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| Project Number | 570 |
| Date of Summary | June 3, 2008 |
| Subject | Measurement of the Effect of Depth Below Mudline of Charge Placement During EROs |
| Performing Activity | Explosive Service International (ESI) |
| Principal Investigator | William T. Poe |
| Contracting Agency | Minerals Management Service |
| Estimated Completion | December 31, 2008 |
| Description |
The Offshore Federal Oil & Gas infrastructure includes over 4,000 platforms,
some extending in life over 40 years. Due to the depletion on underlying
reserves, the offshore’s corrosive environment, damage due to third parties,
natural disasters such as hurricanes in the Gulf of Mexico, or any
combination, many facilities have been decommissioned and therefore subject
for removal. The current practice used by Industry to remove platforms is to
place bulk charges inside the tubular (“pile”) structure to be severed at a
point that is 15' or less below the seafloor ("mudline"). In most cases,
removal of structures at this depth prevents the pile members left in place
from future exposure, however, seafloor ground movement from mudslides,
current channeling, sea storms, hurricanes, earthquakes, and other events
may cause piles left in-place to become exposed above the mudline and
therefore potentially impair vessel traffic, drift nets, marine life, etc.
in shallow water regions. Due to these concerns and the many challenges of
removing these multi-ton structures, alternatives to the current use of bulk
charges are desirable to both promote safe removal operations and protection
of the environment. This study serves to provide MMS with additional information beyond what had been gained through a similar research effort (Project 429) funded by the MMS and completed in June 2004. The prior research assessed engineered explosive charge design for use in severing piles at depth of no less that 15” below the mudline. The goal was to reduce the explosive quantity used in offshore decommissioning operations from the 50 pound net explosive weight commonly used in "bulk" charges to less than ten pounds or, in some cases, less than 5 pounds in the engineered charges and to compare the physical and environmental effects of the engineered charges to that of the bulk charges. The result of that prior study found that engineered charges can provide the cutting effect necessary to sever large offshore piles, can reduce flaring of the piles thus increase cutting depth, and provide a significant reduction in the harassment zone for marine mammals. The objective of the new (current) research effort proposed by ESI is to further test and measure the engineered charges designed under the prior research effort using different charge placement techniques to improve the charge’s cutting effect as well as applying these charges at additional depths of twenty (20), twenty-five (25) and thirty (30) feet below the mudline. These tests will generate new data for use by MMS and other agencies to verify the added safety benefits to personnel, lower environmental effects of the reduced explosive weight, and provide additional mitigation achieved by increasing the depth below mudline for charge placement. |
| Progress |
ESI and MMS collectively produced a list of candidate platforms. From the
list, ESI has generated options for multiple platform removal
and communicated with the platform's operator and MMS for the option(s) that
best serves the operators schedule for abandonment and the needs of this
research to provide quality findings/readings for future modeling and
mitigation efforts. To date, ESI conducted one series of explosives testing as part of platform structure decommissioning operations being conducted by Maritech. The work was performed under collaboration between Maritech (operator), Tetra Applied Technologies (Contractor) and sup-contractors Global Industries, ESI and Sonalyst. Although no engineered charges were tested during this portion of the testing, 50-lb bulk charges and one 75-lb bulk charge were tested with pressure, impulse and energy flux density data gathered for each shot. The information gained from this testing will be combined with data from the engineered and bulk charges testing planned in the Fall of 2008 to provide comparative information towards demonstrating mitigation of environmental impacts offered by engineered explosive deployment. |
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