SLATT, R. M., H.A.AL-SIYABI, C.W. VAN KIRK, and R.W. WILLIAMS, Colorado School of Mines, Golden, CO
Abstract: From Geologic Characterization to 'Reservoir
Simulation' of a Turbidite Outcrop, Arkansas, U.S.A.
Detailed correlation
of several outcrop exposures and subsurface cores of the Jackfork Group
in the DeGray Lake area,Arkansas, has provided a 3D geologic model of a
mile-long, steeply-dipping turbidite succession that is separated into
two blocks by a strike-slip fault. The model was scaled-up into four stratigraphic
zones, and net/gross and thickness were determined for each. By choosing
the present day topographic ground surface as an unconformity top-seal
and a lower topographic elevation as an oil-water contact, this outcrop
can be considered a turbidite "reservoir
."
Reservoir
performance simulation
was conducted using GeoQuest's ECLIPSE program in 3D, 3-phase black oil
mode.
Reservoir
parameters were input into a 4-layer, 1936 cell model (100
x 200 ft. cells). Fault and stratigraphic zone boundaries were assigned
zero transmissibility.
Drilling scenarios simulated
for both water drive
and depletion
drive
cases included single vertical
wells in each fault block through the crest of the 'structure' and on the
flank with the most permeable zone, and horizontal wells that penetrated
all four zones. Water
drive
simulations produced more oil than depletion
drive
simulations. In both cases, the least amount of oil was produced
from the vertical wells drilled on the crest of the structure, even though
those wells drained the most areally extensive zone. More oil was produced
from a thinner, more permeable flanking zone as well as from the horizontal
wells.
The results demonstrate the
ability to simulate outcrops when a sufficient 3D geologic characterization
is available.When standing at the outcrop on the 'oil-water contact', the
following points can be illustrated: (1) drilling the crest of a structure
may not produce the largest volume of hydrocarbons; (2) vertical wells
targeted to penetrate strata with the best stratigraphically-controlled
reservoir
quality can be more productive than wells targeted for the thickest
strata; (3) horizontal wells can be more productive than vertical wells
in reservoirs with steeply dipping strata.
AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England