Survey map of the PSD-IZ attribute. Green circles display the PSD-IZ value of each station. Four levels of signal strength are used for the interpolated map using a standard kriging algorithm. Red indicates the location of the highest values. There are, among others, two areas with relatively high values: One on the right is in the producing part of the survey and the other on the left is in a chosen exploration zone.

Low Frequency (LF) seismic anomalies associated with hydrocarbon reservoirs have been observed by various industry and academic groups. Some of the early observations showed quite dramatic results, although many of these experiments were conducted in producing oil fields which made the handling of noise especially important.

Spectraseis has invested heavily in both research and in computer software to develop workflows for reducing both transient and stationary noise, calling on our experience with over 30 LF surveys around the world.

Data is acquired using well known, standard equipment. These broadband seismometers nominally record data for 24 hours to capture a full diurnal cycle. Noise is then separated from potential hydrocarbon reservoir related signals utilizing methods in the time, frequency, and spatial domains.

After analyzing the data for possible near surface effects, statistical attributes are calculated that can be related to hydrocarbon potential and ultimately to reservoir parameters. These LF attributes are displayed in either profile or maps, depending on the acquisition geometry. An example of a survey in Mexico is shown in the figure, in which the known accumulation of hydrocarbons are clearly identified and used for calibration so that new areas with exploration potential can be identified.