A

{
  "id": "MLC-T-OAG-004209",
  "term": "A",
  "field": "Oil and gas",
  "definition": "The tortuosity or lithology factor in Archie's equation, which relates formation resistivity to porosity and water saturation. It accounts for variations in pore geometry and the path length that electrical current must travel through the rock's interconnected pore network. The value of 'a' is determined empirically from core analysis and is often assumed to be 1.0 for many sandstones, but it can range from 0.6 to over 1.5 in different lithologies.",
  "subject": "Formation Evaluation",
  "url": "https://mlchart.com/terminology/oil-and-gas/a-term/"
}