Page 408 - Practical Well Planning and Drilling Manual

Section 3 revised 11/00/bc 1/17/01 12:00 PM Page 384

[ ] Practical Wellsite Operations
3.4.1

with a special vessel or it can be done from the rig after arrival, with
the rig pinned on bottom before full preloading.
The conductor is made up and run through the rotary. Once the
shoe reaches the seabed, check the tide/current conditions. An inclina-
tion survey can be run inside the conductor on wireline with a cen-
tralizer to check that the conductor is vertical. If necessary, wait on
slack water so that the conductor starts off vertical. When ready, con-
tinue to run the conductor. Normally it will freely penetrate the top
part of the seabed (freefall) before it stands up and driving can begin.
Driven conductors are usually driven to refusal. Refusal is a speci-
fied maximum number of hammer blows per foot of penetration at a
particular hammer power setting. This maximum is determined by
potential damage to the drive pipe and/or hammer, which can occur if
driving with insufficient penetration. Consult the hammer manufactur-
er for recommendations if the company or normal area practices indi-
cate a suitable refusal point for a particular hammer and power setting.
If several wells are drilled closely spaced (such as on a platform),
conductors can be driven directionally using a drive shoe that imparts
a side force. This technique, if successful, gives better separation of the
wells at the shoe. However, once started it is impossible to control and
it is quite possible for the conductor to go completely off course. If this
happens, the slot may be unusable.
Conductor connections are normally heavy duty quick connect
types, such as the Vetco Squnch Joint. The connector has to be suitable
for driving operations.
If driving several conductors from a template or platform, stagger
the shoe depths a little. If the shoes are all located close together at the
same depth, communication between them may occur soon after
drilling out the shoe, since this is the shortest leak path. If this is
thought likely, spot 30-50 ft of cement inside each conductor before
drilling out the first one to prevent such losses from the drilled con-
ductor to undrilled ones. Shallow gas could also follow this path,
which is another reason to spot cement.
Sometimes a mudline suspension system will be used. A landing
ring is positioned in the conductor string such that at the expected
penetration, the landing ring will be 5-10 m below the seabed. It is not
usually a problem if the landing ring is a little too deep; however, if it
is not deep enough, the suspended well may stick up too much above

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