Oil and gas production is the milestone of hydrocarbon field development. First products lifted from sub-soil assets actually start operation of underground production horizons.
Basis of field development project is the feasibility study for mining works. The document shows how many wells (production and injection) shall be drilled for hydrocarbon production. The first ones are intended for lifting oil or gas to the surface, the second ones are engineering facilities which serve, for example, for water pumping in order to maintain reservoir pressure.
The well is the main structure used for hydrocarbons recovery. But oil and gas production procedures and technologies as well as equipment used differ radically.
Submersible equipment for oil production
Oil well can work in “depletion” mode. Well flowing happens in Russia not so often. Formation pressure is high enough that fluid comes from the bottom hole (lower part of the well bore) by itself to the well mouth (on the surface) via the production casing from well tubing strings (WTS).
In field experience, when natural mode is absent or short, equipment for oil production has to be used, which actually serves for compulsory oil lifting. During the well operation the following is used:
- multi-stage centrifugal pumps (ESP);
- sucker rod pumps (SRP) or “pumping units”;
- screw, diaphragm, hydraulic piston pumps.
Downhole and surface equipment for gas production
In contrast to oil, “blue gold" production is performed always with flow method. Pressure difference between the formation and the surface allows to lift hydrocarbon mixture via well bore naturally. Nevertheless, during its production, complexes are used equipped with shut-off valves, column disconnectors, packers. They are used for well operation with specified recovery rate and for leak-tight closure of christmas tree during emergency situations.
In order to meet production fluid characteristics with regulations required for its supply to the pipeline, on the surface gas is fed to a complex treatment unit. Here the feedstock is cleaned of hydrocarbons in liquid state, mechanical impurities, moisture, it is dried and cooled and then fed via the booster pump station to the manifold for transportation to the processing plant.
Gas production practice from single- and multi-layered formations
Hydrocarbon field can consist of one productive formation or several horizons which are feasible for development. In the first case gas production is done with several wells specified in the development project.
If the formation is of multi-layer type, specialists decide: drill one well passing through all horizons and simultaneously, in one well bore, collect fluids which can differ in physical and chemical properties, or use another natural gas production practice. The other approach means that every formation is operated separately. This is achieved due to packer installation — devices which separate formations. For these purposes directional and horizontal drilling is also used.
This is economically more viable rather than drilling “own” well for every formation.