## Stripping/Snubbing Calculations

Breakover point between stripping and snubbing

Example: Use the following data to determine the breakover point:

 DATA: Mud weight = 12.5 ppg Drill collars (6-1/4 in. ? 2-13/16 in.) = 83 lb/ft Length of drill collars = 276 ft Drill pipe = 5.0 in. Drill pipe weight = 19.5 lb/ft Shut-in casing pressure = 2400 psi Buoyancy factor = 0.8092

Determine the force, lb, created by wellbore pressure on 6-1/4 in. drill collars:

• Force, lb = 6.25 2 0.7854 2400 psi

Force = 73,631lb

Determine the weight, lb, of the drill collars:

• Wt, lb = 83 lb/ft 276 ft 0.8092

• Wt, lb = 18,537 lb

Additional weight required from drill pipe:

• Drill pipe weight, lb = 73,631 lb ? 18,537 lb

• Drill pipe weight, lb = 55,094 lb

Length of drill pipe required to reach breakover point:

• Drill pipe length, ft = 55,094 lb (19.5 lb/ft 0.8092)

• Drill pipe length, ft = 3492 ft

Length of drill string required to reach breakover point:

• Drill string length, ft = 276 ft + 3492 ft

• Drill string length = 3768 ft

Minimum surface pressure before stripping is possible

• Example: Drill collars 8.0 in. OD 3.0 in. ID = 147 lb/ft

• Length of one stand = 92 ft

• Minimum surface pressure, psi = (147 lb/ft 92 ft) ...

##### Products & Services
Snubbing Units
Snubbing units are used to perform well intervention on live or dead oil and gas wells. They are used to drive pipe into a well bore and overcome well pressure that is preventing conventional drill rig operations.
Drill Collars
Drill collars are a component of the drill string that makes up part of the bottom hole assembly (BHA). They are thicker-walled, heavier, and more rigid than drill pipes and are primarily used to weigh down the drill bit while dampening vibration and impact forces.
Drilling Rigs
Drilling rigs are machines that creates holes (boreholes) and/or shafts in the ground. They are equipped with deck engines or truck engines, hoists or lifts, compressors, pumps, and pipe-handling equipment.
Rotary Subs
Rotary subs are short sections of API certified threaded pipe used for crossover connections, tool handling, lifting, or other specialty application related to the making and breaking of the drill string.
Measurement While Drilling (MWD) Systems
Measurement while drilling (MWD) systems report wellbore position, drill bit performance, and drill string orientation to an operator to maximize drilling productivity. It is related to logging while drilling (LWD).

##### Topics of Interest

Subsea Considerations Casing pressure decrease when bringing well on choke When bringing the well on choke with a subsea stack, the casing pressure (annulus pressure) must be allowed to decrease by...

Volumes and Strokes Drill string volume, barrels Annular volume, barrels Strokes to displace: drill string, annulus, and total circulation from kelly to shale shaker Example: Determine volumes and...

Kill Sheets and Related Calculations Normal kill sheet Prerecorded data Original mud weight (OMW) ______________________________ ppg Measured depth (MD) ___________________________________ ft Kill...

Kick Analysis Formation pressure (FP) with the well shut-in on a kick Example: Determine the formation pressure using the following data: Shut-in drill pipe pressure = 500 psi Mud weight in drill...

OVERVIEW This appendix presents the detailed MathCad solutions for the illustrative examples in Chapter 11. Illustrative Example No. 11.1: DTH MathCad Solution (USCS) F-2 Illustrative Example No.

Product Announcements