Page 238 - The Geological Interpretation of Well Logs
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- THE GEOLOGICAL INTERPRETATION OF WELL LOGS ~
DELTAIC-FLUVIAL ENVIRONMENTS
A. CHANNEL-POINT BAR 8. DELTA BORDER PROGRADATION
alluvial or fluvial
grain size
25m
erosion
GR or SP
MARINE ENVIRONMENTS
C. TRANSGRESSIVE MARINE SHELF
grain size
GR or SP
25m
DEEP SEA ENVIRONMENTS
PROXIMAL DISTAL
E. SLOPE CHANNEL F. INNER FAN G. MIDDLE FAN H. SUPRA-FAN 1, BASIN
CHANNEL CHANNEL DEPOSITIONAL PLAIN
LOBES
26m 9.8
GR or SP GR or SP
Figure 14.5 Facies indications from gamma ray (or SP) log shapes. These are idealized examples both of log shape and
sedimentologic facies, (Modified from Serra, 1972; Parker, 1977; Galloway and Hobday, 1983).
in grain size, rather than the direct change in grain Visher, 1968; Doveton, 1986; Finley and Tyler, 1986;
size itself. However, the principles are similar (Figure Cant, 1992). Once an interval is reliably identified, then
14.5). the variations in log shape within that interval give an
Once established, the log shape system can be used indication of facies variations and hence, an indication
in a number of ways. Maps made of the geographical of palacogeography (Figure 14.6). More recently, log
distribution of log shapes, are effectively both facies shapes have been used as a too! for sequence stratigraphy
distribution and palaeogeographic maps (Saitta and (Van Wagoner er al., 1990), with variations in log shape
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