Page 46 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 22

[ ] Well Design
1.3.1

(TD) in 8 /2 in hole with a 7 in liner and 5 in production tubing could
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be TD’d in 6 in with a 5 in liner/5 in monobore completion with no loss
of production for significantly less cost. This would not be termed
“slimhole” according to the current definition (completed in 4 /4 in
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hole or smaller) but it takes advantage of some of the slimhole devel-
opments to drill a cheaper, fit-for-purpose well while avoiding the
complications of true slimhole.

1.3.1. How the Completion Relates to the Well Design

The completion will affect the entire well design, especially the
casing design. The completion proposed must be considered for all
stages of the well’s lifecycle: running the completion, pressure testing,
production, stimulation, workover, and abandonment.
Refer to the requirements of the well proposal in regard to what we
need to know about the completion.
Preparation for the completion. There may be work required after
the production casing or liner are cemented and before the completion
is run. This work may just be a bit and scraper run or it may be nec-
essary to install packers, perforate, and gravel pack, etc.
The following preparations may affect the production casing
and/or liner string, including the cement:

Perforated intervals require high-compressive strength cement
(2000 psi is recommended) and a competent (360˚ coverage)
sheath for zonal isolation. If it is a gas well, gas-blocking additives
may be called for. Where future recompletions on other zones are
anticipated, these intervals also need to have carefully tailored
cement. Wells with bottom hole static temperatures above approx-
imately 230˚F require silica flour in the cement for long-term tem-
perature stability.
The sump required below the bottom perforation (e.g., to drop
guns after perforating) will affect the final TD. Below the sump will
be the shoetrack (normally two casing joints plus float equipment)
and a pocket below the shoe.
Fluid gradients, temperatures, and potential surface pressures will
dictate the strength of the casing required for any treatments car-
ried out before the completion is run.

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