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Basic Well Logging Design.pdf
- 1. Basic Well LoggingDesign Presentedby M Bakhsh Roll No 2k15-PET-36 NFC IET Multan Pakistan A One-day Courseon ConsortiumAlumni Association Presents
- 2. Agenda • Introduction(8:15) • Lecture‐IBasic Theory/Interpretation • Break (10 – 10:15) • Lecture‐II LoggingProgram/Design • Break (12:00) • Workshop (1:30 – 4:00) • Wrap‐up (4:00 – 5:00)
- 3. Objectives Get toknow various logmeasurements Recognizefluid type and lithologyof majorreservoirs, and some practicalapplication of log data Familiarizewith factors affecting the logresponse Understand the strategy in wellevaluation Get to knowvarious approaches to well loggingdesign Exercisewith well logdesign
- 4. According to 4th Editionof J.A.Jackson’s Glossary of Geology: Log : A continuous record as a function of depth, usually graphic and plotted to scale on a narrow paper strip, of observations made on the rocks and fluids of the geologic section exposed in the well-bore. Definition
- 5. WirelineLogging Logging whileDrilling Cable T ools LWDTools Mudin Mud out Drill Bit
- 6. Well LoggingHistory • Thefirst electrical log was introducedin 1927 in Franceusingstationed resistivitymethod. • The first commercialelectrical resistivitytool in 1929 was used in Venezuela, USA andIndonesia. • SP was run alongwithresistivityfirst timein 1931 • Schlumbergerdevelopedthefirst continuous recordingin1931 • GR andNeutron logs was startedin1941 • Microresistivity array dipmeter and lateralog were first time introduced in 1950’s • The first induction tool was used in 1956 followed by Formation tester in 1957, Fomation Density in 1960’s, Electromagnetic tool in 1978 and most of Imaginglogs weredevelopedin1980’s • Advancedformationtester was commercialized in early1990’s
- 7. The “First” Logrecorded in 1927 Well in Pechelbronn -France Surface Recording Instrument
- 8. Log Measurements Practical definitionof a log Log is an indirect measurement of formationproperties exposed by the well‐bore acquiredby lowering a device or a combinationof devicesin the well bore. A Formation Evaluation Specialist is essential tounderstand The theory of measurements, quality control, interpretation principles, geophysics and petroleum geology as well as petroleum reservoirs
- 9. Advantagesand Limitationsof WellLogging Advantages: -Continuous measurements - Easy and quick to work with - Short time acquisition - Better resolution than seismic data - Economical Limitations: - Indirect measurements - Limited by tool specification - Affected by environment - Varying resolution
- 10.
- 11. Logsare ImpliedMeasurements • Logisnot adirect measurementof formationproperties,itis an implied measurementbasedon one or combinationof thefollowing devices • Electrical (Resistivity and Induction) • Acoustic • Nuclear • Electromagnetic • Magnetic
- 12. BasicTheory onResistivity Current path Rw Currentpath Unit volume filled with only water Ro Unit volume with water and matrix
- 13. Typical Formation Water Sand grain Currentpath Rt Measured by thetool Grain surface water Oil
- 14. Resistivityand MeasurementConcept Resistivity isthe ability of a substance to impade the flow of electrical current Rw - Formation Water resistivity E - Voltage difference across theformation A - Cross sectionalArea L - Length of brine containerr I - Current E *A Rw = I * L I E A Rw L
- 15. Resistivityand MeasurementConcept Schematic diagramof how an induction tool works Secondarymagnetic field Created bythe ground loop Secondarymagnetic field Inducesa current to flow in the receiver Magnetic field induces a current in the ground loop Primary magnetic field created by transmitter Transmitter Receiver
- 16. Resistivity is thekey to hydrocarbon saturation determination Sh = 1 - Sw Water Saturation Estimation Archie’s Equation ResistivityApplication F * Rw Rt Sw = ( SW - Watersaturation Rw - Formationwater resistivity Rt - True Formationresistivity ) 1/n where F = 1.0 Por m Resistivity is also used for well to well correlation, and to pick fluid contacts F - Formationfactor n - Saturationexponent m - Cementationfactor
- 17. Spontaneous PotentialLog(SP) • SPmeasurement is based on Electrical currentsflowingin the mud from electrochemicaland electrokinetic • Salinitydifference betweenmud flitrate and formationwaters, ions movement creates currentsmeasured in mVolt • Negativeor PositiveSP curve deflectionrepresentswhich fluid, formationor mud filtrate,has more ionic charge. • It only works in waterbased mud ! • The use of SP log; bed boundary,distinguishingpermeablefrom impermeable rock, shalyness indicator , Rw determinationand well correlation.
- 18. Spontaneous Potential(SP) SP Shale Sand - -- - - - - - - - - - - - Thick clean wet sand (-) (+) Thick shaly wet sand Thick clean Gas sand Rmf >> Rw in all sands Thick shaly Gas sand Hydrocarbon effect
- 19. Spontaneous Potential(SP) SP 40 mV 20 Limitation SPis not reliable when you have no or very small contrast Between Formation water salinity and mud filtrate salinity resulting in no to small SP deflection 7470 Determine Rw ? 7430 Given: Rmf = 0.51 at 135 F Rm = 0.91 at 135 F TD = 8007 ft Bottom hole temp.= 135 F Surface temp. = 60 F
- 20. Rw calculationfromSPlog SSP =-Klog Rmfe Rwe Steps of Calculation; - Determine Temperature at Depth of interval - Correct Rm and Rmf to this temperature (gen-9) - Determine SP (log) from shale baseline - Correct SP to SSP using SP thickness corr.chart - Determine Rmf/Rwe ratio using SP-1 chart - Determine Rwe from above equation or SP-1 chart - Correct Rwe to Rw using SP-2 chart
- 21. Gamma Ray Log(GR) •GR toolmeasures naturalradioactivityoftheformationfrom theemmision of all these;(T otalGR) Potasium,Uranium andThorium • GR log is usedfor; ‐ Well to well geologicalcorrelation ‐ Bed definition, more accurate than SP log ‐ Shale Volume Indicator (mostreliable) ‐ Lithologyand mineralogyindicator(NGT) IGR = GRlog - GRmin GRsh - GRmin IGR - Gamma ray index GRmin - GR clean GRsh - GR shale baseline
- 22.
- 24. Gamma Ray Log(GR) MineralDensity DT GR Quartz 2.64 56 0-15 Calcite 2.71 49 0-15 Dolomite 2.85 44 0-15 Orthoclase 2.52 69 220 Micas 2.82 49 275 Kaolinite 2.41 - 80-130 Chlorite 2.76 - 180-250 Illite 2.52 - 250-300 Montmorillonite 2.12 - 150-200 Anhydrite 2.98 50 low Pyrite 4.99 39 low Coal 1.47 high low
- 25. Gamma Ray Log(GR) Well-1Well-7 Well-2 GR Res GR Res GR Res
- 26. NaturalGamma Ray Log(NGT) •NGT tool measures the spectrum of Potasium,Uranium, and Thorium • NGT log is used for; - Study of Depositional Environments - Geochemical logging - Shale typing - Source Rocks - Diagenetic History - Vclay content correction • With combination of Photoelectric curve can be used for clay and mica type identification
- 27. NaturalGamma Ray Log(NGT) 00 2 4 6 K, Potasium (%) 8 10 2 4 6 8 10 Pe Kaolinite Montmorillonite Illite Glauconite Muscovite Biotite
- 28. DensityLog • Density toolis one of themost important instrumentsused to evaluateformationswhich measures formation density and directly ties to formationporosity • The density tool measures theelectrondensity , by emitting gamma ray from radioactivesource and returning to two detectors • The amount of Gamma rays that return depend on the number of electrons present, electron density is related to bulk density of mineral orrock • In most cases environmentalcorrectionforDensity log is not significant, field log density can be readily used for interpretation
- 30. DensityLog Main categories inthe process of GR energy loss due to collisions with other atomic particles: Compton Scattering is selected to be the energy level to generate GR of the Cesium 137 radioactive source at 662 keV
- 32. DensityLog POR = • Porositydeterminationfromdensitylog: RHOBma- RHOBlog RHOBma - RHOBfluid RHOBma - Matrix density RHOBfluid - Formation fluid density RHOBlog - Log density PORd - Density derived porosity Exercise: Determine porosity of limestone with field log density inicated 2.5 gr/cc.
- 33. NeutronLog • The toolmeasures theHydrogen Index which is thequantityof Hydrogen per unitvolume • The tools emit high energy neutrons eitherfrom radioactive source or minitron.They are sloweddown by collisionswith formation nuclei, collisionwill result energy loss,and the elementmostlyslowed down is H • Water has high neutron counts,Oilhas a littlelesscounts than Water , Gas will havevery low neutron counts • Neutron log is very sensitiveto environment change; bore hole size, mud cake,mud weight, temperature, stand‐off, pressure and formation salinity , measurement is compensation of far and near countrates.
- 35.
- 36. NeutronLog • Neutron toolhas a wide rangeof applications ‐ PorosityDetermination ‐ Gas Detection ‐ Borehole and formationsalinity ‐ ReservoirSaturation ‐ ReservoirMonitoring ‐ Borehole Fluid dynamics • Neutron radioactivesourcein normally usesAm 241 Exercise Neutron Log environmental correction Given: Uncorrected neutron porosity of 34%, 14” borehole size, 0.25” mud cake, 200 kppm borehole salinity, 12 ppg mud at 170 F, 5000 psi pressure, using water based mud with formation salinity of 50 kppm.
- 37. AcousticLog • Sonic toolgeneratesacousticsignalsto measure thetimetravel to pass through a formation,log measurement in time required to travel in one foot formation(microsec/foot) • Rock properties can be implied from sonic measurements; Porosity , Lithology , Gas shows, Compaction and Rockstrength • Maincurrent use : ‐ SeismicTie ‐ Mechanical properties ‐ Fracture identification • T ooltypes; Borehole compensatedsonic Long spacingsonic Array sonic tool Ultrasonic boreholeimage Dipole shear sonicimage
- 38.
- 39.
- 43. SpecialTools • Resistivity BasedImaging Tool - Pad device on 4 to 6 arm caliper, few mm resolution - Application: Thin bed Evaluation, Dip meter, Paleostream direction, fracture evaluation, stratigraphy. • Nuclear Magnetic Resonance - Using Permanent magnet to realign hydrogen protons to new magnetic field, a Lithology dependance porosity, saturartion and permeability estimation • Dipole Shear Sonic - Shear measurement, AVO and Rock mechanics applications • Borehole sonic imaging - Acustic based bore hole imaging for 360 deg coverage, lower resolutionthan resistivity based imaging tools.
- 44. SpecialTools continued • ModularFormation Test - Very robust formation tester with the capability to take unlimited pressure tests, pump the fluid into the borehole, identify the fluid type before sampling • WellboreSeismic - VSP: Vertical seismic profile surface guns, wellbore detectors - SAT:Seismic acquisition tool - WST: Well seismic tool - DSA: Downhole seismic array tool (3 axis geophones)
- 45.
- 46. Log and SeismicTieEffort • Log DataValidation ‐ Checkthe logquality ‐ See if thereis any missing logdata ‐ Determinewhethersonic peaks/anomaliesrepresentingformation • Logediting • Velocity CorrectionSonic over VSP (using4‐2 msecresolution) • SyntheticSeismicGeneration ‐ AcousticImpedance ‐ Convolution Waveletto tie seismicand logpeaks * Extracted Wavelet‐ to utilize wavelet as seen in theseismic it is highlyrecommended(similarapperance) * RickrWavelet‐ commonly used to havezerophase
- 47. SyntheticSeismograms • SyntheticSeismogramsareused tocorrelate seismicsections • Theoretically this method uses many simplificationand assumptionsput intothemodel • It provides importantlinkto understandthetiebetweenseismicdataand well log responses
- 48.
- 49. Velocity Survey • Velocityor check shot surveys areperformedin the wellboreto obtain vertical travelpaths through the formationsby locatingsourcesand detectors/receivers at certainconfiguration,normallythe receiversare placednearthe gelogicalhorizons • The surveyonly utilize first arrivalto use in the recordedseismictrace • First arrivalsarethen convertedintovertical travel timeson time‐depth graphs whichcan be used to calculate averagevelocities • Sonic log calibrationneeds to be done prior to generationof synthetic logs,normallyborehole effects arefound veryoften causingdriftwhichis to be removedto preventshiftingin timeof seismicreflectionsor pesudoevents
- 50. Vertical SeismicProfile • VerticalSeismic Profiling (VSP) uses both entire recorded seismic trace and first break. Receivers are spaced at very closed intervals in the wellbore in order to geta seismicsection in thewellbore • The seismicwaveand alleffects aremeasured as a function of depth as it propagates through theformations • Thr receiversare close to reflectorswhere up‐going and down‐goingwaves are recorded as a function ofdepth • The down‐going waveletsareused to design deconvolutionfilters • In general VSP provide much betterspatialandtemporalresolution,the signal changes intermof bandwidth and energy loss aremeasured • Applicatiosof VSP are to correlatetheactualseismiceventswith more confidence,and with much betterresolution due to shorter travelpathsit can provide a tool to generatehigh resolution maps,and betterestimateof rockproperties
- 51.
- 52.
- 53. Offset VSP • OffsetVSPareused to detect faultsand pincouts developedto illuminatestructureaway from thewellbore Multiple offset and walkaway VSP • Multiple offset VSP were developed to provide high-resolutionseismic structuraldetailsin the area where interference from the shallow layers • The disadvantages is very time consuming, it requiresfew days for the acquisition by puttingmultiplesourcepositioned in different locations
- 54.
- 55. BasicLogInterpretation Logs DataApplications • Determinedepthand thickness • Identify productive zones • Distinguishfluid types, gas, oil and water • Estimatehydrocarbonreserve • Help geological correlation and subsurface mapping • Determinefacies and drilling locations
- 56. BasicLog Interpretation Continued CommonTools in the Logging Industry • GammaRays • Self Potential • Resistivity • Induction • Density • Neutron • Sonic • Magnetic Resonance • FormationTest
- 57. Typical properties impliedor estimatedfrom the log Measurements: • Porosity • Water Saturation • Permeability Fluid types • Fluid contacts • Lithology • Dip angle • Velocity Basic Log Interpretation Continued
- 58. the followings; -Density - Neutron - Sonic Volume of pores Porosity = Total Volume of Rock Porosity= “Storage Capacity” Porosity is estimated using one or combination of Combination of three inputs will get better estimate Density Porosity: POR = (DENmatrix – DENlog)/(DENmatrix – DENfluid) Petrophysical Properties
- 59. Formation Water inthe pores SW = Total pore space in the rock Water Saturation is estimated using combination of the followings; - Porosity - Resistivity It requires formation factor and saturation index derived from core analysis, and formation water resistivity Petrophysical Properties Rt Archie’s Equation Sw = ( SW - Water saturation Rw - Formation water resistivity Rt - True Formationresistivity ) 1/Porm * Rw 1/n n - Saturation exponent m - Cementationfactor
- 60. Permeability Estimationfrom Logs K= 93*Por Swi Permeability (K) is a measure of rock property to get the fluid passes through the rock. The equations are based on empirical study, accurate K estimation can be obtained from formation test, drillstem test (DST) or from core analysis ( 2.2 ) 2 K= 250 *Por Swi ( 3 )2 Timur’s Tixier’s where Swi = Irreducible water saturation Petrophysical Properties
- 61. Objectives Get toknow various logmeasurements Recognize fluid type and lithology of major reservoirs,and some practicalapplications of log data Familiarizewith factors affecting the logresponse Understand the strategy in wellevaluation Get to knowvarious approaches to well loggingdesign Exercisewith well logdesign
- 62. Fluidand Lithology IdentificationFromthe Logs
- 63. Fluidand Lithology IdentificationFromthe Logs Gas Oil W ater Oil-Water Contact Water filled Sand Oil Sand Gas Sand Gas-Oil Contact Water filled Sand Water filled Sand Coal Carbonate/Limestone
- 64. RES 0.1 100 Fluid andLithology Identification From the Logs Oil-Water Contact Gas-Oil Contact Oil Sand Gas Sand Water filled Sand Water filled Sand Water filled Sand Coal Carbonate/Limestone
- 65. How Can WeRemember TheseEasily? About LithologyInterpretation • Claystone ‐ has large amount of water, and radioactive materials, is denser when ithas less water, is not harder than limestone and is very conductive. • Sandstone‐ is less dense than limestone, has less water than clay , contain more water than limestone except when itis saturated with dry gas,its conductivity is depending on fluid type it contains, has small to none radioactive fragments. • Limestone‐ is harder than both clayand sand, contains least water of the three, very resistive,it has low radioactivity materials, fastvelocity , high density . • Coal ‐ Normaly low radioactive,rarely radioactive,lowest density and very resistive
- 66. How Can WeRemember TheseEasily? About Fluid Interpretation • High Radioactivity • Very Conductive • High Water • High Gas • High Oil ‐ High GR ‐ Low Resistivity ‐ High Neutron and LowResistivity ‐ Low Neutron and HighResistivity ‐Higher Neutron than Gas, denser than gas Less Neutron than water, less dense than water, more resistivethan water, less‐ resistivethan gas when other properties are the same ‐ Very resistive,largest density neutron crossover ‐ Largerdensity‐neutron crossover than oil with low GOR ‐ Reservoir filled with high resistivewater • Dry Gas • High GOR • Fresh Water
- 67. Are There AnyAnomalies? About Fluid Interpretation • In a gaszone ‐Mud filtrateinvasion will causethe neutron‐density crossover looks like thatof oil zone, the shallowinvestigation resistivitywill be less resistivethan thatof deeperdepthof investigation,resistivitydifference is largerwhen conductive mud isused ‐High Irreduciblewater (water bounds in clays and grains’ surface)will demonstratelittle density‐neutroncrossover similar tothatofoil or water zonesbut less resistivethan gas or oil zones withless irreduciblewater • In an oil zone‐ similarto above
- 68. How Is LogAnalysis Calibrated? • Core Data Routie CoreAnalysis- For Porosity and PermeabilityCalibration Special Core Analysis - For detailed rock and fluid propertiessuch as X Ray Diffraction, ScanningElectronMicroscopy, Petrophysical parameters(a,m and n determination), PVT, Gas Analysis and finger printsof fluid samples, and etc. • Formation Test Fluid Identification from the logs is not direct, when the parametersare not well established,formation test fluid samples can be used to calibrate fluid identification using the logs. Formation test is also used when possible log responseanomaliesencountered to get conclusive fluid identification.
- 69. Modern Formation ForFluid Identification Electric Power Module Fluid Description Module Hydraulic Power Module Test Probe MDT StringConfiguration Large sample Chamber Multi sample Chambers
- 70. Basiccomponentsof thetool Probe Multi-sample Chambers Resist. sensor Pump Out Module Pre-Test StrainGauge Quartz Gauge Isolation Valve Optical Fluid Analyzer Flowline Probe HPGauge V alve Pre-Test Two Sample Chambers OLD NEW
- 71. OFA Gas DetectorOptics Gas Detector System Light Emitting Diode Cylindrical Lens Polarizer Fluid Flow Gas Liquid Gas Sapphire Prism Photodetector Array Sapphire window
- 72. OFASpectrometer How OFA DiviceOperates Fluid flow Sapphire Lamp Filter Lens Catridge Light Distributor Source Light path Solenoids Chopper motor Measure Light Path Filter lens Photodiode
- 73. OFASpectrometer How Can WeDifferenciate Fluid Types ? Fuel Oil Diesel Mud Filtrate Crude OilA Crude Oil B Water Near infra-red 0.0 4.0 Visible Optical Density 500 1000 1500 Wave Length - (NM) 2000
- 74.
- 75.
- 76.
- 77. Are There AnyOther LogsApplications? ➢Selecting Drilling Location ➢Well Completion ➢Subsurface Geological Mapping ➢Reservoir Characterization All are useful for The Logs Can Help Us to Determine: • Volume ofHydrocarbon • Fluidcontinuity • ReservoirExtent • ReservoirRockProperties • DepositionalEnvirontment • Diagenesisand Compaction • Trapping • Heterogeneity
- 78. Hydrocarbon Reserves Estimate Oilrec = 7758 * (1-Sw) * h * Por * RF *A Where : RF - Recovery Factor h - Thickness, A- Area BoI - Oil Vol. factor BoI = 1.05 + 0.5 * (Gas Oil Ratio/100) BoI (43560 * DEPTH*0.43)* (1-Sw)* h* Por*RF*A Gas rec = 15
- 79. LateralContinuity ? Well-1 Well-2 Well-7 GRRes GR Res GR Res
- 80.
- 81. Objectives Get toknow various logmeasurements Recognizefluid type and lithologyofmajor reservoirs,and some practicalapplications of log data Familiarizewith factors affecting the logresponse Understand the strategy in wellevaluation Get to knowvarious approaches to well loggingdesign Exercisewith well logdesign
- 82. Depth of Investigationand Resolution of Logging Tools 2 cm 0 cm 50 cm 200 cm 150 cm 100 cm Depth of Investigation 250 cm 5 cm 60 cm 20 cm 30 cm 40 cm 80 cm 80 cm Micro resistivity Micro log Dipmeter Sonic Density Radioactivity Gamma-ray Neutron Laterolog Induction log Resistivity Acoustic Resistivity Resolution
- 83. AIT SDT LDTCNT SGT LEH TCC AMS Additional combinable tools: - Dipmeter - Magnetic Resonance - Borehole Imager - Dipole Sonic - Formation Tester - Others Tools Size and Measuring point for Typical Oil Based Mud Environment Induction Sonic Density Neutron GR Measuring point from the bottom of the tool Tool Length This slide helps you to configure the tool string that is appropriate for yourwell
- 84.
- 85. Resistivity MeasurementProblems andLimitations Resistivitymeasurements are not reliable when you have: Severe invasion due to overbalanced mud Large washed-out borehole Shoulder bed affects High content of conductive minerals Some older tool generations have limited vertical resolution
- 86.
- 87. InvasionProfile Fresh Mud Rmf> RW Salt Mud Rmf < Rw Rxo Rxo Rt Rt Rm Rm S M D D M S Low High
- 88. SP LogLimitations The toolis only for water based borehole environment SP is not reliable when you have no or very small contrast between Formation water salinity and mud filtrate salinity resulting in no to small SP deflection GR Log Limitations Standard GR tool is not reliable when you log an interval with radioactive mineral rich rocks. NGT is recommended to use for this type of Formation to get reliable GR derived clay volume calculation. GR measurements in cased hole environment need to be normalized due to casing, and cement attenuation Density Log Limitations Density log is a pad device, it is very sensitive to the pad contact with The borehole wall, make sure to consult with your petrophysicist prior to using the data for any other applications.
- 89. Neutron LogLimitations Neutron logis very sensitive to environment change; bore hole size, mud cake, mud weight, temperature, stand-off, invasion, pressure and formation salinity, measurement is compensation of far and near count rates. Sonic Log Limitations Sonic log is likely affected by strong attenuation when we log unconsolidated formation, fractured formation, gas saturated reservoirs, aerated muds, rugose and enlarged borehole sections. Typically shows some curve skippings. Formation Test Log Limitations Formation test problems normally occur when you don not have a good Rubber pad seal, causing a communication with the mud giving you much Higher pressure reading. Depleted and highly invaded zone would cause long fluid pumping before you get clean sample or fluididentification
- 90. Objectives Get toknow various logmeasurements Recognizefluid type and thelithologyofmajor reservoirs, and practicaluses of logdata Familiarizewith factors affecting the logresponse Understand thestrategyof a well evaluation Get to knowvarious approaches to well loggingdesign Exercisewith well logdesign
- 91. Why Wireline Welllogging 1.Better Resolution 2. More advanced tools 3. Better depth control 4. Only choice available (certain tools) 5. More certain on data quality
- 92. DisadvantagesofWireline logging 1. Invasion effect 2.Hole condition dependant 3. Unable to log in high angle wells (>60 deg) 4. Acquired after drilling, more rig time 5. More uncertainty in getting data or good data in problem prone wells
- 93. Important Issueswith Running Wirelinelogs 1.Borehole fluid type 2. Borehole size 3. Welldeviation 4. Tool combination 5. High Mud Weight resulting in over balanced
- 94.
- 95. Why LWD? • ReduceRigTime • Real TimeDecisions • Minimized BoreholeProblems • High Angle/Horizontal Wells
- 96. Disadvantages ofLWD • Boreholesize and rugosity are not known • Good data collected only when the toolis rotating • Data qualityis ratedependant • Log resolution is generally poorer than that of wireline • Abilitytoconfigurethetools is limited • Not a good application fora slow drillingrate for cost considerationespecially for expensiverig. • Depthcontrolis poorer thanwireline data
- 97.
- 98.
- 99. LWD Real timeand RecordedLogs GR GR D. RES D. RES DEN DEN NEU NEU X500 X600 X700 X500 X600 X700
- 100. Selecting the Toolstorun What tools do you run in the hole? Itdepends on whattypeof informationyou are about to get and thecostyou are willing to spend. Need Want What is the value of information you are getting?
- 101. Ability to DefineYourNeed • Geological • Geophysical • Reservoir • Petrophysical • Mechanical
- 102. Typeof Information toAcquire •Geology ‐ Sand development and sandthickness ‐ Stratigraphic information ‐ Lateralcontinuity ‐ Hydrocarbonsource • Geophysics ‐ Velocity uncertainty ‐ Well to seismic tie ‐ Seismic and fluids/lithology correlation
- 103. Typeof Information… continued •Petrophysics ‐ Porosity ‐ Watersaturation ‐ Permeability ‐ Mineralogy • Reservoir ‐ Compartment ‐ Fluid properties ‐ Reservoirpressure ‐ Reservoirmonitoring • RockMechanics ‐ Stress direction ‐ Pressure profile ‐ Fracture orientation
- 104. Understand the ScalesOfObservation Seismic Section Wireline Logs Out-Crops/Core Thin Sections
- 105.
- 106. Objectives Get toknow various logmeasurements Recognizefluid type and thelithologyofmajor reservoirs, and practicaluses of logdata Familiarizewith factors affecting the logresponse Understand the strategy in wellevaluation Get to know various well loggingdesigns Exercisewith well logdesign
- 107. Well Logging DesignObjective Theobjectives of a well logging design should follow your drilling objectives, if drilling objective is not met, the objectives of logging program should be adjusted accordingly. A logging program would vary depending on drilling Objectives.
- 108. Well LoggingDesign‐1 • Onshorewell Adevelopmentwell,A‐5,is todrill updip structureofA‐Sand to accelerate oil production,the A‐4 well has produced this Reservoir for a year , and currently produces 80% water . The reservoir has a strong aquiverdrivemechanism.
- 109. Well LoggingDesign‐1 continued •Drilling objective is todrill and complete theA‐Sand Level • Logging program objective for this well is then to locate the top of theA‐Sand and make sure that theinterval is still in the oilcolumn. • Other information:Strong water drive means it has good pressure maintenance, therefore, no need totake pressure data. • Rigtype: Onshore Rig (inexpensive), a vertical well. • Logging Design :WirelineGR‐Resistivity‐Neutron‐Density
- 110. Well LoggingDesign‐2 • Offshorewell Athird appraisal well is proposed on the west flank of the structure. First two‐wellssuggest that well to well log correlationis not easy,however pressure data has helpedthe well to well correlation. This well is to reveal the lateral continuityand the compartmentissue of the reservoirs.
- 111. Well LoggingDesign‐1 continued •Drilling objective is todrill and tofind out the lateral continuity of somereservoirs. • Logging program objective is to collect as much datato confirmlateral continuityand well towell correlation. • Otherinformation:Thewell is still in theappraisalphase. • Rigtype: OffhoreRig (expensive), directional well? • Logging Design: ‐ LWD GR‐Resistivity‐Density‐Neutron ‐ Wireline GR‐Resistivity‐Density‐Neutronascontigency in case LWD data is not reliable ‐ Wireline formationtest forpressure correlation ‐ Wireline OBMI forstratigraphic information to help well to wellcorrelation
- 112. Example‐1‐ LoggingProgram • 26“Conductor ‐ 3500’to3700’MD None • 20”Casing ‐ 3700’to 4100’MD None • 17‐1/2”Hole section 4100’to 6000’MD ‐ LWD: GR‐Resistivity • 12‐1/4”Hole Section 6000’to 9000’MD ‐ LWD: GR‐Resistivity‐Density‐Neutron ‐ Wireline: T riple combo only when LWDfail Formationtestasrequired • 8‐1/2”Hole section 9000’to 12000’MD ‐ LWD: GR‐Resistivity‐Density‐Neutron ‐ Wireline: T riple combo only when LWD fail Formationtestas required Borehole image as required Nuclear Magnetic tool asrequired
- 113. Example‐2Logging Program Continued •8‐1/2”Hole Section 9000’to 12000’MD LWD: GR‐Resistivity‐Density‐Neutron Wireline: T riple combo as a contingencywhen LWDfail Wet Case: T riple combo as a contingencywhen LWD datais not reliable Formationtestsfor pressures and watersamples H.C.Case: T riple combo as a contingencywhen LWD datais not reliable Formationtestsfor pressures and fluidsamples Borehole image log for dip and stratigraphicinformation Nuclear Magnetic tool when considerablethick‐shalysand reservoirsare penetrated Borehole seismicfor velocitysurvey
- 114. Important Aspects ToConsider •Risk • Cost • Environment • Hole Size • WellDesign • ToolSpeed
- 115. Important Aspects ToConsider Someexamples • Risk ‐While we are running in hole with wireline tools, the tools could not go down at certain depth. Thecompany representativehas decidedto pull out of hole to run different toolconfiguration. ‐In case of a risk that we are not able to go down passing the same depth withnew tool configuration, the petrophysicisthas asked thelog engineer to log up while pulling out of hole to get data assurance.
- 116. Important Aspects ToConsider Someexamples • Cost ‐Afterthe well reached TD at 6000 ft, the team found out that they do not have room to get all log data tothe baseof the reservoir near TD if they use typical triple combination wireline tools, to drill additional50 ftwould take24 hour rig time including RIH andPOOH. ‐The petrophysicisthas then decidedtosplitthe tools into tworuns, whichonly require additional6 hour rig time for second wireline run. By doing that it would have saved 18 hour rig time if they drill additional50 ft to have only one logging run
- 117. Important Aspects ToConsider Someexamples • Environment ‐The well is to drill complex lithology interval in Jurasic section. Where coal, shale, sand, limestone can be penetrated in thesamehole section. ‐The geologist and petrophysicisthave suggested their drilling team to drill the well with oil based mud to help possible swelling clay problem, formationof limestone ledges and washed‐out sand section, therefore it would promotea smooth and successfullogging operationafter they reach TD.
- 118. Important Aspects ToConsider Someexamples • Hole Size ‐The Drillingengineer has suggested torun only LWD in the 12‐1/4” hole sectionto reducewell cost. ‐The petrophysicisthas argued and suggested to run wireline becausebased on previous wells in this field where they havedrilled at average rate of 300 ft/hrresulting in not reliable data.The team has supported theirpetrophysicistto run wireline because it would help to support field certification.
- 119. Important Aspects ToConsider Someexamples • Well Design ‐Afterthe G&G team provide the targets to the drilling engineer , theteam has to end up witha well design that it requires a highly deviated well exceeding 60 deg. ‐LWD log data acquisitionis then put in their logging programbecausebased on theirexperience in this field 50 deg well was the highest deviated well that they could log withwireline.
- 120. Important Aspects ToConsider Someexamples • ToolSpeed ‐Based on thestatistics drillingthe Pliocenesectionis very quick, averaging400 ft/hr , the company is drilling a horizontalgas well at about 3000 ftTVD. ‐LWD engineer and the petrophyscisthave worked together and havegivena recommendationtodo controlleddrillingat about 200 ft/hrtoget an acceptable log data quality.
- 121. What do youhavein mind? On Shore Development Well Off Shore Deep water development-well In respect to Risk, Cost, Environment, Hole Size, Well Design, Tool Speed
- 122. ExploratoryWell • Seismic Information •Regional GeologyInformation • Drilling the well using “Learning while doing” concept • HighRisk but must be manageable • Mostly Verticalwell
- 123. DevelopmentWell • In Manycases with littleto no need of seismic information • Local GeologyInformation • Drilling with fullknowledge • Low Risk mainly mechanical • Vertical,highly deviated to horizontalwells
- 124. An Exampleof rathercomplexLoggingProgram DecisionTree West Seno Data Gathering Strategy Standard well PAY Fully Loade d Wireline Full Cor es SAMPLING LWD SAMPLES LWD 12 1/4 “ WIRELINE PAY PRESSURE P.O PEX MD T CST Cor es Special Logging Velocity Uncertainty UBI or CBL SAMPLING Cased HoleGR CSAT or VSP GR to bottom of 13 3/8 “ STOP STOP Y N Y Y Y Y Y Y Y Y Y Y N N N N N N N N N N N N LWD MDT Objective Objective driven-logging De epest Well VSP STOP N
- 125. Another Way ToSaveCost! •ACQUIRE DAT A WITHOUT USING COSTL Y RIG TIME (PIPE DECISION NOT NECESSARY ‐NO DRY HOLES) – GATHER DATAREALTIMEWHILEDRILLING – GATHER DATATHROUGHTUBING AFTERCOMPLETION – COMBINATION OFBOTH
- 127. Project BaseApproach UOME companyhas $200 MM programfor exploratory wells for the year 2004. As a follow up of their exploration campaign, UOME Company has $ 600 MM program for developing a new deepwater field for the year 2005 that willhave peak productionof 100,000 BOPD
- 128. Objectives Get toknow various logmeasurements Recognizefluid type and thelithologyofmajor reservoirs, and practicaluses of logdata Familiarizewith factors affecting the logresponse Understand the strategy in wellevaluation Get to knowvarious well logging designs Exercisewith welllogdesign
- 129. Exercise‐1 • PT IndooilCo.,the sole owner of mineralright on BlockA, on‐shore, 2 km in adjacenttoa known oil producing areain the Block B.The company is looking ata prospect to drillthe firstwell, Indoco‐1,in the block targetingforthe same producing intervalin BlockB atabout 4000 ft depth,and itis estimated50ft down dip in thisblock. • The costsfor various availablelog dataacquisitionareas follow: • Wireline GR ‐ $1/ft,Induction ‐ $4/ft,BHC Sonic ‐ $1/ft,Density‐$2/ft,Neutron‐$2/ft • Formationtest‐$100/pressure,$1000/fluididentification,$2000/fluidsample • Depth charge for each Wireline tool isfree. • LWD GR and Induction ‐ $10,000/day ,Densityand Neutron ‐ $10,000/day • The rig cost is$5000/day • 1) What is your recommended datagatheringstrategyand welllogging designfor the well? • 2) While drilling, thewellpenetrates5 thicksand units with high mud log gas from 3,000to 4,200ft.How do you recommend the company on the logging design? • 3)After the wellreached the proposed TD,there were no encouragementseenfrom the mud log signs,what would you do for your logging program?
- 130. Exercise‐2 • The exercise‐1was seismically to test the amplitudeanomaly at Orangehorizon,equivalenttothe Berani Clastic Formation. The Indoco‐1 well encountered 300 ft of Oil column and was completed and produced from this level for over one year with cumulative production of 4 mmbo.The company is looking at similarseismic character 1‐1/2 km away from Indoco‐1 well, which was connectedby dim event to the amplitudeat theIndoco‐1 well. It has been interpreted as a different channel lobe. The companydid low profile and ran only simplewireline GR,resistivity, density, neutron and sonic on the Inoco‐1well. • What is your data gathering strategy forthis Indoco‐2 well?
- 131. Exercise‐3 • Asubsurfaceteam isevaluatinga four‐wayclosure structure offshore East Kalimantan, based on their synthesis,if the timing of migrationis right, it is a big structurefilled with hydrocarbon.The water depth around the prospect isabout 4500 ft. T oproperly evaluate the prospect, the team thinks that they need at least 8 wells drilled at various locationson the structure. Some apparent faults due to regional compressivestress cut the structureinto possible many compartments. • Make assessment on options the companyneeds todo and make recommendationon well evaluationstrategy.
- 132. Exercise‐4 • An offshorewell is proposed to redrill the A‐5 well with updip direction fromthis well to get the gas leg of clean and blocky sand found with gas water contact in the A‐5 well.The company is trying toget more gas production. The team is looking at drilling horizontal well with about 500 ft of producing section. What is your recommended logging programfor this well and why?