Lost circulation is defined as the total or partial loss of drilling fluids or cement to high-permeability zones, cavernous formations and natural or induced fractures during the drilling or completion of a well (Bensted, 1998). In Geothermal drilling, lost circulation often occurred with different severity level, which are:

  1. Seepage : <50 bph
  2. Partial : 50 – 100 bph
  3. Severe : >100 bph
  4. Total : No return to surface

(Rabia, 1986)

There are several causes of lost circulation, below are some examples.

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