Print this pageABSTRACT: Fill'er Up, Tony ... and Check the Oil: Petroleum Migration into Pay Sands at the Mars Field, Deepwater Gulf of Mexico
TITUS, MARSHALL W., ALAN S. KORNACKI*, and MICHAEL J. MAHAFFIE
Several oil pools
at the Mars field are trapped adjacent to salt bodies that are inferred
to have served as vertical migration pathways for oil generated by more
deeply-buried source rocks. This geometric relationship can be intepreted
as evidence that charging these pay sands required a `backfilling' mechanism
(i.e., incremental charge entering at the crest of each pay zone had to
displace an underlying buoyant oil column). For example, 
structural
cross
sections give the impression that backfilling occurred on both flanks of
Mars. But a rigorous analysis of oil migration at Mars shows that backfilling
mechanisms do not need to be invoked to explain how oil migrated into and
through these turbidite reservoirs.
The traps at Mars combine several
structural and stratigraphic elements. The general structure of the Mars
field is that of an inclined, east-plunging trough lying within a salt
embayment. The largest oil columns occur on the northern major limb of
the trough. Smaller oil columns are found on the minor limb of the trough
wrapping around the northern face of the Venus salt diapir (which probably
provided a vertical entry `front' for oil charge into Mars).
Our key conclusions are that:
(1) oil migrating up the plunge of the Mars trough along the Venus salt-sediment
interface from structural lows on the minor limb spilled across the trough
axis to fill traps on the major limb of the structure without requiring
backfilling from structually-high charge entry points along both limbs
of the trough; and (2) the suture between the Venus and Antares salt bodies,
and stratigraphic complexities within turbidite deposits both played key
roles focussing oil charge in and around the Mars field.
AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana
