Drilling methods Flashcards
Drilling is used in
a) site assessments – collection of samples
b) installing water monitoring wells
c) installing producing water wells
How to choose a drilling method
a) purpose of drilling program
b) geology
c) drilling depth
d) site accessibility
e) cost/availability of eqpt.
Make footage
Drilling as fast as you can
Cavings
Pieces of sides of the boreholes which have collapsed into the hole
Lost circulation
Drilling fluids seep into poros or high K units, drilling fluids leave the borehole
Mud cake (filter cake)
Build up of solids from the mud onto the borehole walls across from permeable zones
Cuttings (chips)
V. small pieces of rock that have been ground up by the drill bit
Lag time
time b/t when the chips are cut and when they come to surface
Tripping in/out
The time it takes to put the bit in or out of the borehole
Fishing
Drillers of loggers have lost a tool downhole
Driven wells
Dry point or sand point
installed by using a sledge hammer
Shallow, small borehole, unconsolidated
Direct push wells
Hydraulic units, mounted on trucks, push a steel barrel in the ground
Shallow, unconsolidated
3 types of auger wells: Rotary bucket
NO FLUIDS
90cm cylindrical bucket, unconsolidated material
3 types of auger wells: Hollow stem auger
NO FLUIDS
hollow stem pipe encircled by flights, driven by a rig w/ a rotary head
monitoring wells can be placed down the hollow stem before removing the auger
3 types of auger wells: solid stem auger
NO FLUIDS
Solid stem pipe encircle by flights, driven by a rig w/ a rotary head
Cable tool wells
Earliest developed, drilling stopped periodically to remove cuttings, 40-60 cm diameter
2 types of drilled wells: Conventional rotary
USE FLUIDS
Rotation of a bit on the end of a drill pipe at high speeds
drilling fluids carry cuttings through the annulus
mud and air rotary fluids
2 types of drilled wells: Reverse rotary
Same drilling process as for conventional mud rotary but the mud circulation is reversed
borehole is 60-180cm
Types of drilling bits
Bits chosen based on geology
a) drag bits – for unconsolidated sediments
b) roller cones – for rocks
c) diamond core drill bits
Down the hole air hammer wells
Pneumatic drill at the end of the drill pipe hits the rock as the drill pipe is rotated, air is used to remove cuttings
Straight well
perfect alignment of the casing sections
Plumb well
The borehole will track an imaginary line from the surface to the center of the earth
Drilling safety
- steel toed boots
- safety goggles
- vest
- hard hat
- gloves
