This is excellent oilfield footage about the overall process of offshore deepwater drilling and completion. It has about 5 minutes with good animation that will give you clearer picture of how the deepwater operation works from the beginning.
We also add VDO transcription for anybody who cannot catch all the content of the VDO.
Offshore drilling rigs have all the functions of onshore rigs but also need to stay on station in a variety of sea state and allow for secure connections between the surface and the seafloor. To start an offshore well, a thick wall large diameter hollow tube called a conductor is embedded in the seafloor. With the aid of a bit, the jets away the sediment with high-pressure seawater when the conductor has penetrated about 250 feet the jet bed is retrieved and the drill bit introduced. The cuttings it just washes to the top of the well by seawater pumped through the bit. A second run of conductor is now lowered into the hole. The bottom of the conductor is a guide shoe that stops the conductor snagging on the wellbore.
Above the shoe is a flap valve called a float collar. A cementing tool is connected to the top of the conductor. A plug that pushes the seawater out is driven downwards by high-pressure cement that fills the conductor. On reaching the float color this plug is ruptured and cement flows out of the bottom of the conductor and up the annular space between the wellbore and the conductor.
The cement plug tool is removed and when the cement is set, drilling continues with a smaller diameter bit penetrating the cement plugs and float collar into fresh rock. After a suitable depth is been drilled, the drill string is removed then steel tubing known is casing is lowered into the hole and cemented in place.
This first casing run hasn’t attached wellhead. A blowout preventer, BOP, a robust set of valves they can shut in the well even if the drill string is down the hole is then lowered and locked onto the wellhead. The BOP is connected to the sea surface by large diameter tubing known as a riser which allows drilling fluids to be returned to the surface.
From this point onwards, the drilling procedures are similar to those used to drilling onshore well. With the rise in place, seawater is replaced by a special fluid known as drilling mud that is pumped down the string and exits through ports in the bit. The mud not only cools the bit but also clears the cuttings from the hole.
The cuttings are captured at surface and examined by geologists to characterize the rock types that are being penetrated. As drilling continues, sets of decreasing diameter bits and casing runs are used as the well penetrates deeper into the rock. Each one of casing is cemented in place to provide integrity a sealed system from top to bottom. The density of the mud is controlled by the mud engineer adding dense minerals when needed the aim is to produce a column of dense mud which exert sufficient pressure in the well to counteract pressure from fluids encountered in the rock. This combination of the dense mud column contains improperly cemented casing aims to control pressures in the well.
The BOP provides a further level of security. When the well penetrates a potential reservoir rock the oil or gas may be detected by analyzing the drilling cuttings for traces of gas and/or oil. At this stage it is essential to gather as much information as possible about the reservoir to methods provide most of the information in the first the drill bit is replaced with a diamond studded coring bit at the bottom of a core barrel. This can cut a complete section of the reservoir rock and return it to surface for detailed analysis. in The second stage coring may be replaced or complemented by running a suite of geophysical logging tools which are run on electric wireline.
These are instruments that can measure the physical properties of the rocks as they pass slowly through the wellbore. When as much information as possible has been gathered from the reservoir a decision is made on whether to complete the well for production, suspend efforts with the option to return to the well at a later date is more information on the reservoir becomes available or to plug and abandon the well. If the well’s seem to have production potential the reservoir interval is lined with casing the casing is then perforated to allow reservoir fluids to enter the well and travel up the installed completion production string to surface.