Drilling Flashcards
What is the Pore and Fracture pressure gradient?
Pore pressure is the pressure in the formation fluids and fracture gradient is the max hydraulic load on the formations.
Pore pressure forces oil and gas out of the rock and into the the well if this pressure is not countered by mud with same pressure as the pore pressure. If pressure in mud column is less than pore pressure the well is underbalanced and can collapse and create kick.
If fracture gradient is exceeded the rock will fail and cracks will be created and drilling fluid will be lost. This will also lead to drop in pressure and can create a kick.
What is the mud window and what is the importance of the mud window?
(a) Area between the pore pressure gradient and fracture pressure gradient, on the “pressure gradient vs depth”- chart is called mud window.
(b)The mud density for each formation should be selected with in the range of mud window and BHP (Bottom hole pressure) should be also in the range of mud window
What is the Sub Surface Safety Valve and what it does and what is the Production Packer?
(a) SSSV is a valve installed below the wellhead. It is used in case of fire on the well it will be close automatically and save the well from burning OR if surface control fail.
(b) The production packer is an anchor to handle force and transmit the force to the casing - as well as seal between the tubing and casing.
What is the TGB (temporary guide base) and why do we have mud circulation in the well?
To get the well started (drilling) a heavy steel template needs to be place on the seabed by using the drill pipe and running tool which, we call TGB.
(b) to transport cuttings to surface, to support formation from caving in, and have enough hydrostatic pressure not to allow formation fluid to come into well.
Why do we have shale shaker on the rig and what it does, what is the difference between subsea and land BOP stack in the standard set up?
(a) Shale shaker is a first tool that the mud will flow on that when it comes out the wellbore and it will separate the cuttings from the liquid part of the mud by the shaking and vibrating of the screens on it.
(b) land BOP: one annular preventor, 2 pipe rams, one blind/shear ram
Subsea BOP: 2 annular preventor, 3 pipe rams, one blind/shear ram
What are the similarities of Guide shoe and Float collar in operation? explain that and (b)what is the difference between Mill tooth and Insert Roller Cone bits?
(a) Both guide shoe and float collar have one-way valve to avoid the fluid to come and flow into the casing from annulus. (b) milled tooth bits are used for drilling soft formations and insert bits are used for drilling medium hard formations.
What are the minor and major function of drilling mud?
Major Functions:
- Control Subsurface Pressure
- Transport cuttings
- Support and stabilize the wellbore
Minor Functions:
- Support Weight of Tubulars
- Cool and Lubricate the Bit and Drill String
- Transmit Hydraulic Horsepower to Bit
- Provide Medium for Wireline Logging
- Assist in the Gathering of Subsurface Geological Data and Formation
- Evaluation
What are the typical rams in the BOP package? (b) how many of these rams should be in one BOP package?
(a)Blind ram, pipe ram and shear ram (b) one shear ram and 2 pipe rams
Pipe Ram – Function of pipe ram is to restrict the flow of fluid between the wellbore and outside of drill pipe.
Blind Ram – Function of blind ram is to cut off the opening for tubing or drill string when no production is going on from a well.
Shear Ram – Function of shear ram is to seal the wellbore even if there’s a tubing or drill string inside by cutting through the pipe.
Blind Shear Ram – It functions as a blind ram as well as a shear ram.
List for function of cement behind the casing? (b) what is the difference between the top plug and bottom plug, in cementing operation? (c) why do we have one way valve in the guide shoe (2 main reasons)?
-To prevent the movement of fluids from one formation to another or from the formations to surface through the annulus between the casing and borehole.
-To support the casing string (specifically surface casing)
-To protect the casing from corrosive fluids in the formations.
-Isolate a hydrocarbon bearing formation from other formations,
(b) bottom plug has a membrane which separate mud from cement and the membrane will be rupture if pressure apply to that. the top plug will drop into well when the cement volume is finished and no way to break it down.
(c) no influx come into the casing and no cement enter to the casing because of u tube effect.
Which tool in the well bore will allow us to be able to apply WOB (weight on bit)? (b) what is the purpose of using stabilizer along the drill string?
(a) drill collar (b) keep the drill collars centralized, vibration control and also for directional drilling purposes
What are the design and selection parameters for drill collar?
- WOB requirements
- Stiffness
- Vibration
- Hydraulic program
What is the riser and what is the reason of using for?
Riser is used to connect the rig floor to wellhead and BOP at the seabed and prevent the sea water to enter the wellbore
What are the forces in the hoisting system set up?
Fast line force, deadline force and block load (string load)
Main components of circulation system
Shale shaker, Desander, degasser, desilter, centrifuge - tank and mud pumps.
