For an explorer seeking oil, gas or minerals in Alaska’s resource rich lands, the general absence of roads and the seasonal nature of surface access can prove formidable hurdles. In part to address this problem, the state’s Geologic Materials Center in Anchorage maintains a vast collection of rock samples that enable rocks to be examined and investigated at negligible cost. And recently the facility has also been providing access to modern seismic data, made publicly available under the state exploration tax credit rules. Access to samples and data can prove particularly valuable for newcomers to the state, enabling preliminary investigations of exploration concepts.
Easy access
Ease of access to geologic materials that are otherwise difficult or impossible to reach also makes the center invaluable as an educational resource - the center has mineral and rock samples that can be made available for educational purposes, geologist and GMC curator Kurt Johnson, told Petroleum News. He and geologist Jean Riordan, aided by two interns, currently operate the center.
For example, the center has rock cores from wells drilled through the Nanushuk formation in the northeastern National Petroleum Reserve-Alaska, a part of the North Slope rock sequence that has become of particular interest for oil exploration in recent years. Students can examine reservoir-quality Nanushuk sands, and the impermeable layers within the sequence that can trap oil. Similarly, it is possible to hold and examine conglomeratic sands from the Ivishak, the main reservoir in the Prudhoe Bay field.
Johnson sees scope for further expanding a partnership that the center enjoys with the University of Alaska Anchorage. Researchers from UAA already use the center’s rock collection. Johnson thinks that UAA could bring equipment to the center and make use of the center’s expertise - the center has a workshop for cutting and preparing rock samples.
Voluntary donations
Much of the material in the center is voluntarily donated, although some well cores come via the Alaska Oil and Gas Conservation Commission in connection with well data becoming publicly available. Oil company Shell, for example, has donated a huge quantity of well cores and surface rock samples, some dating back to the early days of that company’s involvement in the state. Cores have come from old Middle Ground Shoal and West Foreland wells in Cook Inlet, and from exploration wells drilled in the Chukchi Sea between 1989 and 1991. The center is currently collating a huge collection of rock samples donated by Amoco.
Both the Shell and Amoco collections include surface rock samples from areas in the Arctic National Wildlife Refuge that are no longer accessible, Johnson said.
Other well core samples have come from even more remote locations, in the Gulf of Alaska and in some of the offshore basins in the Bering Sea, where exploration was conducted a number of years ago.
There are also rock cores from coalbed methane drilling in the Matanuska-Susitna Borough, and engineering rock cores obtained during investigations into the possibility of building a hydroelectric dam at Watana on the Susitna River. The center has a set of cores obtained from seismic shot holes dating from the days when dynamite was used in seismic surveying in the NPR-A. These cores can, for example, provide insights into where gravel may be mined for the construction of roads and pads in the region, without the need to conduct new tundra travel or surface coring, Johnson commented.
The U.S. Geological Survey has also donated a collection of some 150,000 rock samples, collected while conducting geologic research in Alaska.
World class collections
The center houses a world-class collection of microscope slides of plant spores and pollen, used in particular for determining the age of sediments. The center also holds the world’s largest collection of fossil Alaska foraminifera, tiny organisms used for aging rocks and for other purposes. Alaska geologist Robert Blodgett told Petroleum News that, for example, foraminifera in the collection demonstrate that during the Cretaceous period there was a major temperature contrast between Arctic Alaska and what is now the more southerly part of the state.
Larger fossils to be found in the center’s collection can be spectacular: beautifully preserved ancient sea stars, and many types of shell fish, for example.
One of the more curious set of samples in the center’s collection consists of rock samples obtained in the Aleutian Islands before and after nuclear bomb testing in the region - the idea was to determine what impact, if any, the explosions had on the rocks, Johnson said.
The center also holds a collection of aerial photographs of Alaska through the 1950s to 1980s. These photographs can prove invaluable in, for example, assessing coastline and vegetation changes in the state, Johnson said.
Altogether the center houses about 700,000 geologic samples in 170,000 boxes, Johnson said. And those numbers grow, as more material makes its way into the center. Given the huge cost of, for example, drilling a well in Alaska, the scale of the center’s collection represents a massive investment.
On-line catalogue
Although all of the boxes have been indexed and catalogued, the examining, identifying and cataloguing of all of the boxes’ contents is an on-going work in progress, especially as new material continuously arrives at the center. Catalogue information goes into the center’s computer database. Members of the public can access the database through the center’s website, to search for available samples and microscope slides. People can either conduct text searches, or they can use an interactive map system, to search for the availability of samples from a particular area. Data can be downloaded from the site. The website also provides information about publicly available seismic data that the center holds.
The center itself operates almost like an oversize box store, with sample boxes barcoded and handheld barcode readers used for stock taking and locating samples.
And the center has its own computer server system, with data storage arrays that amount to around two petabytes, and with an arrangement for data mirroring in Fairbanks for data protection.
In the age of online data access, the center is evaluating its future role and types of service that it can provide. For example, the center may try to use a spectral reflectance technique that reveals the components of a rock without any damage to the rock samples. The results could perhaps be made available online, for viewing anywhere in the world, Johnson commented.
With resource development being such an important aspect of the Alaska economy, the state places great value in the services that the GMC can provide. However, the geologists that frequent the center tend to think that this treasure chest of rocks and data could see more use. It is possible to make tremendous discoveries here, Blodgett said.
“It’s amazing. The unrealized potential of this place,” he said.
Insights into North Slope oil sources
The North Slope of Alaska has a reputation for being particularly rich in oil source rocks, the rocks that have generated the oil in the region’s prolific oil fields. And among the valuable resources in the state’s Geologic Materials Center in Anchorage are samples of various North Slope oil types and of the rocks that sourced the oil. It is possible to use the samples to, for example, characterize different oil types, to figure out where the oil associated with oil discoveries has likely come from. That, in turn, can provide insights into the nature of a particular discovery, and into the potential for making further, similar oil finds.
Geologist Art Banet showed Petroleum News some of the oil samples in the center’s collection and explained some of the nuances of oil categorization and identification. There are perhaps 10 different types of oil across the North Slope, Banet said.
The oil found in the Prudhoe Bay oil field, for example, is relatively dark and heavy, a factor that led explorers to seek similar oil elsewhere on the North Slope. Thus, while people were looking for reservoir rocks stained with that particular oil type, they may have overlooked lighter and relatively colorless oil that is also prolific in the region, Banet suggested. This possible “bypass oil” is now being discovered in the northeastern National Petroleum Reserve-Alaska, he said.
The center’s collection includes oil samples from various natural oil seeps in Arctic Alaska. The biggest seeps in the region are at Cape Simpson. However, the second and third largest seeps are two locations on the coast of the Arctic National Wildlife Refuge. Then come seeps at Umiat and a location known as Fish Creek.
At one time the state was able to use oil samples at the center to demonstrate to federal officials that the oil from Simpson came from a natural seep, and not from oil drilling, Banet said.
Rock specimens in the center may also provide insights to the origin of oil in the Triassic Shublik, one of the most prolific oil source rocks under the North Slope. The center’s collection includes tasmanites, a kind of algae-rich oil shale, from strata in the Brooks Range equivalent in age to the Shublik. Could this algal material have generated the Shublik oil?
Ken Bird, a geologist who is an expert on Alaska and North Slope geology, has told Petroleum News that there was initial skepticism over the tasmanite origin hypothesis, given a lack of reports of tasmanite being found in well penetrations of the Shublik. However, it is likely that when the Shublik was heated to oil generating temperatures or above, the tasmanite algae were destroyed, Bird said. And, in general, tasmanite algae have been found in surface and subsurface rocks across the North Slope region, he said.
The conclusion is that tasmanite algae have likely contributed to some undetermined extent to North Slope petroleum generation, Bird said.
- ALAN BAILEY
