Remote Sensing Imagery Improves Safety and Logistics of Arctic Operations
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Many forms of remote sensing imagery can be used, along with data sets and the resultant products, to improve the efficiency and safety of upstream oil and gas operations on the North Slope of Alaska, which is characterized by limited road access, seasonally restrictive operations, and stringent environmental regulations. This paper discusses how optical satellite and aerial imagery, high-resolution light detection and ranging (LiDAR) for digital elevation and digital surface models, and synthetic aperture radar (SAR) have enabled one operator to undertake detailed logistical planning of field operations in the Alaskan Arctic by gaining a better understanding of the landscape, environment, and overall regional investigations.
Significant growth in remote sensing systems and techniques has enabled advanced desktop studies and technical investigations, particularly in remote areas such as the Alaskan Arctic. Arctic regions are, by nature, highly inaccessible and consequently problematic to investigate for the purposes of logistical planning of field operations. The North Slope, covering approximately 100,000 acres of northern Alaska and bounded on the north coast by the Chukchi and Beaufort Seas, exemplifies these qualities. Less than 1% of this region is covered by gravel road systems. North Slope oil fields are concentrated in a very small portion of this area. Extensive regulation governs both ground and air access to protect and preserve the environment and wildlife in the region, and to respect the cultural resources and Inupiat lifestyle of the 10,000 residents spread among eight villages.
Meandering and braided fluvial systems and stationary waterbodies vary seasonally in size, volume, and state. The environment has been sculpted by significant fluvial systems that drain from the Brooks Range into the Beaufort Sea. High-energy river drainages with steep-cut banks and expansive gravel bars leave abandoned channels and oxbows across the dynamic landscape. The tundra is marked by numerous waterbodies with a wide range of depths. Small ponds and lakes often have the most significant depth profiles. Light or deep snow levels; thin, thick, or grounded ice conditions on lakes; and overflow conditions on the rivers can plague preparation and execution of North Slope winter operations.
Because of the substantial portion of the North Slope that is inaccessible by road, winter tundra access for exploration operations is the only option for most of the region. North Slope winter-season length is established on the ability of the tundra to reach predetermined frost depths and snow thickness, which must be achieved to commence work. The formal annual opening and closing of the tundra is governed by federal and state agencies. All off-road winter operations must adhere to these regulations. The winter season has varied from 97 to 145 total days during the past 15 years. On top of the short winter work season, the Arctic is also known for its winter darkness. More than 50 days of the winter season have no daylight, which dramatically affects health, safety, and environment (HSE) regulations for working in the North. However, given the 24 hours of darkness, International Association of Oil and Gas Producers standards and operator HSE regulations allow for 24-hour operations.
Remote Sensing Data Sets
For Arctic operations, the environmental surface feature catalog includes the primary remote sensing data set of optical satellite and aerial imagery, which can be collected and analyzed at various spectral and spatial resolutions, as well as LiDAR data and SAR. Most standard-resolution optical and aerial data sets are available publicly through a variety of government and agency websites and databases. Optical processing can include enhancements using various spectral combinations, high-pass filtering to generate the highest possible spatial resolution for each type of sensor, and classic-neural-networks analysis to classify vegetation. Optical imagery, when available, is an outstanding monitoring tool. However, it is often hampered by weather conditions. Satellite remote sensing provides an opportunity to monitor vegetation at a variety of spatial and temporal scales.
The LiDAR system’s primary component is a laser scanner mounted onto a fixed-wing aircraft flying under 2,000 ft. The sensor emits optical pulses at a rate of 20,000–100,000 pulses per second. The light is transmitted from the aircraft to a surface, and the energy is reflected back to the sensor, where travel time is recorded. The velocity of the pulse is equal to the speed of light, and the two-way travel time is converted easily to distance. LiDAR uses an active sensor and therefore is independent of sun angle and can be collected during the day or night, but it cannot penetrate clouds or rain because most of the energy is reflected. Limited library LiDAR data sets are available in the Arctic because of its low level of activity. Most LiDAR volumes are proprietary to operators who see the value in its use. There is a restrictive LiDAR acquisition window during the summer as a result of the wait on snowmelt conditions and poor summer weather.
Primary LiDAR products include two types of digital elevation models (DEMs). The first is a full-feature data set that includes all reflected elements, such as vegetation, trees, buildings, and bridges. The second DEM is simply bare earth with all aboveground features removed, thereby exposing land features that would otherwise go undetected by only aerial photography. The North Slope has limited full features but still provides significant uplift for vegetation mapping. Additional processing for the application discussed in this paper included algorithms for generating waterbody outlines, multiple DEM generations at fit-for-purpose resolutions, spectral enhancements for various terrain, and vegetation types.
SAR imagery is acquired in the microwave region of the electromagnetic spectrum and has several unique characteristics when compared with optical imagery. The advantage of radar as a remote sensing tool is that it can image Earth’s surface through rain and cloud, regardless of whether it is day or night. This is particularly useful for monitoring areas that are prone to long periods of darkness. SAR imagery, when acquired in multipolarization, can provide a proxy for ice thickness. Sentinel imagery was used to monitor lake-ice freeze progression.
Methodology and Results
Only select vegetation types exist in tundra areas, and water systems and summer growing season dramatically affect vegetation growth. Damage to vegetation is often unnaturally reparable in this harsh environment. Accurate understanding of water systems and existing vegetation provides helpful insight for responsible operations.
The complete paper explains how optical imagery provides environmental information that aids in classification of surface features and waterbodies and in preplanning of remote winter operation for both routes and logistics. The paper also discusses how seismic acquisition preplanning, field operations, and survey work can be optimized using the LiDAR data set. This dramatically reduces HSE exposure in the field in high-density seismic acquisition with high station count (Fig. 1).
The authors explain how SAR imagery was used to monitor surface conditions when optical imagery was not available during night conditions. SAR was also used to calculate ice-thickness proxy maps for eventual field operations. Finally, the imagery was used to derive waterbodies (lakes and rivers) as a cross-check for the classified Landsat (optical) imagery.
Remote sensing imagery and its derived products demonstrably improved reconnaissance exploration, environmental monitoring, and detailed logistical planning of Alaskan Arctic operations. Optical imagery provided information about surface features such as lake outlines, general drainage, active channels in the Colville River, general lake-ice conditions, and classification of vegetation types. The LiDAR data were used to generate slope maps for vehicles, general topographic conditions, and field operations. The SAR imagery was used to monitor surface conditions when optical imagery was not available during night conditions. SAR imagery was also used to calculate the ice-thickness proxy maps for eventual field operations. All of these products contributed directly to environmental baseline studies and improved field operation efficiency and general safety of the company’s operations.
Remote Sensing Imagery Improves Safety and Logistics of Arctic Operations
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