Geology Reference
In-Depth Information
The most monumental contributions into geologic aspects of pres-
sure abnormality was made by M.Hubbert, A.Levorsen, V.Illing,
G.Dickinson, G.Chilingar, H.Hedberg, P.Gretener, W.Fertl, D.Timko,
K.Magara, B.A.Tkhostov, К.А.Anikeyev, V.S.Melik-Pashayev, М.К.Kalinko,
V.M.Dobrynin, N.A.Yeremenko, А.Е.Gurevich and many others. They estab-
lished that the main mechanisms generating AHPP and AHFP in sediment
sequences are:
t
Gravity (lithostatic) load from the overlying rocks (partial
or total transfer of time-increasing load of the overburden to
the fluids within the underlying rocks).
t
Tectonic pressure (neotectonic stress, basement fault-block
motions, earthquakes, etc.).
t
Differential in piezometric levels in the charge, waterhead
generation and discharge areas in infiltration geo-hydrody-
namic systems (artesian pressure gradient).
t
Differential in heat expansion between ground waters and
the enclosing rocks; as the temperature grows it causes an
aquathermal pressure increase in closed-elastic reservoirs.
t
Increasing the hydrocarbon volume in accumulations due
to phase transformations as the formation temperature
increases with depth.
t
Dehydration of clay minerals with the ensuing release of
constitutional water into the free phase.
t
Secondary cementation of some pore space in closed lens-
shaped reservoirs by new mineral growth due to physico-
chemical interactions between ground waters and rocks and
due to temperature and pressure increase at depth.
t
Migration of high-pressure fluids from zones of high nor-
malized pressure into interval of lower pressure.
t
Osmosis.
In terms of the implementation of natural energy, the first seven mecha-
nisms may be joined as a single group of
syngenetic AHPP and AHFP
emerged
out of internal energy resource of sedimentary complexes. The
last two mechanisms should be attributed to
epigenetic
modifications
associated with the injection of foreign high-pressure agents into restricted
closed-elastic capacity spaces (Durmishyan and Muradian, 1973, 1980;
Rachinsky, Muradian, 1977). In either case, the major condition for the
conservation of the abnormal pressure is the total or partial hydrodynamic
isolation in the geological medium. Each type is specific in its manifesta-
tion and diagnostic indices. Thus, it may be identified. This, it turn, enables
