science behind well logging_dileep p allavarapu

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science behind well logging_dileep p allavarapu

  1. 1. Well-Logging Exercise for Students Dileep.P.Allavarapu dpa.taeching@gmail.com /or motherindia.energy@gmail.com 9703070878
  2. 2. EACH DISCIPLINE HAS ITS OWN IMPORTANCE & ROLE in E&P RESERVOIR MODELING OPEN HOLE LOGGING (RES, POR, LITH LOGS) -LWD/WL MUD LOGGING CORE ANALYSIS DRILLING &LOGGING STATIC MODEL INTERPRETATION MODEL & UNCERTAINITY CERTAINITY CORE ANALYSIS 3D & VSP GEOLOGY & SEISMIC CASED HOLE /PL LOGGING (cement eval,flow rate ,fluid Tests) -WL INJUCTION DATA FLUID STUDIES DYNAMIC MODEL FLUID STUDIES 4D
  3. 3. THE ULTIMATE GOAL OF conventional log INTERPRETATION Calculation of S Hc * φe in each reservoir rock unit Preparation of a PARA LOG
  4. 4. Important Points
  5. 5. Sand Stones: Log Analyst: Composition (Sand Stone) Framework of Quartz and Feldspar Grains(Majority)/ Other Fragments (Non Majority)/ Cement (Quit Limited)) Processing Engineer: Matrix (Sand Stone) K-Na, Ca Al Si3 O8 Si O2
  6. 6. Shales: Frame work ,Matrix, Cement are Clay Minerals ( Kaolinite,Montmorilllonite,Illite) Minute percentage of Non Clay Minerals. 90% Clay Minerals K Feldspar derived Radio Active K rich clays Rain water derived U,Th Br salts K (12%),U Th (<500ppm) Laminar ,Dispersed, Structural Lime Stone: CaCO3 chemically precipitated calcium Dolomite: Mg CO3(upto 12%)+CaCO3 chemically precipitated
  7. 7. Traps : Structural (tectonics), Stratigraphical (depositional environment), Combinational What is Local Gravity High(LGH) ? Anhydrate /Denser minerals in hydrothermal fluids closed to intrusive salt dome remains as top . Gravity is low over dome , central part have comparatively high gravity In past ,North Brazilian sea have potassium rich salts.
  8. 8. STUDY THE LOG RECORD (to take proper action in any stage of interpretation ) UNDERSTANDING LOG HEADer- MAINfo- TAILer,…. DISPLAY INFORMATION . TOOL SKETCH , CALIBRATION , PERFORMANCE & REMARKS ……… MARK THE INTERESTED ZONES QUICK LOOK INTERPRETATION (to take the readings ) POROUS –PERMEABLE ZONES : WATER /HC BEARING ,OTHER RESERVOIR ROCK UNITS TAKE READINGS & LIST OUT THE INERPRETATION FORMULA (to calculate the interpretation parameters) GR , SP , CALIPER, RESTIVITY ,MICRO RESISTIVITY, NEUTRON ,BULK DENSITY ,SONIC TRANSIT TIME DETAILED INTERPRETATION
  9. 9. GR FOR IGR SP/RESISTIVITY &NEUTRON FOR Rw RESISTIVITY FOR Rt NEUTRON , BULK DENSITY ,SONIC TRANSIT TIME FOR φe CALIPER, MICRO RESISTIVITY FOR k indication FOR S w, S hc, S movable , PAY
  10. 10. Archie's Equation : Archie's experiment concludes an empirical relationship between resistivity of the water bearing formation and water, pore volume it contain and also water saturation.
  11. 11. If Sw = 1 , means water-bearing formation Resistivity of water Resistivity of waterbearing formation Formation factor
  12. 12. Volume of Shale: The percentage of shale present in the rock unit Response in the zone of interest Shale Clean formation Indonesian Equation
  13. 13. GR: The record of count rate of Natural GAMMA as a result of emission from RADIO ACTIVE MINERALS present in the ROCK UNITS RADIO ACTIVE MINERALS are more in the CLAYS & SHALES GR infer the LITHOLOGY whether rock unit is having CLAYS & SHALES or not In the first /each run (lowering tool), first track (left side of log paper) 0-100 API (10intervels) along with CALIPER,BIT SIZE , SP. GR around 30 -SAND up to 50 -SAND SHALE up to 80 -SHALE SAND up to 100- SHALE more than 100-CLAY Volume of Shale DEPTH GR Vsh
  14. 14. SP: The record of voltage variation as a result of electrolytic conduction due to salinity variation between fluids present in the ROCK UNITS electrolytic conduction is more across porous –permeable rock unit SP infer the LITHOLOGY whether rock unit is having porous& permeable SAND or not In the first /each run (lowering tool), first track (left side of log paper) 0-100 units (10intervels) along with CALIPER,BIT SIZE ,GR. SP +Ve : R mf <R w : Shale Base Line is in left side of Sand Deflection Line SP in the same well either +Ve or –Ve : crossover indicates the presence of HYDROCARBON
  15. 15. OR K=61+0.133T°F R we to R w conversion chart DEPTH SSP K 10 ˆ(SSP/K) Rwe R w
  16. 16. BIT SIZE : size of the drill-bit used CALIPER: size of the drilled hole Grater than BIT SIZE : absence of permeable rock units / factures Less than BIT SIZE : presence of permeable rock units /MUD CAKE RESISTIVITY : Apparent resistivity of the formation (can calculate true resistivity by using at least three apparent resistivity values ) Using Resistivity Tool: in saline muds , good contact between annulus electrode and BH wall. Using Induction Tool : in non saline muds In the first run (lowering tool), first track (middle of log paper) 0.2-2000 units (log scale) Configuration : App resistivity = (Geometrical factor × Observed voltage difference)/ Sending current Characteristic charts used to calculate true resistivity from apparent resistivity
  17. 17. DLL MSFL Invasion Correction charts DLL MSFL LOG RECORD (R t / R LLD )× R LLD = R t DEPTH LLD LLS MSFL LLD/LLS LLD/MSFL Rt/LLD Rsh = Rt in shale RO = Rt in WBZ Rt
  18. 18. NEUTRON: The count rate of back scattered neutron/gamma as a result of energizing rock units with neutrons (source: Am Be -16 curie) Sending neutron lose total energy and collapse into the nuclei of HYDROGEN and release a Gamma Response α Hydrogen Index In the first run (lowering tool), third track (right side of log paper) 0.54 - -0.06 (10intervels) along with SONIC ,DENSITY. NEUTRON : Gas < Oil <Water in sand Sand < Shale (bounded water) Correction for shale: Φ Nc = ΦN-(Vsh× ΦN in shale) Neutron Porosity Φ N = ΦN corrected calibration
  19. 19. Chemical Sources: Neutron sources o Am241-Be9 : emits neutrons with mean energy of 4.2 MeV. oz Californium(Cf252) : emits neutrons with mean energy of 2.35 MeV. Gamma sourceso Cesium(Cs137) produce a steady flux of gamma rays at 662 KeV Electrical Generators: This device produces 14 MeV neutrons by accelerating deuterium ions into a tritium target (up to 125,000 V DC).
  20. 20. NEUTRON SOURCE ENERGY LEAVING SOURCE NEUTRON ENERGY (e V) 106 104 102 10 eV APPROX. EPITHERMAL ENERGY REGION 1 .4 eV AVERAGE THERMAL ENERGY . 025 EV CAPTURE 01 1 10 TIM E ( µ s ) 100
  21. 21. Φ N RT GR 20 97 24 24 78 23 22 69 25 28 72 26 30 52 23 Will get Rt =100 Sand Stone Matrix Point ∆t = 48, φN =0 , ρb =2.65 ΦN = 0 10 20 30 40 50 Choose Φ=20
  22. 22. now mark the point φ=20,Rt=156.25 & draw the 80% saturation line Rw=4.878 Sw =80% =0.8 Rt = 100/0.64 = 156.25 now replace the 0.64 by 0.36,0.16,0.04 …..to get the 60%,40%,20%,…… saturation lines
  23. 23. SW =1=100% Red Points GR=23-30 Blue Points GR=30-40 Yellow Points GR=40-50
  24. 24. Sw=0.8=80%
  25. 25. Ro =F Rw Rt= F Rwa Different Trend HC indication Main Trend Rwa line WBZ
  26. 26. 50 = φ DC -10 0 10 20 30 40 GAS -10 0 10 20 30 40 50= φ NC
  27. 27. DENSITY : The count rate of back scattered gamma as a result of energizing rock units with gammas (source : Cs 137) Sending gamma undergone Compton Scattering no of collisions α no of electrons in rock unit ρe ρb = 1.0704 ρe + 0.1883 In the first run (lowering tool), third track (right side of log paper) 2.8 -1.8 (10intervels) along with SONIC ,NEUTRON. DENSITY: Gas < <Oil <Water in sand Correction for shale: Φ Dc = ΦD-(Vsh× ΦD in shale)
  28. 28. Effective Porosity: Volume of interconnected pores Neutron Correction for shale: Φ Nc = ΦN-(Vsh× ΦN in shale) Density Correction for shale: Φ Dc = ΦD-(Vsh× ΦD in shale) DEPTH Φ N cal Φ NC ρb φD φDC Φeff
  29. 29. Indonesian Equation S HC = (1-SW) DEPTH Rw Rt Φ eff S W S Hc S Hc × Φ eff
  30. 30. Here our goal need more data from ROCK PHYSICS LABORATORY, so it limited to S hc × φ e
  31. 31. Conventional Open hole logs Lithology logs (SP,GR with CALIPER) Porosity logs (NEUTRON, DENSITY ,SONIC) Resistivity logs (RESISTIVITY, MICRORESISTIVITY) Lithology (shale ,sand ,…) Porous –permeable beds (no of ,thickness) Shale volume Effective porosity Type of fluid Contacts (GSC,GOC,OWC,GWC) Uncompacted Formation water & True resistivity Saturation MHI Permeability indication
  32. 32. GSC GOC WOC
  33. 33. General Information
  34. 34. Lithology GR Rt φN Sand Stone ( more compacted & dry ) Less=25 Less clay minerals More=1000 SiO2 insulator / no electrolytic conduction Less<10 More=2.6 No fluid / no H2 Closed grain packing Sand Stone ( less compacted & wet) Less=25 Less clay minerals Less<100 Saltwater conductor / electrolytic conduction More=10-30 Having H2 Moderate=2.1 (30% H2O=1 /70% SiO2 =2.6) Having oil Less=25 Less clay minerals Moderate >100-700 Oil insulator (at least 5times of R0 ) More=10-30 Having H2 (less than water zone) Moderate=1.9 (less than water zone) Having gas Less=25 Less clay minerals More >700 Gas insulator (at least 5times of More=10-30 Having H2 (less than oil Less =1.8 Having water ρb
  35. 35. Lithology GR Rt φN ρb Sand-Shale ( more compacted & dry ) Less=30-50 More or less clay minerals More<100 Dry clay insulator ,bounded water in composition / not much electrolytic conduction Less=20 No fluid / bounded water H2 More=2.5 Closed grain packing (30%shale =2.3,70%sio2=2 .6) Sand-Shale ( less compacted & wet) Less=30-50 More or less clay minerals Less<50 Wet clay conductor / more electrolytic conduction More=20-40 Having H2 Moderate=2.2 (20% H2O=1 ,50% SiO2 =2.6 30%Shale 1.82.6) Having oil Less=30-50 More or less clay minerals Moderate >100-700 Oil insulator (at least 5times of R0 ) More=20-40 Having H2 (less than water zone) Moderate=1.8 (less than water zone) Having gas Less=30-50 More or less clay minerals More >700 Gas insulator (at least 5times of oil zone ) More=20-40 Having H2 (less than oil zone) Less =1.7 Having water
  36. 36. Lithology GR Rt φN ρb Shale ( more compacted & dry ) More =80-100 More clay minerals (80%) More<50 Dry clay insulator / not much electrolytic conduction Less=30-40 No fluid / bounded water H2 More=2.3 Closed grain packing Shale ( less compacted & wet) More =80-100 More clay minerals Less<10 Wet clay conductor / more electrolytic conduction More=40-50 Having H2 Moderate=1.9 (30% H2O=1,70% shale=2.3) , More >100(120) More clay minerals More<50 Dry clay insulator /Less<10 Wet clay conductor Less=30-40 More 2.4 Having water Clay
  37. 37. Dileep.P.Allavarapu dpa.taeching@gmail.com /or motherindia.energy@gmail.com 9703070878 Contact any Institution Dept. of Mathematics, MGR Junior College Dept. of Chemistry, LAMP Degree College Dept. of Geophysics , Andhra University Logging Base ,ONGC –Rajahmundry Asset Oil and Gas Deliveries, Infotech Enterprises Limited Gravity Observatory , Gravity Group-NGRI Seismological Observatory, Warna Canal Division-MERI UV Physics Academy Analog IAS Academy THANK U

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