A well that produces 100,000 SCFD of gas as a minimum, but periodically reaches a peak production rate of 300,000 SCFD once a day, is continuously loading and unloading liquids. The sequence of events are: • The velocity of gas flowing up through the tubing is insufficient to entrain liquids out of the tubing to… Read More »
Although we have been talking about wellhead pressure (both shut-in and flowing tube), the wellhead pressure is just an indirect indication of the really important parameter-that is, the bottom hole pressure. It is the pressure inside the casing at the level of the perforations that determines gas flow. By lowering a pressure sensing instrument suspended… Read More »
We are assuming that the reservoir pressure and porosity are adequate — that is, there is a plentiful supply of gas in the ground for the well to draw on. Also, we are assuming that the permeability of the reservoir is sufficient to allow a relatively free flow of gas to the perforations in the… Read More »
There are three basic problems which reduce the flow of gas from a well which has a sufficient gas pressure, porosity and permeability in the surrounding sand formation to sustain a much higher production rate: 1. Restriction to flow down hole such as occurs when sand covers the perforations in the casing. 2. Liquid loading… Read More »
Compressors are used whenever it is necessary to flow gas from a lower pressure to a higher pressure system. Flash gas from low-pressure vessels used for multistage stabilization of liquids, oil treating, water treating, etc., often exists at too low a pressure to flow into the gas sales pipeline. Sometimes this gas is used as… Read More »
The design of any of the distillation processes discussed requires choosing an operating pressure, bottoms temperature, reflux condenser temperature and number of trays. This is normally done using any one of several commercially available process simulation programs which can perform the iterative calculations. Some typical parameters for design are shown in Table 9-4. The actual… Read More »
The bottoms liquid from any gas plant may be sold as a mixed product. This is common for small, isolated plants where there is insufficient local demand. The mixed product is transported by truck, rail, barge or pipeline to a central location for further processing. Often it is more economical to separate the liquid into… Read More »
Figure 9-3 shows a typical cryogenic plant where the gas is cooled to -100°F to ~150°F by expansion through a turbine or Joule-Thompson (J-T) valve. In this example liquids are separated from the inlet gas at 100°F and 1,000 psig. It is then dehydrated to less than 1 ppm water vapor to assure that hydrates… Read More »
In a refrigeration plant the inlet gas is cooled to a low enough temperature to condense the desired fraction of LPG and NGL. Either freon or propane is used as the refrigerant. Figure 9-2 shows a typical refrigeration plant. The free water must be separated and the dew point of the gas lowered before cooling… Read More »
The oldest kind of gas plants are absorption/lean oil plants, where a kerosene type oil is circulated through the plant as shown in Figure 9-1. The “lean oil” is used to absorb light hydrocarbon components from the gas. The light components are separated from the rich oil and the lean oil is recycled. Typically the… Read More »