American Oil and Gas Reporter - February 2015 - 101

SpecialReport: Gulf of Mexico Update

Advances In Seismic Rejuvenate Shelf
By Brad Torry
HOUSTON-As 2015 begins amid uncertainty about commodity prices, one
region in the Gulf of Mexico bears an interesting revival that should survive these
prices swings: the "Shelf region."
For all intents and purposes, we will
classify the Shelf region as the area
covered by Outer Continental Shelf blocks
in the five-year-term window (see Figure
1), which encompasses the historical postsalt and flex trends. With significant advancements in drilling technology, activity
in the Gulf of Mexico over the past 10
years has seen an increased focus on the
deepwater exploration prize.
From 2005 to the present, many major
exploration and production companies have
divested assets on the Shelf to a new breed
of independents, many of which have technical teams that departed the majors. In
the traditional cause and effect relationship,
this has re-established a round of activity
in this highly prospective region.
We believe a number of factors are
driving this revival: new geologic targets,
infrastructure capacity, and new technology
(seismic and drilling). Combine this with
a willingness to push the envelope to
identify and pursue new play concepts
and previously inaccessible pay that was
not recognizable with available data, and
a revival is occurring.
Although the GOM Shelf region has
had extensive seismic coverage (Figure
1), the majority of these data are limited
to narrow-azimuth ocean bottom cable
or streamer data, which means they were
gathered with limited offsets and azimuths.
With historical production occurring at
depths ranging from 5,000 to 15,000 feet
(fewer than 5 percent of wells exceed
15,000 feet) in this complex depositional
and structural (salt) environment, increased
spatial (lateral) and temporal (vertical)
resolution from seismic is required to resolve smaller/thinner geologic targets.
Early revival was made possible by
advances in data processing algorithms
and computational power that led to enhanced subsurface images. However, challenges remain, based on input data.
Where accessible (with accessibility
being the key), the acquisition of wideazimuth (WAZ), multiwide-azimuth
(MWAZ) and full-azimuth (FAZ, although
gaps remain with streamer acquisition)

data acquired with a variety of streamer/vessel configurations has made a material
impact, particularly in the deep water.
Each of these configurations fundamentally
offers long-offset, broad (not full) azimuth
data to image prospective zones and unlock
subsalt potential.
However, if current Shelf coverage
(Figure 1) is limited to only what would
be considered modern wide-azimuth seismic (long offsets that have a minimum
of 30 percent azimuthal coverage), a significant void in new data coverage becomes
evident (yellow and blue areas).
This challenge creates opportunity. Independents have identified the considerable
untapped potential. Given the advancement
in ocean bottom node (OBN) technology,
a step change or new paradigm for new
full-azimuthal nodal data (FAN) will support
the resurgence of activity in this region.
Why Now?
After the last round of major Shelf
activity in the early part of the new millennium, most discoveries now are on
decline. The new breed of independent
operator has recognized the significant
amount of bypassed pay, pool extensions,
deeper reservoirs, and enhanced recovery
opportunities. Add to this an increased
understanding of depositional environments (through extending onshore interpretations to the Shelf) and the expanded

understanding of salt tectonics, and the
region has experienced numerous new
ideas and learnings.
Add new technology (WAZ, FAN, and
short-leg horizontal drilling) with proper
application, and these opportunities have
led to strong return on investment for
operators and the identification of new
potential geologic fairways.
Examples of this can be found in the
success of companies such as Energy XXI,
which has increased reserves and production
from existing fields, and Freeport McMoRan with its deep exploration drilling
program (Davy Jones, Blackbeard and
Lafitte prospects). Although the final verdict
on these deeper wells remains outstanding,
I believe they have and will provide significant geotechnical information that will
lead to ongoing exploration and development on the Shelf.
Figure 2 provides an excellent visual
summary of the concepts that are returning
people to the Shelf. The final piece of information that needs to be added to this
equation is modern geoscience data. The
industry's ability to integrate and model
these data from source to sink, and to understand their complexities from local
stratigraphy to basin-scale, thermal maturation models, has reopened the door to
prospectivity.
What exactly do I mean by this? I
have mentioned the application of WAZ

FIGURE 1
Map of GOM Shelf Region With Seismic Coverage

Plans Filed in Past Six Months

Shelf Trend

Submitted Application for Permit to Drill

TGS 3-D Projects (in Progress)

2014 Data

TGS 3-D Surveys

New Data
Early Vintage
Year Established Unknown

FEBRUARY 2015 101

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