A.V. Gvozdeva, E.A. Taratyn
 
Geological and geophysical substantiation of clay cap prediction in the Sukhodudinsky Formation (Tanamo-Malokhetsky mega-swell, Yenisei-Khatanga petroleum region)
DOI 10.31087/0016‑7894‑2018‑5‑37‑49

Alternati on of reservoir rocks and impermeable beds in the section, along with the other factors, is a necessary condition for formation of hydrocarbon accumulations. The problem of prospecting for hydrocarbons within the Tanamo‑Malokhetsky swell out of the zone of clinoforms development, is associated with the lack of regional impermeable beds in the Sukhodudinsky section. Because of this, investigations of caprocks is of current importance in the territory. The paper discusses geological and geophysical substantiation of impermeable beds prediction in the section. Object of our research is Lower Cretaceous Sukhodudinsky formations identified within the Malokhetsky‑Upper‑Sukhodudinsky reservoir. In the territory of the Tanamo‑Malokhetsky mega‑swell, the formation is represented by alternation of sandy‑siltstone‑clay rocks. Irregularity of impermeable beds is typical for the reservoir. Presence of hydrocarbon accumulati ons is governed by zonal and mainly local occurrence of clay seals. Well log suite from 32 wells was used as the actual data. According to well tops, the Sukhodudinsky Fm (K1sd) occurs in the depth interval from 400 to 2750 m, which corresponds to the stages of early and meso‑catagenesis. Lithological breakdown of the section is carried out. Potenti al impermeable beds are identi fi ed in the secti on. Caliper logging data were used to identi fy a swelling clay in the promising traps of the Sukhodudinsky formati on. Vugs of larger depth are a sign of higher swelling clay. It is shown that quality of potenti al seal depends not only on its thickness, but also on the total content of a swelling clay. Threshold values of a seal thickness and a swelling clay content are obtained for water‑saturated secti ons, and also for the sections that can be gas‑saturated or water‑saturated, and only gas‑saturated. It is found that position of the potential impermeable bed in the section is defined by the subsea depth of top and bottom of the Sukhodudinsky Fm. This provision allows predicting the areal distribution of seals.

Key words: Yenisei-Khatanga petroleum region; Tanamo-Malokhetsky mega-swell; Sukhodudinsky formati on; catagenesis; impermeable bed; swelling clay; seal; well logging.

For citation: Gvozdeva A.V., Taratyn E.A. Geological and geophysical substantiation of clay cap prediction in the Sukhodudinsky Fm (Tanamo‑Malokhetsky mega‑swell, Yenisei‑Khatanga petroleum region). Geologiya nefti i gaza = Oil and gas geology. 2018;(5):37–49. DOI: 10.31087/0016‑7894‑2018‑5‑37‑49.

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A.V. Gvozdeva

FGBU «All‑Russian Research Geological Oil Institute», Moscow, Russia;

gvozdeva.a.v.91@gmail.com

E.A. Taratyn

FGBU «All‑Russian Research Geological Oil Institute», Moscow, Russia;

edyardtaratyn@yandex.ru