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Moving Up The
Passive Seismic Learning Curve
Bob Hardage,
Bureau of Economic Geology at the University of Texas at
Austin, published an article about passive seismic in the
July 2008 issue of AAPG’s Explorer magazine. It is an
excellent foundational article for those wanting to learn
where passive seismic fits in the exploration bag of tricks.
Passive seismic involves collecting seismic data without
using an active seismic source. There are many sources of
low frequency energy—ocean waves (even far inland), wind,
noise, passing aircraft, and mechanical vibrations from
operating equipment. However, if one focuses in on the 1 - 4
Hz range, noise from ocean energy (generally below 1 Hz) and
anthropogenic sources (generally above 4 Hz) is minimized.
It’s not yet known why higher energy in this range is
associated with subsurface hydrocarbons, but the evidence
from work in several continents is confirming it is. By
itself, amplitude tells nothing about depth or size of the
source, but researchers are working around this by applying
reverse time modeling.
Passive seismic can be more than just
an exploration tool. Subsurface microseismic events can be
related to the progression of dynamic reservoir processes,
such as hydraulically stimulated fracture growth (think frac |
monitoring, which is widely accepted), injected fluid
movement, reservoir compaction, fault movements, etc.
Those
interested in seriously exploring this topic might consider
an international workshop (www.eage.org/events/index.
php?eventid=94): Passive Seismic; Case Studies and Applications
for Field Development and Exploration planned for March 2009
in Cyprus.
SEC Proposes Rule Changes to
Reserves Reporting
In late June the Securities and Exchange Commission (SEC)
announced that it has proposed revised oil and gas company
reporting requirements to help provide investors with a more
accurate and useful reserves picture.
The proposed rule
changes will allow companies to determine their reserves in
a manner consistent with existing technologies and will
allow investors to better understand the reserve quantities
and their implications. The SEC’s proposed rule changes
include:
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- Enabling companies to additionally disclose their
probable and possible reserves to investors. Current rules
limit disclosure to only proved reserves.
- Allowing
previously excluded resources, such as oil sands, to be
classified as oil and gas reserves. Currently these
resources are considered to be mining reserves.
- Requiring
companies to report the independence and qualifications of a
preparer or auditor, based on current Society of Petroleum
Engineers’ criteria.
- Requiring the filing of reports for
companies that rely on a third party to prepare reserves
estimates or conduct a reserves audit.
- Requiring companies
to report oil and gas reserves using an average price based
upon the prior 12-month period-rather than year-end prices,
to maximize the comparability of reserve estimates among
companies and mitigate the distortion of the estimates that
arises when using a single pricing date.
Excerpted from SEC
press release (www.sec.gov/news/press/2008/2008-122.htm)
Public comment on the proposed rule changes should be
received by the SEC no later than 60 days after their
publication in the Federal Register. |
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