Slow formation

{
  "id": "MLC-T-OAG-003458",
  "term": "Slow formation",
  "field": "Oil and gas",
  "definition": "A formation whose shear velocity is lower than the compressional velocity of the borehole fluid, so no shear headwave is refracted into the borehole and shear slowness cannot be read from a monopole tool. Soft, unconsolidated or poorly cemented sands and shales are typical. Shear is instead obtained from the low-frequency limit of the dipole flexural wave or, in logging while drilling, from a quadrupole mode.",
  "subject": "Formation Evaluation",
  "url": "https://mlchart.com/terminology/oil-and-gas/slow-formation/"
}