Page 155 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 131

Preliminary Work For the Drilling Program [ ]
2.1.2

taxes or by taking part of the government share of produced
hydrocarbons.)
5. After the well, decisions made can be reviewed in the light of the
intentions behind the decisions. This allows a full evaluation of
how successful those decisions were and will help in improving
future drilling performance.

The technical justification refers to the drilling program and not
the well design upon which it is based. Therefore, items such as cas-
ing design will be referenced as part of the well design justification.
(The well design refers to the final well status that is to be reached
for the objectives of the well. The drilling program shows how this
will be achieved.)
Example from a technical justification (from a mythical explo-
ration well, Monty 1). This shows the kind of information that can be
usefully included.

Drilling an 8 1 /2 in Hole Section

Hole condition did not seem to cause any problems on any of the
offset Brecon wells in the Lower Cretaceous. Pore pressures were fair-
ly high with RFTs over 0.72 psi/ft. Brecon 2 had a kick at 3176 ft
below the top of the Lower Cretaceous (0.797 psi/ft @ 10,833 ft);
Monty 1 is also prognosticated to drill 3176 ft into the Lower
Cretaceous. Bearing in mind that Brecon field is about 13 miles away
from the Monty field, the potential for high pressures certainly exists
on Monty though Brecon can only be used as a rough guide.
The mud will maintain the same density as the end of the previ-
ous section initially and will be increased during drilling to 0.80 psi/ft
at TD for the same reasoning as on the previous section. The
sequences of shale and sandstone caused no serious hole problems
(overpulls or enlargements) with gyp mud or KLM mud on the Brecon
2 and 3 wells. Uneven hole enlargement was noted in some shales on
Brecon 2; with a 4-arm caliper, the major axis was out to18.5 in with
the minor axis at about 10 in in 8 /2 in hole in places.
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