Bathymetric and Shallow Sediment Core Sampling in McKinley Bay, NWT
Principal Investigator: Hammer, Lorne (1)
Licence Number: 14019
Organization: Canadian Petroleum Engineering Inc.
Licenced Year(s): 2006
Issued: Jul 04, 2006

Project Description: Shell Exploration and Production Company (Shell) is proposing to mobilize the Mobile Offshore Drilling Unit (MODU), Kulluk, from McKinley Bay, Northwest Territories to offshore Alaska, to initiate preparations for an offshore exploration drilling program to be carried out over the next several years. The Kulluk has been inactive and moored in McKinley Bay since 1993. Prior to that, the Kulluk had successfully completed a number of exploration drilling programs in the Canadian and American portions of the Beaufort Sea ending in 1993. Canadian Petroleum Engineering Inc (CPE) has been retained by Shell to initiate the process of re-commissioning the Kulluk and to have the MODU re-certified to meet current national and/or international standards by Det Norske Veritas, a leading international certification organization. To carry out the necessary recommissioning/re-certification and mobilization program,CPE with the assistance of a number of Inuvialuit enterprises, plans to conduct a bathymetric survey of the McKinley Bay channel to confirm the water depth measurements made in 1999 and 2001 by the Geological Survey of Canada, and a shallow core survey to sample the material which has infilled some portions of the channel.

Sonar (sound based) technology will be used to obtain bathymetric information. Sonar measures distances underwater by emitting a high frequency signal and measuring how long it takes for the sound signal to reflect back to the source. Transducers on the bottom of the survey vessel’s hull are used to transmit and receive signals. As the vessel moves forward, the transducers emit signals downward. The result is a profile of depth measurements perpendicular to the vessel’s movement. Two technologies will be used for measuring the water depth in the McKinley Bay channel: single beam and sweep echo sounding. Sweep echo sounders use a series of six single beam echo sounders placed in a row. Instead of using only a single beam echo sounder beneath the vessel, a sweep echo sounder system uses series of single beam echo sounders placed at regular intervals. The echo sounders to be used in this study transmit sound waves of 250 kHz, similar to that of fish finders. The Kulluk will serve as a base of operations for the bathymetric survey. Land based activities will be minimal for this program. The vessel from which these surveys will be conducted is a newly constructed Catamaran Offshore Survey Vessel. This catamaran is a research vessel used for hydrographic surveying. The vessel contains an array of computer equipment, echo sounder equipment, and transducers used for hydrographic studies. The vessel is a specifically built boat that is capable of surveying in the open offshore waters as well as in the shallow areas of the Mackenzie Delta.

Once the bathymetric survey is completed and areas of interest (i.e. less than 10 m water depth) are identified, the types and competency of the material infilling the channel may be sampled. The seabed soil competency can then be assessed by a freefall penetrometer, deployed from the survey vessel. A mini Remote Operated Vehicle (ROV) unit may be deployed to obtain video transects of the dredged channel. The survey vessel will be used to deploy a freefall penetrometer to measure the dynamic load bearing strength of the seabed. The AGO Sting system will be used for this survey. This unit is a self-contained tethered probe that will withstand the harsh conditions expected during this survey. It is released from sea level so that it drops freely through the water, reaching terminal velocity, and impacts into the sea floor vertically with its calibrated shaft and foot. Internal microprocessor-based electronics record the deceleration as the shaft embeds itself into the layers of the bottom sediment. Successive drops can be performed during a single deployment by simply raising the probe several meters off the bottom. After the unit is brought back to the surface the data is downloaded to a laptop computer. Software is then used to determine various kinematic parameters for each impact event and to compute an estimate of the seabed bearing strength profile. Primary interpretation of all data will be completed during the field surveys. This will be undertaken either by the field survey team if conditions allow, or by office-based processing through the internet. If the results of the bathymetric and sediment survey identify constraints to extracting the Kulluk from McKinley Bay in a safe and responsible manner, a plan will be developed to address those constraints. If channel depth is a constraint, dredging the channel may be considered. Any dredging plans will be subject to all the required and appropriate regulatory consultation, review and approval prior to implementation.
The bathymetric and sediment surveys will be conducted from July 4 to October 31, 2006 in the McKinley Bay navigation channel, which is approximately 12 km in length. Sampling locations will be specified at approximately eight locations along the area of interest of the channel. The coordinates of these test locations will be chosen from data obtained in the bathymetric survey. GPS using space based differential augmentation will be used to navigate to the specified locations.