UNITS The units are micro seconds/ft, which is the inverse of velocity. Porosity - Sonic Log (Wyllie et al., 1958) The calculation of sonic derived porosity, can be done from the time average Wyllie (Wyllie et al., 1958) equation, which is expressed the following way: Where: ɸS= sonic porosity; Δtma= matrix interval transit time; Δtlog= interval transit time of the formation (from the sonic log) An equation for estimating effective porosity values from sonic and a gamma ray (GR) log was established for different lithologies. 1 (d). In the late 1970's, sonic waveforms were … Hello =) I'm new around here and have a question. Unshaded black curve is probably valid. Its main use is to provide information to support and calibrate seismic data and to derive the porosity of a formation. I have well log data (in LAS format) and need to get porosity (in %). This equation yields good porosity values when compared with the actual porosity existing in the same field. To calculate sonic porosity for unconsolidated formation, we can start by getting the product of the Wyllie et al. SONIC OR ACOUSTIC LOGS 2. The combination of sonic, neutron and density logs might indicate the presence of fractures (Schlumberger). We continue to use travel time in this Handbook - it's hard to teach old dogs new tricks. The combination of the density and neutron logs provides a good source of porosity data, especially in formations of complex lithology. In general, the sonic log is unsuitable for these formations and should not be used to determine porosities. The inverse of slowness is speediness or velocity. Similarly, for well B, the coefficient of variation for sonic log derived porosity and density log derived porosity became 29% and 37% respectively. Array sonic logs were developed to provide information about a variety of acoustic properties such as porosity, permeability, gas zones, acoustic impedance, and elastic properties of a formation. •The Sonic Log is the best tool if the hole is irregular, secondary porosity is important, or heavy minerals (such as pyrite) are present. Acoustic or sonic logs provide another technique for measuring porosity. In this method, it is assumed that the sonic log provides matrix porosity. Porosity - Sonic Log (Wyllie et al., 1958) The calculation of sonic derived porosity, can be done from the time average Wyllie (Wyllie et al., 1958) equation, which is expressed the following way: Where: ɸS= sonic porosity; Δtma= matrix interval transit time; Δtlog= interval transit time of the formation (from the sonic log) However, if only the sonic log has been run, then it is possible to correct for this underestimation, an empirical correction factor, C p, is used, as follows: ∅= Sonic log 1. Wyllie, M., Gregory, A., and Gardner, G., 1956, Elastic wave velocities in heterogeneous and porous media: Geophysics, 21, 41-70. The combination of sonic, neutron and density logs might indicate the presence of fractures (Schlumberger). ♦ The sonic log device consists of one or more sound transmitters and two or more receivers. This information can also be used to derive the velocity of elastic waves through the formation. 4. Porosity log types 6 Neutron tool • Neutron source. Based on the reformulation of a certain known equation, it is essential to apply it in a shaly formation.

Sonic Log. red curve is sonic log from adjacent well, possibly with lower porosity. When sonic porosities are compared with neutron and density porosities, the total porosity can be subdivided between “primary porosity” (interparticle porosity) recorded by the sonic log and “secondary porosity” (vugs and/or fractures) computed as the difference between the sonic porosity and the neutron and/or density porosity [24]: porosity logs. – Sonic log – Density log – Neutron log • None of these logs measure porosity directly • The density and neutron logs are nuclear measurements • The sonic log use acoustic measurements • A combination of these logs gives good indications for lithology and more accurate estimates of porosity The Density Log measures the electron density ρ e, of the formation (the electron density is the number of electrons per unit volume). ARRAY SONIC LOGS Newer sonic logging systems, called full wave sonic or array sonic logs, provide access to more acoustic information than traditional tools. Traces 8 to 13 in Figure 6.11 show that FPR2, m*, FIDX, and FID2 are generally consistent … 5. To accurately calculate porosity, the analyst must know: • Formation lithology • Fluid in pores of sampled reservoir volume 6.

Porosity log types 3 Main Log Types • Bulk density • Sonic (acoustic) • Compensated neutron 5 These logs do not measures porosity directly. Porosity log types 6 Neutron tool • Neutron source.