English to Spanish Tech/Engineering Geology

Downhole logging is used mostly in
conjunction with ***open hole rotary
mud drilling*** which is a relatively
rapid, low cost drilling method. It may
be difficult to obtain representative
samples (core, rock chip) of
unconsolidated sands and gravels
which host the deposits by using
conventional drilling methods such
as reverse circulation. Rotary mud
drilling is often used because it
causes minimal disturbance of the
soft unconsolidated sands, and mud
coating of the walls keeps the hole
open for sufficient time to complete
logging with a downhole probe.
However, with rotary mud drilling,
there is severe lag of sample material
and mixing across sample intervals.
Consequently, chemical analyses
of sample cuttings are usually not
undertaken for grade determination
because they are not normally
representative of specific sample
intervals. Electrical logging methods
(resistivity and induction) are used
down the hole to provide accurate
information on lithologies.