Page 52 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:55 PM Page 28

[ ] Well Design
1.3.3

9. Limited potential to reuse the original wellbore for sidetracks to
other reservoirs.
10. May limit information obtained if the hole size prevents all
required logging tools.

Relevant developments.

1. Monobore completions.
2. Coiled tubing drilling.
3. Developments in downhole equipment (i.e., motors, drillstring,
bits).
4. Computerized systems to efficiently monitor the operation and to
detect very small influxes (<1 bbl).
5. Better understanding of wellbore instability and superior muds
now available compared to previously have reduced the risk of los-
ing a well while drilling smaller holes than in the past.
6. Better understanding of downhole hydraulics.
7. All regular logging equipment exists for holes down to 4 1 /8 in hole,
150˚C, 15,000 psi.
8. Full production testing capability now exists with 3 1 /8 in OD tools.

1.3.3. Multiple String Completions

Where a well penetrates several zones that need to be produced
but cannot be commingled, it is possible to run two completion strings
using special dual packers to separate the zones. Planning to use dual
completions clearly introduces some special considerations.
The two strings will generally be made into a dual packer, such as
the Baker RDH (retrievable dual hydraulic) hanger. There will be two
strings from above this packer to the dual hangers set in the wellhead.
Below the dual packer will generally be a short tailpipe on one side and
a long string with a seal assembly on the other side. When the com-
pletion is run, the seal assembly on the long string will sting into a
packer previously set downhole, so that production is possible along
the long string from below this seal assembly depth or along the short
string from between this seal assembly and the dual packer.
The long string can also selectively produce from different zones.
Sliding side doors that can be opened or closed by wireline can open
the long string between different seal assemblies.

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