Heavy Weight Drill Pipe Specs & Selection

Heavy Weight Drill Pipe Specs are important to understand as they are the entrance to the heavy-weight drill pipe design. This article will discuss its specs and how to select the drill string design. In addition to that, we will talk about its main functions. You can also download the spec sheets for any size of heavy-weight drill pipe.

Heavy Weight Drill Pipes Definition

In the past, the two main components of the Drill String consisted of the Drill Pipe and the Drill Collars. The transition Zone is the point where the relatively small OD and flexible Drill Pipe connect to the large stiff Drill Collars. Oilfield studies have shown that almost all of the Drill Pipe fatigue failures result from an accumulation of fatigue damage occurring when the Drill Pipe joints were run in the Transition Zone or were stressed above the endurance limit in crooked holes.

Downhole data has indicated that the large change in diameter at the transition zone caused accelerated fatigue damage due to the concentration of cyclic bending stress reversals in the bottom joints of the flexible Drill Pipe since the stiff Drill Collars bend very little from these stress reversals. So heavy weight drill pipe specs definition will be a drill pipes with higher thickness to withstand the stress in the transition zone.

HWDP Function

Before discussing heavy weight drill pipe specs, let’s understand its function. Heavy weight drill pipe absorbs the stresses being transferred from the stiff Drill Collars to the relatively flexible Drill Pipe. The major HWDP benefits are:

• Increased wall thickness
• Longer tool joints
• It uses more hard-facing
• It may have a long central upset section

Heavy Weight Drill Pipe Specs

• Quality Standard: API 7 and API 5DP.
• Steel Grade: Integral heavy weight drill pipe: AISI 4145HM; Welded HWDP : AISI 1340.
• Hpipe body, AISI 4140HM.
• Outer Diameter: 2 7/8” – 6 5/8”.
• Weight Range: 6.27#/FT through 27.72#/FT.
• Lengths: Range 2 and Range 3.
• End Finishes: Internal Upset, External Upset, Plain End Upset, Non Upset.
• Heavy Weight Drill Pipe Tool Joint type: NC38, NC46, NC50, 5-1/2 FH.

Heavy Weight Drill Pipe Specs Sheets From Work Strings International

Heavy Weight Drill Pipe Specs Selection And Design

Field tests indicated that fatigue build-up in the Drill Pipe in the transition zone is related to the relative stiffness of the Drill Collars and the adjacent Drill Pipe. The stiffness ratio of two sections of pipe in the drill string is expressed by the equation,

The field tests showed that the higher the stiffness ratio at the transition zone the greater the fatigue build up. Criteria for permissible stiffness ratio vary between different operators and areas. The following maximums are typical:

• For shallow or routine drilling or low failure rate experience, keep the stiffness ratio below 5.5.
• For more severe drilling or for significant failure rate experience, keep SR below 3.5.

In order to reduce the stiffness ratio and increase the service life of the drill pipe, heavy-weight drill pipe having the same OD as the drill pipe and a wall thickness of up to 1 in and weight up to 78 lb/ft is used between the drill pipe and the drill collars. The number of joints used varies between 15 to 21 joints.

The use of HWDP Offers the Following Advantages

• Reduces drilling cost (check also drilling cost per foot) by eliminating Drill Pipe failures in the transition zone.
• Significantly increases the performance of small rigs through the ease of handling.
• Provides substantial savings in directional drilling by replacing most of the Drill Collars string, reducing downhole drilling Torque and Drag.
• Reduces the tendency to become Deferentially stuck. This is because large diameters are easier to stick than small diameters.

Heavy weight drill pipe normally has the same external dimensions as the regular Drill Pipe. In some types of Heavy Weight Drill Pipes, the tool joints are longer and, in some types, an extra mock tool joint is located in the center of the joint as shown in the below drawing.

Heavy weight drill pipe specs vary for different manufacturers. Typical dimensions are shown in the below table: