STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

722 Drilling and Well Completions
Drill Collar Connections
It is current practice to select the rotary shoulder connection that provides
the balanced bending fatigue resistance for the pin and the box. The pin and
the box are equally strong in bending if the cross-section module of the box in
its critical zone is 2.5 times greater than the cross-section module of the pin at
its critical zone. These critical zones are shown in Figure 4-127. Section modulus
ratios from 2.25 to 2.75 are considered to be very good and satisfactory
performance has been experienced with ratios from 2.0 to 3.2 [39].
The above statements are valid if the connection is made up with the
recommended makeup torque. For practical purposes, a set of charts is available
from DRILCO, Division of Smith International, Inc. Some of these charts are
presented in Figures 4-128 to 4-132. The method to use the connection selection
charts is as follows [38]:
The best group of connections is defined as those that appear in the shaded
sections of the charts. Also, the nearer the connection lies to the reference line,
the more desirable is its selection.
The second best group of connections is defined as those that lie in the
unshaded section of the charts on the left. The nearer the connection lies to
the reference line, the more desirable is its selection.
The third best group of connections is defined as those that lie in the
unshaded section of the charts on the right. The nearer the connection lies to
the reference line, the more desirable is its selection.
(text continued on page 731)
The section modulus,