Guidelines to Contracting Geophysical Services
Geophysical surveys are best applied early in an exploration program as an intelligent guide to drilling. This is especially true for site selection questions over large or complex areas. Projects that require a more complete understanding of the subsurface often request these surveys especially if the area will also receive geological, engineering, hydro-geological or hydrologic coverage. Geophysical surveys are most effective prior to drill testing and often pay for themselves by reducing the number of boreholes needed to characterize a site. The late application of geophysical surveys often elevates project costs above those where geophysics was applied early and incorporated into the later studies.
Things to do when contracting geophysical surveys:
- Define the scope of work in a written contract with input from both the customer and the contractor. A well-written contract gives clear objectives and requirements for all phases of work.
- Good communication is important.
- Daily progress reports and plots of preliminary data are useful to monitor progress and data quality.
- Quality-of-measurement issues must be defined. Often the accuracy of positionning in 3D space for each measurement has a strong influence on survey cost.
- Flexibility is important in the contract. Variations to the agreed scope of work are common in geoscientific projects as the project progresses and knowledge increases.
- Costs for standby time due to bad weather, instrument operation costs, instrument down-time, and insurance coverage are important. Costs for analysis and reporting should be clear. Define the time schedule for each phase.
- Cost estimates are more accurate if done by an experienced estimator during a site visit with the customer.
- Survey production rates depend upon:
- ease of access and commute time to the property,
- local topography and vegetation,
- season , weather, & insects,
- experience and resourcefulness of the field survey crew,
- instrumentation age and upkeep,
- the type of survey required and quality of measurement,
- local noise/interference sources to the signals of interest,
- safety considerations.
- For high-quality results the geophysicist must have access to all relevant maps, photos, borehole logs, and other geoscientific reports for the property and local area.
- The phased approach, is highly recommended in the application of geophysics. Ground-truth the results at each stage.
- A bailout clause should be included in all contracts to permit either the customer or the contractor to terminate the contract. If field tests do not meet the objectives then both sides can withdraw gracefully.