Geothermal Exploration 'Takes Flight' with Full Tensor Gravity Gradiometry (FTG)

Key Points

  • Identifying faults is paramount to evaluating geothermal resources. Full Tensor Gradiometry (FTG) can be used to quantify subtle changes in density contrast associated with faulting.

  • FTG sees density contrasts in the near-surface where seismic acquisition is difficult to constrain.

  • Additional sources of density contrast related to geothermal activity include Silica precipitation in pore space. 

Geothermal energy is a hot topic in the energy space. However, locating geothermal energy requires complex surveys. There are many options, but innovative companies are taking to the skies.

Discussing how these surveys work with FTG (Full Tensor Gradiometry), Bell Geospace Lead Geophysicist Alan Morgan joined host Hilary Kennedy on the company’s podcast. Morgan is an expert in gradiometry exploration and data acquisition.

First, Morgan explained how FTG works. “FTG detects density contrasts. By flying FTG surveys, what we are doing is detecting faults and constraining the "cup" that holds the heated fluids’’. The difference with FTG compared to standard gravity surveys is that it measures the rate of change of gravity in all directions. “FTG offers a 3D measurement,” Morgan added. Essentially this is a better resolution image and provides more details on the shape, depth, size... etc.

Using FTG for gradiometry exploration and data acquisition supports seismic, especially in the near subsurface–up to 500mwhere seismic data is difficult to constrain. Additionally, FTG is routinely utilized to perform quantitative 2D modelling along seismic profiles to evaluate sedimentary density as a function of porosity.

Morgan shared several specific surveys that had anomalies. Anomalies are something he’s always interested in digging into, and, on occasion, he’s able to go to the location. He shares some of his stories. 

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