Prior

RATIO OF VAPOR MOLE FPAC PRIOR TO ASSOCIATION. 

Figure 7.12 Energy emd capital cost targets can be combing to optimize prior to design. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195,...

For more complex examples, total cost profiles return step changes such as shown in Fig. 7.12 (due to changes in Nu ts and /Vshklls)-These step changes are easily located, prior to design, through simple software. Most important, extensive experience has shown that predicted overall costs are typically accurate within 5 percent or better. ... 

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

Primary or pretreatment of wastewater prior to biological treatment involves both physical and chemical treatment depending on the nature of the emission. 

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Arosolvan process A process for the extraction of benzene and toluene from a mixture of aromatic and saturated hydrocarbons using a mixture of water and N-methylpyrrolidone. The process is used when naphtha is cracked to produce alkenes. To prevent extraction of alkenes these are saturated by hydrogenation prior to extraction. 

Some techniques have been described that are based on the concept of flame ionization used in gas chromatography. The results are generally unsatisfactory because it is necessary to evaporate the solvent prior to introducing the mixture into the detector. 

For hydrocarbon studies, analyses can be made without prior assumptions, since the carbons not carrying protons can be excited directly, this of course not being the case for hydrogen (e.g., quaternary carbons in alkanes, substituted carbons in aromatic rings). 

The octane number is a measure of a fuel s ability to resist auto-ignition during the compression phase prior to ignition. 

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Once the field development plan (FDP) is approved, there follows a seguence of activities prior to the first production from the field ... 

The production phase commences with the first commercial quantities of hydrocarbons ( first oil ) flowing through the wellhead. This marks the turning point from a cash flow point of view, since from now on cash is generated and can be used to pay back the prior investments, or may be made available for new projects. Minimising the time between the start of an exploration campaign and first oil is one of the most important goals in any new venture. 

Eventually, only the drilling of an exploration well will prove the validity of the concept. A wildcat ls drilled in a region with no prior well control. Wells may either result in discoveries of oil and gas, or they find the objective zone water bearing in which case they are termed dry . 

Exploration activities are potentially damaging to the environment. The cutting down of trees in preparation for an onshore seismic survey may result in severe soil erosion in years to come. Offshore, fragile ecological systems such as reefs can be permanently damaged by spills of crude or mud chemicals. Responsible companies will therefore carry out an Environmental Impact Assessment (EIA) prior to activity planning and draw up contingency plans should an accident occur. In Section 4.0 a more detailed description of health, safety and environmental considerations will be provided. 

If no prior drilling activities have been recently carried out in the area, usually an environmental impact assessment (EIA) will be carried out as a first step. An EIA is usually undertaken to ... 

Prior to moving the rig and all auxiliary equipment the site will have to be cleared of vegetation and levelled. To protect against possible spills of hydrocarbons or chemicals the surface area of a location should be coated with plastic lining and a closed draining system installed. Site management should ensure that any pollutant is trapped and properly disposed of. 

Particularly for jack-up rigs, site surveys may have to be carried out prior to each reemployment to ensure that the rig is positioned away from the previously formed footprints (depressions on the sea-bed left by the jack-up legs on a previous job). 

For the very first section of the borehole a base from which to commence drilling is required. In a land location this will be a cemented cellar in which a conductor or stove pipe will be piled prior to the rig moving in. The cellar will accommodate the Christmas tree (an arrangement of seals and valves), once the well has been completed and the rig has moved off location (Fig. 3.13)... 

Between the top hole and the reservoir section in most cases an intermediate section will need to be drilled. This section consists of more consolidated rocks than the top hole. The deviation angle is often increased in this interval to reach the subsurface target and eventually a casing is set prior to entering the reservoir sequence. 

Once the cementation has been completed the rig will wait on cement (V OC), i.e. wait until the cement hardens prior to running in with a new assembly to drill out the plugs, float collar and shoe, all of which are made of easily drillable materials. 

Plug back cementations, i.e. cement placement inside the casing and across the perforations may be required prior to sidetracking a well or in the course-of abandonment. 

Bottom hole assemblies and certain types of downhole equipment (e.g. logging tools, MWD tools) cost several US 100,000. Some logging tools will have radioactive sources which may need to be recovered or isolated for safety and legal reasons. However, prior to commencing fishing operations, a cost - benefit assessment will have to be made to establish that the time and equipment attributable to the fishing job is justified by the value of the fish or the cost of sidetracking the hole. 

The time taken to complete a base line study and EIA should not be underestimated. The baseline study describes and inventorises the natural initial flora, fauna, the aquatic life, land and seabed conditions prior to any activity. In seasonal climates, the baseline study may need to cover the whole year. The duration of an EIA depends upon the size and type of area under study, and the previous work done in the area, but may typically take six months. The EIA is often an essential step in project development and should not be omitted from the planning schedule. 

This section will look at formation and fluid data gathering before significant amounts of fluid have been produced hence describing how the static reservoir is sampled. Data gathered prior to production provides vital information, used to predict reservoir behaviour under dynamic conditions. Without this baseline data no meaningful reservoir simulation can be carried out. The other major benefit of data gathered at initial reservoir conditions is that pressure and fluid distribution are in equilibrium this is usuaily not the case once production commences. Data gathered at initial conditions is therefore not complicated... 

Nearly all reservoirs are water bearing prior to hydrocarbon charge. As hydrocarbons migrate into a trap they displace the water from the reservoir, but not completely. Water remains trapped in small pore throats and pore spaces. In 1942 Arch/ e developed an equation describing the relationship between the electrical conductivity of reservoir rock and the properties of its pore system and pore fluids. 

STOIIP" s a term which normalises volumes of oil contained under high pressure and temperature in the subsurface to surface conditions (e.g. 1 bar, 15°C). In the early days of the industry this surface volume was referred to as stock tank oit and since measured prior to any production having taken place it was the volume initially in placd. ... 

A container full of hydrocarbons can be described in a number of ways, from a simple measurement of the dimensions of the container to a detailed compositional analysis. The most appropriate method is usually determined by what you want to do with the hydrocarbons. If for example hydrocarbon products are stored in a warehouse prior to sale the dimensions of the container are very important, and the hydrocarbon quality may be completely irrelevant for the store keeper. However, a process engineer calculating yields of oil and gas from a reservoir oil sample will require a detailed breakdown of hydrocarbon composition, i.e. what components are present and in what quantities. 

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 . 

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. 

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 template will be constructed and fitted out at a fabrication yard and then transported offshore to the drilling location. The template is lowered to the seabed using a crane barge or, if small enough, lowered beneath a semi-submersible rig. Prior to drilling the first well, piles are driven into the sea bed to hold the template in place. 

Prior to the calculation of tax, certain allowances may be made against the gross revenue before applying the tax rate. These are called fiscal costs and commonly include the royalty, opex and capital allowances (which is explained later in this section). Fiscal costs may also be referred to as deductibles. 

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