Page 302 - Origin and Prediction of Abnormal Formation Pressures

272 H.H. RIEKE, G.V. CHILINGAR AND J.O. ROBERTSON JR
t
80,000 80,000

70,000 B 70,000

~
cud
Q..
60,000 60,000 ff
(!) I1)
0
.Q
.Q 50,000 50,000
!._
0
t~O 0
(1)
"0 0
0 40,000 40,000 r
"0 C~
"0
om
30,000 30,000
E
L_ x
0
L_
20,000 20,000 O..
<
10,000 10,000

3000

4 th 3 rd 2 nd 1 st
Number of adsorbed water
layers from clay surface
Fig. 10-29. Cross-plot showing the approximate pressures required for the removal of successive
monomolecular layers of water from a calcium smectite. (Based on data from Van Olphen, 1963. Powers,
1967, fig. 2, p. 1243).

Na +, Mg 2+, Cl-, and SO42- contents in the expelled water decreased after a slight initial
increase. Both K + and Ca 2+ contents gradually increased after an initial decrease. More
work is needed to fully understand the mechanisms operative in experiments involving
both oil and water.

FLUID CHEMISTRY COMPACTION MODELS
The writers have presented field and laboratory evidence that the concentration
of squeezed-out pore water from saturated argillaceous sediments decreases with
increasing overburden pressure. Numerous models at various scales have been proposed
in the literature to explain this behavior. Several modeling approaches have been