Sunday, 5 November 2017

WHAT IS THE COMMON DRILL PIPES LENGTHS, HOW TO DESIGN & RUN

what is Drill Pipes Lengths design run

What is The Common Drill Pipes Lengths 

The Drill String is made up of several sections of Drill Pipes. The term "stand" consists mainly from  two or three drill pipes joints which will have a length around 60 to 90 feet . every joint of pipe, referred to as a "single". According to API, there are three ranges of drill pipes lengths ; R1, R2, and R3.

Range 1 (R1) is shortest in length, more common for sizing production tubing or Casing, and ranges from 18 to 22 ft. 

Range 2 (R2) is considered the standard length for Drill Pipe and ranges from 27 to 31 ft.

Range 3 (R3) is common in Casing and also deployed in deep water drilling applications. The increased length decreases the number of tool joints in each stand of drill pipe. The fall back being that the load exerted on each tool joint is greater increasing wear and reducing the expected life of the drill pipe. R3 ranges from 38 to 45 ft.

How To Perform Drill Pipes Lengths Design

The Drill String is designed so that the uppermost joint of each section of Drill Pipe is loaded to no more that 80% of the minimum tensile yield strength of that particular weight and grade pipe for a single size and grade drill pipe. 

The total load exerted on the top joint of the drill pipe consists of 

the buoyed weight of the drill pipe plus the buoyed weight of the bottom hole assembly (heavy-weight drill pipe plus drill collars) and the margin of overpull (MOP)

The MOP is the desired amount of load in excess of the buoyed  weight  of  the  drill  string  to  account  for  hole  drag  and  provide  excess  pull capacity in the event the drill string becomes stuck in the hole. 

The amount of overpull ranges from 50,000 to 100,000 lb. 

The design criterion can be expressed as,

Determine Drill Pipes Lengths
where,
L      = length of DP, ft
W    = Actual weight of drill pipe, lb/ft
Lc       = length of drill collars, ft
Wc     = weight of collars, lb/ft
LH     = length of heavy weight drill pipe, ft
WH    = weight of heavy weight drill pipe, lb/ft
MOP = Margin of overpull, lb
Bf         = buoyancy factor
Y       = minimum yield strength, lb

Solving above Eq for the maximum length of drill pipe that can be used,

Determine Drill Pipes Lengths

If the Drill String consists of two sections of drill pipe of different grade and weight, then the maximum length of the second drill pipe section (top section) is,

Determine Drill Pipes Lengths

where,
L1   = length of first section of drill pipe (lower section), ft
W1 = actual weight of first section of drill pipe, lb/ft
L2   = length of second section of drill pipe, ft
W2 = actual weight of second section of drill pipe, lb/ft
Y2 = minimum tensile strength of second section of drill pipe (top section), lb.


In drill string design the pipe of the lowest grade (weakest) is placed on bottom. Each section of Drill Pipe is designed starting with the Bottom Hole Assembly BHA and working upwards. This design is checked at various depths, for often the most critical section of hole is not at TD, but further up the hole due to mud weight changes.

How To Run This Drill Pipes Lengths While Drilling

This video describes how to run drill pipes inside the well.




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