About This Item
- Full text of this item is not available.
- Abstract PDFAbstract PDF(no subscription required)
Share This Item
The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Seal Controls on Trap Capacity and Migration
By
The capillary properties of sealing
rocks can control hydrocarbon column
heights and influence the geometry and
position of migration pathways. We have
used mercury-injection capillary pressure
(MICP) data to investigate the sealing
properties of both cap rock and fault
seals, and apply the results to predict
trap seal capacities and model migration
processes.
Most mudrock seals, irrespective of depositional environment, have extremely fine pore-throat systems that are capable of trapping large (>1000 ft.) hydrocarbon columns. These seal capacities are typically greater than trap closure heights, and only limited vertical leakage is expected through matrix pores. Results to date suggest that seal quality does not degrade significantly until total clay contents fall to <30 wt.%. Flow simulations show that in these silty "waste" zones, long-distance lateral migration can occur at geologically-rapid rates.
The capillary-pressure response of several
North Seal fault
seals is highly variable,
due to differences in lithology and
deformation conditions. Grain-scale
deformation and cementation dramatically
increase capillary entry pressures
relative to the undeformed reservoir.
However, entry pressures are not generally
as high as those measured on common
top seals. These results show that
fault
zone material can provide an effective
hydrocarbon seal, but may trap only
limited
fault
-dependent column heights.
The rock property data can be integrated
into a "fill-and-spill" type migration
model that assumes: ( 1) impermeable
top seals, (2)rapid migration rates,
and (3) bottlenecking at faults. In places
where vertical migration is critical (e.g.,
Gulf of Mexico), we propose that the
same fault
can seal an accumulation and
provide an effective migration pathway.
End_of_Record - Last_Page 9---------------