Drilling 101: How a deep water well is drilled
0:02
Shell Deep Water is fueling the growth of Upstream Americas
0:06
by safely developing new reserves
0:09
and maximizing the potential of its existing producing assets
0:12
in the Gulf of Mexico, Brazil, and Venezuela.
0:16
Drilling a safe, deep water well
0:18
can take years of planning and preparation.
0:21
After identifying potential oil and natural gas reservoirs 8 00:00:25,900 --> 00:00:29,100 beneath the seafloor using seismic technology
0:29
a drill site is selected.
0:31
Shell geoscientists choose the drill site location on the seafloor
0:35
based upon the safest well path
0:37
that will encounter the targeted oil and natural gas.
0:40
For an exploratory well
0:42
in water depths up to 9000 feet deep
0:42
this seafloor location is generally directly above the reservoir.
0:50
A drilling rig is required to drill a well
0:54
In deepwater, the rig may be on one of three vessels:
0:58
a Drillship
1:00
a Semi-submersible vessel
1:02
or it may be part of a floating production platform.
1:06
All rigs have a hoisting system to raise and lower the drill pipe
1:11
and tools needed to drill the well,
1:13
a Blow Out Preventer or BOP stack, 24 00:01:16,500 --> 00:01:17,900 and a pumping system
1:17
to circulate fluids in and out of the well while drilling
1:21
It’s time to drill the hole or well bore using a drill bit.
1:26
This initial step is called “spudding in” the well.
1:30
The shallow sediments just below the seafloor are often very soft and loose.
1:36
To keep the well from caving in and carry the weight of the wellhead,
1:40
a large diameter base pipe or casing is drilled or jetted into place.
1:45
The base pipe is assembled at the rig floor
1:48
and a drill bit connected to a drill pipe
1:51
is run thru the inside to the bottom of the casing.
1:54
The entire assembly is lowered to the seafloor by the rig hoist.
1:58
At the seafloor
2:00
the driller “spuds" the assembly into the seafloor sediments
2:04
then turns on the pump.
2:06
Water or a drill fluid is used to “Jet” the pipe into place
2:10
until the wellhead is just above the seafloor.
2:13
With the base pipe and wellhead at the right depth
2:17
the driller will release the bit
2:19
and drill string from the jet pipe and drill ahead.
2:22
While the well bore is being drilled
2:24
mud is pumped from the surface down through the inside of the drill pipe,
2:28
the mud passes through the jets in the drill bit,
2:31
and travels back to the seafloor through the space between the drill bit
2:35
and the walls of the hole.
2:36
Drilling mud is used to
2:39
1) lift rock cuttings from the hole,
2:41
2) keep the drill bit cool and lubricated
2:45
and 3) fill the well bore with fluid to equalize pressure
2:49
and prevent water or other fluids in underground formations
2:52
from flowing into the well bore during drilling.
2:55
The “mud” is an environmentally friendly water based mixture of clay for thickness
3:02
and fine ground rock or barite for weight.
3:05
At the planned depth
3:08
the driller will stop drilling and pull the bit out of the hole.
3:11
A smaller pipe or casing string is then screwed together
3:16
connected to the drill pipe
3:17
and run down to the seafloor and into the well.
3:20
To permanently secure the casing in place,
3:24
cement followed by mud
3:25
is then pumped down the inside of the drill pipe.
3:28
To separate the cement from the mud, a cementing plug is used.
3:32
The plug is pushed by the mud to ensure the cement is placed outside of the casing
3:37
filling the annular space between the casing and the open hole wall.
3:42
On some locations a second surface casing is needed,
3:46
thus the well is drilled even deeper
3:49
In this second surface casing interval
3:52
the well is cemented using a second smaller casing string.
3:56
Repeating the same process used in the last hole section.
3:59
At this point in the well
4:02
the pressure in the deeper rock
4:03
may be too high to continue with the simple water based clay mud
4:07
or there may be the potential to encounter oil or gas.
4:11
Before drilling below this point
4:13
a Blowout Preventer with a riser will be installed at the seafloor.
4:17
The BOP stack is a massive system of valves and rams
4:22
that protect the rig and environment from oil and gas flows
4:26
should the weight of the drilling mud be too low.
4:29
The BOP stack is connected to a pipe called a riser.
4:33
The riser connects the rig to the well
4:35
and allows us to circulate the drilling fluid
4:38
and rock cuttings all the way back to the rig on the surface.
4:41
The BOP stack is fully tested before we drill further.
4:46
Drilling now resumes with the drill bit
4:50
and drill pipe always operating through the BOP stack.
4:53
Just as we did further up the hole,
4:56
casing strings are run and cemented in place
4:59
when needed to cover up the open hole sections
5:02
When the oil and gas zones targeted by the geologists are reached
5:06
and the presence of an oil or gas zone is proven,
5:09
a final casing string may be installed
5:12
if the seafloor location is favorable for future development.
5:16
This final casing string allows for the future safe production
5:20
of the oil and natural gas.