Directional Drilling Flashcards
Over what distance does it take to make a well completely horizontal?
900metres at standard deviation rate (build up rate) of one degree per thirty meters
What is KOP
Kick off point. The point in the well where it starts to deviate from being completely vertical.
What is the Drop off radius and what is it relevant for?
A drop off is done once you get to approximate desired depth after drilling down at an angle from the kick off point. If geology is not sure of exact depth you switch from angle drill to vertical hole to find exact target depth by analysing samples. Having identified exact target depth you fill in the drop off hole and you have a 2nd KOP towards the desired depth.
What are the risk areas on measuring and target depths?
Drilling teams will measure the hole length (ie pipe length down the hole) whereas geologists will measure absolute vertical depth. Further geologists’ zero point is the seabed whereas for the drillers it is the well floor. Further if rig changes during drilling (eg different hole area or perhaps for perforation) the rig floor height can be different.leads to lots of errors nonstandard international or cross functional agreement.
What are 3 types of rotary assemblies, what does each achieve?
Rotary assemblies involve the placement of drill pipe stabilizers the weight and levering of which result in directional wells
- Pendulum Assembly. (Drop) One stabilizer far back from the drill bit will result in sag in the pipe meaning the bottom side of the drill it is pushing down and thus the well inclined to go vertically down
- Fulcrum / lever (build). Heads up, high WOB by stabilizer being directly behind the bit, which levers bit off the bottom and it’s inclined upward..builds angle.
- Stabilization / stiff (horizontal) multiple stabilizers used behind the bit to keep the bit flat and without sag, so balanced and drills flat.
What is PDM and how does it benefit directional drilling?
Power displacement motor
Is a combination of turbine (powered drill bit) which has a bent housing to drill directionally with only WOB but no rotary drill pipe action. Once on trajectory you can disengage the turbine bit and use rotary drill pipe action to continue on track.
What is BHA
Bottom hole assembly, refers to the kit at the bottom of the well in the drill bit, e.g. Collar, flex collar, single bend motor
What is the “push the bit” system, what else is it called?
Other name: non rotating stabilizer.
A non rotating stabilizer sits on the drill pipe and the drill pipe rotates within the stabilizer. The non rotating stabilizer has hydraulic pads in it on three sides and pushes against the casing on desires side to steer / push the bit. This tool lets you keep turbine drilling and rotary drilling maximizing speed. It also contains navigation tools and feeds back navigational data with on onboard tools.
How do you wirelessly communicate with your tools down the well?
Mud pulse telemetry systems
A device such as a positive pulse device, adds for example seven bar pulses to the mad which are per a binary code which can be listened for and interpreted at surface.
How is the direction in which the bit is inclined to drill referred to?
Tool face.
What does rss refer to? What is it?
Rotary steerable system. This includes the “push the bit” and autotrak system and the these are directional steering systems which enable you to drive in a direction with turbine drill bit combined with rotary drill pipe action.
What is tv and what is ah, what is ss, what is td?
Tv = true vertical depth (geological)
Ah= distance along hole (ie ftah feet along hole)
Ss= depth subsea from zero level
td=true depth
What is a screen used for?
Screen is basically a sieve put in the bottom of well (like a mesh) that filters the hydrocarbon where there’s a risk of sand being produced from unconsoidated rock
Why would you have steel in your cuttings? How is it identified?
Indicates you may have hit another well and are drilling cuttings. Often you’ll drill parallel and take some off the side, likelihood of penetration is low. It is identified by use of a magnet in the cuttings shale shaker.
