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Alex is responsible for the company’s equipment, managing both rentals to third parties and equipment sent out on the field for SJ Geophysics’ projects. He also oversees and offers training for companies that rent the equipment, while making sure the equipment works in the clients’ best interest. Alex has been with the company for a long period of time, understanding and being able to coordinate the projects in order to attain the objectives for both the clients and the company.

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Contact Alex Visser

Borehole surveys involve the acquisition of geophysical data from within a borehole. They can be separated into two types: those measuring the physical properties of rocks near the borehole and those measuring the properties of objects located further away from the borehole.

Key features and benefits of borehole

• Suited to measure the response from targets that are too deep, small, or complex to identify with surface surveys,
• Wide variety of borehole survey types possible: electromagnetic, resistivity/induced polarization, magnetic, radiometric, etc.,
• Used to provide data complementary to surface surveys,
• Added value to drilling programs.

Services provided by SJ Geophysics

• Borehole-EM
• Borehole-Mag
• Borehole-IP (cross-hole, surface to borehole, combined borehole and surface 3DIP surveys)

Unique to SJ Geophysics

We can survey below the drill bit. Utilizing our unique Volterra borehole acquisition system, all data is logged within the acquisition unit downhole eliminating the need for expensive cables. The borehole survey occurs as the drill rods are removed from the hole. This means drillholes at high risk of collapse can be surveyed reducing the risk of not collecting data.

Controlled source electromagnetic surveys use the principals of electromagnetic induction to measure the electrical properties of the ground. EM data is acquired by transmitting a time-varying signal that induces currents in the ground which are then detected by a receiver unit. The induced currents in the ground are generated by the transmitter using either a surface loop or a grounded wire dipole. The measured response provides information on the subsurface distribution of rocks and minerals whose electrical properties are known to span many orders of magnitude.

Key features and benefits of EM

• Low impact survey method. Based on the principals of induction, no ground contact is required by the receiver units,
• Wide variety of EM techniques are available including both ground and airborne options,
• Ideally suited to identify conductive bodies within resistive host rocks,
• EM is successfully used to identify conductors such as graphite and metallic bodies, massive sulphide deposits, and buried metallic cultural objects.

Services provided by SJ Geophysics

Ground acquisition of electromagnetic data:

• Volterra-EM (fixed-loop, moving-loop, in-loop soundings etc.)
• Volterra-CSAMT
• Max-Min
• VLF

Magnetotelluric surveys are an unique electromagnetic technique that utilizes natural energy as its source. Measurement in the variation of these natural magnetic B(t) and electrical E(t) fields can be used to derive the electrical properties of the subsurface material.

Key features and benefits

• Low impact survey method. MT only requires the use of magnetic sensor and a few electrodes,
• Natural source (hence no need for use of transmitter and generator),
• Expands investigation depth greater than galvanic electrical methods,
• Integrated MT and DC Resistivity/IP data acquisition.

Services provided by SJ Geophysics

• Tensor
• Scalar
• CSAMT

Magnetic surveys are a passive potential field method that measures variations in the Earth’s magnetic field (due to induced secondary fields caused by magnetic/ferrous materials). These variations can be used for the direct detection of metallic ore bodies or the identification of structural trends and geological framework.

Key features and benefits of magnetic surveys

• Low impact survey method. Acquisition is logistically simple and cost effective,
• Availability of both ground or airborne surveys,
• Direct detection of the presence or absence of magnetite (pyrrhotite, hematite),
• Suited to identify different rock units (sedimentary vs volcanics) based on the characteristics of the magnetic response,
• Used to map the distribution of geologic structures and rock units,
• Focused on identifying magnetic bodies such as magnetic ores or buried cultural objects (eg. tanks and drums).

Services provided by SJ Geophysics

Ground acquisition of magnetic data:

• GEM magnetometer
• Volterra BH-magnetic

Data Analysis involves the process of reviewing and evaluating data sets. A key objective is to identify and account for issues that might affect the quality of the data interpretation. SJ Geophysics has experience working with geophysical data in many forms and from various types of surveys.

In terms of data analysis, our company provides:

• Detailed assessment of the quality of 3^rd party data,
• Data extracted, manipulated, and converted from multiple sources,
• Quality assurance and quality control (QA/QC) of geophysical data,
• Broad understanding and treatment of errors from a variety of sources such as survey design, instrumentation, acquisition method, cultural noise, data processing, etc.

Interpretations help clients understand the geophysical results in the context of their project to facilitate the achievement of the project objectives. Because exploration projects are often run by geologists, SJ Geophysics’ expertise adds valuable insight into geophysical data.

Our interpretations can:

• Describe how the geology and geophysics are connected,
• Identify structural trends represented in the geophysical data,
• Identify geophysical signatures which tend to correspond with areas of interest for mineral exploration,
• Provide recommendations for project advancement, future surveys, and drillholes.

Survey evaluation and design (SED) aims to create custom surveys based on a project’s individual objectives and property characteristics. It is a two stage process (evaluation and design) that SJ Geophysics offers to clients, aiming to provide the best guidance in terms of project expectations.

As part of our services SED involves:

• Working with clients to identify objectives,
• Evaluating and reprocessing existing data to better understand the context and target type,
• Determining the ideal custom survey type and parameters to meet the objectives,
• Developing a cost effective budget within financial constraints.

Exploration programs invest a lot of resources in performing surveys on their property. By combining the results and displaying them in 2D and 3D visualization environments, we give our clients a coherent picture of their exploration target.

Our services include:

• Compilation of historical and new data sets for a comprehensive understanding of the project,
• Integration of geological, geochemical, geophysical, and GIS datasets,
• Creation of a 2D or 3D visualization project in a format compatible with our client’s platform requirements,
• Guided visualization sessions with our 3D projector for data review with the exploration team.

Inverting and modelling geophysical data provides insights for prospecting and drill targeting. SJ Geophysics builds 3D models of the subsurface using the geophysical data collected.

In terms of modelling and inversion, our company provides:

• 2D and 3D inversions of geophysical data,
• 3D models for visualization of the subsurface,
• Expertise in multiple inversion packages including UBC-GIF (DCIP2D, DCIP3D, Mag3D, Grav3D) and CSIRO,
• Forward modelling (UBC and Maxwell).

SJ Geophysics uses their expertise and experience to manage successful geophysical projects. Project management often includes elements from many of the other consulting services offered by SJ Geophysics. On top of managing the geophysical surveys we perform ourselves, we also manage projects performed by other teams.

Our services include:

• Contract verification,
• Survey design, subcontractor selection, and supervision of airborne surveys,
• Training helpers to assist with geophysical surveys,
• Training contractor teams to perform geophysical surveys.

Gravity surveys are a passive potential field method that measures variations in the earth’s gravitational field. These variations are the result of changes in the subsurface density distribution of rocks and minerals. Gravity data requires careful data reduction procedures to remove influencing factors such as the earth’s ellipticity, lunar tidal forces and local geographic effects. After corrections have been made, subtle features can be identified in the data.

Key features and benefits of gravity surveys

• Suited to indicate regions of mass excess or mass deficiency. A region of mass excess could be caused by the presence of base metals (high density) while a region of mass deficiency could be caused by voids or graphite (low density),
• Density distribution gives information on the subsurface geology,
• Used to map dense mineral deposits such as volcanogenic massive sulphides and kimberlites,
• Focused on identifying subsurface caverns.

Services provided by SJ Geophysics

• Ground acquisition of gravity data

Resistivity (DC) and Induced Polarization (IP) is an electrical survey method used for measuring the electrical properties of the subsurface. In a DCIP survey, a time-varying current is injected into the ground using two current electrodes and the resulting potential field voltage distribution is measured. The measured response is then used to calculate the apparent resistivity of the ground. When the current is removed, materials capable of holding a charge (i.e. polarizable), will have residual currents that decay over time. The resulting change in voltage over time represents the chargeability of a material.

Key features and benefits of IP

• Used to identify the subsurface distribution of electrical properties: resistivity and chargeability,
• Wide variety of survey arrays and configurations that are selected based on the survey objectives: pole-dipole, dipole-dipole, and 2D, 3D,
• 2D and 3D inversion algorithms are used to generate subsurface models,
• Commonly used for mapping stratigraphy, structure, and alteration of rocks and soils,
• Direct detection of disseminated sulphides using chargeability (i.e. porphyry copper deposits).

Services provided by SJ Geophysics

Ground acquisition of IP data:

• Volterra-IP
• 2D & 3D data acquisition / data inversion

Joyce has been involved with SJ Geophysics since the company was founded in 1989. She is in charge of the day to day operations of the office; this includes overseeing billing and invoicing, project scheduling, coordination of field logistics of personnel and supplies and communications.

Contact Joyce Visser

Shawn received his B.Sc. majoring in geophysics from the University of British Columbia in 1996. Prior to joining SJ Geophysics Ltd., Shawn spent 6 years working in the oil and gas exploration sector with Schlumberger. Working throughout Alberta, Louisiana, the Northwest Territories and Texas, his work focused on survey design and seismic acquisition quality control.

Shawn joined SJ Geophysics Ltd in 2003 as a field geophysicist and conducted IP (2D & 3D), MaxMin, magnetic and VLF surveys throughout Alaska, British Columbia, Nevada and Utah. Shawn’s current responsibilities include coordinating International and US-based field surveys, managing data flow and providing geophysical support for daily operations.

Contact Shawn Rastad

Syd began his mining career in 1965. A graduate of the Haileybury School of Mines (1971), Syd also completed a B.Sc. (Honours) in geology and geophysics from the University of British Columbia in 1981. Prior to founding SJ Geophysics, Syd worked as a geophysicist at Cominco Ltd. Syd’s experience includes gravity, horizontal loop electromagnetic, IP, magnetic, seismic, VLF, (surface and borehole) UTEM surveys from the ground and the air in countless locations around the world. Currently he is the head of the Research and Development department, leading the technological breakthroughs that SJ Geophysics commits to.

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Contact Syd Visser