The tremendous (large) demand of some petroleum fractions in our modern world today has drive some professionals (experts) in oil sectors into exploration and drilling operation which is aimed at locating the mineral oil deposit and extracting it from beneath the earth surface with aid of some vital exploration techniques and drilling machine (ng) on which drill string consisting of drill pipe, drill rods, drill stem and drill bit are attached on it.

During drilling operations, a drill bit that is attached to along pieces of hollow pipes called the drill string is used to drill the wells into the occan floor. As the drill bit spirals its way down through the ground, crushing rocks and stones as it goes, additional lengths of drill pipe are continuously added. First, from the starter hole, they drill a surface hole down to a pre-set depth, which is somewhere above where they think the oil trap is located.

There are five basic steps to drilling the surface hole.

1.                  place the drill bit, collar and drill pipe in the hole.

2.                  attach the Kelly and turntable and begin drilling

3.                  as drilling progresses, circulate mud through the pipe and out of the bit to float the rock cuttings out of the hole.

4.                  add new sections (joints) of drill pipe as the hole gets deeper and finally, remove (tripout) the drill pipe collar and bit when the preset depth is reached.

Once they reach the pre-set depth, they must run and cement the casing by placing casing pipe section into the hole to prevent it from collapsing on itself. The casing pipe has spacers around the outside to keep it centered in the hole.

Drilling continues in stages; they drill, then run and cement new casings, then drill again. When the rock cuttings from the mud reveal the oil sand from the reservoir rock, this implies the final depth reached.

At this point, they remove the drilling apparatus from the hole and perform several test to conform this finding.

Once the final depth has reached, the crew completes the well to allow oil to flow into the casing in a controlled manner. First, they lower a perforating gun into the well to the production depth. The gun has explosive charges to create holes in the casing through which oil can flow.  A small-diameter pipe after the casing has been perforated is run into the hole as a conduit for oil and gas to flow up the well.

A device termed packer is run down the outside of the tubing finally,  a multivalved structure called a Christmas tree is connected to the top of the tubing and cement it to the top of the casing and thus, Christmas tree allows for the control of oil flow from the well.

Once the well is completed, oil is made to flow into the well for limestone reservoir rock, acid is pumped down the well and out of the perforations and it dissolves channels in the limestone that lead oil (into the well for sands tone reservoir rock, a specially blended fluid containing proppants( sand, wallnutshell, alluminium pellets) is pumped down the well and out the perforations and pressure from this fluid makes small fractures in the sandstone that allow oil to flow into the well, prop pants hold these fractures open.



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