American Oil and Gas Reporter - October 2018 - 50

SpecialReport: Gulf of Mexico Engineering Revival
export pipeline.
According to the downhole fluid samples, fluids from Who Dat's multiple
horizons and reservoirs vary from lean
gas to 16-degree API gravity oil. In order
to install the optimal pipeline system,
extensive studies were performed to model
the hydraulics, pressure, temperature,
wax appearance, hydrate formation, slugging, commingling of zones, shutdown
and restarts.
Three subsea drill centers are being
used to develop the field. Drill center A
has one manifold and drill center E has
two manifolds. Each drill center's manifolds are connected to the FPS via dual
six-inch nominal wet insulated flowlines

and flexible risers with the capability of
roundtrip pigging. Another drill center,
G, was installed in 2014 with a similar
setup (Figure 2). These infield flowlines
are three miles long and the geometry
of the seafloor results in down-sloping
flow paths.
Geological Modeling
Figure 3 shows a northwest-to-southeast
seismic section across the Who Dat Field.
The field is a conventional mini-basin
amplitude play located a bit north of the
prolific Mars Basin. Who Dat's reservoirs
sit above salt, which controls a basin rim
fault (the field's updip limit). The reservoirs
are well imaged, with well-developed

FIGURE 2
Who Dat Subsea Layout

FIGURE 3
Northwest-to-Southeast Seismic Section
A
-8,000
-9,000
-10,000
-11,000
-12,000
-13,000
-14,000
-15,000
-16,000
-17,000
-18,000
-19,000
-20,000
-21,000
-22,000
-23,000
-24,000
-25,000
-26,000

Source: Courtesy of TGS

50 THE AMERICAN OIL & GAS REPORTER

A'
Reservoir Age
* L. Pliocene
* Miocene

aquifers of varying sizes. The 11 stacked
horizons range from Pliocene turbidite
channel sands to amalgamated and nonamalgamated Miocene lobate sheet sands.
All of the reservoirs are integrated
into a single geocelluar model, ensuring
that the reservoir descriptions are internally
consistent and aide reservoir optimization
efforts. The static model includes the
downdip aquifers. The most significant
reservoir is the Upper Miocene 4600 at a
subsea depth of 15,000 feet. The productive
area has an associated bright-amplitude
in the pay section (Figure 4A). Faulting
provides structural complexity in the
updip area.
The 4600 reservoir sands were deposited in a healed slope setting controlled by updip faulting. With more
than 60 feet of true vertical thickness,
the sands thin rapidly into the basin
and the production history supports minimal aquifer support. Within the main
area, the 4600 reservoir is well developed, with high net-to-gross, fine-grained
sands that have excellent porosity and
permeability (Figure 4B).
The model construction incorporates
petrophysical properties of net-to-gross,
effective porosity, and permeability. Facies
curves were generated using the evaluated
curves. The facies were stochastically
distributed across the reservoir using a
sequential indicator simulation tool with
variograms based on well logs and cokriging the amplitude maps for the most
important reservoirs. The evaluated curves
were linked to the facies types and stochastic properties were distributed by
facies type. The smaller reservoirs that
have not yet been produced use a simpler
method to assign net-to-gross and also
are assigned stochastic porosity and permeability properties.
Reservoir Surveillance
The objective of production and pressure surveillance at Who Dat is to give
the project team access to the status of
the wells so engineers can make optimal
short- and long-term decisions. Supporting
these decisions consists of automatic,
semi-automatic, and manual production
and pressure surveillance.
Raw surveillance data come from pressure gauges, production meters, chokes,
etc. Seven of the 10 producing wells have
smart completions, so each well has a
common gauge, an upper gauge, and a
lower gauge for pressures and tempera-

American Oil and Gas Reporter - October 2018

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