Advanced Geological Services

Providing Comprehensive Geophysical Solutions

Geophysical well logs provide a continuous profile of the in-situ response versus depth in the well. Typically, direct soil/rock sampling is undertaken at intermittent intervals. A substantial amount of information can be obtained from a few logging runs in a well. In addition, the data can be correlated easily between adjacent wells.

Advantages:

The data collected in a borehole represents a single point in the plan view of a site.  Also, the radius of investigation may be small, and not completely representative of the bulk formation.

Limitations:

Sample Borehole Log

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Method and Applications:

AGS uses borehole geophysical methods to physically characterize the sediments, rocks, and fluids in existing boreholes and wells. The data are acquired by moving a string of instruments up or down the borehole, and measuring the electrical, natural gamma, sonic, electromagnetic, borehole diameter, fluid flow, and temperature responses. Borehole camera data may also be collected to review existing well conditions in real time.   Information gained from borehole logging can help constrain geologic conditions and tie multiple wells together.  AGS uses borehole techniques to determine:

· Lithology Correlation/Geologic Structure

· Stratigraphic Correlation/Depositional Environment

· Hazardous Waste Evaluation

· Relative Porosity/Permeability

· Water Saturation, Formation Factor

· Grain Size, Grain Sorting

· Formation Fractures, Solution Cavities

· Borehole Diameter

· Depth to Groundwater

· Groundwater Producing or Receiving Zones

· Water Quality

· Elastic Properties of Sediments and Bedrock

· Well Construction Information

Borehole geophysical methods involve the collection, correlation, and interpretation of measurements made in the borehole. Electrical and electromagnetic methods include the 64-inch normal resistivity, 16-inch normal resistivity, 40-inch lateral resistivity, single point resistance, induction logs, and the spontaneous potential log. The natural gamma ray instrument is sensitive to the presence of radio-elements that are common to particular soil/rock types. The sonic instrument measures the velocity of an acoustic wave along the borehole wall. The caliper log measures the diameter of the borehole, and the fluid flow meter measures the volumetric rate of flow of borehole fluid that moves up or down the borehole. The temperature probe measures minute changes in borehole fluid temperature.

Sample Optical Televiewer Log

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Borehole Logging