e.% at a constant declining

rate% the (owing condition is characteri-ed as thepseudosteady#state (ow. @athematically% this defnitionstates that the rate o change o pressure with respectto time at every position is constant% or

*0#1+

It should be pointed out that the pseudosteady#state (owis commonly reerred to as semisteady#state (ow and8uasisteady#state (ow.

!igure shows a schematic comparison o the pressuredeclines as a unction o time o the three (ow regimes.

7/21/2019 fj6242


RE%ER+:R GE+ETR;

7/21/2019 fj6242


!or many engineering purposes% however% the actual (owgeometry may be represented by one o the ollowing(ow geometries:

• Hadial (ow

• 9inear (ow

• ;pherical and hemispherical (ow

/ecause (uids move toward the well rom all directions and

coverage at the wellbore% the term radial fow is given tocharacteri-e the (ow o (uid

into the wellbore. !igure 0#" shows ideali-ed (ow lines andiso#potential lines or a radial (ow system.

=igure 871 :deal radialflow into a

7/21/2019 fj6242


flow into awell!ore

Li)ear Flo'

9inear (ow occurs when (ow paths are parallel and the

7/21/2019 fj6242


9inear (ow occurs when (ow paths are parallel and the(uid (ows in a

single direction. In addition% the cross sectional area to

(ow must beconstant. !igure 0#< shows an ideali-ed linear (ow system.

!igure 0#< Ideal linear(ow

into vertical racture

Sp0eri!al a)2 5emisp0eri!al Flo'

7/21/2019 fj6242


'epending upon the type o wellbore completionconfguration% it is possible to have a spherical orhemispherical (ow near the wellbore. $ well with a

limited perorated interval could result in spherical(ow in the vicinity o the perorations as illustratedin !igure 0#1. $ well that only partially penetrates thepay -one% as shown in !igure 0#0% could result inhemispherical (ow. The condition could arise where

coning o bottom water is important.!igure 0#1 ;pherical (ow due to limited entry

7/21/2019 fj6242


=igure 878 Hemispherial flow in a partially penetrating well

7/21/2019 fj6242


FU6ER += =L+:FG =LU:/% :F THE RE%ER+:R

There are generally three cases o (owing systems:

• ;ingle#phase (ow *oil% water% or gas+

• Two#phase (ow *oil#water% oil#gas% or gas#water+

• Three#phase (ow *oil% water% and gas+

The description o (uid (ow and subse8uent analysis o

pressure data becomes more diMcult as the number omobile (uids increases.

7/21/2019 fj6242


Horiontal ells

LECTURE 1D

;ince "G64 hori-ontal wells began capturing an ever increasing

7/21/2019 fj6242


;ince "G64% hori-ontal wells began capturing an ever#increasingshare o hydrocarbon production. 7ori-ontal wells oer theollowing advantages over those o vertical wells:

• 9arge volume o the reservoir can be drained by eachhori-ontal well.

• 7igher productions rom thin pay -ones.

• 7ori-ontal wells minimi-e water and gas -oning problems.

• In high permeability reservoirs% where near#wellbore gas

velocities are high in vertical wells% hori-ontal wells can beused to reduce near#wellbore velocities and turbulence.

• In secondary and enhanced oil recovery applications% longhori-ontal inJection wells provide higher inJectivity rates.

• The length o the hori-ontal well can provide contact with

multiple ractures and greatly improve productivity.

7/21/2019 fj6242


The actual production mechanism and reservoir (ow regimesaround the hori-ontal well are considered more complicated

than those or the vertical well% especially i the hori-ontalsection o the well is o a considerable length. ;omecombination o both linear and radial (ow actually exists%and the well may behave in a manner similar to that o awell that has been extensively ractured.

$ssuming that each end o the hori-ontal well is represented bya vertical well that drains an area o a hal circle with aradius o b% Noshi *"GG"+ proposed the ollowing two methodsor calculating the drainage area o a hori-ontal well.

#et0o2 I

Noshi proposed that the drainage area is represented by

7/21/2019 fj6242


N p p g p ytwo hal circles o radius b *e8uivalent to a radius o avertical well rev+ at each end and a rectangle% odimensions 9*<b+% in the center. The drainage area othe

hori-ontal well is given then by:

!igure 2#"

7/21/2019 fj6242


09713

where

$ = drainage area% acres

9 = length o the hori-ontal well% t

b = hal minor axis o an ellipse% t

#et0o2 II

Noshi assumed that the hori-ontal well drainage area is an

7/21/2019 fj6242


Noshi assumed that the hori-ontal well drainage area is anellipse and given by:

*2#<+

with

*2#1+

where a is the hal maJor axis o an ellipse.

Noshi noted that the two methods give dierent values orthe drainage area $ and suggested assigning the

average value or the drainage o the hori-ontal well.@ost o the production rate e8uations re8uire the valueo the drainage radius o the hori-ontal well% which isgiven by:

7/21/2019 fj6242


09783

Ahere

reh = drainage radius o the hori-ontal well% t

$ = drainage area o the hori-ontal well% acres

7/21/2019 fj6242


Fatural =low Reo&ery

LECTURE 1

7/21/2019 fj6242


' thorough understanding of the flowing well is

neessary prior to plaing it on artifiial lift "There are two surfae onditions under whiha flowing well is produed # that is # it may !eprodued with a ho$e at the surfae or it may!e produed with no ho$e at the surfae" ThemaBority of all flowing wells utilie surfaeho$es " %ome of the reasons for this aresafety I to maintain prodution allowa!le I tomaintain an upper flow rate limit to pre&entsand entry I to produe the reser&oir at themost effiient rate I to pre&ent water or gas

oning I and others"<

7/21/2019 fj6242


< :n partiular # flowing wells utilie a ho$e in their

early stages of prodution " 's time progresses #the ho$e sie may ha&e to !e inreased ande&entually remo&ed ompletely in order to try tooptimie prodution "

< The seond ondition that we are onernedwith is produing the flowing well with norestritions at the surfae e(ept normalChristmas tree turn # !ends# et " E&en these may!e streamlined in order to o!tain the ma(imum

flowing rate possi!le "<

7/21/2019 fj6242


< :n order to analye the performane of a on&entionallyompleted flowing well # in is neessary to reognie thatthere are three distint phases # whih ha&e to !e studiedseparately and then finally lin$ed together !efore ano&erall piture of a flowing well@s !eha&ior an !eo!tained " These phase are the inflow performane # the&ertial lift performane # and the ho$e 0or !ean 3performane"

< The inflow performane # that is # the flow of oil # water #and gas from the formation into the !ottom of the well # istypified # as far as gross li.uid prodution is onerned #!y the P: of well or # more generally # !y the :PR "

< The &ertial lift performane in&ol&es a study of thepressure losses in &ertial pipes arrying two7phase

mi(tures0gas and li.uid3"

7/21/2019 fj6242


ehanial Reo&ery0rod system3

LECTURE 2>

< +il well pumping methods an !e di&ided into two

7/21/2019 fj6242


< +il well pumping methods an !e di&ided into twomain groups,

< Rod systems"Those in whih the motion of thesu!surfae pumping e.uipment originates at thesurfae and is transmitted to the pump !y means of arod string"

< Rod less systems"Those in whih the pumping

motion of the su!surfae pump is produed !ymeans other than su$er rods"

< +f these teo groups#the first is represented !y the!eam pumping system and the seond is represented!y hydrauli and entrifugal pumping systems"

7/21/2019 fj6242


< The !eam pumping system onsists essentially of fi&eparts,

< The su!surfae su$er rod5fri&en pump"< The su$er rod string whih transmits the surfae

pumping motion and power to the su!surfae pump"'lsoinluded is the neessary string of tu!ing andJor asingwithin whih the su$er rods operate and whihonduts the pumped fluid from the pumpto the surfae"

< The surfae pumping eauipment whih hanges therotating motion of the prime mo&er into osillatinf linearpumping motion "

< The power transmiddion unit or speed reduer"

< The prime mo&er whih furnishes the neessary powerto the system"

7/21/2019 fj6242


=omation /amage Control

LECTURE 22

S1i) Fa!tor

7/21/2019 fj6242


It is not unusual or materials such as

mud fltrate% cement slurry% or clay

particles to enter the ormation during

drilling% completion or wor)overoperations and reduce the permeability

around the wellbore.

Skin Factor

7/21/2019 fj6242


This effet is ommonly referred to as a wellbore damage

and the region of altered permea!ility is alled the skin zone.

This one an e(tend from a few inhes to se&eral feet from

the well!ore" any other wells are stimulated !y aidiing or

fraturing whih in effet inrease the permea!ility near the

well!ore" Thus# the permea!ility near the well!ore is alwaysdifferent from the permea!ility away from the well where the

formation has not !een affeted !y drilling or stimulation" '

shemati illustration of the s$in one is shown in =igure 879"

Those actors that cause damage to the ormation canproduce additional locali-ed pressure drop during (ow.

7/21/2019 fj6242


p p p g This additional pressure drop is commonly reerred to as∆ps)in. n the other hand% well stimulation techni8ues

will normally enhance the properties o the ormationand increase the permeability around the wellbore% sothat a decrease in pressure drop is observed.

!igure 0#2

7/21/2019 fj6242


• Positi"e S1i) Fa!tor* s 6 7

Ahen a damaged -one near the wellbore exists% )#s)in is

less than ) and hence s is a positive number. Themagnitude o the s)in actor increases as )#s)indecreases and as the depth o the damage r s)inincreases.

. Negati"e S1i) Fa!tor* s 8 7

Ahen the permeability around the well )#s)in is higherthan that o the ormation )% a negative s)in actorexists. This negative actor indicates an improvedwellbore condition.

• +ero S1i) Fa!tor* s 9 7

Oero s)in actor occurs when no alternation in thepermeability around the wellbore is observed% i.e.% )#s)in

= ).

7/21/2019 fj6242


Re&ision

LECTURE 24I28

7/21/2019 fj6242


LECTURE 29

=:F'L TE%T

Date post:	05-Mar-2016
Category:	Documents
Upload:	abu-naser
View:	9 times
Download:	0 times

fj6242

Documents