Evacuate

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. 

Before designing a process scheme it is necessary to know the specification of the raw material input (or feedstock) and the specification of the enc/procfucf desired. Designing a process to convert fluids produced at a wellhead into oil and gas products fit for evacuation and storage is no different. The characteristics of the well stream or streams must be known and specifications for the products agreed. 

In this section we describe hydrocarbon processing in preparation for evacuation, either from a production platform or land based facilities. In simple terms this means splitting the hydrocarbon well stream into liquid and vapour phases and treating each phase so... 

Produced water has to be separated from oil for two main reasons, firstly because the customer is buying oil not water, and secondly to minimise costs associated with evacuation (e.g., volume pumped, corrosion protection for pipelines). A water content of less than 0.5% is a typical specification for sales crude. 

Where space and weight are considerations (such as on an offshore facility) plate separators may be used to dehydrate crude to evacuation specification. Packs of plates are used to accelerate extraction of the water phase by intercepting water droplets with... 

In this section gas processing will be described in the context of site needs and evacuation, i.e. how gas may be processed for disposal or prior to transportation by pipeline to a downstream gas plant. Gas fractionation and liquefaction will be described in Section 10.1.4 Downstream Gas Processing . 

To prepare gas for evacuation it is necessary to separate the gas and liquid phases and extract or inhibit any components in the gas which are likely to cause pipeline corrosion or blockage. Components which can cause difficulties are water vapour (corrosion, hydrates), heavy hydrocarbons (2-phase flow or wax deposition in pipelines), and contaminants such as carbon dioxide (corrosion) and hydrogen sulphide (corrosion, toxicity). In the case of associated gas, if there is no gas market, gas may have to be flared or re-injected. If significant volumes of associated gas are available it may be worthwhile to extract natural gas liquids (NGLs) before flaring or reinjection. Gas may also have to be treated for gas lifting or for use as a fuel. 

The most common contaminants in produced gas are carbon dioxide (COj) and hydrogen sulphide (HjS). Both can combine with free water to cause corrosion and H2S is extremely toxic even in very small amounts (less than 0.01% volume can be fatal if inhaled). Because of the equipment required, extraction is performed onshore whenever possible, and providing gas is dehydrated, most pipeline corrosion problems can be avoided. However, if third party pipelines are used it may be necessary to perform some extraction on site prior to evacuation to meet pipeline owner specifications. Extraction of CO2 and H2S is normally performed by absorption in contact towers like those used for dehydration, though other solvents are used instead of glycol. 

After passing through several stages of processing, gas pressure may need to be increased before it can be evacuated, used for gas lift or re-injected. Inter-stage pressure increases may also be required for further processing, particularly where wellhead pressure is low. Gas is compressed to increase its pressure. 

The gas processing options described in the previous section were designed primarily to meet on-site usage or evacuation specifications. Before delivery to the customer further processing would normally be carried out at dedicated gas processing plants, which may receive gas from many different gas and oil fields. Gas piped to such plants is normally treated to prevent liquid drop out under pipeline conditions (dew point control) but may still contain considerable volumes of natural gas liquids (NGL) and also contaminants. 

Once oil and gas have been processed the products have to be evacuated from the site. Stabilised crude is normally stored in tank farms at a distribution terminal which may involve an extended journey by pipeline. At a distribution terminal, crude is stored prior to further pipeline distribution or loading for shipment by sea (Figure 10.28). 

The function of offshore production facilities are very much the same as those described for land operations. An offshore production platform is rather like a gathering station hydrocarbons have to be collected, processed and evacuated for further treatment or storage. However, the design and layout of the offshore facilities are very different from those on land for the following reasons ... 

This section describes the main types of offshore production platform and satellite development facilities, as well as associated evacuation systems. 

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 areas where seabed relief makes pipelines vulnerable or where pipelines cannot be justified on economic grounds, tankers are used to store and transport crude from production centres. The simplest method for evacuation is to pump stabilised crude from a processing facility directly to a tanker. 

In case of a major disaster, one platform in a region will be equipped to act as a control centre from which rescue operations are co-ordinated. Evacuation routes will be provided, and where large complexes are clustered together, a standby vessel will be available in the region to supply emergency services such as fire fighting and rescue. 

Companies which own process facilities and evacuation routes, but no longer have the hydrocarbons to fill them, can continue to operate them profitably by renting the extra capacity or by charging tariffs for the use of export routes. 

Cryogenics We use several types of evacuated stainless steel cryostats of about 1 htre capacity to provide the 77 K cooling with hquid nitrogen. The simplest, best valued and easiest to handle one is a ordinary thermos flask available from the supermarket (see fig.3). It is sufficient for a measurement period of more than 12 hours. A specially designed stainless steel vessel gains cooling periods of 30 hours. 

Fig. XVI-5. Resonance Raman spectra of MDMA adsorbed on ZnO (a) in the presence of 100 torr of NH3 (b) after evacuation of the NH3 from the cell. [Reprinted with permission from J. F. Brazdil and E. B, Yeager, J. Phys. Chem., 85, 1005 (1981) (Ref. 79). Copyright 1981, American Chemical Society.]...

The p V work temi is not nomially measured. It can be eliminated by suspending the calorimeter in an evacuated space (p = 0) or by holding the volume of tire calorimeter constant (dF= 0) to give... 

The energy released when the process under study takes place makes the calorimeter temperature T(c) change. In an adiabatically jacketed calorimeter, T(s) is also changed so that the difference between T(c) and T(s) remains minimal during the course of the experiment that is, in the best case, no energy exchange occurs between the calorimeter (unit) and the jacket. The themial conductivity of the space between the calorimeter and jacket must be as small as possible, which can be achieved by evacuation or by the addition of a gas of low themial conductivity, such as argon. 

Preparation of films for sufficiently volatile molecules can also be perfonned by evaporating tire molecules in vacuum (gas-phase deposition) or by tire use of a desiccator which contains tire substrate and tire dilute solution in a vessel separately and which is evacuated to 0.1 mbar and kept under vacuum for several hours ( 24 h). This also results in a vapour-phase-like deposition of tire molecules onto tire substrates. 

Thus, we have found unexpected complexities and even in this simple system have not yet been unable to accurately extrapolate the results of simulations done over periods varying from 1 to several hundred ps, to the low-friction conditions of extraction experiments performed in times on the oi dc r of ms. The present results indicate that one should not expect agreement between extraction experiments and simulations in more complex situations typically found in experiments, involving also a reverse flow of water molecules to fill the site being evacuated by the ligand, unless the simulation times are prolonged well beyond the scope of current computational resources, and thereby strengthen the conclusion reached in the second theoretical study of extraction of biotin from it.s complex with avidin [19]. 

The tube is fitted with a two-way tap, so that B can be used for evacuating the tube. 

To appreciate the action of a drying agent of class (a), let us imagine some anhydrous copper sulphate in an evacuated vessel provided with a pressure gauge, and water is allowed to enter slowly the temperature is assumed constant at 25°. The results may be best expressed by means of a vapour pressure - composition diagram (Fig. 7, 20, 1). The initial system is represented by the point A the pressure will rise along AB until the monohydrate CuS04,H20 commences to form at B. 

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