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Lecture items

Lecture items. Compositions of the Uphole- Downhole Instruments. Field Operation (Data Acquisition, Processing and Transmission) Log Runs Borehole Environment opposite a Permeable Zone. Structure of a Log head. Recording Format Images logs Basic reservoir characteristics.

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Lecture items

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  1. Lecture items • Compositions of the Uphole- Downhole Instruments. • Field Operation (Data Acquisition, Processing and Transmission) • Log Runs • Borehole Environment opposite a Permeable Zone. • Structure of a Log head. • Recording Format • Images logs • Basic reservoir characteristics

  2. Compositions of the Uphole- Downhole Instruments. • Uphole Instruments include the Logging Truck and the Rig. The logging Truck mainly consists of mechanical Winches and ordinary driving machine. • Downhole Instruments are represented by Cables and Sondes. • Sondes differ in function from measurement to another based on the required physical property to be measured (GR , Resistivity, Neutron, Sonic, Density, Magnetic, Thermal, etc) • Sonde normally consists of two main parts: • Sensor: It is an electronically complicated part used for picking the required property. It is usually shielded with fibers in the modern tools. • Cartridge: Surrounding the sensor in the modern tools and do three functions: • * Powering the sensor to be ON/OFF . • * Processing the acquired data (First step of processing). • * Data transmission along cables to the up-hole instruments.

  3. Modern Cable

  4. Complicated Sondes

  5. Field Operation • Data Acquisition (by Sondes) • Data Processing (Three steps) • Data Transmission (Two stages)

  6. Data Transmission

  7. Log Runs

  8. Borehole Environment When a hole is drilled into a formation, the rock and the fluids in it (rock-fluid system) are altered in the vicinity of the borehole. A well’s borehole and the rock surrounding it are contaminated by the drilling mud, which affects logging measurements. Figure 1 is a schematic illustration of a porous and permeable formation which is penetrated by a borehole filled with drilling mud.

  9. Borehole Environment

  10. Borehole Environment

  11. dh – hole diameter • di – diameter of invaded zone (inner boundary; flushed zone) • dj – diameter of invaded zone (outer boundary; invaded zone) • Drj – radius of invaded zone (outer boundary) • hmc – thickness of mudcake • Rm – resistivity of the drilling mud • Rmc – resistivity of the mudcake • Rmf – resistivity of mud filtrate • Rs – resistivity of shale • Rt – resistivity of uninvaded zone (true resistivity) • Rw – resistivity of formation water • Rxo – resistivity of flushed zone • Sw – water saturation of uninvaded zone • Sxo – water saturation of flushed zone

  12. Invasion Profile

  13. Invasion Profile

  14. Invasion Profile

  15. Annulus zone • An annulus profile is often recorded on a log because it rapidly dissipates in a well. The annulus profile is detected only by an induction log run soon after a well is drilled. However, it is very important to a geologist because the profile can only occur in zones which bear hydrocarbons. As the mud filtrate invades the hydrocarbon-bearing zone, hydrocarbons move out first. Next, formation water is pushed out in front of the mud filtrate forming an annular (circular) ring at the edge of the invaded zone. The annulus effect is detected by a relatively lower resistivity values.

  16. Structure of a Log Head

  17. Recording Formats

  18. Recording Formats

  19. Modern Formats

  20. Image Logs

  21. Basic reservoir characteristics • Porosity,φ (Total, effective, primary, secondary and intercrystalline) • Permeability (K) (Absolute, relative) • Saturation (S) (Sw, Sxo, Sh, So, Sg, Shr, Shm) and their interrelationships.

  22. POROUS MEDIUM STANDARD REALITY

  23. Various pore geometries with different effective path length

  24. Water Saturation (Sw) is the fraction of the pore space containing water • Sw = Vw / f • Porosity is the volume of pores to the total volume of rock • φ = Vp / VR * 100 %

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