test 2.8 Flashcards
list 6 drilling problems
- Junk in hole
- Stuck Pipe
- Lost Circulation
- Formation Damage
- H2 S Embrittlement
- Kick and Blowout
what is the majority of junk lost in the hole
broken pipe
what are two types of tools to retrieve broken pipe
- spear - fits into and grips the inside of the pipe
- overshoot - Fits and grips the outside of the pipe
what causes drill string twistoff
- Rough pipe handling
- Faulty drill string
- Improper torque and stress
- Damage on the drill string
how do you know drill string twist of has occurred
- Loss of drill string weight
- Lack of penetration, increased rotary speed
- Reduced pump pressure, increased pump speed
what are 8 types of fishing tools
what are two reasons for stuck pipe
- mechanical sticking
- differential sticking
what causes mechanical sticking
- Inadequate hole cleaning
- Unconsolidated formations
- Sloughing shale (b/c shale too heavy)
- Hole Geometry
- ) Ledges: Soft rock above and below the hard rock washed out
- ) Key seating: The drill pipe wears a groove in the side of the well
what are ledges
Soft rock above and below the hard rock washed out
what is key seating
The drill pipe wears a groove in the side of the well
how do you locate the stuck point of a drill string?
using a stuck-point indicator tool or stuck-pipe log
what is back-off?
Unscrew the free section of the drill string caused by mechanical sticking
what are 3 ways to cut stuck pick
- Chemical cutter: Hydrofluoric Acid
- Jet cutter: Shaped explosive charge
- Severing tool: Powerful explosive
what is differential pressure sticking
what is the solution to differential pressure sticking
- Reduce hydrostatic pressure
- Pipe release agents to reduce the surface tension
- Sudden movement of the drill string (Jarring)
what is lost circulation
drilling mud into the hole > drilling mud out of the hole
what are the causes of lost circulation
- High formation permeability
- Faults and fractures
- Low formation pore pressure
- Drilling fluid characteristics
what is the solution to lost circulation
- Decreasing circulation rate
- Decreasing mud weight
- Mud additives (fibers, granules)
- Minimizing pressure loss
- Use of casing
what is formation damage
Reduction in formation permeability
- Physical plugging of pores by mud solids
- Migration of fines into pore throats
- Clay swelling in pore spaces
what is abnormally high pressure
pressure greater than the hydrostatic pressure
what causes abnormally high pressures in
- ) Reservoir with large, aerial extent
- ) Isolated reservoirs with limited extent
what are indications of a kick or blowout
- Out-flow rate increase
- Mud pit volume increase
- Flowing well with pumps off
- String weight change
what causes a kick or blowout
- Insufficient mud weight
- Improper hole fill-up during trips
- Pipe pulling speed
- Lost circulation
why is H2S embrittlement bad
- H2 S corrodes and weakens the metal
- Diffused hydrogen makes steel brittle
how do you prevent H2S embrittlement?
- Using drill string with more resistant steel
- Adding chemicals to the drilling mud
