Casing offshore operations

The economic viability of enhanced oil recovery with C02 flooding is limited to the cases where C02 is available at low cost. This is the case for the West-Texas fields, where C02 from natural sources is available, or at the Weyburn field in Canada, where C02 can be made available from the North Dakota Gasification Plant. Unlike the situation in the United States, almost the entire European oil production is located offshore. There, enhanced oil recovery activities would be more costly, simply resulting from the larger spatial extent of production units and the entire higher costs of offshore operations. Furthermore, there are no low-cost industrial C02 sources available in the closer vicinity of the North Sea oil fields, nor is there an infrastructure for C02 transport. 

The first safety cases prepared for the process industries were those developed for North Sea offshore oil and gas operations following the Piper Alpha disaster that occurred in the year 1988. The Cullen report (Cullen, 1990) that was written following that accident was highly critical of offshore operating practices and recommended that a safety case approach be implemented. The Seveso incident that occurred in Italy further prompted the increased use of safety cases. Since that time the use of safety cases has spread to other industries (such as mining and railway operations) and to other nations, primarily in Europe and Australasia. (It is notable that the safety case regime approach has not been taken up for offshore oil and gas operations in the Gulf of Mexico—instead a more prescriptive approach based on industry consensus standards is used.)... 

Virtually all the numerous rules and standards the MMS enacted or adopted by reference from private sources are prescriptive and technically detailed, and require company compliance in the design and conduct of a proposed operation. Most were originally developed by API as voluntary standards for discretionary use by its member companies, and when later adopted or formally incorporated by reference by MMS, became mandatory and enforceable as MMS rules. This reliance on API enabled the MMS to capitalize on API s technical expertise and ability to gain industry consensus. But it also created a situation where the regulated industry can be said to have determined the pace of risk reduction in offshore operations and which, in the case of deepwater operations, lagged behind the risks being encountered. 

Contractors play a vital role in the conduct of offshore operations. A large percentage of the workers on a typical rig or platform are contractors in some cases the operator may have just one or two of their own people on board. Frequently,... 

With regard to offshore operations, the development of Safety Cases in the UK sector of the North Sea received a major impetus following the Piper Alpha catastrophe. Although Safety Cases had been used before that event, it is probably not an exaggeration to say that the modem Safety Case for offshore work came into being following the publication of The Cullen Report. 

Whether onshore or offshore drilling is carried out, the basic drilling system employed in both cases will be the rotary rig (Fig. 3.7) and the following summarises the basic functions and parts of such a unit. Three basic functions are carried out during rotary drilling operations ... 

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. 

Computer assisted operations (CAO) involves the use of computer technology to support operations, with functions ranging from collection of data using simple calculators and PCs to integrated computer networks for automatic operation of a field. In the extreme case CAO can be used for totally unmanned offshore production operations with remote... 

Mechanical Drives. Mechanical drive gas turbines are widely used to drive pumps and compressors. Their application is widely used by offshore and petrochemical industrial complexes. These turbines must be operated at various speeds and thus usually have a gasifier section and a power section. These units in most cases are aero-derivative turbines, turbines, which were originally designed for aircraft application. There are some smaller frame type units, which have been converted to mechanical drive units with a gasifier and power turbine. 

From a human reliability perspective, a number of interesting points arise from this example. A simple calculation shows that the frequency of a major release (3.2 x lO"" per year) is dominated by human errors. The major contribution to this frequency is the frequency of a spill during truck unloading (3 X10" per year). An examination of the fault tree for this event shows that this frequency is dominated by event B15 Insufficient volume in tank to imload truck, and B16 Failure of, or ignoring LIA-1. Of these events, B15 could be due to a prior human error, and B16 would be a combination of instrument failure and human error. (Note however, that we are not necessarily assigning the causes of the errors solely to the operator. The role of management influences on error will be discussed later.) Apart from the dominant sequence discussed above, human-caused failures are likely to occur throughout the fault tree. It is usually the case that human error dominates a risk assessment, if it is properly considered in the analysis. This is illustrated in Bellamy et al. (1986) with an example from the analysis of an offshore lifeboat system. 

CASE STUDY 5 AUDIT OF OFFSHORE EMERGENCY BLOWDOWN OPERATIONS... 

Bilges and ballast waters are one of the most difficult areas of this nature to deal with, especially in machinery spaces, since not only are they almost impossible to keep dry or even to dry out while the offshore installation is in operation, but effective maintenance of protective coatings at ail areas is in any case quite impossible except at major overhauls and refits, because of inaccessibility or very high temperatures and humidities. Good initial... 

In some cases radiation shields are provided to protect against heat effects from fire incidents and operation requirements. The shields usually are of two styles either a dual layer wire mesh screen or a plexy-giass see through barrier. The shields provide a barrier from the effects of radiant heat for specific levels. They are most often used for protection against flare heat and for barriers at fixed firewater monitor devices, most notably at the helidecks of offshore facilities. 

A fire water main should be provided to the shore terminus area of the wharf. Hydrants and monitor nozzles should be located so that effective fire water streams can be remotely applied to any berth or loading/unloading manifold from two directions. Where the wharf is of such length that onshore monitors cannot adequately cover the berths, the fire water main should be run onto the wharf to permit the required monitor and fire hose coverage. Monitors located on marine wharves may be remotely operated from onshore and use of elevated monitors is common. The offshore segment of the main can be a dry system. In all cases, isolation valves and fire department connections should be provided at the wharf-to-shore connection (ISGOTT, 1996). 

When a platform is not a practical way to develop an offshore field, the operator may complete the well using a submerged production system, in which case, the Christmas tree and other wellhead equipment are installed on the sea bottom and pipelines are connected to carry off the petroleum, either to shore, to a nearby platform, or to a vessel or storage buoy moored in the area. Divers can be used to make the necessary connections. 

Forty-six case studies of hydrate plug formation and remediation are recorded in Hydrate Engineering (Sloan, 2000). In every case, hydrate plugs were remediated. In addition, a rule of thumb is that most of the offshore flowline shut-ins are less than the 10 h no touch time, which requires no antihydrate operation before restart (J.E. Chitwood, Personal Communication, August 1, 2003). However, hydrate prevention methods are very expensive, as shown in the above Canyon Express and Ormen Lange examples, or in the fact that deepwater insulation costs are typically U.S.Sl million per kilometer of flowline. 

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