Transport in Shale Reservoirs

150 Pages·2019·17.613 MB·English

by  Kun Sang Lee, Tae Hong Kim

Transport in Shale
Reservoirs
KUN SANG LEE
Hanyang University
Seoul, South Korea
TAE HONG KIM
Hanyang University
Seoul, South Korea
]

TRANSPORTINSHALERESERVOIRS ISBN:978-0-12-817860-7
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Preface
As global energy consumption is steadily growing, the principlesinshalereservoirs,state-of-the-arttechnology
hydrocarbon sources from unconventional shale reser- onthemodeling,applicationsintherealfield,andideas
voirsareincreasingrapidly.Althoughtheshaleindustry forfutureresearch.
has made rapid progress in recent years, there is still a Chapter 1 serves as an introduction to the topic by
lackofknowledgebothinindustrialandacademicfields. tracingthedevelopmentandcurrentstatusofshaleres-
Because shale reservoirs have distinctive features ervoirs.Chapter2reviewspetrophysicalcharacteristicsof
different from those of conventional reservoirs, an ac- shalereservoirssuchaslithology,mineralcomposition,
curate evaluation on the behavior of shale reservoirs organicmatter,poregeometry,andfracture-matrixsys-
needsanintegratedunderstandingonthecharacteristics tem.Chapter3discussesmajortransportmechanismsin
andtransportofreservoirandfluids.Thisbookaimsto shalereservoirsincludingnon-Darcyflow,gassorption,
presentacomprehensiveandmathematicaltreatmentof moleculardiffusion,geomechanics,andphasebehavior
characterizationandmodelingofshalereservoirs. in nanopores. Chapter 4 focuses on the simulation of
Whileseveralbooksexistforshalegasreservoir,many shalegasandoilreservoirs.Chapter5presentsemerging
of them focused on geological, economic, environ- technologiesinshalereservoirsincludingmulticompo-
mental aspects. There has been a void for a compre- nenttransportintheCO injectionprocessandconsid-
2
hensivebookthatfocusesonthetransportphenomena erationoforganicmaterialinshalereservoirsimulation.
throughshalereservoirs.Thisbookemphasizesallrele- Thisbookwouldneverhavebeenpublishedwithout
vant aspects of petrophysical characteristics and their theableassistanceofElsevierstafffortheirpatienceand
impact on transport mechanisms. The book also dis- their excellent editing job. We shall appreciate any
cusses a systematic approach in the modeling of shale commentsandsuggestions.
reservoirs based on the complicated transport mecha-
nisms.Theauthors’desireisthattheinformationinthis KunSangLee
book provides a clear presentation of the transport Seoul,Korea
v
Contents
1 Introduction,1 4 Simulation of Shale Reservoirs,69
2 Petrophysical Characteristics of Shale 5 Challenges of Shale Reservoir
Reservoirs,7 Technologies,105
3 Specific Mechanisms in Shale
Reservoirs,35 NOMENCLATURE, 133
INDEX, 137
vii
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CHAPTER 1
Introduction
ABSTRACT kerogen. CBM is natural gas contained in the coal
As conventional hydrocarbon resources have depleted seam. Gas hydrate is an icelike form of crystalline
and global energy consumption has grown steadily, water-based solid that contains gas molecules in its
interest of unconventional resources has increased molecularcavities.Ingeneral,unconventionalresources
steadily. Especially, production of shale gas and oil are more expensive and more difficult to extract and
resources increases rapidly after development of process. As shown in Fig. 1.1, resources in the lower
hydraulic fracturing and horizontal drilling techniques partofthepyramidpresentahigheramountofreserves,
inNorthAmerica.Eventhoughshaleindustryhasgrown theincreaseddifficultyofproduction,andhigherdevel-
dramatically, fluid flow in shale reservoirs still has not opment cost than resources in the upper part. Among
beenfullyunderstood.Unconventionalshalereservoirs variousunconventionalresources,shale gas and oil are
showedcomplexflowmechanismscomparedwithcon- themostcommercializedresourcessofar.
ventionalreservoirs.Shalereservoirshaveintricatepetro-
physical characteristics such as various lithologies and
GEOLOGIC FEATURESOF SHALE
mineralcomposition,organiccomponent,tinyporege-
ometry,andnaturalfracturesystem,andtheyaffectfluid RESERVOIRS
behavior significantly. Non-Darcy flow, adsorption/ Recently,shalereservoirshavereceivedsignificantatten-
desorption, fluid flow and phase behavior change in tionbecauseoftheirpotentialtosupplytheworldwith
nanoscale pores, molecular diffusion, and stress- animmenseamountofenergyandthedepletionofcon-
dependent deformation should be considered for ventional reservoirs. Because shale reservoirs have
evaluationoffluidflowinshalereservoirs.Foraccurate variousspecificfeaturesdifferentfromconventionalres-
understanding of transport in shale reservoirs, this ervoirs, there is still a lack of understanding for them.
book presents comprehensive study of petrophysical Conventional reservoirs are comprised of source rock,
characteristics, transport mechanisms, and application reservoir rock, trap, and seal. In a typical source rock,
infield-scalereservoirsimulation. some of the hydrocarbons are driven out and migrate
intoreservoirrockunderthetraps.Inshaleoilandgas
Becauseofrapiddepletionofconventionalresourcesand reservoirs, the generated hydrocarbon cannot be
increaseofglobalenergyconsumption,conventionalhy- migrated,andthesourcerockitselfbecomesthereservoir
drocarbon resources cannot satisfy the energy demand. rock because of its tight features. Shale is a fissile and
AccordingtoWorldEnergy Outlook2017(IEA,2017), laminated sedimentary rock mainly composed of clay-
global energy will expand by 30% between today and sized mineral grains. Normally, ina broad sense, shale
2040.Althoughvariousresearcheshavebeenperformed reservoir rock contains clastics (quartz, feldspars, and
to develop sustainable and renewable energy, it is still micas),carbonates(calcite,dolomite,andsiderite),clay
significantly expensive to be commercialized. Conse- minerals (montmorillonite, illite, smectite, and
quently, unconventional oil and gas resources have kaolinite),pyrite,andtheotherminorminerals(Passey,
attracted considerable attention in recent decades. Bohacs,Esch,Klimentidis,&Sinha,2010;Quireinetal.,
Unconventional oil and gas are hydrocarbon resources 2010;Ramirez,Klein,Ron,&Howard,2011;Sondergeld,
that cannot be produced with conventional extraction Newsham, Comisky, Rice, & Rai, 2010). Especially,
techniques. Fig. 1.1 shows the hydrocarbon resources black-colored shale rock includes organic matters such
pyramid. Unconventional resources include tight oil, askerogenandisanessentialsourceofshaleoilandgas.
shale oil, oil shale, coalbed methane (CBM), tight gas, Amount of organic materials, which indicates the
shale gas, and gas hydrates. Oil shale is a rock that capacity to produce and store hydrocarbons, is signifi-
includessignificantamountsoforganicmatterssuchas cantinshalereservoirs.Asaconventionalsourcerock,
TransportinShaleReservoirs.https://doi.org/10.1016/B978-0-12-817860-7.00001-2
Copyright©2019ElsevierInc.Allrightsreserved. 1
2 TransportinShaleReservoirs
FIG.1.1 Hydrocarbonresourcespyramid.
roughly0.5%totalorganiccarbon(TOC)isconsidered (Fig. 1.2). Organic matter pores can be divided into
as a minimum or threshold. For shale reservoirs, primaryorganicporesandsecondaryorganicpores.Sec-
approximately2%is regarded asaminimum TOCfor ondary organic matter pores also can be divided into
commercialproduction,anditmayexceed10%e12% organic matter bubble and spongy pores. Inorganic
in some reservoirs. Kerogen types are primarily classi- porescanbedividedintointerparticleandintraparticle
fied into four categories (Tissot &Welte, 1984). Based mineral pores. The pore size of shale reservoirs ranges
onthecharacter,elementalcontents,anddepositional from nanometers to micrometers. The complexity of
environments of kerogens, kerogens are classified to pore geometry and fracture networks significantly
types I, II, III, and IV. Investigation of these kerogen affectsthebehaviorofhydrocarboninshalereservoirs.
types is important to understand the processes of Understanding of geologic features of shale rock is an
storage, retention, and release of hydrocarbons. importantprerequisiteforanalysisoftransportinshale
Commonly, oil is produced from shale reservoir con- reservoirs.
taining kerogen types I and II, and gas is produced
from a reservoir containing kerogen type III. Thermal
maturity, which indicates maximum temperature
exposureofrockandextentoftemperature-time-driven
reactions, is another critical parameter in shale reser-
voirs. The organic materials whose vitrinite reflectance
is lower than 0.65%R are considered as immature
o
organicmatters(Mani,Patil,&Dayal,2015).Thermally
matureorganicmatters,whichpresent0.6%e1.35%R
o
of vitrinite reflectance, commonly produce oil. The
postmatureorganicmaterials,whichshowhigherthan
1.5%R of vitrinite reflectance, generate wet and dry
o
gas(Manietal.,2015;Tissot&Welte,1984).
Unconventionalshalereservoirsalsoshowcomplex
pore geometry because of various lithology, mineral
composition, and organic matters. Pore networks of
shale formations consist of organic matter pores, FIG.1.2 Viewoforganicandinorganicmattersandnatural
inorganic material pores, and natural fracture system fractureinshalereservoirs.