Stress Field Detection (SFD®) is a patent pending gravity-based instrument. It detects gravitational perturbations which arise due to the physical contrast of density and stress conditions between geologic discontinuities and non-anomalous or “background” geological conditions. Presently, SFD® is the only method capable of providing information on changes in subsurface homogeneity relating to fluid entrapment. These changes are influenced by rock types and rock properties in a sedimentary basin (e.g., porosity and permeability) and factors such as fluid accumulation and significant stress variations within entrapped reservoirs.
An extensive library of SFD® data correlated with other geophysical information (especially seismic data) has shown SFD® to be an effective indicator of potential hydrocarbon traps, independent of other geophysical techniques.
In traditional gravimetry, the magnitude and direction of the accelerating force produced by mass-density variations in the subsurface are measured and analyzed. SFD® offers a new approach to investigate gravity effects. The fundamental difference in anomaly identification is that SFD® relies on the analysis of signal pattern evolution resulting from wave properties of a small oscillating mass assembly in the SFD® sensors. The signal detection is achieved through the dynamic interaction of SFD® with the gravity field as it is traversed, where motion is an inherent part. Effectively, SFD® is highly sensitive to small-scale gravitational anomalies, and trades off the quantitative measurement accuracy of traditional gravimetry in favour of qualitatively higher detection sensitivity, thus allowing SFD® to “see” or respond to large trapped fluid accumulations.