Chemical Engineering @ChemengFiles.Com

Most oil wells are drilled with rotary method. In this method, a tower holding the drill string, consisting of a series of coupled tubes.

The string attaching it to the bank spins rotating in the floor of the tower. The drill bit at the bottom of the chain usually consists of three bevel-tooth hardened steel. The bit is brought to the surface by a continuous flowing fluid system driven by a pump.

The oil trapped in a reservoir is under pressure, if it were not trapped by impermeable rocks would have continued to rise due to buoyancy until it pours into the earth's surface.

Therefore, when drilling a well that leads to a buildup of oil pressure, oil spreads into the low pressure zone created by the well in communication with the earth's surface.

However, as the well is filled with liquid shows a counter pressure on the tank and quickly stop the flow of additional liquid into the well if there were no other circumstances.

Most of the oil contains a significant amount of natural gas in solution, which remains dissolved due to the high pressures of the reservoir. When oil goes to the low pressure zone of the well, the gas ceases to be dissolved and begins to expand. This expansion, together with the dilution of the column of oil by gas, less dense, making the oil floats to the surface.

As the site continues removing fluid from the pressure of the gradually decreases and the amount of dissolved gas. This makes the rate of flow of fluid into the well becomes less and less gas is released. When the oil no longer reaches the surface it is necessary to install a pump in the well to continue extracting oil.

Finally, the oil flow rate is so small, and the cost of raising to the surface increases so that the operating cost of the well is higher than the revenue to be gained from the sale of oil (after deducting operating expenses, taxes, insurance and capital gains). This means that it has reached the economic limit of the well, so its operation is abandoned.