Abstract: Sugmut Field; A Forced Regression Deposit within the Neocomian Prograding Clinoform Complex, West Siberian Basin, Russia
ARMENTROUT, JOHN M. and OLEG. M. MKRTCHYAN
The Volgian-Neocomian interval
of the Middle Ob Region of the intracratonic West Siberian Basin consists
of between 35 and 45 regional transgressive/regressive cycles infilling
a basin which had an average water depth of approximately 200 meters. Within
local clinoforms, wells have encountered elongate shelf-edge sandstone
bodies ranging from 15 to 100 kilometers in strike-oriented length. In
most areas the seismic interval correlative to the reservoir sandstone
pinches-out against the foreset of the preceding clinoform. This geometric
relationship and the sharp-based log pattern of sandstones along the more
landward margin of the sandstone body suggest that the sandstone may have
been deposited as a consequence of marked downward shift in baselevel as
part of a lowstand prograding complex, or possibly as a late highstand
forced regression deposit.
The Sugmut field, located in
the northeast part of the study area, is 12 km wide east-west and 75 km
long north-south, and grades laterally into shale to the west, south and
east. Relative to the late regressive phase isopach, the initial transgressive
phase isopach thick shifts slightly northward and eastward indicating the
probable direction of littoral drift and marginward transgression. In the
northern part of the field the shelf-edge sandstone interval may correlate
with a thin depositional-dip oriented shelf sandstone mapped within the
transgressive interval. This mapped pattern may be interpreted as lowstand
incision of a fluvial system
supplying sand to a shelf-edge delta followed
by infilling of the fluvial valley during transgression. Subsequent down-to-the-north
regional tilt resulted in
structural
closure forming the Sugmut field
trap
.
AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria