The National Petroleum Reserve – Alaska (NPRA)
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fs024-01 4/11/01 10:34 AM Page 1 The National Petroleum Reserve–Alaska (NPRA) Data Archive ALASKA Introduction Beaufort Sea Point Barrow The area currently known as the Cape Simpson National Petroleum Reserve–Alaska Prudhoe Bay Approximate location of (NPRA, fig. 1) was originally designated in 3-mile boundary between Chukchi Sea State and Federal jurisdiction 1923 as Naval Petroleum Reserve No. 4 National Petroleum (NPR–4). It was one of four U.S. regions Reserve–Alaska thought to contain significant amounts of C oil that were to be reserved for national A Arctic National a la n crises. Geographic and geologic knowledge a s Wildlife Refuge d k a of the NPR–4 was only superficial in 1923. Brooks Range Front a Earlier exploration, however, had shown that the region contained the ingredients Trans-Alaska necessary for oil accumulations to exist: 100 mi Pipeline source rocks, reservoir rocks, and geologic structures that could trap petroleum. Oil seeps on the coast and the size of the area Figure 1. Location of the National Petroleum Reserve–Alaska and the Prudhoe Bay oil field. The North Slope is north of the Brooks Range. (some 37,000 square miles, about the size of Indiana) reinforced the notion that signif- were published in 1930. The report was Between 1974 and 1977, seven test wells icant quantities of petroleum were present. based on traverses along the larger rivers were drilled in the northeast corner of the Since 1923, various exploratory pro- and reconnaissance-scale maps of the geol- NPR–4; although they followed the trend grams have been undertaken in the NPR–4, ogy and geography. Oil shale source rocks of Prudhoe Bay, no significant accumula- first by the Navy, then by the U.S. Geologi- and anticlinal and overthrust structures tions were found. In 1976, the NPR–4 was cal Survey (USGS), and, most recently, by were documented in the Brooks Range, but redesignated as the NPRA. At the same industry. The government programs result- prospectors were cautioned about the time, the USGS was charged to assess the ed in the discovery of several small, non- adverse geographic factors and the conse- oil and gas potential of the NPRA and to commercial oil and gas deposits and the quential high costs. The report recommend- discover commercially producible petrole- accumulation of a vast array of data, which ed drilling near the Cape Simpson oil seep- um accumulations. From 1974 to 1982, have been stored in many locations by sev- ages as the next step in evaluating the extensive seismic surveys were conducted eral agencies. Although reports and maps petroleum potential, followed by geologic (fig. 2), and 28 test wells were drilled, documenting these programs have been field studies and then additional drilling in nearly every one of which had shows of oil areas that appeared favorable. and gas. Two gas accumulations were dis- published, large amounts of the basic data In 1944, the Navy began a more covered that were later turned over to the remain in hard-to-access paper copies or detailed exploration program that included North Slope Borough to supply the village deteriorating, old- or outdated-format mag- field mapping, seismic profiling, and aero- of Barrow. netic tape or poorly archived rock samples. magnetic surveys; the geologic component Recent discoveries of oil near the of this work was the responsibility of the northeast corner of the NPRA have USGS. This pioneering effort in Arctic renewed industry interest. In response to petroleum exploration resulted in the this interest and the initiation of lease sales drilling of 45 shallow core tests and 36 test by the U.S. Bureau of Land Management, wells. The program ended in 1953 and the USGS has undertaken a program to resulted in the discovery of several small ensure availability of the information accu- oil and gas deposits. Even though no com- mulated since 1923. To the extent possible, mercial deposits were found, the vastly these data will be available in digital format. improved understanding of the geologic history of northern Alaska served as a Exploration History foundation for future exploration and estab- 100 miles For an area intended as a secure lished the feasibility of petroleum explo- source of petroleum, very little was known ration and production in the Arctic. in 1923 about NPR–4’s petroleum poten- Motivated by private industry’s 1968 tial. Accordingly, the Navy requested that discovery of oil at Prudhoe Bay (the largest Figure 2. Locations of lines in the NPRA along the USGS map and assess the petroleum oil accumulation in North America) and the which seismic data were acquired from 1974 resources of this area. The task was com- oil embargo of 1973, the Navy authorized a to 1981 as part of the Government exploration pleted between 1923 and 1926, and results new exploration program in the NPR–4. program. U.S. Department of the Interior USGS Fact Sheet FS–024–01 U.S. Geological Survey March 2001 fs024-01 4/11/01 10:34 AM Page 2 Point Barrow Alpine • Demultiplexed seismic-reflection data curves selected and digitized into Log Field collected along about 15,000 line-miles. ASCII Standard (LAS)-format digital The data and supporting files are on well logs. Both the images and the digi- about 3,500 9-track tapes and are tal well logs are being cataloged and 1999 Lease accompanied by about 14,000 pages of archived on CD. Sale paper documents. • Drill cores.—The drill cores are being Planning Area • Processed seismic data and supporting slabbed, photographed, cataloged, and files on about 1,000 9-track tapes. archived at the USGS Core Research • Drill records for more than 100 wells Center in Denver, Colo. and including 745 mylar well logs. • Aeromagnetic and gravity data.—The 100 mi These records occupy seven file cabi- data files are being scanned and con- well nets. verted to graphic images or transcribed • More than 1,400 geologic reports, maps, into spreadsheets or data bases. The data Figure 3. Location of the Alpine oil field, Gov- and cross sections. are cataloged and stored on CD. ernment-drilled wells, and the 1999 Lease • About 10,000 feet of drill core, which Sale Planning Area in the NPRA. represents about 2 percent of the total footage (500,000 ft) of wells drilled in When the NPRA government explo- the NPRA. A split of about half of the ration program ended in 1982, responsibili- 10,000 feet of core is in the USGS Core ty for management and protection of the Research Center in Denver, Colo. The NPRA was transferred to the U.S. Bureau complete set of cores is at the Alaska of Land Management. The U.S. Congress Geologic Materials Center, Eagle River, authorized competitive oil and gas leasing, Alaska. and four lease sales were held between • Aeromagnetic and gravity data, which 1981 and 1984. One exploratory well was were available largely as paper records drilled on a lease in 1985; it was a dry hole. consisting of interpretive maps and data tables. Technological Advances The 9-track seismic data are 20 or In the two decades following the 1968 more years old; over time, tapes deterio- discovery of the Prudhoe Bay oil field, rate, are misplaced, or are separated from Figure 4. Drill core photograph from exploration focused on similar-scale, multi- the paper documentation. Well logs on USGS Open-File Report 99–015. billion-barrel fields because fields contain- mylar and related paper drilling records are ing less than a billion barrels were not eco- The first rescued information is avail- accessible only by one person at a time and nomically viable then. In the past 15 years, able in USGS Open-File Report 99–015, thus have limited use. The well cores are technological advances—notably 3-D seis- Selected Data from Eleven Wildcat Wells unprocessed and are not easily accessible mic profiling, sequence stratigraphy (a rel- in the National Petroleum Reserve in by USGS or other scientists. atively new technique of geologic analy- Alaska. The CD contains the following information: sis), and advances in well-site develop- Data Rescue ment—have reduced the costs of explo- • Drill core photographs (fig. 4) The USGS is capturing, cataloging, ration and development to the point that • Depths to selected stratigraphic horizons and archiving the data to make them readi- now fields as small as 100 million barrels • Geologic and drilling reports, scanned ly available in a usable form to USGS sci- that are tens of miles from infrastructure from originals entists and the public. Rescue methods for may be economic. Exploration has • LAS-format core gamma ray data different types of data are described below: increased on the North Slope of Alaska in • LAS-format borehole log data recent years, and several small but viable • Digital seismic data, supporting files, • Permeability, porosity, and grain-density fields have been discovered, including the and paper documentation.—The digital data 429-million-barrel Alpine field (fig. 3). seismic data are being copied from the Open-File Report 99–015 also con- With this discovery in 1994, industry inter- original 9-track tapes to compact discs tains full reference information, including est in the NPRA increased, and the Federal (CD’s). The paper documentation is metadata and sources of all information on Government reopened part of the NPRA to being scanned and converted to graphic the CD. The information is accessible leasing in 1999. images. These items will be combined through commonly used web browsers and with the ASCII supporting files on CD Data Archive Problems text readers. Future publication plans and organized by acquisition year and include a combination of CD’s and Internet The Federal Government archives all seismic line identifier.