Nowadays deep water drilling is one of vital players for oil and gas exploration and production industry and there are many people who would like to know how deep water drilling works. We’ve found one excellent VDO demonstrates the deep water drilling process in a simple way. This VDO will give you clearer picture about the topic and we also add full VDO transcript in order to help more people understand the content clearly. We wish you would enjoy learning from this VDO and please feel free to give us feedback : )
Full VDO Transcript – How Does Deep Water Drilling Work
Credit: Image from Wikipeida
How does the deep sea drilling vessel Chikyu drill into the sea floor? When the vessel arrives at the drilling site it receives a satellite signal that helps the vessel moves into the exact position required. The vessel has six propellers that rotate a full 360 degrees and keep the vessel in one position preventing it from drifting due to the wind, waves or sea current.
First the conductor pipe is installed. As the drill pipes are connected, the conductor pipe and guide are run down to the sea floor. After the conductor pipe penetrates the sea floor the drill pipe is released and pulled back to the vessel. A large drill bit connected to the bottom of the drill pipe is run down to the sea floor. The drill bit is lead down to the bottom of the hole through the conductor pipe. The drill bit rotates and drills the sediment and rock below the sea bed. Sea water is sprayed from nuzzles on the drill bit to raise the cuttings to the sea floor.
After drilling several hundred meters the drill bit is pulled back to the vessel. A casing pipe about 50cm in diameter is set into the drill hole to keep it from collapsing. The casing pipe is run down through the conductor pipe and is inserted into the hole using the drill pipe.
Cement is pumped into the space between the hole and the casing pipe to fix the pipe in place. After cementing, the drill pipe is released and pulled back to the vessel. The Chikyu is equipped with a riser system in order to drill into the earth even deeper. As the riser pipes are added one after the other, the Blow Out Preventer is run down to the sea floor. The Blow out Preventer is connected to a well head which is located on top of the casing pipe. The vessel is now connected to the sea floor via the riser pipe.
A drill bit, smaller than the one first used is run down the through riser pipe and casing pipe. The drilling begins. Once the riser pipe has been connected, drilling mud is used instead of sea water. When the target depth is reached the drill bit is pulled back to the vessel. To drill the hole even deeper, a narrower casing pipe is sent to set in the drilled hole. After the casing pipe has been installed, cement is pumped into the space between the hole and the casing pipe to fix the pipe in place. Again, an even smaller drill bit is run down through the riser pipe and casing pipe and the drilling continues. Repeating this process, the Chikyu will drill through the ocean crust to collect fresh live mantle. This is something that has never been done before.
Rotary Drilling is used for ocean drilling. Let’s look at the features of this method.
First the drill pipes are connected one after another as they run down to the sea floor. The work of connecting the drill pipes and drilling the hole are powered by a motor on the derrick. The drill pipe has a drill bit attached to the bottom. With rotary drilling, the drill pipe is rotated and the drill bit at the end crushes sediment and rock to make the hole. After a while, cuttings accumulate at the bottom and drilling cannot go any further. Sea water or other liquid is then pumped from the vessel down through the drill pipe and is jetted out of the nuzzles on the drill bit. This liquid current forces the cuttings up to the sea floor. That is Rotary Drilling.
The deep sea drilling vessel Chikyu can drill over 7 kilometers below the sea floor into the earth. To drill even further before the sea floor. A riser system is used. With the riser system mud is used instead of sea water. There are several reasons for using mud. First it has greater viscosity than sea water to force cuttings from the bottom of a deeper hole. Also with the increase in pressure at the greater depths the formation pressure becomes much greater than the pressure in the hole filled with sea water. The hole will collapse if a certain differential pressure between the outside and the inside of the hole is reached. Mud has a higher density than water. Therefore the pressure inside the hole remains higher and the hole will not cave in allowing deeper drilling.
The drilling mud is artificially conditioned with various kinds of product and it is expensive. Discharging it on the sea floor is bad both environmentally and economically. The mud is therefore collected and reused. For this purpose the riser pipe is connected all the way from the vessel to the sea floor. The drilling mud sprayed out of the drill bit returns to the vessel through the riser pipe together with the cuttings and is collected and recycled at the vessel. Riser drilling not only makes it possible to drill deep into the earth; it is a break through drilling method that is environmentally and economically sound. Riser drilling will make it possible to drill all the way down into the earth’s mantle. A depth never before reached in all of history.