Geology Reference
In-Depth Information
in the said intervals. This mechanism results in a pulsating-stress fluid
“pushup” up the section, into the post-Valanginian intervals. Powerful tec-
tonic compression of the reservoir members with syngenetic AHFP results
in geologically instantaneous pressure increase in them to the level above
the hydraulic fracturing pressure. This causes the development of fractur-
ing facilitating and amplifying the vertical fluid-mass transfer.
he
Neocomian-Albian
sediments have been tested mostly at the pros-
pects over the southeastern plunge of the Caucasus Major Meganticlinorium
(Begimdagh-Tegchay, Sobetabad and Gyadysu).
Water flows (sometimes with films of oil) were produced from all pros-
pects. The rates were 10-20 CMD, sometimes with small amount of gas. In
individual cases when the wells intersected faults, the water rates reached
100 CMD. The wellhead pressure was 10-20 MPa. The interval comprises
compact relatively thin lens-shaped reservoirs within a section of rather
consolidated, sometimes even argillite-like clays. Drilling through it was
only possible with heavy muds (about 1.85-2.00 g/cm
3
; Akhmedov, Salayev
and Ismailov, 1961). It was usually accompanied by intense water shows,
blowouts, mud gas cutting and circulation loss. These phenomena were
connected commonly with the most tectonically affected crestal areas and
decreased toward the flanks and plunges. In general, pressure abnormal-
ity, generation is practically identical to the Jurassic-Valanginian section
with additional participation of epigenetic AHFP component caused by
the invasion of some volume of high-pressure fluids from the underlying
intervals.
he
Upper Cretaceous
deposits are composed in the
Cenomanian-
Coniacian
interval by flyshoid alternation of compact calcareous clays,
marls, limestones and nonuniform thin lens-shaped calcareous sand-
stones. The Santonian-Danian range comprises a similar alternation but
now with incompact plastic clays. These deposits were penetrated and in
individual wells tested on most structures of the southeastern plunge of
the Caucasus Major meganticlinorium (the Nasosnaya, Kabandagh, East
Kabandagh, Yunusdagh, Kurkachidagh, Yashma, Gyadysu, West Agburun,
Geytapa, Sobetabad and other prospects). They were also drilled within the
North-Apsheron zone of highs (prospects Two Brothers Bank, Tsyurupa
Bank, Apsheron Bank, Khazri), in the Balkhan zone of highs (Karadepe,
Kum-Dagh, Kobek, Boyadagh, Syrtlanly, Urundzhuk, Monzhukly and
Suydzhik) and in the Resht segment of the Elburs Trough (Enzely-More,
well Khazar-1).
At all prospects, drilling through the Cenomanian-Coniacian sediments
was conducted without much problem and with mud usually not heavier
than 1.50-1.65 g/cm
3
. Shows while drilling commonly were moderate and
