Oilfield Terminology & Definitions.
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Exploration & Geology

Exploration and subsurface activities involve locating hydrocarbon deposits and evaluating the geological formations that contain them. Techniques such as seismic surveying, well logging, and reservoir modeling guide drilling decisions and optimize production.

  • Oil Window
    20

    The oil window is the range of burial depth and temperature in which a source rock’s kerogen generates liquid oil, below the immature zone and above the gas window.

  • Kerogen
    15

    Kerogen is the insoluble organic matter locked in sedimentary rock, the buried remains of plankton, algae and plants that becomes oil and gas when the rock is heated deep enough.

  • Core Sample
    54

    A core sample is a cylindrical section of rock or sediment extracted from the subsurface during drilling operations. It provides a direct, physical record of…

  • Drill Stem Test
    66

    A Drill Stem Test (DST) is a temporary completion of a wellbore interval during drilling operations to evaluate the reservoir’s potential to produce hydrocarbons. It…

  • Cap Rock
    59

    Cap rock (also known as seal or top seal) is a low-permeability, often ductile rock unit that overlies a porous reservoir rock and prevents upward…

  • Anticline
    56

    An anticline is a type of geological fold that arches upward, with the oldest rock layers at its core and younger layers draped over the…

  • Density Log
    57

    A density log is a well logging measurement that records the bulk density of a formation along the borehole wall. It is a fundamental tool…

  • Amplitude
    65

    Amplitude refers to the strength or energy of a reflected seismic wave, measured as the maximum displacement from the zero baseline of a seismic trace.…

  • AVO
    68

    AVO stands for Amplitude Versus Offset (sometimes called Amplitude Variation with Offset). It is a seismic analysis technique used in petroleum exploration and reservoir characterization…

  • Cuttings
    51

    Cuttings are the small fragments of rock, sediment, and formation material that are generated by the drill bit during the drilling of a wellbore. As…

  • Direct Hydrocarbon Indicator
    66

    A Direct Hydrocarbon Indicator (DHI) is a geophysical anomaly observed on seismic reflection data that suggests the presence of hydrocarbons (oil or gas) in subsurface…

  • Fault
    47

    A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock-mass…