Offshore applications

Figure 9.18 provides an overview of the application envelope and the respective advantages and disadvantages of the various artificial lift techniques. As can be seen, only a few methods are suited for high rate environments gas lift, ESP s, and hydraulic systems. Beam pumps are generally unsuited to offshore applications because of the bulk of the required surface equipment. Whereas the vast majority of the world s artificially lifted strings are beam pumped, the majority of these are stripper wells producing less than 10 bpd. 

In an offshore application the process gas flowing into a 3,600 kW turboexpander was compatible with the magnetic bearing material and a suitable seal gas source was available. This made it possible to use a pressurized bearing housing. 

Air and gas, unstable foam and stable foam techniques are used almost exclusively for onshore drilling operations, rarely in offshore applications. Aerated mud, however, is used for both onshore and offshore drilling operations. 

Metallurgical and Inspection Requirements for Cast Sacrificial Anodes for Offshore Applications, RP-0387-87, NACE, Houston (1987)... 

Zinc anodes do not find application at temperatures in excess of 50°C. Zn-Al-Cd alloys suffer intergranular decohesion, and high purity zinc will passivate. Zinc anodes are not predominant in onshore or offshore applications, but they find considerable use under both conditions. 

It should be appreciated that the attachment may be required to withstand the launching and pile driving of a steel jacket for offshore applications. 

Offshore, both Ag/AgCl and metallic zinc electrodes are used for potential measurements and are also employed for current density surveys undertaken on the offshore platforms and pipelines, as discussed below. It has been found beneficial for offshore applications to install together an electrode of each type on a structure, one acting as a function check on the other. ... 

Report 23 Offshore Applications of Polymers, J.W.Brockbank, Avon Industrial Polymers Ltd. 

Oil-based muds are being replaced now by synthetic muds. Diesel oil is harmful to the environment, particularly the marine environment in offshore applications. The use of palm oil derivative could be considered as an alternative oil-based fluid that is harmless to the environment [1869]. Hydrated castor oil can be used as a viscosity promoter instead of organophilic quater-nized clays [1285]. 

D. Osborne. The development in the use of FRE (fiber reinforced epoxy) pipe systems for industrial and offshore applications. In Proceedings Volume, number 7, pages 27 5. 10th BHR Group Ltd et al Pipe Protect Int Conf (Amsterdam, Netherlands, 11/10-11/12), 1993. 

Aero-derivative gas turbines are typically used for offshore applications where weight and efficiency are a premium, to drive compressors for natural gas pipelines, and stand-alone power generation applications for peak periods of high power demand. For stand-alone applications, gas turbine efficiency becomes a critical issue. However, if heat is to be recovered from the gas turbine exhaust, the efficiency becomes less important as the waste heat is utilized. 

The smokeless dare tip has been used successfully offshore to reduce radiation intensity levels and resulting flare boom length. Turndown of the different types of flare tips has been a problem but has largely been solved by the vendors. The smokeless flare tip without assist from water or steam, Coanda-effeet type, has particular promise for offshore application. 

An example of the compact nature and modularity of membrane units is shown in Figure 7.4 where the two membrane units in the foreground replaced the amine-absorption system in the background for removal of C02 from natural gas. This application was mentioned earlier with regard to SACROC and subsequent larger offshore applications where space is at a premium. 

Similar results have been observed in an offshore application using alumina membranes [Guibaud, 1989]. With a flux of 1,600 L/hr-m, the membranes employed reduces the oil level in the treated water to less than 5 ppm. The filtered sea water can be either reinjected into the well or discharged to the sea. 

Heavy industrial gas turbines are usually to be found in refineries, chemical plants and power utilities. They are chosen mainly because of their long and reliable running times between major maintenance overhauls. They are also capable of burning most types of liquid and gaseous fuel, even the heavier crude oils. They also tend to tolerate a higher level of impurities in the fuels. Heavy industrial machines are unsuitable for offshore applications because -... 

The most frequently used insulating compounds are PVC, XLPE and EPR. For most onshore applications PVC and XLPE are preferred because of economic reasons, and XLPE is becoming more popular than PVC. Marine and offshore applications tend to prefer XLPE and EPR. EPR is usually more expensive than XLPE. Both compounds have the advantage that they permit the conductors to operate at higher temperatures (85 to 90°C) than those of PVC (70°C). PVC compounds can be specially manufactured to tolerate conductor temperatures up to 85°C. Silicon rubber can be specified if high conductor temperatures (up to 180°C), and for even higher temperatures (up to 260°C)... 

Hoses for offshore applications are in most cases made of abrasion-resistant materials such as poly(vinyl chloride) or polyurethane. Polytetrafluoroethylene hoses have been developed for use as intercormectors to oil or gas combustion chamber burners or turbines. The inert qualities, abflity to withstand the hostile environment, and high-pressure capability suit them to this application. 

However, no details are given here of these offshore applications, which are considered by the writers to be outside the scope of this paper. 

Another major offshore application, albeit still potential, lies with the stiff lightweight adoption of aluminium and/or polymer composite topside structures in order to reduce weight. Structural aluminium sections may be created by bonding together individual extrusions, and a most convincing demonstration of the potential has been developed by British Alcan (see Chapter 8). 

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