Brief explanations of the specialized terms and names used on our website, along with their meanings.
Amplitude Versus Offset (AVO) is a geophysical technique used in seismic exploration to analyze how the amplitude of a seismic reflection changes with the distance between the seismic source and receiver (offset). AVO analysis helps identify fluid content (e.g., hydrocarbons), lithology, and porosity in potential reservoirs.
AVO “true” anomalies are amplitude increases with offset that clearly deviate from the background (wet) trend and are more likely linked to hydrocarbon‑charged reservoirs with (class IV, III, IIp, I) or without (class II) impedance contrasts relative to the overlying and underlying, usually shaly, strata.
Bright spot in geophysics refers to a local high-amplitude seismic attribute anomaly observed on a seismic section, can be misleading but is commonly used as a direct hydrocarbon indicator (DHI) in hydrocarbon exploration. It can indicate the presence of a hydrocarbon filed reservoir or be due to anisotropic rock properties in the overlaying shale.
Class IV, III AVO responses are typically considered bright spots, but they can also occur in wet reservoirs with high net‑to‑gross ratios encased in anisotropic shales, so they are not always diagnostic of hydrocarbons.
Class II AVO response shows little or no impedance contrast with the overlying and underlying, usually shaly, strata, so it appears as a dim spot on most stacks. Class IIp AVO response is especially difficult to promote because its associated anomalies also look dim on full‑stack data but flips the polarity from near to far. Class I likewise appears dim on full‑stack data and does not present as a bright spot. Class I reservoirs dim onto structure.
Estimated Ultimate Recovery (EUR) in oil production refers to the total quantity of oil or gas that is expected to be economically recoverable from a well or reservoir over its entire productive life. It is a critical metric used to assess the viability, profitability, and valuation of oil and gas projects.
Internal Rate of Return (IRR) is the discount rate that makes the net present value (NPV) of all cash flows from an investment equal to zero. It represents the annualized rate of return an investment is expected to generate over its lifetime, accounting for the time value of money.
Petrophysical properties in geophysics refer to the measurable physical and chemical characteristics of rocks that are linked to their ability to store and transmit fluids, particularly in subsurface reservoirs. These properties are central to evaluating hydrocarbon potential and are derived from well logging, core analysis, and geophysical measurements.
The Powder River Basin (PRB) is a geologic and topographic basin in southeastern Montana and northeastern Wyoming, spanning approximately 120 miles east to west and 200 miles north to south. It is the largest coal-producing region in the United States, containing one of the world’s largest deposits of low-sulfur sub-bituminous coal.
In geophysics, seismic derivatives refer to the mathematical transforms—typically with respect to time or space—applied to seismic pre or post stack data to extract physical or geological information. These derivatives are used to analyze changes in seismic wave properties and enhance interpretation.
A sweet spot is a location within a seismic dataset that exhibits the strongest combination of geophysical indicators associated with commercially productive hydrocarbons.