Page 157 - Well Logging and Formation Evaluation

Production Geology Issues 147

(total vertical depth subsea). B o is 1.3rb/stb (reservoir barrels/stock tank
barrels)

1. Make a map of the top structure and draw contours every 25m.
2. Construct area-depth maps for the top and base of the structure.
3. Estimate the GBV, NPV, and STOIIP.
4. Consider what the effect on STOIIP would be if in fact S w were
10% for depths shallower than 25m above the contact, and 30% for
0–25m above the contact.

10.2 BASIC GEOLOGICAL CONCEPTS

10.2.1 Clastic Reservoirs

Clastic rocks are defined as being composed of consolidated sediments
formed by the accumulation of fragments derived from preexisting rocks
and transported as separate particles to their places of deposition by purely
mechanical agents. These fragments may be transported by water, wind,
ice, or gravity. The manner of their movement may be by suspension,
saltation, rolling, or solution. The effect of the transportation is to change
any of the following characteristics of the fragments (or grains):

• Size
• Shape
• Roundness
• Surface texture
• Orientation
• Mineralogical composition

Measurement of these changes may provide information on the trans-
portation mechanism. The types of environmental deposition are as
follows:

Desert
Waddis
Aeolian dune systems
Sabkhas
Fluvial
Alluvial fans
Floodplains