Unmanned air vehicles (UAVs) have considerable application in exploration and production activities, and the UAV with a 22-lb payload has much to offer. However, before such UAVs will find widespread use, issues to do with reliability, flying in non-segregated air space and reputational damage need to be addressed.

UAVs are robotic aircraft that have seen a huge upsurge in development and deployment, primarily by the military services of many countries. The US military in particular has poured massive resources into UAV development and production.

Not surprisingly, UAVs in current production tend to be military in nature and range from the small, hand-launched Dragon Eye by AeroVironment, with a maximum endurance of 1 hour and a price tag of less than US $100,000, to the massive Northrop Grumman Global Hawk RQ-4, with a maximum endurance of 36 hours and a price tag in excess of $27 million.

Can UAVs be used in E&P activities?
Several reports outline activities involving the use of UAVs.
• UAV Systems: The Global Perspective 2005. “Aeronautics Defense Systems of Israel is using its short range Aerostar UAV to provide protection and patrol services for Chevron Texaco’s operations in Angola under a 2-year contract awarded last year and reportedly worth $4 million. The Aerostar carries a payload of up to 110 lbs and has an endurance of 14 hours.” From “UAV Systems:…” by Blyenburgh & Co.
• InSitu/Fugro Airborne GeoRanger. Fugro Airborne Surveys reported on the development and deployment of the Fugro GeoRanger. The 40-lb GeoRanger, based on the InSitu Scan Eagle, is capable of fully autonomous flight. It has an endurance of up to 10 hours and a cruise speed of 45 mph (75 km/hr). The maximum fuel and payload weight is 13.2 lbs. This UAV is typically used in magnetic surveys. See www.insitu.com and www.fugroairborne.com Web sites for more information.
• Magsurvey Prion. This 66-lb UAV is targeted for use in Cesium vapor magnetometer surveys. See www.magsurvey.co.uk.
• “Shell may enlist pilotless planes to aid in exploration.” According to a written statement by Terzah Poe of Shell Oil, “Drones are being investigated as an alternative to manned aerial flights for marine mammal monitoring in order to reduce the safety risk to humans associated with flights over remote stretches of Arctic Ocean. The unmanned aerial vehicle, or drone aircraft, would be used to monitor and track marine mammals in the areas where we are operating” from www.alaskajournal.com.

Advantages
The advantages of using UAVs in exploration and production (E&P) activities are numerous. They include:
• The ability to stay in the air for up to 30 hours;
• The ability to fly in hostile regions where there is a real risk to the life of a pilot;
• The ability to always “fly on instruments” under precise computer control to perform a very precise raster scan of a region, fly at night to minimize sunspot interference and fly at very low levels to increase data resolution;
• A considerable size differential over their manned counterparts, consequently introducing less of a disturbance to the parameters being measured, such as the magnetic or gravitational field;
• Lower operating costs since they are less expensive to purchase; are easier to manage, meaning a UAV operator can manage several UAVs; will use less than 20% of the fuel used by a manned aircraft (payload-dependent); and may not need to use an airfield for takeoff and landing. Because of the relatively low acquisition and operating cost of the UAV, one can perform repeated surveys to build up a differential (or “4-D” = 3-D + time) representation to detect changes over time, for example, depletion of an oil reserve or leakage from a pipeline.
• More environmental friendliness since they require fewer materials to build, uses less fuel per mile traveled, create less pollution per mile traveled, make less noise in flight and are easier to dispose of at the end of their lives.

Type 1 UAV applications
These applications include high-resolution 3-D visual imaging. For a true

Figure 1. The InSitu/Fugro GeoRanger on a ship. The GeoRanger has a maximum fuel and payload capacity of 12 lbs, but that is likely to improve with ongoing developmental work. (Photo courtesy Insitu Inc./Fugro Airborne Services)
3-D image, one would use five-high resolution cameras, each weighing around 3.5 lbs.
A description on www.gadgetshow.com sums up the process. “To consider what is involved in 3-D imagery, by 2008 Microsoft aims to have used manned aircraft to photograph 900 European cities. It’s an exercise in precision flying with a detailed flight plan. The pilots fly in straight lines over the city, 1,310 ft (400 m) apart — they must keep within 80 ft (24 m) of the flight plan and have to fly slower than 122 mph (200 Km/h) or the pictures become too blurred to use. The images are so detailed that every pixel represents just 6 in. at ground level.”
Applications also include:
• Scanning LIDAR for a Digital Elevation Map (DEM), where a typical scanning system weighs 20 lbs;
• Differential thermal imaging to detect leakage in underground pipelines using a 320 by 240 pixel microbolometer camera sensitive to wavelengths from 7.5 to 13 mm;
• Hyperspectral imaging involving the use of three imagers to cover the wavelengths from 100 nm to 2,300 nm with 960 spectral slices, each slice 2.5 nm wide;
• Cesium magnetometer such as the Scintrex CS-3Sl. Four such instruments could in principle be used to derive a vector magnetic field measurement; and
• Gas sensing using a quantum
cascade laser to detect minute amounts of ethane and other gases.
The above applications could in principle be managed by a UAV with a 22-lb payload capability.
Type 2 UAV applications
These applications require heavier equipment and thus a larger UAV. They include:
• Gamma ray mapping. The typical size of a sodium iodide crystal is 4 in. x 4 in. x 16 in. and weighs around 32 lbs. If we add a nominal 5.7 lbs for the photomultiplier tube and associated electronics, and note that a typical array consists of 14 such crystals, we end up with a total weight of 554 lbs.
• Gravity field measurements. Gravity meters and gravity gradiometers are heavy, almost regardless of type. Typical weights are 990 lbs.
• Airborne ElectroMagnetic (AEM) probing. An AEM probing system requires a power supply that can supply a pulsed current of up to 1,000 amps to a 80-ft (24-m) diameter coil. The estimated weight of such electrical equipment is from 550 lbs to 770 lbs. A UAV that comes close to this requirement is the Elbit Systems “Hermes 1500” UAV. This UAV has a wingspan of 60 ft (18 m) and a payload capability of 770 lbs.

Multiple UAV applications
We expect better quality data from a survey in which many UAVs are used, since the precision flight capability of the UAVs, with their computerized flight control and navigation systems, enables several UAVs to operate in close proximity if necessary to complete a survey. Also, several UAVs can each cover the same area to enable the identification and subsequent removal or reduction of instrument errors and instrument drift.

Additionally, the use of several UAVs to cover the same area enables noise reduction through data averaging.

The small UAVs introduce less of a disturbance to the magnetic and gravitational fields, either of which may be the subject of the survey.

UAVs can fly in total darkness at night, or at any other time when the sunspot activity and the cultural noise level is at its lowest, enabling measurements to be taken with minimal background noise. UAVs can fly very close to the ground (“tight drape”) through the use of precision navigation and computer-controlled flight. This low-level flying enables higher precision data to be gathered.

Since many UAVs can be used, the UAVs can fly relatively slowly and still complete the survey in time. The slow-flying UAVs can then make use of time averaging of measured data to reduce noise levels.

The use of several UAVs also introduces a fault tolerance to the survey.

If one UAV experiences problems of any sort, that UAV can be returned to base, allowing the other UAVs to continue and complete the survey.

Outstanding problems
One of the recurring issues with UAVs is reliability. Because many of the current UAVs are intended for use in military applications, where the need for the UAV has outweighed the
Figure 2. Example of 3-D imagery planned for Microsoft Maps. (Photo courtesy of www.gadgetshow.com)
lack of reliability, most of the UAVs require improvements to be made to their reliability.
Flight in civilian airspace is also an issue. For a UAV to fly in civilian air space, the UAV must satisfy national air worthiness criteria if the all-up-weight at takeoff is less than 330 lbs, or international criteria if it is larger, and support “sense and avoid” capability with respect to other aircraft equivalent to that of a piloted plane. Sense and avoid systems are at an early stage of development.

The UAV must also be able to respond to ground-to-air and air-to-air voice communications. For long-range UAVs one needs reliable satellite communications.

Another major concern is the damage to the reputation of an exploration organization caused by the crash of a UAV. The damage caused by a flying vehicle is related to the kinetic energy of the vehicle. Light, slow flying UAVs minimize crash damage.

Conclusions
UAVs have much to offer in the areas of oil, gas and mineral exploration as well as pipeline and facility monitoring. Many of the tasks can be accomplished with a UAV with a 22-lb payload. More attention needs to be paid to the reliability of the UAV. Efforts to enable the UAV to fly in non-segregated air space need to reach fruition before large-scale use can be made of this technology. UAV development is the fastest growing activity in the aerospace sector: with the current rate of progress, UAVs will see an increasing application in E&P activities.