Well Logging and Interpretation PDF

WELL LOGGING AND INTERPRETATION IPES Course Course Content: ◼ Introduction ◼ Introduction to Wireline Logging ◼ Main Logging Tools ◼ Rw Determination ◼ Lithology and Porosity Determination ◼ Shaly Formations Evaluation ◼ Others Important Logging Tools (NML, Dipmeter, Formation T...

WELL LOGGING AND INTERPRETATION IPES Course Course Content: ◼ Introduction ◼ Introduction to Wireline Logging ◼ Main Logging Tools ◼ Rw Determination ◼ Lithology and Porosity Determination ◼ Shaly Formations Evaluation ◼ Others Important Logging Tools (NML, Dipmeter, Formation Testing) ◼ Appendix and Exercises 2 INTRODUCTION 3  Generalities FROM GEOPHYSICS TO RESERVOIR : PRINCIPLE OF SEISMIC REFLEXION 4 VIBRO-TRUCKS ON LAND Emission Recording Truck Source : Virbro Reception Receivers : Geophones OFFSHORE ACQUISITION Source Well  Generalities EXAMPLE OF SEISMIC SECTION SEAL ? RESERVOIR ? TRAPPED HYDROCARBONS ? Time in ms Source Rock? MIGRATION OF HYDROCARBONS ? Well  Drilling phases and bit sizes Drill Bit Sizes : 26 inches 17.5 12 ¼ 8½ 6 Casing Diameter (OD) : 20 inches 13 3/8 9 5/8 7 5½ (Most common sizes ) Casing Open Cased Cement Hole Hole Phase -1 2 Casing Phase 2 Cement Phase-3 Drilling Seal Mud Gas Reservoir 3 Oil Reservoir Water Reservoir Well  Mud logging/Wireline Logging/MWD & LWD INTRODUCTION As soon as an oil target has been defined by geological and geophysical studies a well positioning analysis is performed to optimize chance of oil encountering and drilling can begin. The measurements in boreholes correspond to a set of techniques whose purpose is to obtain local information on the formations being drilled, the fluids that they contain and the state of the well; this information can confirm or not the surface studies. The direct information (cuttings, cores, fluid samples) is always insufficient, so it needs to be supplemented by a whole series of downhole operations called logging, a term including all the various methods used for carrying out measurements in a borehole. The logging operations are regrouped in three categories: 1) Mud Logging 2) Wireline Logging 3) MWD/LWD – Measurement While Drilling & Logging While Drilling 7  Mud logging/Wireline Logging/MWD & LWD Mud Logging Its aim is to ensure the well site geological monitoring, the behaviour of the weII, while also maintaining the desired drilling conditions. Mud Iogging is carried out during the entire drilling of the hole and the information is: - Recorded from sensors positioned on the rig or - Recorded by physical analysis of the cutting coming out of the hole inside the mud. The Mud Logging Record covers the whole geological study of the well by analysis of the cutting as well as the complete drilling parameters for each drilling phase. 8  Mud logging/Wireline Logging/MWD & LWD WeII Logging (Wireline logging) These are measurements of physical parameters (electrical, acoustic, nuclear etc.) carried out periodically during the halt phases in the drilling, (usually after the completion of a drilling phase) after the drill pipe string has been pulled out. The measuring equipment is incorporated inside sondes that are lowered in the hole by means of an electrical cable. The information measured by the logging equipment is sent to the surface computer through the electrical cable and is recorded in “real time” which means that no time delay exist between the measurement inside the hole and the interpretation of the data by the computer. Since the logging equipment is lowered inside the hole by a cable, this technique cannot be executed when the angle of hole deviation exceed 75 ° 9  Mud logging/Wireline Logging/MWD & LWD Measurement/Logging While Drilling (MWD- LWD) Both of these types of measurements are carried out during drilling, and yield information obtained via sensors placed on the drill pipe string, above the drilling bit. This measured information can relate to the drilling conditions and is then called Measurement While Drilling (MWD) or can be related to the petrophysical parameters of the formations being drilled and is than called Logging While Drilling (LWD) In highly deviated wells and in horizontal wells LWD is often the logging technique used to acquire formation parameters. 10 MUD LOGGING 11  Mud Logging DEFINITION Mud logging involves measurements that are done while the drilling operation is in progress. It is done from the beginning of the drilling (spudding) to the end of the drilling of the last phase It includes: ◼ Drilling parameters: Parameters needed to optimize the drilling operation (weight on bit, rate of penetration, rotational speed and drilling fluid pumping rate). ◼ Operational variables: Parameters that monitor the good progress of the drilling operation (rotary table torque, mud pump, discharge pressure, drill string depth, flow of the return mud and levels in mud tanks, mud properties (inlet and outlet)) ◼ Geological variables: Parameters and properties associated with the geological formations that are drilled (cuttings composition, dissolved gas composition) 12  Mud Logging RIG INSIDE CABIN (Geological side) MUD LOGGING UNIT 13 Mud Logging 14 Mud Logging Real Time Measurement 15  Mud Logging INSTANTANEOUS PARAMETERS LAGGED PARAMETERS HOOK HEIGHT ➔Bit depth and Rate of Penetration ▪ GAS IN MUD WEIGHT ON HOOK (WOH) ➔ Weight on Bit HYDROCARBONS : C1  C5 RPM (Rotations per minute) HYDROGEN SULFIDE (H2S) TORQUE CO2 (optional) INJECTION PRESSURE (Stand Pipe Pressure) H2 (Optional) WELL HEAD PRESSURE (Annular Pressure) MUD PIT LEVEL ▪ MUD PARAMETERS OUT MUD PARAMETERS IN DENSITY DENSITY TEMPERATURE TEMPERATURE CONDUCTIVITY CONDUCTIVITY MUD FLOW RATE OUT MUD FLOW RATE IN ▪ FORMATION Lithology (cuttings %) Calcimetry (% of Calcium) 16 Mud Logging 17  Mud Logging Geological side Drilling Control side 18  Mud Logging CATCHING SAMPLES ON THE SHALE SAMPLE OBSERVATION & SHAKERS DESCRIPTION 19 Mud Logging 20 Mud Logging 21 Geological Log 22 Geological Log 23 Coring 24 Coring 25 Coring 26 WIRELINE LOGGING (ELECTRICAL LOGGING) 27  Wireline Logging Introduction Wireline Well Logging began in 1927 when the Schlumberger brothers (Marcel and Conrad) carried out the first resistivity measurement in a drilled well at the Pechelbronn field in France. Since this first resistivity measurement the techniques of wireline logging have continuously improved both in technology and in new concepts. The need for reducing risk in oil filed development has been the drive for logging companies to develop equipment capable of precisely analyse reservoir characteristics in order to estimate the volume of oil in place with the best possible accuracy. Now days the Wireline logging companies (Schlumberger, Halliburton, Baker Atlas) are all major oil industry services providers capable of making huge profits. The wireline logging techniques use the latest available technology and wireline logging cost can be as high as 10% of the cost of the whole well. 28  Wireline Logging Introduction What is a LOG? ◼ A Log is the graphic representation of the variations of one parameter as a function of depth (or time) ◼ Wireline logs are measurements of physical parameters in the formations penetrated by borehole. They are run when drilling has been stopped (typically at the end of a drilling phase after the well has been stabilized and the drill string has been pulled out). They are therefore different from mud logging operations which is carried out while drilling. ◼ The logs are usually in the form of curves that show the measurements performed on a graph with a depth scale of generally of two-hundredth or even one-thousandth. (200 or 1000 meters of formation are represented by a graph of 1 meter length) ◼ The log are nowadays recorded also as an electronic file (ASCII file) for easy input in well logging interpretation software. 29  Depth scales Scale 1/1000 Scale 1/500 Scale 1/200 GR DEPTH GR DEPTH GR DEPTH 0 GAPI 100 METRES 0 GAPI 100METRES 0 GAPI 100METRES CALI DT_1 CALI DT_1 CALI DT_1 6 IN 16 140 US/FT 40 6 IN 16 140 US/FT 40 6 IN 16 140 US/FT 40 1795 1800 1800 1800 1825 1810 1805 1850 1820 Depth Scales 1830 1810 1/500 or 1/1000 : Scales for geological correlations 1840 1815 1/200 : Standard scales for reservoir 1850 identification and characterisation; Selection of intervals to tests and perforate Well  Wireline Logging Introduction What is a LOG? ◼ The measuring equipment which is lowered inside the borehole is made of several tubes usually 3 ½” in diameter which contains electronics equipment and sensors (called sondes). This equipment is capable to withstand temperature of 175 °C and pressure of 15000 psi. ◼ The logging equipment is run inside the borehole at the end of a wireline cable. This cable (1/2” diameter) has 7 electrical wires capable of sending current to the downhole equipment as well as sending the measured parameters to the surface computers positioned inside the Logging Unit. The wireline cable which have a length of over 6000 m is wound on a drum situated in the logging unit. The logging cable has also the mechanical properties to withstand his own weight and the weight of all the equipment (10 Tons pulling capability) ◼ The logging operation which is usually done at the end of a drilling phase consists of a series of run inside the borehole with different equipment and can last 2 to 3 days for large logging operation. 31 Wireline Logging Unit 32  Logging cabin Log Control screen Panels Reference Log Tool Power Well  Wireline Logging Tools SONIC BHC Sonde Caliper SONIC DSI Sonde Centralizer Electronic Cartridge Stand-off 34  Wireline Logging Tools ◼ The logging tools have a diameter ranging from 3.5 to 5 inches and their lengths vary from 30 feet to 100 feet ◼ They are run inside the well either Pad Tool centralized (in the middle of the borehole or decentralized (against Back-up arm the wall of the borehole) ◼ Some tools which have imperatively to be decentralized are Pad incorporated inside “Pad”. 35 Wireline Logging Op. 36  Well Logging Operations Sheave Cable or wireline Depth Tension Measurement Measurement Kelly Bushing Drill Floor DF KB or Ground Level Rotary Table RT Cable Drum GL Truck and Computer Measured Depth Measured Depth MD below DF MD below DF (Deviated well) (Vertical well) Vertical Well Head Tension Measurement Deviated Well Logging tools 37 RIG UP ON LAND  DEPTH - REFERENCES MD - TVD - TVDSS Deviated Well On Land Offshore Kelly Bushing KB Drill Floor DF or Rotary Table RT DF Ground Level DF GL MSL MSL Mean Sea Level (Reference) TVD TVD-SS MD GL TVD TVD-SS MD WOC WOC Reservoir Well Log 40 Well Log 41 Computer Log Interpretation 42  Well Logging – Observation Scale In well logging the observation scale is roughly 10 to 15 cm SEISMIC SECTION WELL LOG CORE CORE THIN SECTION PLUG TENS_1 11000 LBF 1000 PEF_1 0 B/E 20 DRHO_1 -0.35 G/C3 0.15 BS_1 RHOB_1 4 IN 14 1.95 G/C3 2.95 METRES DEPTH GR_1 IDPH_1 NPHI_1 0 GAPI 100 0.2 OHMM 2000 0.45 V/V -0.15 CALI_1 IMPH_1 DT_1 4 IN 14 1510.2 0.2 OHMM 2000 140 US/F 40 4 25 mm mm 1515 1 km 1520 1 mm 1525 25 m 1 m 1530 10 m 1535 1 mm 500m 1540 1545 1550 100  1555 ELECTRONIC MICROSCOPE 1560 43  Well Logging - Definitions ◼Sampling: The vertical distance between two consecutive measurement – It is usually 6”. ◼Depthof investigation: the distance inside the formation until which the measurement will be made. From a few inches to several feet depending on the nature of the measurement ◼VerticalResolution: the smallest measurable thickness of a bed. It can range from a few inches but is mostly between 2 to 3 feet. ◼Tool Calibration: like all precise measurements Wireline logging tools are calibrated regularly in the Logging company base and these calibration are checked on the well site before and after each trip in the drilled hole ◼Repeat Section: The measurement is repeated on a short interval (usually 200 ft) to check for proper repeatability of the measurement ◼Overlap: A part of the well which is logged at two different times during two different operations ◼Header:The part of the log that contains the required information necessary to validate the measurement (Well name, Position of the well, mud data, casing data….) ◼ASCII file: the data being recorded on electronic format (usually *.las) 44  VERTICAL RESOLUTION RELATIONS between LAYER THICKNESS and VERTICAL RESOLUTION of the TOOLS 10 cm Log True value value True Layer value thickness Log value MACRO-DEVICES MICRO-DEVICES DIPMETER Gamma Ray Micro-resistivity Neutron Density Sonic Laterologs Inductions 45  DEPTH OF INVESTIGATION & VERTICAL RESOLUTION Symbol Average Approximate Vertical Depth of Resolution investigation ◼ NATURAL RADIOACTIVITY GR 0,5 - 1m 0,5 m ◼ POROSITY NEUTRON N DENSITY b 0,5 - 1m 0,3 m SONIC t ◼ RESISTIVITY LATEROLOG Rt 0,5 - 1m 2-3m INDUCTION Rt 0,5 - 1m 2-3m MICRO-RESISTIVITIES Rxo 0,2 - 0,3m 0,1m ◼ SPONTANEOUS POTENTIAL PS 1m ◼ DIPMETER 0,01 m 0,1 m 46  ASCII File Example ~A DEPT BS1 CAL1 SP MSFL LLS LLD ILD SFLU DT BS CALI GR NPHI RHOB DRHO 6010.0000 12.2500 13.0330 -41.4800 3.6500 9.4390 9.5840 6.6990 8.8780 84.3630 12.2500 12.2620 26.3580 -999.2500 2.2970 0.0130 6010.5000 12.2500 13.0330 -41.7740 3.7630 8.8770 9.7320 7.2120 9.1990 84.1990 12.2500 12.3160 26.9970 0.2290 2.2970 0.0130 6011.0000 12.2500 13.0330 -42.0860 4.0630 8.7420 9.5840 7.8530 9.3910 84.5260 12.2500 12.4440 30.1920 0.2290 2.2960 0.0130 6011.5000 12.2500 13.0330 -41.3130 4.2540 8.7420 10.1900 7.6600 9.4550 85.3430 12.2500 12.5760 33.3870 0.2301 2.3000 0.0130 6012.0000 12.2500 13.0330 -40.1380 4.6640 8.4780 10.0350 7.1870 9.2590 86.2320 12.2500 12.7080 39.9040 0.2313 2.3410 0.0130 6012.5000 12.2500 13.0520 -39.3540 4.6320 8.3500 9.7320 6.5980 8.9420 86.4870 12.2500 12.8100 42.6410 0.2330 2.3370 0.0150 6013.0000 12.2500 13.1110 -37.4690 4.7720 7.9130 9.2240 5.7730 8.7160 86.5320 12.2500 13.2790 48.3890 0.2400 2.4050 0.0500 6013.5000 12.2500 13.1640 -35.6580 4.8090 7.7340 8.8770 5.3030 7.9560 86.6210 12.2500 13.7710 54.7340 0.2470 2.4200 0.1160 6014.0000 12.2500 13.1960 -33.7820 4.5930 6.4350 6.7890 4.7750 6.8460 86.7110 12.2500 13.9140 56.9640 0.2720 2.3930 0.1480 6014.5000 12.2500 13.2240 -30.7630 3.1590 5.8690 5.9600 4.5590 5.5120 86.8000 12.2500 13.5500 52.8610 0.3070 2.3210 0.1040 6015.0000 12.2500 13.1660 -27.7320 1.6200 4.5930 5.3130 4.2650 4.4130 87.1410 12.2500 13.0710 48.4320 0.3560 2.2350 0.0370 6015.5000 12.2500 13.0900 -27.5810 1.9770 4.4770 4.4540 4.0260 4.3380 87.7940 12.2500 12.9100 45.3320 0.3590 2.2080 0.0170 6016.0000 12.2500 13.1350 -28.1060 2.2350 4.3460 4.3200 3.8940 4.4540 88.7750 12.2500 13.0900 44.7440 0.2880 2.2730 0.0110 6016.5000 12.2500 13.2500 -28.6630 4.6640 4.2540 4.4540 3.7960 5.0210 88.4480 12.2500 13.2890 47.6820 0.2610 2.3280 0.0250 6017.0000 12.2500 13.4300 -28.1530 4.5580 4.8830 5.3130 3.7350 5.3920 87.9580 12.2500 13.4850 51.5620 0.2660 2.3790 0.0380 6017.5000 12.2500 13.6480 -27.1370 3.7630 5.4360 5.6060 3.6830 5.5630 87.3040 12.2500 13.6680 55.2040 0.2860 2.4270 0.0710 6018.0000 12.2500 13.8140 -26.3040 3.9750 5.3620 5.6060 3.7350 5.4280 87.1410 12.2500 14.3920 56.1970 0.3090 2.4330 0.0990 6018.5000 12.2500 13.8780 -21.7800 4.3870 5.3050 5.4360 3.7460 5.2810 87.4670 12.2500 14.6910 62.6290 0.3220 2.4240 0.1290 6019.0000 12.2500 13.9180 -20.3530 3.6640 5.1920 5.0740 3.7480 5.0060 89.2730 12.2500 14.7730 64.8160 0.3260 2.3520 0.1130 6019.5000 12.2500 13.8920 -18.7170 2.8470 4.8240 4.8830 3.7470 4.8230 91.7160 12.2500 14.6360 66.9680 0.3340 2.2980 0.0770 6020.0000 12.2500 13.7920 -18.5110 2.1350 4.5230 4.5230 3.7380 4.4980 93.1860 12.2500 14.4340 67.9870 0.3520 2.2530 0.0400 6020.5000 12.2500 13.6930 -18.8170 2.6860 4.2540 4.0630 3.6890 4.1770 91.7160 12.2500 13.9630 64.6000 0.3500 2.2680 0.0070 6021.0000 12.2500 13.5950 -19.1420 3.0840 3.7400 3.7920 3.6980 3.8580 91.3890 12.2500 13.6420 60.2830 0.3490 2.2810 0.0420 6021.5000 12.2500 13.4990 -19.4830 3.6500 3.4860 3.7060 3.8410 3.5360 90.5720 12.2500 13.2730 56.1720 0.3540 2.2900 0.0670 6022.0000 12.2500 13.2520 -19.8470 2.5660 3.6500 3.6500 3.9050 3.4530 91.7160 12.2500 12.5310 48.3940 0.3720 2.2860 0.0640 6022.5000 12.2500 12.9220 -19.1300 3.3630 4.0630 3.8800 4.2750 3.6960 92.3690 12.2500 12.3310 37.4360 0.3540 2.2410 0.0440 6023.0000 12.2500 12.6520 -18.1220 5.4360 5.1920 4.9590 4.6190 4.6830 93.0230 12.2500 12.2910 31.3930 0.3200 2.2100 0.0230 6023.5000 12.2500 12.6200 -17.1000 5.6920 7.1630 7.5000 4.8940 7.3970 93.3500 12.2500 12.2790 25.9930 0.2850 2.2110 0.0050 6024.0000 12.2500 12.5820 -16.0760 5.3430 8.0980 8.8100 5.2690 8.9860 92.3690 12.2500 12.2490 22.6780 0.2500 2.2280 0.0050 6024.5000 12.2500 12.5450 -15.0530 4.9970 9.5840 9.4390 6.1700 9.0460 90.7350 12.2500 12.3070 23.5570 0.2170 2.2680 0.0060 6025.0000 12.2500 12.5680 -14.0320 4.8090 9.2870 9.4390 6.1740 8.9730 88.7750 12.2500 12.3420 22.5070 0.1920 2.3040 0.0200 47 Logging Run number, Overlap Sections and Composite Log 48  Tool Combination When measurement are combined some extra drilling is needed in order to measure the requested interval Dual Laterolog – Litho-Density-Neutron Microresistivity - GR GR Gamma Ray Gamma Ray Neutron Dual Laterolog Litho-Density Microresistivity 49  Tool Combination The need to save rig time by offering many combined services: Logging Tool Combination : PEX Platform Express (Schlumberger) Telemetry Gamma Ray Neutron Litho-Density- Microresistivity + + + + + + Sonic + + + + + + Resistivity : Laterolog or Induction 50  Well Logging Rig-Up Drill Floor DF Tool « Zero » on Drill Floor DF Rotary Table RT Bottom of the tool Ground Level GL Rig view and Logging Truck KB Caliper Calibration Depth Measurement Head of the tool 51  Well Logging - Generalities The parameters measured are of two natures 1)Natural phenomena (hole diameter, temperature, natural radioactivity, spontaneous potential) These measurement are achieved with only a measuring section and are usually run together with other measurements. These measurement is usually easier to manufacture, is not too voluminous and easily combined with other measurement 2)Induced phenomena ( electrical logs, radioactive induced logs, sound wave propagation, electromagnetic logs) These measurements are achieved with a transmitter section and a measuring section and therefore require more electronics equipment. These measurements are more complicated to manufacture and are more voluminous They can be grouped according to their application: ◼ Well to well Correlations ◼ Reservoir characteristics ◼ Seismic Acquisition (VSP) ◼ Drilling and completion logs ◼ Production logs 52  Well Logging - Generalities Wireline logs are recorded at several different times in the life of an oil field: 1) During the exploration stage,. Since the geological layers being drilled through are not known, the logging program is very large, includes many measurements, in order to gain as much information on the formation in order to make decision. 2) During the appraisal phase, wireline logs are run to gain as much information as possible on the amount of hydrocarbon in place, the pore pressure and the permeability. These information are essential to decide on the development of an oil field. After the appraisal phase, the knowledge of the volume of hydrocarbon (OOGIP) in place should be known with sufficient accuracy for the decision to develop to be taken with limited risk. 3) During the production phase, wireline logs are run to improve and refine the reservoir model in order to predict the depletion process and estimate final recovery more precisely. This is very much needed to predict the economy viability of the project. 53  Well Logging - Generalities There are five major types of logs depending on their primary function and the department within the oil company that will be using them: 1) the ones used by geologists for Well to Well correlations. 2) the ones used by petro-physicists and reservoir engineers to evaluate the characteristics of the formations and fluids and quantify them. Reservoir Evaluation Logging 3) the ones used by geophysicists for seismic interpretation (well seismic Logging) 4) the ones providing technical data on the well status (used by drilling engineers and completion engineers to optimize well engineering) 5) the ones used by production engineers to study fluid nature and fluid- flow phenomena in producing wells. (Production Logging) 54  Well to Well Correlation Objectives: ➔To correlate equivalent strata from one well to nearby wells within a field. Logs from different wells are matched for similarities or for characteristic log response to lithological markers. Well to well correlation studies permit the determination of : ◼ The depth of formation tops ◼ Whether the well being drilled depth has reached the targeted horizon ◼ The presence or absence of fault between wells ◼ Computer modelling of the reservoir Log mostly used: ◼ Gamma Ray (Natural radioactivity) ◼ SONIC (Measurement of sound velocity inside the rock) 55 Well to Well Correlation 56 Well to Well Correlation 57  Well Logging - Reservoir evaluation These logs are used by petrophysicist and reservoir engineers in order to evaluate the amount of oil in place Reservoir Characterization: ◼ Permeable beds identification: (Gamma Ray, Spontaneous Potential (SP), Caliper) ◼ Porosity measurements: (Sonic, Density, Neutron Porosity, Nuclear Magnetic Resonance) ◼ Water Saturation: (Resistivity and Micro resistivity, Electromagnetic Propagation) ◼ Permeability: (Formation Testing (RFT) Nuclear Magnetic Resonance) ◼ Pore Pressure and fluid analysis: (Formation Testing) ◼ Formation stratigraphy and facies: (Dipmeter and Formation Scanning - Borehole imaging) ◼ Formation coring: (Sidecore Sample Taker, Core Slicer) 58  Estimation of Oil In Place Surface of base of Structural Closure Oil Surface Net Thickness Hu = ? Effective Porosity = Phie ? Structural Ht Closure Oil Saturation So = ? Hu G A O h Spill point w w Vrock : Rock Volume w Vrock = Surface x Thickness N/G = Net/Gross ratio OOIP = Vrock  Φe  (1 − S w )  Original Oil in Place Net 1 N Hu = Ht At Surface conditions  G in Millions m3 or MM Bbls Gross B o Phie : Effective Porosity Net 1 Sw = Water Saturation OOIP = Area  ht  Φe  S O   So = 1 – Sw = Oil Saturation Original Oil in Place Gross B o Bo : Oil Volumetric Factor HCPV = Area  hu  Φe  SO at reservoir conditions HCPV : Hydrocarbon Pore volume 59  Well Logging – Reservoir Evaluation TENS_1 11000 LBF 1000 PEF_1 0 B/E 20 DRHO_1 -0.35 G/C3 0.15 BS_1 RHOB_1 4 IN 14 1.95 G/C3 2.95 METRES DEPTH GR_1 IDPH_1 NPHI_1 0 GAPI 100 0.2 OHMM 2000 0.45 V/V -0.15 CALI_1 IMPH_1 DT_1 4 IN 14 0.2 OHMM 2000 140 US/F 40 1510.2 1515 1520 1525 1530 1535 1540 1545 1550 1555 1560 1565 1570 1575 1580 1585.0 CLASSICAL COMPOSITE LOG BOREHOLE IMAGING LOG 60  Well Seismic Well Seismic Acquisition: This measurement consists in recording the sound wave emitted by a surface source (Air gun or Vibroseis truck) and reaching a recording tool situated inside the well at a given depth. It is either: ◼ Check Shot Survey: Only the time needed for the sound to reach the downhole tool is measured. By displacing the recording tool inside the well, a plot of time versus depth can be drawn an will allow a depth indexing of the surface seismic maps. ◼ Vertical Seismic Profile(VSP):The entire sound waveform is recorded. By moving the recording tool and the surface source a n acoustic image of formation layers situated between the source and the well can be derived. 61 Well Seismic – Checkshot Survey 62 Well Seismic – Checkshot Survey 63 Well Seismic – VSP Survey 64  Well Seismic – VSP Survey Typical VSP Processing Tasks Reading data Sorting Filter First break picking Statics Preparation of TVD curve & Velocity listing True amplitude Recovery (TAR) o Horizontal rotation o Vertical rotation o Separating up-goings/down-goings (PP/PS) o Deconvolution (Removal of multiples) o Velocity Modeling o NMO (Normal Moveout) o VSP-CDP Transformation (Migration) o Final Outputs (PP & PS sections) ➔ 65 Well Seismic – VSP Survey 66 Well Seismic – VSP Survey 67  Well Logging – Drilling and Completion surveys ◼ Hole Geometry (Diameter of the drilled hole - deviation and direction of the hole trajectory) ◼ Drill pipe stuck point and drill pipe back off (to remove stuck drill pipes from a well) ◼ Cement evaluation (to analyse casing cementing quality) ◼ Casing inspection and casing corrosion (measurement of casing internal diameter and casing thickness) ◼ Casing perforation (to allow fluid to flow from the reservoir to the borehole) ◼ Plugs and Packers (completion equipment needed to bring the oil at surface) ◼ Severing (Casing and tubing cut): for work over operations in order to regain full control of the well. 68  Production Logging Production Logging is made while the well is producing by means of a special sealing device called Well Head Pressure Control Equipment It consists of the recording of some flow parameters to analyse the depletion of the reservoir ◼ Bottom hole temperature ◼ Bottom hole pressure ◼ Bottom hole flow rate ◼ Bottom hole produced fluid density ◼ Bottom hole water hold up 69 MWD-LWD 70  MWD-LWD Generalities MWD & LWD Tools ➔ The first MWD tools appeared in the 70’s allowing the development and sophistication of directional drilling ➔ MWD (Measurement While Drilling) tools initially measured hole Inclination and Azimuth as well as Tool Face, using s Accelerometers and Magnetometers sensors; This allowed the plotting of the well trajectory in 3D. Later were incorporated measurement related to the drilled formation (Gamma Ray and Resistivity) ➔ LWD (Logging While Drilling) tools were later developed to measure formation parameters while drilling to allow measurement to be made in highly deviated or horizontal holes. ➔ These tools are integrated inside Drill Collar (DC) positioned above the bit. The MDW Drill Collar are made of non magnetic material (K-Monel) to allow magnetic measurement to be made. The signal is transmitted to surface by a “Mud Pulse Telemetry” ➔ LWD measurements which involve many curves cannot be easily transmitted to surface by “Mud Pulse Telemetry” which is limited and some data must be stored inside memory chips inside the downhole equipment. The data is read when the equipment is brought back to surface. 71  MWD Generalities MWD Tools ◼ Deviation Measurements Inclination Azimuth Tool face ◼ Drilling parameters Torque Vibration Annular pressure ◼ Formation evaluation Gamma ray Resistivity Temperature 72  LWD Generalities ◼ Deviation Measurements ◼ Formation evaluation Inclination Azimuth Gamma ray Tool face Deep Resistivity ◼ Drilling parameters Density and Photoelectric effect Torque Neutron Porosity Vibration Temperature Annular pressure 73  MWD-LWD Generalities MWD – Telemetry The most widely used telemetry is a Mud Pulses Telemetry. They allow real time measurement of the formation being drilled. ◼ Information is digitally coded (a series of bit each bit being 0 or 1) ◼ A mechanical system (the pulser system) generates over or under pressure waves in the mud column, creating “trains” of pulses which travel inside the drill string up to surface where they are detected using a very accurate pressure transducer. − Positives pulses (0 bit) increase of pressure − Negative pulses (1 bit) depression ◼ Mud pulses systems are very dependant on the drilling fluid ◼ They cannot work with air or foam ◼ Power is supplied by battery (recharged by mud turbines) ◼ Sampling is time depending (ROP should be adapted) 74 MWD-LWD Surface Read Out Panel 75 WIRELINE LOGGING GENERALITIES 76  Definitions POROSITY Φ = Porosity = Fraction of the bulk volume occupied by voids Φ = Porosity = Ratio of pore volume to total rock volume Vpore Vtotal − Vsolid = = Vtotal Vtotal Grains Pores 77  Definitions POROSITY: - Porosity is expressed in % or V/ V or Porosity units (PU). - In general, reservoirs have porosity value ranging from 2% to 35 %. 0 <  < 5% low porosity 5% < 