Alberta, industry work to minimize seismic footprint in protected areas

Aug. 18, 2003
Industry and government banded together in Alberta to improve seismic imaging and reduce overall oil and gas project costs in areas adjacent to protected places.

Industry and government banded together in Alberta to improve seismic imaging and reduce overall oil and gas project costs in areas adjacent to protected places.

Alberta Community Development, an agency based in Edmonton, provided WesternGeco with limited access to the 1,766-acre Saskatoon Mountain Natural Area in west-central Alberta to test "zero-impact" seismic methods.

The exercise, which results from a cooperative effort between the Alberta government and several industry groups, is designed to contribute to more effective management of the natural area while helping industry to better image the subsurface resources adjacent to it, the agency said.

The cost of seismic acquisition rises, but better imaging could trim companies' gross exploration spending by enabling more optimum placement of fewer well pads and possibly the drilling of fewer wells, especially dry holes, said Ken Lengyel, chairman, Canadian Association of Geophysical Contractors (CAGC). Saskatoon Mountain is 20 miles west of Grande Prairie near the British Columbia line.

Program evolution

Alberta continually auctions leases to oil and gas companies, and in the late 1990s the province identified Special Places 2000, areas designated for protection. Some of the special places and adjacent areas had been leased for oil and gas exploration.

Rather than attempt to ban exploration in the areas, Community Development offered to consider allowing seismic surveys if impacts could be minimized, Lengyel said.

CAGC, the Canadian Association of Petroleum Producers, and the Petroleum Services Association of Canada formed a committee to set up criteria to satisfy geophysical needs while lessening the impacts. CAGC alone represents 10,000-15,000 people, he said.

What resulted is a set of guidelines that are being implemented in the Saskatoon Mountain project. Lengyel characterized the likely results as minimal rather than zero impact.

The special places and parks are known as green areas, while adjacent privately owned lands are known as white areas. The guidelines provide that seismic acquisition be carried out with little or no footprint, no cutting of large trees or limbs, helicopter assistance, and project coordination to protect the public.

Work principles

The guidelines call for seismic crews to establish and respect restricted access zones, or RAZs.

These are to be 200 m around the perimeter of green areas and extending 200 m into the surrounding white areas. Also, a 100 m buffer zone would be respected around public use areas and operations within 1 km of those areas conducted in daylight only.

Within RAZs is permitted only foot traffic, no line cutting by mechanical means, and tree limbs are tied back. Part of the reason is to satisfy a government desire that seismic operations not open access routes along the boundaries of special areas.

Source points are located only on existing roads, and detonators are placed just prior to shooting. The more stringent of two hole-plugging protocols is used in all areas.

Outside the protected areas, crews use mechanical mulchers rather than bulldozers. The mulchers, on tracks or flotation tires, can clear 2 m wide lines for seismic surveys or 6 m lines for pipelines. They reduce fire hazard by cutting bushes and small trees, leaving the roots for regrowth.

All front-end work in special places is to be delayed as long as possible but allowed to proceed when necessary, just before the recording crew begins work. This lag time can be as long as 6 months on large 3D seismic surveys, said Lengyel, a member of WesternGeco's multiclient group. "Within 2 weeks anyone would have a hard time finding any of our lines," he added.

Measuring results

Participating organizations will videotape the project, which will undergo a full review upon completion to determine its success.

Community Development and WesternGeco are working with local environmental groups during all phases of the program to facilitate an effective assessment by all parties. The pilot project was scheduled to take place in three weeks during late July and August.

Saskatoon Mountain Natural Area consists of a 60 to 70-m hill with both gentle and steep sides. The hills are forested with a mixture of aspen and balsam poplar, white spruce, and birch. There are a number of small slough and sedge wetlands. The natural area is noted for a number of disjunct plant species typically found in the Rockies.

The area was a provincial park from 1936 until 1955. The site was then leased to the Canadian Department of National Defence for radar tower from 1966 to 1988.

WesternGeco Canada has managed four spec seismic surveys using contract acquisition crews in western Canada since deciding last fall to discontinue the field acquisition component of most of its North American onshore business (OGJ, Oct. 28, 2002, p. 42). It also maintains its processing function.