What is wellhead gas?

Wellhead gas is the natural gas or methane (CH4) that is produced at the wellhead of oil and natural gas wells.

 

Wellhead pressure

Wellhead pressure – pressure at the top of the well, i.e., at its wellhead. It is measured by pressure gauges of the wellhead fittings. There are static and dynamic wellhead pressures.

Static wellhead pressure is gauged in the abandoned well and depends on reservoir pressure, well depth and density of the filling medium. Numerically it equals the difference between reservoir pressure and hydrostatic pressure of the liquid column from wellhead to reservoir.

Dynamic wellhead pressure is measured in the operating well and depends on the same parameters as the static pressure + on the well rate or on injection agent flow rate, as well as on the pressure in the pipeline near the well and on the pressure differential in shut-off elements of the wellhead fittings. Excess wellhead pressure (versus atmospheric pressure) may reach 100 MPa and more (in gas wells, at hydraulic fracture).

Gas and oil wells that are nearly depleted are often abandoned. Even though considerable amounts of gas and oil could still be extracted. The remaining oil and gas can no longer be recovered efficiently and cost-effectively with conventional methods. The well gas pressure is not enough to transport produced gases or liquids upwards through the production tubing. 

In order to facilitate the production of mature gas fields, a possible solution is installing compression. By introducing compression, the well head pressure is reduced allowing larger gas flow rates. Wellhead compression (WHC) is the solution by which a compressor acts locally over one or a number of wells. As a result, the back pressure for a number of selected wells can be reduced. WHC extends the life of oil and gas wells and boosts their production output. 

A conventional wellhead system uses either small, individual wellhead compressors or large central units handling several wells or an entire field. The small compressors can be as small as five horsepower. The large central units can be several thousand horsepower. These compressors need to have a relatively low capital costs and operate reliably more than 95 percent of the time. 

The nearer the compressor is to the wellhead, the more likely the gas will be saturated. Some tolerance of this liquid is desirable in the design of a field unit. The standard machine should be capable of wellhead gas compression of as much as 2 percent H2S without serious corrosion problems. Reciprocating compressors are generally utilized in gas-gathering applications. Some rotary positive units are used in low-pressure applications, and both can be used as wellhead gas compressors.

Natural Gas Wells

In natural gas wells, the increase in gas velocity made possible by the use of a wellhead compressor system. This system eliminates a drop in pressure at the bottom of the borehole, eliminating production constraints due to liquid loading.

Oil Wells

In oil wells, wellhead compression units reduce the pressure on pipes. They also largely preclude the development of backpressure which could impair production. Problems with air entrapment no longer occur, and the pump's delivery rate increases.

 

Gas Gathering compressor is compulsory for each gas well. The compressor in this application is used to collect the gas from one well or several wells to boost and transport to downstream gas treatment plant. Since in most of the cases the compressors are located at or near wellhead and there might be no availability of civil utility such as power supply, instrument air or drain pit and furthermore heavy condensate is also contained in the gas, thus a specific solution is made for this application to satisfy the site and gas condition. Furthermore, while time goes on year by year, the gas pressure shall deplete, therefore a specific configuration is designed especially for this case.

Wellhead Gas Compressors are used in oil&gas field.Compressor is used for one or several gas wells.
Compressors are used to collect gas from wellhead(s) to boost and transport to downstream gas treatment plant.Compressor usually is located at or near wellhead(s),with compression stage from one to five.

Wellhead gas compressors are build on rigid structural skids,which can be removed as requirements.
We design compressors specially for customers,ensuring performance,safety and reliability of wellhead gas operations according to gas components and other enviromental conditions.Constantly wellhead gas is not clean,containing heavy condensate,water,carbon dioxide even hydrogen sulfide.We take options to meet these
particularities.

These options include but not limited to:

Stainless Steel materials for piston rods and valves,
Two compartment distance pieces,
Purged packing case,
Special heat treatment for pressure vessels and welded connections...

 

 

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