Page 209 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 185

2.4.2
Drill Bit Selection, Parameters, and Hydraulics [ ]

Normalized trip time assumes 1 hour per 1000 ft.
Next bit ream time is the time spent reaming back to bottom as a
direct consequence of this bit coming out undergauge.
Therefore, by entering all offset bit runs into the BITREX database,
a printout can be generated that shows the NBPI for each bit which can
then be put onto the hole section summary against each bit run.
The database allows sets of bits to be selected from the database for
generating reports. The bit selection can be done manually (by “tag-
ging” each record of interest) or it can be done based on various crite-
ria (such as field and range of depths in, well and bit size, bit serial
number, etc.). Selection by criteria adds to the current selection. Thus
bit runs of interest can be quickly examined and compared.
Once a decision is made as to which bit is to be used for a certain
interval, another report can be generated showing all runs in the data-
base with that bit type and size. This can give an indication of expect-
ed bit life and performance with various parameters.
Comparison of bits run in the 12 /4 in Obaiyed hole sections. The
1
following analysis was made from the BITREX database comparison of
the 12 /4 in hole section bits run on the Obaiyed field in Egypt. It com-
1
pares the best performing bit in each formation with the second best
bit. The percentage of improvement shown is taken by comparing the
Normalized Bit Performance Indices.

In the Abu Roash, the (best) Hughes ATM05 (417X) outperformed
the Smith F1 (517X) by 20%. (The Smith bit was third best after
the two ATM05 bits.)
In Lower Abu Roash and Bahariya, the Hughes ATM11HG (437X)
outperformed the Hughes ATM22GD (517X) by 15%.
In the Kharita, the Security SS84FD (517X) outperformed the
Smith F2OD (517X) by 14%.
In the Dahab and Alamein, the Reed EHP51HD (517X) outper-
formed the Hughes ATM22 (517X) by 20%.
Alam el Bueib did not perform enough complete runs for analysis.

It can be seen immediately that in no case did a harder bit outper-
form a softer bit. This might imply that we can probably make better
progress with slightly softer bits than the previous best in some cases;
it would help to examine all the bits run in a particular formation, not
just the best two.

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