PE3_WellLoggigigkng_Lecture2_052831.pptx

Well logging in_7_ [ SP-log]_052629

1. PE -3- Well Logging Lecture 2: Introduction Dr.Ali Mohammed Al Tameemi

2. Well logs – an interesting tool The Geophysicist: Are the tops where you predicted? Are the potential zones porous as you have assumed from seismic data? What does a synthetic seismic section show? The Geologist: What depths are the formation tops? Is the environment suitable for hydrocarbon (HC) accumulation? Is there evidence of HC in this well? What type of HC? Are HC present in commercial quantities? How good a well is it? What are the reserves?

3. The Drilling Engineer: What is the hole volume for cementing? The Reservoir Engineer: How thick is the pay zone? What is the volume of HC per m3 Are HC present in commercial quantities? How good a well is it? What are the reserves?

4. Introduction What is a well log / well logging? Why do we need to learn well logging? How do we measure well logs? What type of well logs are there? What are the uses of well logs? How do we read a well log?

5. What is well logging? Well Logging is the practice of making a detailed record ( log ) of the geologic formations penetrated by a borehole. The log may be based on visual inspection of samples brought to the surface (geological logs; core logs) or physical measurements made by instruments lowered into the hole (geophysical logs).

6. Well logging May have different names: Borehole geophysics Petrophysics Formation evaluation

7. What is a log? A “log” can refer to: The tool that makes the measurement. The paper (or digital) representation of those measurements. A single measurement (a “curve” or a “trace”).

8. The first well log 175m 170m 165m 160m 155m 12 13 9.5 7.7 6.9 5.2 5.3 2.1 4.8 5.8 6.4 5.9 4.3 4.3 5.4 7.8 8.6 3.3 9.5 19.6 15.9 14.5 9.9 12.4 10.5 M. verte schisteuse M. brun rouge M. rouge av. gypse M. grise M. rouge. gypse Greg marneux M. brune gypse Cristaux degypse M. grisa stratifiee gypsifere The first electric well log, Pechelbronn , France, September 5, 1927

9. Why do we need to learn well logging? Well logging helps us to evaluate the formation. Reservoir characterization Production strategy Reservoir estimates Well logging is an integral part in “measuring” the reservoir.

10. Formation evaluation: Scale

11. Basic Log Types Open Wireline Log Wireline Cased Hole Logging Logging While Drilling (LWD) Class Focus

12. Measurement Recording Undisturbed Formation Mud Mud Cake Filtrate Invasion Depth Measurement Surface Signal Conditioner Reproduction Processor CPU Recording Device End Product Log / Tape

13. Some tools are run centralized in the borehole in order to measure properly. These include laterolog and sonic devices. Special centralizers are put on the tool. Centralized Decentralized Stand-Offs Some tools are run decentered , pushed, against the borehole wall. In some cases this is done with an bow springs or caliper arm. Some tools are run with “ stand - offs ” to position them at a fixed distance from the wall. The induction family are usually run in this manner.

14. What type of well logs are there? Borehole geophysics is the science of recording and analyzing measurements of physical properties made in wells or test holes. Probes that measure different properties are lowered into the borehole to collect continuous or point data that is graphically displayed as a geophysical log.

15. Types of well logs Electrical Resistivity log Spontaneous Potential log Nuclear Gamma Ray log Density log Neutron log Acoustic Sonic log Other categories: Temperature log Caliper log Dipmeter log Image log

16. What questions can be answered? Are hydrocarbons present? Is it oil or gas? How much, where is it? What’s the lithology ? One reservoir or multiple? Quantification of reservoir parameters (saturation, porosity) residual hydrocarbons

17. Well log analysis The majority of well log information is qualitative. A single well log does measurement does not give a definitive answer.

18. Uses of well logging Determination of reservoir parameters: Lithology , porosity, permeability, fluid saturation Determination of formation fluids Recognize depositional systems or other geological features Correlation to geologic maps or seismics Detection of overpressure zones Detection and estimation of hydrocarbon zones Oil in place Reservoir management reassessment

19. Depositional Environments

20. Structure determination

21. Overpressure detection

22. How to read a well log A well consists of Well log header Comments Main pass (recorded data) Tracks Scales Speed markers Footer (Calibrations, Tool string assembly) Reading a log is a skill well worth developing. Many misinterpretations can be traced back to a misunderstanding of what the log data represented, especially these days when much of this data is loaded directly to workstation projects.

23. A well log Track 1 Track 2 Track 3 Depth Track Scales identify the curves and their values (if you have a secret decoder ring) Depth lines appear every two feet (in this display). Curves are distinguished by line color, width, and style

24. Grids & scales

25. Common Log Type : Schlumberger: Baker Atlas: Halliburton: Por Mnemonics osity Density Compensated RHOB DEN RHOB Lithodensity RHOB, RHOM, RHOZ ZDEN RHOB Neutron Compensated NPHI, TNPH, NPOR CNC, CN NLP,NPHI Sonic / Acoustic Compensated DT DT DT Long-Spaced DT DT (None) Dipole ( Pwave ) DTCO DT DTC Spectral Gamma Ray SGR GRS GRS URAN, THOR, POTA U, TH, K GRU, GRTH, GRK Resistivity Induction Dual RILD RILD ILD Phasor Dual RTPH RIPD HDRS Array AF90, AT90 M4CX, M2CX HRD Laterolog Dual LLD RD LLD Azimuthal LLD RLD (None) Focused SFL FL DFL Microresistivity Micro-Spherical RXO, RXO8 (None) MSFL Microlaterolog RMLL RMLL (None) Microlog BMIN, BMNO RLML, RNML LAT, NOR Electromagnetic Propagation EATT, TPL (None) (None) Pulsed Neutron Thermal Decay SIGM SGMA SGFM Mnemonics