Low Impact Seismic (LIS) - for Discussion

Further reference

see the file folder section and download the LIS Best Practice PDFs

Seismic Operations in Boreal, Northern Environments

Current Low Impact Seismic (LIS) Practices

Most operations today are 3D or 4D (a 3D that is being repeated, sometimes called a time-lapse), which require high-density acquisition recording parameters (i.e. closer sensor and line spacings). These high-density parameters are necessary to accurately map and monitor shallow oil sands reservoirs. The surveys can help determine the effectiveness of steam injection and the cap rock integrity in oil sands operations (e.g. SAGD, Steam Assisted Gravity Drainage). Currently, LIS (Low Impact Seismic) practices are employed across most Provinces by the seismic industry. These LIS techniques use meandering avoidance line conditioning techniques to construct sinuous mulched access trails that are: 1.75 m wide for receiver lines and 2.75 m wide for source lines.

Seismic Line Construction Using Mulchers

This construction practice uses small, low ground pressure (LGP under 5 psi), tracked Mulchers. The mulchers are equipped with precise on-board navigation enabling them to meander (reduce line of sight) and avoid large trees (retain fibre), usually within 5 meters of the pre-programmed route. They have extensive cab-guarding to protect the operator from debris and falling trees. The resulting trail removes small brush above ground level that presents a tripping hazard to workers. As most geophysical activity occurs during frozen ground conditions, the snow is compacted (by snow machines or mulcher) for easier and safer crew mobility, particularly in open areas where snow drifting can be extreme.

Typical Mulchers for this operation

CMI Twister C175 - Ground Pressure with Mulcher Head: 4.4 Psi (0.31 kg/cm2) - receivers

CMI Hurricane C250 - Ground Pressure with Mulcher Head: 3.3 Psi (0.23 kg/cm2) – source

For comparison: an unloaded Ford F250 truck – Ground Pressure: 30-35 Psi

This Mulching technique promotes the re-growth of vegetation (as the duff layer remains intact), and most lines recover within a couple of growing seasons.

2-man chainsaw teams traverse the newly constructed mulched line to remove nearby snags, leaners, dangerous trees and other hazards before crew members travel the line.

The mulched trail allows access for ATVs, UTVs, Argos, snow machines, small Drills and Mini-Vibrators. The equipment is used to mobilize people and equipment along the lines. Each line is surveyed, and the receiver and source points are positioned. On programs using an explosive source, LIS Low Ground Pressure drills are used at each source point to drill a shallow hole and load a small explosive charge before recording. The recording crew follows, later deploying the receiver sensors at all the receiver locations. The recording line crew prepare each receiver location with shovels (clears away the snow to the ground) to ensure good receiver coupling. Often, a small portable hand drill is used to drill a very shallow, 10 cm deep hole in which to place the sensor to improve receiver coupling. A Shooter (Seismic Blaster) will detonate each individual shot hole when all the required receiver sensors have been deployed. If Mini-Vibrators are being used as the energy source, the vibrators will travel to each shot point, where they will lower a pad that will input controlled vibrations into the ground. Intermittent access is required for Troubleshooters to quality-check the equipment, swap batteries and/or for supervisors and safety personnel to traverse lines to perform observations, complete safety monitoring and final line clean-up (remove trash).

In the event of an injury or incident, an injured party will be attended to by the Medic or other trained personnel. A casualty would be safely removed either with a stretcher or on a sled towed by a snow machine or UTV. The approximate width of a snowmobile is about 1.2m.

Line Construction with a sub-metre receiver width

In this scenario, Mulchers are NOT used due to the engineering complexities involved in the fabrication of machines with sufficient power and weight to construct safe lines. The industry does not have smaller mulchers. This was tried in the past with the engineering complexities being weight, height, and lack of engine power to drive and mulch. This was attempted with 0.9 m mulchers, unsuccessfully. Smaller lines are hand-cut by a 3 or 4-man chainsaw team working in conjunction with a surveyor or cutting push to accurately position the line. GPS pre-flaggers have been used in the past, but this exposes additional workers to a higher-risk activity. Chainsaw Falling is considered a “High Risk Occupation” and is another reason Mulchers are preferred.

Using chainsaw crews to construct receiver lines requires: more workers (9 times), often more time and significantly more accommodation and logistical support. All required equipment would be hand-carried, including saws, gas, oil, water, spares, tools, axes, spare clothing, food and emergency supplies with no access for snowmobiles or ATVs to extricate an injured worker.

Can it be done without chainsaws?

Most landscapes in the Western Provinces are diverse, with a mixture of boreal forest and wet muskeg areas. The forested areas that are less dense and with open wetter areas, provide an opportunity to minimize the removal of trees; however, sinuous travel along and through these intermittent forest types will still be necessary to remove or pack snow and mitigate hidden hazards. Without bulldozers, snow ploughs, or mulchers, chainsaws are the only option to create a safe trail for workers. Chainsaws are not a viable solution in deep snow. It is not uncommon to encounter waist or chest-deep snowdrifts during seismic recording operations. Mulcher-prepared lines reduce the risk to workers significantly and assist with any emergency egress if necessary.

Caribou timing windows limit seismic operations to those when adverse weather impacts are highest.

The main concern with near-zero-width lines, or very narrow lines, is that they prevent all vehicular travel, which conflicts with the due diligence requirements to keep workers safe and quickly evacuate an injured worker. These narrow, uncut paths can cause a loss or degradation of the GPS signal, impeding the ability to stay online. In under-canopy operations, loss or degradation of signal to GPS navigational devices can impede the ability to accurately stay online. Radio connectivity between GPS rover devices and a GPS base station can be severely compromised or even completely lost in under-canopy operations. Foot travel becomes more hazardous, especially with significant understorey vegetation and deadfall beneath the snow. The majority of seismic programs are conducted during the cold winters in reduced daylight, so well-prepared lines reduce weather exposure risk to workers.

Safety is a priority of Seismic Exploration operations

Safety is a priority of seismic operations and the requirement of Occupational Health & Safety. Employers have an obligation to ensure no worker is endangered in the workplace. Employers must do everything reasonably practicable to ensure the health and safety of workers. The Canadian seismic industry has been engaged with improving safety in operations since the 70s and has developed numerous training courses that are now delivered by Energy Safety Canada. The health and safety success can be quantified by the significant reduction in Lost Time Cases (LTC) over the last thirty-five years. This was achieved by developing safe work practices and a well-trained, competent workforce following sound guidance from Governments, Associations, Employers and Managers.

Boreal Forest of Northern Alberta, B.C. and Saskatchewan

Approximately 85 percent of Canada’s wetlands are located in the boreal forest.

In some areas, more than two-thirds of the landscape is covered by aquatic systems, including:- wetlands, lakes, rivers and deltas. Potential impacts to these essential aquatic systems should be avoided or minimized.