In situ

{
  "id": "MLC-T-OAG-001955",
  "term": "In situ",
  "field": "Oil and gas",
  "definitions": [
    "A Latin phrase meaning \"in position\" or \"in its original place,\" describing materials, properties, or conditions as they exist underground before being disturbed by drilling or production. It applies to measurements of rock properties, fluid saturations, or reservoir pressure taken under natural subsurface conditions. For example, in-situ stress is the state of stress in a rock mass before excavation, which is distinct from stress measured on a core sample at the surface.",
    "Describing materials, properties, or conditions as they exist in their original place underground, before being altered by drilling, coring, or production activities. Measurements of reservoir pressure, temperature, and fluid saturation are considered in-situ when they reflect the undisturbed state of the formation. The term contrasts with ex-situ, which describes measurements performed on samples removed from their original subsurface environment and brought to a laboratory at the surface."
  ],
  "subject": "Geology",
  "url": "https://mlchart.com/terminology/oil-and-gas/in-situ/"
}