GAS INJECTION

Some oil and gas reservoirs contain large volumes of produced natural gas or carbon dioxide (CO2). This gas is produced simultaneously with the liquid hydrocarbons. The natural gas or CO2 is recovered, recompressed, and reinjected into the gaseous portion of the reservoir. The reinjected natural gas or CO2 maintains reservoir pressure and helps push additional liquid oil hydrocarbons out of liquid portion of the reservoir. 

Parts can be molded by gas injection using injection molding machines (Chapter 2). This process is most effective and economical when used for large parts. It offers a way to mold parts with only 10 to 50 percent of the clamp tonnage that would be necessary in conventional IM (1). 

The technique—practiced in several variations, with some patented—involves the injection of an inert gas, usually nitrogen, into the melt as it enters the mold. This is not structural foam, as no foam core is produced instead, the gas forms a series of interconnecting hollow channels in the 

Molded-in stresses are minimal. The thick but hollow sections provide rigidity and do not create sink or warpage problems. The cycle time is reduced because the thick sections are hollow. As the gas is not mixed with the melt, there is no surface splay, which is typical of low-pressure structural foam molding (1). Gas injection is being used with commodity and engineering resins. 

In the past years, hybrid techniques have come up, for example, combining the displacement effect of an expanding solvent like propane, butane, or hexane with the 

Gas injection can also follow the objective of maintaining the pressure of gas condensates above the dew point for keeping condensates (heavier hydrocarbons) in the gaseous phase as long as the pressure is high enough, hence enabling recovery of these components simultaneously [38]. 

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Shelf (elastics) Sheet-like sandbodies resulting from storms or transgression. Usually thin but very continuous sands, well sorted and coarse between marine clays. Very high productivity but high quality sands may act as thief zones during water or gas injection. Action of sediment burrowing organisms may impact on reservoir quality. 

This rather low recovery factor may be boosted by implementing secondary recovery techniques, particularly water Injection, or gas injection, with the aim of maintaining reservoir pressure and prolonging both plateau and decline periods. The decision to implement these techniques (only one of which would be selected) Is both technical and economic. Technical considerations would be the external supply of gas, and the... 

Natural gas cap drive may be supplemented by reinjection of produced gas, with the possible addition of make-up gas from an external source. The gas injection well would be located in the crest of the structure, injecting into the existing gas cap. 

The hardware items with which the processes described in Section 10.1 are achieved are called facilities, and are designed by the facilities engineer. The previous section described the equipment items used for the main processes such as separation, drying, fractionation, compression. This section will describe some of the facilities required for the systems which support production from the reservoir, such as gas injection, gas lift, and water injection, and also the transportation facilities used for both offshore and land operations. 

A considerable percentage (40% - 85%) of hydrocarbons are typically not recovered through primary drive mechanisms, or by common supplementary recovery methods such as water flood and gas injection. This is particularly true of oil fields. Part of the oil that remains after primary development is recoverable through enhanced oil recovery (EOR) methods and can potentially slow down the decline period. Unfortunately the cost per barrel of most EOR methods is considerably higher than the cost of conventional recovery techniques, so the application of EOR is generally much more sensitive to oil price. 

Gas injection into a gas cap overlaying an oil reservoir is considered an EOR method. The resulting repressurization of the reservoir promotes additional oil production. Reinjection of natural gas is responsible for a significant fraction of Alaskan North Slope oil production. 

Foam-mat drying is a process in which a suspension, slurry, or solution is transformed into a stable foam by inert gas injection. The foam stmcture provides porosity and the mat is dried in trays or on a belt in a tunnel compartment, either under vacuum or with ckculating gas. A free-flowing powder capable of rapid rehydration results. Emit juices (qv) are dried successfully in this manner. 

FIG. 14-57 Beam-type gas-injection siipportplate for large columns. 

Onshore or offshore gas plants are designed for either LNG rejection and gas injection, or LNG rejection and transmission for sale. In the case of offshore plants, onshore facilities further process the natural gas before transmission for sale. In either case, natural gas must be treated and then refrigerated to make rejection of heavy hydrocarbons possible. In plants where natural gas is treated for sale purposes, water and hydrocarbon dew points of the gas must also be controlled. 

The seal gas injected into the seal being contaminated upstream of the injection. 

Probably the most common seal is the restrictive ring type, normally used in the form of carbon rings. This seal controls leakage better than the non-floating labyrinth type, although it wears faster. The carbon ring seal does not tolerate dirt as well as the labyrinth seal. The carbon ring seal and the labyrinth seal may be ported for gas injection, ejection, or a combination of both. Any injection gas should be clean. 

Mixing by agitation of liquids normally involves the transfer of momentum from an impeller to the liquid. In some cases, mixing is achieved by gas injection or circulation via a pump loop. An impeller, which is mounted on a shaft driven by an electric motor, is divided into two operation categories ... 

The first stage of the cycle is the flow of molten polymer into the mould cavity through a standard feed system. Before this flow of polymer is complete, the injection of a predetermined quantity of gas into the melt begins through a special nozzle located within the cavity or feed system as shown in Fig. 4.45. The timing, pressure and speed of the gas injection is critical. 

Fig. 4.4S Stages in the gas injection moulding of an automotive handle (courtesy of Cinpress Ltd)...

Figure 9-7D. Typical efficient metal and porcelain support plate designs for gas injection into packing. Designs aiso avaiiabie in piastic-FRP, poiypropylene, PVC, etc. (Aiso see Figure 9-7F.) Used by permission of Norton Chemicai Process Products Corp.

Meter for Measuring Air (or Gas) Volume. A standard orifice meter is generally used to measure air (or gas) injection volume rates. 

Figure 9.7 Capacity reduction by hot gas injection, with compensating liquid injection...

A service well is a well drilled or completed for the purpose of supporting production in an existing field. Wells of this class are drilled for the following specific purposes gas injection (natural gas, propane, hutane, or flue gas), water injection, steam injection, air injection, salt water disposal, water supply for injection, observation, injection for in-situ combustion. 

Development Development well OO Development well OO Exploration well O Auxiliary well O Production well O - oil - gas Injection well O - water - gas - in-situ combustion Appraisal well OO Development well O... 

Nozzles Shutoff Valves Gas injection Equipment Qukkmold-Clamping Systems... 

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