Fundamentals of Applied Reservoir Engineering. Appraisal, Economics and Optimization

229 Pages·2016·17.82 MB·English

by  Richard Wheaton

FUNDAMENTALS
OF APPLIED
RESERVOIR
ENGINEERING
Appraisal, Economics,
and Optimization
RICHARD WHEATON
Senior Lecturer at the University of Portsmouth,
United Kingdom
Amsterdam(cid:129)Boston(cid:129)Heidelberg(cid:129)London
NewYork(cid:129)Oxford(cid:129)Paris(cid:129)SanDiego
SanFrancisco(cid:129)Singapore(cid:129)Sydney(cid:129)Tokyo
GulfProffessionalPublishingisanimprintofElsevier
GulfProfessional PublishingisanimprintofElsevier
50HampshireStreet,5thFloor, Cambridge,MA02139,USA
TheBoulevard,LangfordLane, Kidlington,Oxford, OX51GB,UK
Copyright©2016ElsevierLtd.Allrights reserved.
Nopartofthispublicationmaybereproducedortransmittedinanyformorbyany
means,electronicormechanical,includingphotocopying,recording,oranyinformation
storageandretrievalsystem,withoutpermissioninwritingfromthepublisher.Detailson
howtoseekpermission,furtherinformationaboutthePublisher’spermissionspoliciesand
ourarrangementswithorganizationssuchastheCopyrightClearanceCenterandthe
CopyrightLicensingAgency,canbefoundatourwebsite:www.elsevier.com/permissions.
Thisbookandtheindividualcontributionscontained initareprotectedundercopyright
bythePublisher (otherthan asmaybenotedherein).
Notices
Knowledge andbestpractice inthisfieldareconstantly changing.Asnewresearchand
experiencebroadenourunderstanding, changes inresearchmethods, professional
practices,ormedicaltreatment maybecomenecessary.
Practitioners andresearchers mustalways relyontheirownexperienceand knowledgein
evaluating andusing anyinformation, methods,compounds, orexperiments described
herein.Inusing suchinformation ormethodstheyshouldbemindfulof theirownsafety
andthesafetyofothers,including partiesfor whomtheyhaveaprofessional
responsibility.
Tothefullestextent ofthelaw,neitherthePublisher northeauthors, contributors, or
editors,assume anyliabilityfor anyinjuryand/or damagetopersons orproperty asa
matterof productsliability,negligence orotherwise, orfromany useoroperation ofany
methods,products, instructions,orideascontainedinthematerial herein.
BritishLibraryCataloguing-in-Publication Data
Acataloguerecordforthisbookisavailable fromtheBritishLibrary
LibraryofCongressCataloging-in-Publication Data
Acatalogrecordforthis bookisavailablefrom theLibraryofCongress
ISBN:978-0-08-101019-8
Forinformation onall GulfProfessional Publishing
visitourwebsiteathttps://www.elsevier.com/
Publisher:JoeHayton
AcquisitionEditor:KatieHammon
EditorialProjectManager: KattieWashington
Production ProjectManager:SruthiSatheesh
Designer: MarkRoger
TypesetbyTNQBooksandJournals
LIST OF FIGURES
Figure1.1 Centralroleofreservoir engineering. 1
Figure2.1 Solidgrainsmakingupporous rock(schematic
imageandsandstone photograph). 6
Figure2.2 Wirelinewellloggingdschematic andexamplelog. 8
Figure2.3 Boyle’slawmeasurement ofmatrix volume. 9
Figure2.4 Poreandthroatmodel. 9
Figure2.5 Volumeelementoffluid. 10
Figure2.6 Measurementofpermeabilitydschematic. 12
Figure2.7 Permeability plots.(a)Radial coordinates.(b)Field
unitdimensions. 13
Figure2.8 Porosityepermeability relationships. 14
Figure2.9 (a)Watereoilesolidinterfacialinteractions.
(b)Contactangles.Whereq <90(cid:1),thesystem
c
isknownas“waterwet”andwater willtend
tospreadonthesolidsurface;and whereq >90(cid:1),
c
thesystem isknownas“oilwet”andoilwill
spreadon thesolidsurface. 15
Figure2.10 Waterwetandoil wetsystems. 16
Figure2.11 Capillarypressureinsamplesectionofporespace. 17
Figure2.12 Capillarypressureasafunctionofsaturation.
(a)Drainagecapillary pressurecurve.(b)Drainage
andimbibitioncapillarypressurecurves. 19
Figure2.13 Reservoir pressureandsaturationwithdepth:
oilewatersystem. 21
Figure2.14 Ingressofoilinto reservoir. 21
Figure2.15 Pressureandsaturation withdepthdshallow
capillarypressurecurve (smalltransition zone). 22
Figure2.16 Dependenceofcapillary pressurecurveson
(a)contactangleand (b)permeability. 23
Figure2.17 Pressurewithdepth:gaseoilewatersystem. 24
Figure2.18 (a)Oilewaterand(b)gasewaterrelative
permeabilities. 25
Figure2.19 Oilwetandwaterwetsystems. 26
Figure2.20 (a)Oilegasrelative permeability.(b)Example
ofgaseoilatconnate waterandoilewater
atresidualgas. 27
Figure2.21 (a)Ternaryoilegasewatersaturationdiagram
atgivenpressure.(b)Threephaseoil relative
permeability. 29
Figure2.22 Exampleofuseofarelative permeabilityand
capillarypressureExcel spreadsheet. 31
Figure2.23 Migrationand accumulation ofhydrocarbons
inareservoir. 33
ix
x ListofFigures
Figure2.24 Somecommonreservoir hydrocarbons. 33
Figure2.25 Fluidpropertyreferencepoints. 35
Figure2.26 Rangeofreservoir fluidcompositions. 36
Figure2.27 Single-componentpressure/temperature relationship. 36
Figure2.28 (a)Multicomponentphaseenvelope.(b)Dew
andbubblepointcondition. 37
Figure2.29 Comparisonofphaseenvelopesfordifferentfluid
types. 38
Figure2.30 PTchanges inreservoir andreservoir tosurface. 39
Figure2.31 Pressure-composition phaseenvelopedtwo-
pseudocomponentsystem. 40
Figure2.32 Compositional ternarydiagram. 41
Figure2.33 Single-componentPVTdiagrams. 42
Figure2.34 PVTinamulticomponent system. 43
Figure2.35 Schematicoflaboratory recombinationequipment. 44
Figure2.36 SchematicofRFTequipment. 45
Figure2.37 (a)Constantvolumedepletionand(b)constant
compositionexpansion. 46
Figure2.38 Differentialdepletion. 47
Figure2.39 Idealgaslawschematic andPVTplot. 47
Figure2.40 Realgas(a)PVTplotand(b)Zfactor. 49
Figure2.41 Blackoil representation. 50
Figure2.42 (a)Oiland(b)gasFVFs. 50
Figure2.43 SolutionGOR. 51
Figure2.44 Exampleof“blackoilproperties”spreadsheet. 52
Figure2.45 Schematicforflashcalculations. 55
Figure3.1 Radialcoordinates. 60
Figure3.2 Skineffect. 62
Figure3.3 Wellborestorageschematic. 63
Figure3.4 Pressuredrawdown. 65
Figure3.5 Pressurebuildup. 66
Figure3.6 Hornerplot. 67
Figure3.7 HornerplotsduseofHorner equationtomatch
fielddata. 68
Figure3.8 Logelog derivativeplot. 69
Figure3.9 Radialcompositemodels. 70
Figure3.10 Constantpressureboundary model. 70
Figure3.11 Closedradialsystem. 71
Figure3.12 Fracturedreservoir. 71
Figure3.13 Spreadsheetexampledpressurebuildupanalysis. 72
Figure4.1 (a)p/ZversusDV plot(b) p/ZversusDV /V plot. 77
o o o
Figure4.2 (a)HavlenaeOdehplots (b)HavlenaeOdeh
diagnosticplots. 79
Figure4.3 Drygasdepletiondexampleinputandoutput. 81
Figure4.4 Wetgasdepletiondexampleinput andoutput. 82
Figure4.5 Typicalchanges inproduced GORandcondensate/
gasratiowith pressureforagascondensate. 84
ListofFigures xi
Figure4.6 Exampleofgascondensateratesdgasandliquid
forstraightdepletion. 84
Figure4.7 Gascondensatemodeldsimplegascondensate
sweepmodel. 85
Figure4.8 Excelspreadsheet example. 86
Figure4.9 Exampleofratesofgasandliquid withrecycling. 87
Figure4.10 Exampleblackoilfunctions inmodel. 89
Figure4.11 Exampleofspreadsheetinput andoutput. 91
Figure4.12 Waterinjectionfrontal advance. 92
Figure4.13 (a)Relativepermeability and(b)fractionalflowcurve. 94
Figure4.14 Derivativesoffractional flow. 95
Figure4.15 Pistondisplacement. 96
Figure4.16 Self-sharpening advance. 96
Figure4.17 Nonsharpeningsystem. 97
Figure4.18 BuckleyeLeverett shockfront calculation. 97
Figure4.19 Welgetangentcurve. 98
Figure4.20 Welgetangent. 100
Figure4.21 Productionprofile. 101
Figure4.22 Spreadsheetexample. 102
Figure5.1 Numericalsimulation gridexample. 107
Figure5.2 Gridcells. 108
Figure5.3 GridcellsdCartesian andradial. 108
Figure5.4 Compositional andblack-oiltransport schematic. 109
Figure5.5 (a)Taylorseriesapproximations. (b)Taylorseries
approximationneglectingsecondorderand above. 113
Figure5.6 Explicitsolution model. 115
Figure5.7 Implicitsolutionmodel. 115
Figure5.8 Schematicofgenerationofgridcellpropertiesfrom
geologicaldata. 116
Figure5.9 Exampleofsingleradialnumericalmodel. 120
Figure5.10 Exampleofcoarsegridnumericalmodel. 121
Figure5.11 Exampleofsectormodel. 121
Figure6.1 Examplesofstructural input tohydrocarbon pore
volume. 127
Figure6.2 Gasfieldschematic. 130
Figure6.3 Gascondensaterecyclingschematic. 132
Figure6.4 Gasevolutionbelow bubblepoint. 133
Figure6.5 Variouswater-floodwelllayouts. 134
Figure6.6 Oilfieldwithgascap. 135
Figure7.1 Cashflows. 138
Figure7.2 Effectofdiscountingcashflow. 139
Figure7.3 Comparison ofundiscountedcashflowandDCF. 139
Figure7.4 RelationshipbetweenDCF andNPV. 140
Figure7.5 RealandnominalNPV. 140
Figure7.6 Realrateofreturn. 141
Figure7.7 Paybacktimeandmaximumexposure. 142
Figure7.8 PIratio. 142
xii ListofFigures
Figure7.9 Exceleconomicsspreadsheet. 144
Figure7.10 Case1ebasecase. 145
Figure7.11 Case2ehigherdiscountrate. 146
Figure7.12 Case3ehigherCAPEX. 147
Figure7.13 Case4eshorterplateau. 148
Figure7.14 Effectofoil price,costsandreserves onNPV. 149
Figure8.1 Fieldappraisal anddevelopmentstages. 155
Figure8.2 Schematicofearly appraisal. 156
Figure8.3 Excelaggregationspreadsheet. 158
Figure8.4 Cappedproduction profiles. 158
Figure8.5 Declinecurve plots. 160
Figure8.6 Tornadodiagram. 162
Figure8.7 VOIexample. 163
Figure9.1 Gasproduction bysourcetype andworldwide
shalegasresources. 172
Figure9.2 Natureofshale. 173
Figure9.3 Fracking. 174
Figure9.4 Microseismic. 175
Figure9.5 Coalbedmethane. 178
Figure9.6 Heavyoilrecovery.(a)Typicaldependenceof
viscosityontemperature. (b)Continuous steam
floodingschematic. (c)Cyclicsteam injection. 180
Figure9.7 Combustionproduction schematic. 181
Figure10.1 Fieldmanagementschematic. 185
Figure11.1 Reservesschematic. 189
Figure11.2 Exampledevelopment. 190
Figure11.3 Reservesschematic: technicaluncertaintyversus
projectmaturity. 191
Figure11.4 Tornadodiagram. 192
Figure11.5 ExampleresultsfromMonteCarloanalysis. 194
Figure11.6 Experimentaldesignschematic. 194
FigureA1.1 Gibbsfreeenergyofmixing. 197
FigureA1.2 Gibbsfreeenergyofatwo-component mixture.
(a)Entropyofmixing;(b)Internalenergyof
mixing;(c)Total Gibbsfreeenergyofa
two-componentmixture. 198
FigureA1.3 Relationshipbetweenphasestability ofa
two-componentmixture andcomposition
andpressure. 199
FigureA2.1 Gradients. 201
FigureA2.2 Gradients(oneandtwodimensional). 202
FigureA2.3 Three-dimensionalreferenceframe. 203
FigureA3.1 Pressuredependence. 205
FigureA5.1 Blackoil model. 210
FOREWORD
The aim of this textbook is to provide the fundamentals of reservoir
engineering for BEng/BSc students in petroleum engineering and give an
introduction to reservoir engineering for MSc students who are studying
petroleumengineering for the first time.The bookwould also beusefulto
employees in other disciplines in the oil and gas industry who want to
understand the basics of this important and central subject.
Modern reservoir engineering is very largely centered on numerical
computer simulation, and a reservoir engineer in industry will spend much
of her/his professional career building and running such simulators. High-
powered computers now mean that geological interpretations consisting of
manymillionsofgridscellscanbeusedtobuildreservoirmodels,honoring
the fundamental set of physical laws (conservation of mass, conservation of
momentum, and thermodynamic laws) which will predict the movement
of phases and hydrocarbon components and production through all stages
of field life for any potential development scenario.
These are very powerful tools both in planning and optimizing
developments and in monitoring field behavior once production com-
mences.Becauseofthis,reservoirengineeringhasmovedaheadandisnow
a very different discipline from that of 30e40years ago, when so much
depended on analytical methods based on equations derived from the basic
physicallawsbutneedingnumeroussimplifyingassumptionstobesolvable.
Because of their power and ease of use, there are significant dangers in
thesenumericalsimulatorsandtheyareunfortunatelyoftenmisused.There
is a tendency within industry to construct very large simulation models,
often with millions of grid cells, before first production (or even full
appraisal). These are based on very limited data, and the results are almost
meaningless. Modern simulators also come with very sophisticated “post-
processor”softwarethatprovidesveryattractiveandconvincingproduction
plots and three-dimensional representations of the reservoir. These have a
strong influence on financial decisions at an early stage, and such decisions
can often be difficult to reverse later.
Thekeyforthepracticingreservoirengineeristobeabletousemodels
in an appropriate way, exercising good “engineering judgment,” and to
start the process for any field by using all available methods, including very
simple numerical models, to begin to understand the basic “dynamics” of
xiii
xiv Foreword
the reservoirdwhat are the major factors that will determine its perfor-
mance?Largesimulationmodelscancomelater,whenwehaveasignificant
amount of historical production and other data. It is the aim of this text-
book to encourage future reservoir engineers to use this approach.
A chapter specifically treating reservoir appraisal and development
planningisincluded,asthiswillnormallymakeupalargeproportionofan
engineer’s activities. There is also a chapter on petroleum economics, since
all decisions will ultimately depend on the economics and a reservoir
engineer should understand the basics of this subject.
Unconventional resources (shale gas and oil, coal-seam gas, and heavy
oil) are covered, as they will be a major part of the industry in future.
Excel software is provided, and many of the exercises depend on use of
this. The idea is to provide students and other readers with a simple, easy-
to-use tool for analysis of some basic field data. Exercises which in many
books require long numerical calculations can now be carried out very
effectively using such Excel spreadsheets.
Thereareappendicescoveringtopicssuchasenhancedoilrecovery,gas
well testing, basic fluid thermodynamics, and mathematical operators,
which are peripheral but should help in the understanding of the main
topics.
The aim of this book is give a basis for an understanding of how
hydrocarbon reservoirs work, and to start the process for a student devel-
oping “good reservoir engineering judgment.”
CHAPTER 1
Introduction
The role of a reservoir engineer is a key and central one in petroleum
engineering (Fig. 1.1). He/she pulls together all the available geological,
petrophysical,laboratory,field,andwell-testdatatounderstandthephysical
potential of the reservoir. The engineer then covers the following aspects.
1. Reservoir evaluation.
2. Development planning and optimization.
3. Production forecasting.
4. Reserves estimation.
5. Building numerical reservoir models.
6. Well testing and analysis.
7. Field management.
To do this he/she also needs to understand the facilities and economic
and commercial constraints, so as to provide and optimize a viable and
economic development plan.
Economic/
Commercial Petrophysical
Welltestdata constraints data
Reservoir
Engineering
Geological/Se
Laboratory
ismicdata
data
Facili(cid:2)es
constraints
Figure1.1 Central roleofreservoirengineering.
FundamentalsofAppliedReservoirEngineering
ISBN978-0-08-101019-8 ©2016ElsevierLtd.
http://dx.doi.org/10.1016/B978-0-08-101019-8.00001-6 Allrightsreserved. 1
2 FundamentalsofAppliedReservoirEngineering
To fulfill this role effectively, it is necessary for a reservoir engineer
firstly to understand the basic physical properties relevant to reservoirs: the
concepts of porosity, absolute permeability, wettability, capillary pressure,
andrelativepermeabilitymustbecovered.Fluidpropertiesthenneedtobe
understood: what hydrocarbon mixtures are typically found in fields, how
these can split into oil and gas phases and how these phases behave with
pressureandtemperature.Thereservoirengineeralsoneedstohaveabasic
understanding of how all these properties are measured so that he/she can
critically access the data he/she receives from the laboratory and the field.
Chapter “Basic Rock and Fluid Properties” covers these fundamental
issues.
Chapter “Well-Test Analysis” introduces well-test analysis, which,
before production, provides our best insight into reservoir properties away
from the very immediate vicinity of exploration and appraisal wells. The
standard equations used are derived, and their interpretation explained.
Softwareisprovidedtohelpingainingexperienceonusingtheseequations
to interpret field-test data and also to answer exercises.
Analytical methods using simplified equations and models in the early
evaluation of potential reservoir behavior are an important tool, covered in
chapter “Analytical Methods for Prediction of Reservoir Performance”.
Material balance, mainly used for depletion-type developments,
and Buckley-Leverett/Welge analysis for water-flood developments are
discussed in some detail here. Again, software is available to aid in under-
standing these topics and in answering exercise questions.
Chapter “Numerical Simulation Methods for Predicting Reservoir
Performance” gives an introduction to numerical simulation. The funda-
mental equations of mass balance, conservation of momentum (giving the
Darcy equation), and thermodynamic relationships are combined to give
the “diffusion equations,” which are then solved across the grid cells of the
simulator. The theory behind the use of finite difference methods is
covered. The input data that will be required in any simulator are
explained, and there is emphasis on the best use of numerical simulators.
Use of production data as they become available in “history matching” to
improve our model is discussed.
Onceweunderstandthephysicalpropertiesinthereservoirweneedto
consider the dynamics of the field when we drill wells and produce
hydrocarbons. Pressure drops around the wells, and reservoir fluids move
towardthewell.Dependingonthenatureofthereservoirfluids,therewill
be some form of “drive mechanism” that maintains well production.