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.
Finally, once the oil is flowing, the rig is removed from the site and production equipment is set up to extract oil from the well.
TABLE OF CONTENT
2.1 World crude oil
2.2 Crude oil exploration
2.3 Evaluation of oil well
2.4 Drilling process (drilling methods)
2.5 Crude oil production (oil production methods)
DRILLING PROBLEMS AND ITS SOLUTION
The crude oil is one of the natural resources endowed to man on earth it is a complex and solid hydrocarbons containing also traces of sulphur, nitrogen and oxygen. The crude oil originates from dead remains of small, bigoquatic plant animals and terrestrial plant which has been buried over many millions of years beneath the rock layers and as a result of continuous heaping of masses of the mud, silt and other sediments ones it and also by the active actions of bacterial and heat it is hugely formed. This vital natural resources (crude oil) in Nigeria in past decades was not known to man as a valuable substance.
Thus, the recent over demands for some petroleum fractions as sources of heat and chemical energy and also and raw material both in our homes, oil and gas industries today has continue to drive some of the oil and gas industries all over the world to develop system to reach the reservoirs beneath the earth surface.
Hence, the production of crude oil which is by drilling process is a complex and sophisticated process used in order to extract the oil in commercial quantity. This fact can never be over emphasize with the contributions of the geologist and geophysicists. The exploration of oil basin involves some geophysical techniques namely; magnetic method, gravity method and seismography. They latter which is the most important due to us ease in detecting the large oil basin is mainly used in oil exploration.
Hence, also, the drilling of oil well which commence after oil exploration and well testing involves use of a complex machine term drill rig (machine) on which also drill pipe, drill bit which aids the cutting, grinding of core formation under the surface (well) in order to reach the reservoir is attach to a drill string (long length hollow steel pipe on which drill collar is also mounted on). The drilling action by the drill bit of the drill machine and its penetration speed depends on the power supply to the machine and as well as the geological formation. The economical use of some drilling process (technique) has aid a lot in commercial crude oil production.
In Nigeria, precisely with the development in the drilling technology and oil exploration for example, in Niger-Delta areas, Kaduna and Port-Harcourt more competent, skill and unskill labourers have today gain opportunity to secure jobs in the drilling sectors of Nigeria and also some vital petroleum fractions example gasoline (petro) are now today very much available at some places at good prices.
Drilling a well to extract crude oil is a complicated process, but it is the only way to confirm the extent and existence of the oil beneath the earth crust. After initial exploration in activities sites preparation begins. The type of rig system to be used whether rotary or cable, is determined when the drilled well is completed and turned into a production facility. Capable of bringing a steady flow of oil to the surface, usually for many years, while getting the oil out of the ground may seen complicated, moving it from the point of production to the fuel consumer is just as complex. Today, there are more than 200,000 miles of oil pipeline in the U.S.
In 2000, total domestic crude oil field production averaged 5,822,000 barrels per day. The top crude oil producing states are Texas, California Louisiana etec.