Page 120 - Origin and Prediction of Abnormal Formation Pressures

] 00 L.A. BURYAKOVSKY, R.D. DJEVANSHIR, G.V. CHILINGAR, H.H. RIEKE III AND J.O. ROBERTSON, JR

Recent burial
density = 1.32
~ Pore water

~ ~ Interlayer water
-v

~ [-:.~--'--2"1 Swelling clay solids
t

"~""~'~~ I Non-swelling clay solids

~ ~ ~ Non-clay solids

~ After I st x~
dehydration
After 2nd
density = 1.96
L_ ..... ;;, ~ .. dehydration
~ l ~ ~ "-.. dens ity = 2. 28 Aft r. 3r.cl
e
~:.'zT~.:T:.l .... ~ "" -.-. ~. dehvaraTion
20-/,, ~ "- - ~ ~ V o ~ - - . . . . . . . . . . .

/
.
.
9
~
~ ........................... . .................... .......
;;:~.
- ...... ----- ~:4 ............ ...... :~ ~IU:~i~C."~.~.~ ..-~
.
_ _
..... s,ooe, .p ........ s,ooe,, "I" s,ooe,,,
Fig. 4-3. Marine shale bulk composition during dehydration. (Modified after Burst, 1969, fig. 6. p. 81.)

ORIGIN OF ABNORMALLY HIGH FORMATION PRESSURE
Abnormally high formation (pore) pressure (AHFP) in reservoirs is known to be
caused by several diverse factors. Buryakovsky et al. (1995) suggested that the most
probable mechanism for development of AHFP, in regions with thick terrigenous
sedimentary rocks (sand/shale sequence), is rapid sedimentation and gravitational