The National Methane Hydrates R&D Program
The Alaska North Slope Stratigraphic Test Well - Status Reports
During the drilling and evaluation of the Mt. Elbert prospect well, NETL is maintaining an intermittent log of information relayed from NETL scientists actively involved with the operations on site in Alaska.
Report 3 (February 18) – Borehole Data Acquisition:
On Sunday, February 18, the science team completed the second phase of data acquisition from the Mt. Elbert gas hydrate test well. This phase of the project included two parts; wireline geophysical well logging, and small-scale reservoir pressure response monitoring and water sampling using the Modular Dynamic Tester (MDT) tool. The data collection part of the project is now complete. Through the core acquisition and downhole measurements, the science team has extracted a tremendous volume of high-quality data from this well.
Hydrate saturated, fine grained sand core from the Mt. Elbert #1 well
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On Thursday, February 15, the well logging program was completed with the successful completion of three proposed log runs. Run No. 1 (Schlumberger’s “Platform Express” tool combination) provided three key sets of measurements; 1) a gamma-ray log which provides an indication of the ratio of sand-to-shale at each horizon; 2) a suite of logs (density and neutron logs) that measures the ratio of solid rock to fluid filled pore space; and 3) a resistivity log that provides insight into the nature of the pore filling medium by measuring its ability to conduct electricity.
Run No. 2 added measurements from a dipole acoustic log, which provides additional insight into sediment porosity and also provides much needed information on the presence and concentration of gas hydrate and free gas within the sediment.
Run No. 3 added the combined magnetic resonance (CMR) log, which differentiates the pore-filling fluids into “free water” and several classes of “bound water” based on their mobility, and therefore provides a good indication of the sediment’s natural permeability (the ease with which fluids move through the rock).
Initial analyses of the wireline log data confirm the core-based interpretation that two hydrate-bearing sandstone reservoirs exist at the Mt. Elbert Site. Approximately 46 ft. of the upper most zone (the “D” sand), and approximately 53 ft. of the lower zone (the “C” sand) are gas-hydrate bearing. Gas hydrate saturations in the zones vary (primarily with reservoir quality), with the best zones exhibiting saturations of up to 80% of the pore volume. There is no free gas evident within the system.
Based on the initial data derived from these three sets of logs, the science team developed a plan for two days of testing with Schlumberger’s MDT tool. This powerful tool can extract small volumes of fluids from isolated portions of the reservoir and then monitor the response while the pressure within the formation equilibrates. The results of the testing clearly show the ability of the hydrate-saturated formation found in the Mt. Elbert well to yield gas from gas hydrate through pressure reduction. In addition, unusual (but repeatable) features of the pressure data suggest phenomena unique to gas hydrate reservoirs that will require additional analysis.
Participants in the borehole data acquisition phase of the Mt. Elbert project include:
Mikie Weeks – BP Exploration Alaska
Bob Hunter – Arctic Slope Regional Corporation
Tim Collett – U.S. Geological Survey
Steve Hancock – RPS-APA Energy Canada
Ray Boswell – U.S. Department of Energy
Dennis Weathers and Brian Philpott – Schlumberger
Report 2 (February 10) – Coring Operations Update:
On Saturday morning, February 10, 2007, the Mt. Elbert Science party, the engineers at Corion/ReedHycalog, and the crew of the Doyon 14 rig initiated the cutting of 3-inch diameter core using the Corion wireline coring assembly. Over the next three days, the team collected core across the full extent of the reservoir target interval. The coring tools performed exceptionally well through 23 deployments, recovering 85% of the 504 feet cut. Notably, this program marked the first use of wireline-retrievable coring technology on Alaska's North Slope.
On site examination of the cores confirmed the existence of gas hydrate saturated sandstone in both target intervals. These zones were extensively sampled, including the preservation of four 10-inch whole round core samples in special vessels that enable the samples to be repressurized to reservoir conditions as well as seven 5-inch samples that were quick frozen in liquid nitrogen. In addition, the science team collected more than 250 samples for specialized scientific analyses from both the hydrate bearing rocks and non-hydrate bearing sediments, including pore water samples, gas samples and a variety of whole sediment samples for the study of grain size, porosity, fluid flow capacity, microbiology, and other parameters.
The science team spent Tuesday preparing their samples for safe shipment back to their respective labs, where further analyses and data interpretation will occur. The bulk of the team left Milne Point on Wednesday the 14th as the remaining scientists turned their attention to the set up of wireline well logging and fluid flow testing tools in preparation for the second phase of downhole data acquisition.
The Mt Elbert core sampling and analysis team consisted of the following individuals:
Eddie Vaughn, Greg Burley, Jerry Haberthur, Louis Brown – BP Wellsite Leaders
Mikie Weeks, Larry Vendl, Kevan Sincock – BP Exploration Alaska
Bob Hunter – ASRC Energy Services
Tim Collett, Tom Lorenson, William Waite, Warren Agena, and Bill Winters – US Geological Survey
Marta Torres and Rick Colwell – Oregon State University
Ray Boswell, Kelly Rose, and Eilis Rosenbaum – U.S. DOE/National Energy Technology Laboratory
Grant Mabry, Jordan Smith, Dennis Gamberg, Nick Dubree – Omni
Kevin Leroux, Rusty Linn, Clint Porche, Dane Hately – Corion
Tony Worthen, Rafael Pantoja – DrillCool
Report 1 (February 8): The “Mt. Elbert Prospect” well was spudded on Sunday February 4th . The well was drilled without problems to 1960 feet where surface casing has been run. After the cement has set, the plan is to drill out below casing and begin coring activities sometime on February 8th or 9th. Following the coring, plans are to run wireline logs and then perform multiple low volume sampling/pressure testing using a Modular Formation Dynamics Tester (MDT).
The science party has been at work setting up the laboratories to handle the core and is nearly ready. The science trailers on location include a “warm” trailer where the pore water geochemistry group will work and a “cold” trailer where the physical properties and microbiology groups will work on the core. In addition to the samples analyzed by the onsite science team, samples of the core will be taken when each core segment is brought to the surface, catalogued and stored for later analysis. These will include sediment samples for measuring physical properties and performing sedimentological analysis, and routine drill cutting samples required by the state of Alaska.