A new generation of vehicle with a smooth ride is minimizing the environmental impact of seismic operations.

Oil companies explore many types of terrain in their search for oil and gas. Each environment has different challenges that must be considered, from fragile fauna and habitats to protected species. The large vehicles used in seismic surveys have the potential to be intrusive on land. Therefore, seismic contractors and oil companies are sensitive to the environmental concerns of conducting operations on public, native and private lands.
Modern seismic exploration techniques require the use of ground motion sensors and an energy source such as Vibroseis or dynamite to record acoustic reflections that image prospective oil- and gas-bearing formations. Vibroseis vehicles known as vibrators generate a variable-frequency acoustic energy wave that travels into the earth and reflects back from rock layers. The returning reflections are recorded by the sensors and then used to create a seismic image. 3-D seismic exploration specifications can require up to 10 vibrators to efficiently and effectively send acoustic energy into the ground. As oil companies seek to minimize the impact of exploration activities worldwide, seismic equipment manufacturers have responded with new designs that reduce the environmental impact of geophysical operations. At the same time, the economics of operations must be considered, and seismic contractors are always looking for efficiency improvements.
To overcome these challenges, equipment manufacturers are developing a new generation of vehicle to:
• minimize environmental impact;
• improve move-up times;
• increase mobility; and
• maintain a smooth ride with comparable speeds to current vehicles.
Seismic exploration operations in Alaska cover areas of high snow concentration with river crossings, depressions and mountainous terrain. Traditional tracked vehicles and rubber-tired vehicles have been used in Arctic environments, but they each have problems. Rubber tires have higher ground-bearing pressure, so equipment manufacturers have tried to decrease the ground pressure with the use of higher flotation tires. But this did not give them the mobility required to negotiate areas of deep snow. Tracked vehicles have used a steel grouser bar which, given the wrong situation, could cause tundra damage. Seismic exploration in the Arctic is primarily limited to winter months, and operator experience indicates rubber-tracked vehicles have the greatest mobility with the least surface disturbance. Critical vibrator design parameters specified by operators in Alaska include tundra impact, spill containment and safety.
Responding to oil company demands to reduce the environmental impact of seismic operations in fragile tundra areas of the Northern Hemisphere, Input/Output Inc. (I/O) of Stafford, Texas, designed the X-Vib to take into consideration low ground-bearing pressure, hydraulic oil leak containment, certified roll-over protection and high mobility.
The X-Vib design incorporates four wide, steel-reinforced rubber tracks that distribute weight evenly over a large ground area. The tracks' unique triangular design allows the drive wheel to be raised from the ground, thus reducing the buildup of snow and ice. The large contact area and hydrostatic drive provide good traction for increased mobility and faster move-up times. The track design and low center of gravity add stability over rough terrain and on steep slopes.
Arctic field tests
Successful field trials of the X-Vib prototype occurred during the spring of 2001 near Prudhoe Bay, Alaska, with several seismic contractors in attendance. The vibrator was tested through a series of dramatic turns, steep snow embankments and rough, snow-covered terrain. The vehicle's performance proved to be a distinct advantage over previous adaptations of vibrator chassis as the X-Vib demonstrated good mobility over deep snow banks, river bottoms and steep, difficult terrain.
Operational advantages of the X-Vib include:
• low ground pressure with minimal ground disturbance in environmentally sensitive areas;
• increased mobility in rough terrain and deep snow;
• quicker move-up times when compared to rubber-tired buggy vibrators in difficult conditions;
• greater approach and departure angles by using fully suspended ground-following wheels;
• containment of hydraulic components to eliminate spills;
• a track-aligning system that prevents premature wear of the track belt;
• a low center of gravity with certified roll-over protection; and
• steel-reinforced rubber tracks available in different compounds for desert and arctic regions.
The prototype tests were so well received by contractors and oil companies that I/O has orders for 25 units. The X-Vib units are scheduled for delivery for the 2001-2002 operating season in Alaska, Canada and Siberia.
One of I/O's customers, Veritas DGC Land, tested the X-Vib and recently ordered 10 for its Arctic operations. "We believe this new innovation will significantly improve our productivity in both our Mackenzie Delta and North Slope operations," said Mike Laurin, vice president of North America land operations, Veritas DGC. "We are confident that this new rubber track source configuration will improve productivity while meeting our corporate objective of reducing environmental impact to the tundra."
Desert operations
Desert trials for the X-Vib occurred near Monahans, Texas, in the Permian Basin before a group of seismic contractors in July 2001. The test area consisted of large sand dunes and rough terrain. The X-Vib significantly outperformed a comparable buggy vibrator fitted with sand tires in terms of mobility, move-up speed and ground disturbance. The X-Vib performed well at all orientations on the dunes and climbed inclines efficiently. It is also expected that the X-Vib will reduce the amount of bulldozing needed for line preparation, thus reducing impact on the environment and increasing productivity.
Doug Kirk, sales manager at I/O's Alvin, Texas, manufacturing facility, said the proprietary track suspension of the X-Vib, which gives a smooth ride, will prove to have a long-term maintenance advantage over conventional buggy vibrators. "The full-suspension undercarriage provides a smooth ride, reducing overall wear on the vibrator," he said.
Significant interest in the X-Vib has been received from Middle East oil operators seeking ways to reduce environmental impact and increase operational efficiency in desert regions. I/O will be conducting tests in the Middle East in the first quarter of 2002.
Promising future
The prototype results indicate the X-Vib should also have a promising future in traditional operating areas. In addition to the terrain advantage, the X-Vib should have applications in culturally developed areas, including city and rural locations, especially in active agricultural regions, where there will be less compaction of farmers' fields. Because of the low pressure exerted on the ground, the X-Vib also has the potential to extend the seismic shooting season in some regions. I/O is continuing its research and development on different track treads and looks forward to further testing of the X-Vib in the Middle East as well as other domestic terrain conditions, including the Rocky Mountains.

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