Page 42 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 18

[ ] Well Design
1.2

Identify all potential hazards (surface and subsurface) and poten-
tial drilling problem areas. For each potential hazard or problem
gather as much information as possible, establish the root causes of
the problem, and determine how they can be addressed. Ensure
that the well design takes account of them to minimize impact and
allow safe recovery. At this stage the outline casing points and mud
performance requirements may start to become clear.
Identify completion design or drill stem test (DST) requirements,
including fluids, necessary sand control measures, or other down-
hole equipment (e.g., packers). This should be done before the cas-
ing design since it may have an impact on the casing.
Choose casing points that allow kick tolerances to be maintained,
minimize potential downhole hazards, and minimize potential
drilling problems. Identify casing properties (outside diameter,
weight, grade, connections, etc.) for each casing string, taking into
account the directional plan. This is an iterative process because
the directional plan may depend on the casing design and vice
versa. If the rig is known at this stage, ensure that the conductor
and casings can all be handled (rotary table inside diameter, der-
rick load, handling equipment).
Specify the cementing requirements. Tops of cement slurries; any
particular requirements (e.g., high compressive strength for perfo-
rating).
Define the wellhead and Xmas tree requirements. If the well has to
be suspended this might mean a mudline suspension or subsea
wellhead system offshore.
Check all items on the proposal and ensure that the well is
designed to meet them; obtain dispensations or amendments if
necessary from the sponsoring department.
Issue the well design document for approval.
Estimate times and costs to prepare an authorization for expendi-
ture (AFE) and time/depth curve. (Note: a more accurate estimate
can be made after finishing the drilling program but timescales
usually dictate that an AFE is done sooner.)
Identify long lead time items and obtain approval to place orders in
good time.

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