sonic log / Acoustic logging is one of petrophysical tool to evaluate well parameter oil filed

2. Sonic tool
Sonic tool is one of convention porosity logs

3. porosity !

4. Types of porosity
Primary porosity
 The porosity of the rock that formed at the
time of its deposition.
Secondary porosity
 Develops after deposition of the rock. For
example: Fracture spaces formed in fractured
reservoirs

5. Primary porosity
Effective Porosity
 the pores are connected,
 Effective Porosity liquid can easily flow
through (sponge)
Ineffective Porosity
 the pores are not connected.
 Liquid cannot find a path through; it just gets
stuck in the holes. (cork)
Total Porosity (ΦT) = Effective Porosity (Φe) + Ineffective Porosity (Φi)
The ratio of the entire pore space in a rock to its bulk volume

6. Note !
Effective Porosity
 the pores are connected
Permeability
 Is the ability of the rock to transmit fluid

7. SONIC PRINCIPLE !!

8. Acoustic wave
 P-WAVES
 S-WAVES
 STONELEY WAVES

9. P-WAVES
 is the fastest kind of seismic wave, and, the first to 'arrive' at a seismic station. The P wave can
move through solid rock and fluids
 P wave, particles move in the same direction that the the wave is moving in, which is the
direction that the energy is traveling in

10. S-WAVES
 The second type of body wave is the S wave or secondary wave, which is the second wave you
feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock,
not through any liquid medium
 S waves move rock particles up and down, or side-to-side--perpendicular to the direction that
the wave is traveling in

11. Stoneley wave
 When generated at low frequency, Stoneley waves travel as a
tube wave
 They loose amplitude at the contact of permeable intervals, and
are reflected by fractures.
 The loss of amplitude can be related to formation permeability

12. Wave propagation in a borehole

13. Acoustic wave

14. Acoustic wave

15. sonic tools

16. sonic tools
 The sonic tools create an acoustic
signal and measure how long it
takes to pass through a rock.
Delay time / slowness

17. sonic tools types
 Early sonic tools
 Dual receiver sonic tools
 Borehole Compensated Sonic
 Long spacing sonic tools
 Array sonic tools

18. Early sonic tools
• Early tools had one Tx and one Rx.
• The body of the tool was made from rubber (low velocity
and high attenuation material) to stop waves travelling
preferentially down the tool to the Rx.

19. Early sonic tool problems
 The measured travel time was always too long because the time
taken for the elastic waves to pass through the mud was
included in the measurement.
 he measured time was A+B+C rather than just B. (ii) The length
of the formation through which the elastic wave traveled (B) was
not constant because changes to the velocity of the wave
depending upon the formation altered the critical refraction
angle

20. Dual receiver sonic tools
 These tools were designed to overcome the problems in the early
tools.
 They use two receivers a few feet apart, and measure the difference
in times of arrival of elastic waves at each Rx from a given pulse from
the Tx
 This time is called the sonic interval transit time (Dt) and is the time
taken for the elastic wave to travel through the interval D (i.e., the
distance between the receivers).

21. Dual receiver sonic tools
 The time taken for elastic wave to reach Rx1: TRx1= A+B+C
 The time taken for elastic wave to reach Rx2: TRx2 = A+B+D+E ·
 The sonic interval transit time: DT = (TRx2 - TRx1) = A+B+D+E – (A+B+C)
= D+E-C. ·
 If tool is axial in borehole: C = E, so DT = (TRx2 - TRx1) = D
 The problem with this arrangement is that if the tool is tilted in the hole, or
the hole size changes

22. Dual receiver sonic tool problem
 The problem with this arrangement is that if the tool is tilted in
the hole, or the hole size changes

23. Borehole Compensated Sonic (BHC)
 It has two transmitters and four receivers,
 arranged in two dual receiver sets, but with one set inverted
(i.e., in the opposite direction).
 Each of the transmitters is pulsed alternately, and Dt values are
measured from alternate pairs of These two values of Dt are
then averaged to compensate for tool misalignment, at to some
extent for changes in the borehole size.

24. Long Spacing Sonic (LSS) Tool
 It was recognized that in some logging conditions a longer Tx-Rx
distance could help. Hence Schlumberger developed the long
spacing sonic (LSS), which has two Tx two feet apart, and two Tx
also two feet apart but separated from the Tx by 8 feet. This tool
gives two readings; a near reading with a 8-10 ft. spacing, and a
far reading with a 10-12 ft. spacing

25. Array sonic tools
 Multi-spacing digital tool.
 First to use STC processing.
 Able to measure shear waves and Stoneley waves in hard formations.
 Used for: Porosity. Lithology. Seismic tie in / time-to-depth conversion. Mechanical properties
(from shear and compressional).
 racture identification (from shear and Stoneley).
 Permeability (from Stoneley)

26. Tool Calibration
 The tool is calibrated inside the borehole opposite beds of pure and known lithology, such as
anhydrite (50.0 ms/ft.), salt (66.7 ms/ft.), or inside the casing (57.1 ms/ft.).

27. Time record
 the sonic log record the time T that required for a sound wave
to travel in giving distance on formation
 time record in sonic tool depend on lithology and pore fluid
 porosity decrease velocity increase

28. sonic log presentation

29. Factor affecting in sonic log
 Lithology !
 gas
 Mud type
 Pore hole rugosity
 Secondary porosity
 Compaction
 Overpressure

30. Secondary and Fracture Porosity
 The sonic log is sensitive only to the primary intergranular porosity
 The sonic pulse will follow the fastest path to the receiver and this will avoid fractures
 Comparing sonic porosity to a global porosity (density log, neutron log)should indicate zone of
fracture.

31. Compaction
 As a sediment becomes compacted, the velocity of elastic waves
through it increases
 If one plots the interval transit time on a logarithmic scale against
depth on a linear scale, a straight line relationship emerges
 Compaction trends are constructed for single lithologies, comparing
the same stratigraphic interval at different depths
 Compaction is generally accompanied by diagenetic changes which
do not alter after uplift
 Amount of erosion at unconformities or the amount of uplift from
these trends can be estimated

32. Overpressure
 An increase in pore pressures is shown on the sonic log by a
drop in sonic velocity or an increase in sonic travel time

33. Applications
 Porosity Determination
 Stratigraphic Correlation
 Well to seismic tie
 Identification of Lithology

34. Porosity Determination /interpretation
The basic equation for sonic porosity

35. Stratigraphic Correlation
 The sonic log is sensitive to small changes in grain size, texture, mineralogy, carbonate content,
quartz content as well as porosity
 This makes it a very useful log for using for correlation and facies analysis

36. Well to seismic tie
 Synthetic Seismograms
 Represents the seismic trace that should be observed
with the seismic method at the well location
 Improve the picking of seismic horizons
 Improve the accuracy and resolution of formations of
intere

37. lithology identification

38. questions !