Offshore platform

Offshore platforms are, in essence, similar to buried pipelines because in both, external and internal surfaces are exposed to corroding environments in buried pipelines the external surface of the pipe is exposed to the soil (which is a corrosive environment), and its internal surface is under the corrosive impact of the fluid that is going through, either water, oil or the like. In case of offshore platforms, the whole immersed stmcture is exposed to seawater (a corrosive medium), and the internal surfaces of the systems such as seawater injection systems or oil storage facilities can be considered locations at which corrosion is occurring internally. 

While there could be many ways to classify off-shore platforms and stmctures, one approach to address the basic types of offshore platforms (or, alternatively within the context of this book, offshore drilling units) is as follows  

Reservoir problems such as reservoir sourii because of SRB activity 

In addition to a series of problems/ two main problems resulting from bacterial growth in offshore structures are [20] (1) hydrogen sulphide production (generated, for example, by SRB) that besides being volatile and toxic, thus serious to the personnel safety, causes corrosion and souring of the products (crude oil, for instance) which ultimately affects the quality and final price [21], and (2) the production of bacterial metabolites which could give rise to accelerated materials deterioration. 

Some of such problems are reservoir souring and/or filter blockages in diesel systems (communication with Dr. A.M. Qrshed, Production Services Network, Aberdeen, UK, Ol/June/07). 

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Having defined and gathered data adequate for an initial reserves estimation, the next step is to look at the various options to develop the field. The objective of the feasibility study is to document various technical options, of which at least one should be economically viable. The study will contain the subsurface development options, the process design, equipment sizes, the proposed locations (e.g. offshore platforms), and the crude evacuation and export system. The cases considered will be accompanied by a cost estimate and planning schedule. Such a document gives a complete overview of all the requirements, opportunities, risks and constraints. 

Crude oil and gas from offshore platforms are evacuated by pipeline or alternatively, in the case of oil, by tanker. Pipeline transport is the most common means of evacuating hydrocarbons, particularly where large volumes are concerned. Although a pipeline may seem a fairly basic piece of equipment, failure to design a line for the appropriate capacity, or to withstand operating conditions over the field life time, can prove very costly in terms of deferred oil production. 

In addition, the copper industry s market development activities have resulted in appHcations such as clad ship hulls, sheathing for offshore platforms, automotive electrical systems including electric vehicles, improved automobde radiators, solar energy, fire sprinkler systems, parts for fusion reactors, semiconductor lead frames, shape memory alloys, and superconducting ceramics (qv) containing copper oxides. 

Continuous-Flow Compressors Continuous-flow compressors are machines where the flow is continuous, unlike positive displacement machines where the flow is fluctuating. Continuous-flow compressors are also classified as turbomachines. These types of machines are widely used in the chemical and petroleum industiy for many services. They are also used extensively in many other industries such as the iron and steel industry, pipeKne boosters, and on offshore platforms for reinjection compressors. Continuous-flow machines are usually much smaller in size and produce much less vibration than their counterpart, positive displacement units. 

Public places, for safety to life and property -Offshore platforms etc,... 

Protection with impressed current, with galvanic anodes, and a combination of both processes is used for marine structures and offshore pipelines. Their properties, as well as their advantages and disadvantages, are given in Table 16-1. The protective measures must be optimized for every structure. In the impressed current protection of offshore platforms, for example, the difficulties of maintenance and repair will be of major importance, whereas in harbor installations these problems can be... 

An early study involving a gas proeessing plant design for an offshore platform in the North Sea was performed in the early 1970s. This study indieated that the turboexpander option eontained fewer vessels and equipment. The study results are listed in Table 3-6 note that the turboexpander also represented the option with the lowest operating eost. This plant proeessed natural gas from a eondensate reservoir in a dense phase state. 

Both the Power Industry and the petrochemical industries use the aircraft-type turbine. The Power Industry uses these units in a combined cycle mode for power generation especially in remote areas where the power requirements are less than 100 MW. The petrochemical industry uses these types of turbines on offshore platforms especially for gas re-injection, and as power plants for these offshore platforms, mostly due to their compactness and the ability to be easily replaced and then sent out to be repaired. The aeroderivative gas turbine also is used widely by gas transmission companies and petrochemical plants, especially for many variable speed mechanical drives. These turbines are also used as main drives for Destroyers and Cruise Ships. The benefits of the aeroderivative gas turbines are ... 

The location of the plant is the principal determination of the type of plant best configured to meet its needs. Aero-derivatives are used on offshore platforms. Industrial turbines are mostly used in petrochemical applications, and the frame type units are used for large power production. 

Intermittent operation and peak-load operation lead to more problems and reduee the life of many of the hot parts. Peak-load units aeeount for only about 20% of the units above the 10 MW range. The smaller units (between 1 and 10 MW) are usually operated as standby power generators or for eompressor drives mostly on offshore platforms. Small-unit repair eosts average about 55,000- 100,000. These units are very rarely used for peaking serviees. 

In large facilities and offshore platforms where the escaping gases and liquids could present a source of pollution or ignition, it is common to route the relief valve discharges into a common header that discharges at a remote safe location. Often a vent scrubber is installed in this header to separate the bulk of the liquids and to minimize the possibility of liquid discharges to atmosphere. 

The low profile of fluorescent fixtures often dictates their use in areas with low headroom, such as in wellbays on offshore platforms and in... 

An initial explosion occurred on the production deck of the Piper Alpha Offshore Platform in the North Sea at about 1 00 PM on July 6,1988. The incident escalated into a tragedy that cost the lives of 165 of the 225 persons on the platform. Two additional fatalities occurred on a rescue boat. The Piper Alpha Platform was totally devastated. 

There had been three incidents of gas/oil escapes over prolonged periods on various offshore platforms, and this had prompted the human factors investigation. 

Carter, G. (2000). Offshore Platform Rigs Adapting to Weight-Space Restrictions for Floaters. Offshore 60(4). Devereux, S. (2000). Dnlling Technology. Tulsa, OK PcnnWcll. 

For fixed offshore platform units, the design method should follow the strength level analysis guidelines in API RP 2A. The drilling and well servicing units should be able to resist the deck movement, i.e., the response of the deck... 

Sacrificial anode systems operate without external power source. The anodes are reactive metals such as magnesium and zinc or aluminum alloys. The energy for the process is derived from the anode material. Careful design is required to match the output and lifetime of the anodes with the polarization and life-expectancy requirements of the plant. Sacrificial anode CP is used for offshore platforms, sub-sea pipelines and the inside of ballast tanks on tanker ships. 

Fig. 9.23 Welded areas of an offshore platform structural tubular displaying premature corrosion due to (a) lack of surface grinding (resulting in poor paint adhesion and performance) and (b) the fact that the weld metal is anodic relative to the parent material of the tubular...

Recommended Practice Corrosion of Steel Fixed Offshore Platforms Associated with Petroleum Production, RP-01-76, NACE, Houston (1983)... 

Sacrificial anodes Small land based schemes and for avoidance of interaction problems. Marine structures, e.g. offshore platforms High soil/water resistivities and small driving e.m.f. may require a large number of anodes Reasonably uniform Cannot be applied in high-resistivity environments... 

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. ... 

For potential surveys on offshore platforms it is necessary to locate numerous reference electrodes at all levels on the structure. The hard-wire connections from these electrodes together with, for example, similar connections from specially monitored sacrificial anodes are best terminated and displayed at the surface on mimic display monitoring panels. 

Testing of metals for resistance to sulphide stress cracking at ambient temperatures Accelerated test procedures for screening atmospheric surface coating systems for offshore platforms and equipment... 

A complete range of instrumentation is available from portable units to automatic systems utilising many probes. Transmitter units are available which can be located at the probe and transmit ER data into the 4-20 mA standard instrument signal. Radio linkage from transmitter to control room or nearby offshore platform is available commercially. A satellite link has been used to monitor offshore platform ER probes at the onshore base in a Norwegian oilfield. 

With increased development work from offshore platforms, more non-vertical (deviated) wells are being drilled. Settling of mud solids to the low side of the well bore can result in a continuous channel of undisplaced drilling mud solids in the casing annulus... 

Primary separation facilities process the produced fluids and gases into individual streams of gas, oil and water. These facilities are commonly referred to as Gas Oil Separation Plants (GOSP s), Central Processing Facilities (CPF) or if located offshore on drilling, production and quarters platforms (PDQ s). The offshore platform may either float on the sea or be supported on steel or concrete supports secured to the ocean floor, where it is capable of resisting waves, wind, and in Arctic regions ice flows. In some instances surplus oil tankers have been converted into offshore production and storage facilities. 

Lake Maracaibo, Venezuela, Offshore Platform, UVCE/Fire... 

American Petroleum Institute (API), RP 14J. Recommended Practice for Hazard Analysis for Offshore Platforms. First Edition, API, Washington, D.C., 1994. 

All hydrocarbon process areas containing materials with gaseous materials that are not adequately ventilated (i.e., would not achieve a minimum of six air changes per hour or would allow the build up of flammable gas due to noncirculating air space). Typically applications include compressor enclosures, process modules in offshore platforms and enclosed arctic facilities. 

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