Oil Well Operation
Oil well operation depends on its utilization. Thus, there is always some fluid (drilling fluids) in the well bore. After drilling, it is substituted by service water, and after the well completion, the well bore is filled with brine water.
One condition must be observed for inflow: formation pressure must be higher than hydrostatic pressure in the fluid column.
Well operation is categorized into:
Bottom gas and fluid go along the well bore to the surface only influenced by oil reservoir energy (natural inflow). This method is rather cost-effective, does not require additional energy cost to uplift liquids. It does not require expensive equipment and its maintenance. This type of well is considered as surface work and includes leading head, X-mass tree and delivery line. Underground equipment consists of oil-well tubing, and is pulled down to the level of upper perforation.
The reservoir energy is decreased to the minimum to prevent fluids from going up to the surface, due to that additional energy, like high-pressure gas, is required. Low-density liquid-gas mixture is produced after the mixing of reservoir fluids and gas, that leads to pressure decline in the well bottom, and provides product inflow from the reservoir and pulls out liquid-gas mixture to the surface.
There are two types of gas-lift operation:
- natural-pressure gas-lift operation is based on the use of gas from gas reservoir, pulled by high pressure for gas-lift;
- compressor gas-lift operation is based on the use of compressors to compress the gas until the necessary pressure to pump it down the well.
Advantages of the gas-lift operation:
- equipment is installed on the surface providing easy access for maintenance and repair;
- design of equipment is simple;
- it is possible to pump big amounts of liquids not depending on the diameter and depth of the well flow string;
- it is easy to control the well delivery;
- it is possible to use flooded and sandy wells.
Disadvantages of the gas-lift operation:
- low efficiency of the lift jack and the whole system;
- frequent renewal of tubing string in flooded and sandy wells;
- high expenses for building of gas-distribution booth, gas-compressor station, gas networks;
- High power consumption for extraction of 1t of oil from low-delivery wells with low flowing level.
Liquid and gas lift to surface, exploration, setting of well operation, gum and paraffin control, sand plug prevention and cleaning, borehole washout and corrosion prevention and other measures.See also:
- Oil well equipment