Recoverability

Remediation of petroleum-impacted aquifers where LNAPL is present is typically a phased process. These phases can be simplified as follows  

The time frames associated with the later two phases are dependent on the volume of residual hydrocarbon that remains following initial recovery, hydrogeologic conditions, among other factors, and are further discussed in Chapters 9 and 10, respectively. Important factors such as the presence and extent of residual hydrocarbons, and conceptual understanding of relative permeability and transmissivity as they relate to NAPL recovery, are further discussed below. 

The recoverability of hydrocarbon from the subsurface refers to the amount of mobile hydrocarbon available. Hydrocarbon that is retained in the unsaturated zone is not typically recoverable by conventional means. Additional amounts of hydrocarbon that are unrecoverable by conventional methods include the immobile hydrocarbons associated with the water table capillary zone. Residual hydrocarbon is pellicular or insular, and is retained in the aquifer matrix. With respect to recoverability, residual hydrocarbon entrapment can result in volume estimate discrepancies as well as decreases in recovery efficiency. With increasing water saturation, such as when the water table rises via recharge or product removal, hydrocarbons essentially become occluded by a continuous water phase. This results in a reduction of LNAPL and product thickness as measured in the well at constant volume. When water saturation is decreased by lowering the water table (as during recovery operations), trapped hydrocarbons can remobilize, leading to increased recoverability. 

In general, as viscosity of the hydrocarbon increases and grain size decreases, the residual saturation increases. Typical residual saturation values for unsaturated, porous soil are tabulated in Table 5.5. 

These values are then multiplied by a correction factor to account for hydrocarbon viscosity. Correction factors for different hydrocarbon types are 

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The resulting vapor phase is called associated gas and the liquid phase is said to be the crude oil. The production of gas is generally considered to be unavoidable because only a small portion is economically recoverable for sale, and yet the quantity produced is relatively high. The reservoirs in the Middle East are estimated to produce 0.14 ton of associated gas per ton of crude. 

For example, the many deepwater fields located in the Gulf of Mexico are of Tertiary age and are comprised of complex sand bodies which were deposited in a deepwater turbidite sequence. The BP Prudhoe Bay sandstone reservoir in Alaska is of Triassic/ Cretaceous age and was deposited by a large shallow water fluvial-alluvial fan delta system. The Saudi Arabian Ghawar limestone reservoir is of Jurassic age and was deposited in a warm, shallow marine sea. Although these reservoirs were deposited in very different depositional environments they all contain producible accumulations of hydrocarbons, though the fraction of recoverable oil varies. In fact, these three fields are some of the largest in the world, containing over 12 billion barrels of oil each ... 

RF recovery factor the recoverable fraction of oil initially in place... 

For an offshore field, recoverable volumes of less than 0.5 trillion scf (Tcf) are typically uneconomic to develop. This would equate to an oil field with recoverable reserves of approximately 80 MMstb. 

For the above reasons, gas Is typically economic to develop only if it can be used locally, i.e. if a local demand exists. The exception to this is where a sufficient quantity of gas exists to provide the economy of scale to make transportation of gas or liquefied gas attractive. As a guide, approximately 10 Tcf of recoverable gas would be required to justify building a liquefied natural gas (LNG) plant. Globally there are few such plants, but an example would be the LNG plant in Malaysia which liquefies gas and transports it by refrigerated tanker to Japan. The investment capital required for an LNG plant Is very large typically in the order of 10 billion. 

So far, the economics of developing discovered fields has been discussed, and the sensitivity analysis introduced was concerned with variations in parameters such as reserves, capex, opex, oil price, and project timing. In these cases the risk of there being no hydrocarbon reserves was not mentioned, since it was assumed that a discovery had been made, and that there was at least some minimum amount of recoverable reserves (called proven reserves). This section will briefly consider how exploration prospects are economically evaluated. 

When considering exploration economics, the possibility of spending funds with no future returns must be taken into account. A typical world-wide success rate for rank exploration activity is one commercial discovery for every ten wells drilled. Hence a probabilistic estimation of the reserves resulting from exploration activity must take into account the main risks and uncertainties in the volume of hydrocarbons in place, the recoverable hydrocarbons, and importantly the risk of finding no hydrocarbons at all. 

A considerable percentage (40% - 85%) of hydrocarbons are typically not recovered through primary drive mechanisms, or by common supplementary recovery methods such as water flood and gas injection. This is particularly true of oil fields. Part of the oil that remains after primary development is recoverable through enhanced oil recovery (EOR) methods and can potentially slow down the decline period. Unfortunately the cost per barrel of most EOR methods is considerably higher than the cost of conventional recovery techniques, so the application of EOR is generally much more sensitive to oil price. 

Polymers owe much of their attractiveness to their ease of processing. In many important teclmiques, such as injection moulding, fibre spinning and film fonnation, polymers are processed in the melt, so that their flow behaviour is of paramount importance. Because of the viscoelastic properties of polymers, their flow behaviour is much more complex than that of Newtonian liquids for which the viscosity is the only essential parameter. In polymer melts, the recoverable shear compliance, which relates to the elastic forces, is used in addition to the viscosity in the description of flow [48]. 

It has a covalently bonded structure and is a colourless liquid at room temperature it is hydrolysed reversibly by water, all the germanium being recoverable by distilling the product with concentrated hydrochloric acid GeCl -P 2H2O — Ge02 -P 4HC1... 

The requiiements for scientific software development have continually increased. Besides the algorithmic core functionality, nowadays there is often a demand for a graphical user interface. In addition to the increasing importance of this visible component, which may still be seen as just an add-on, the software development itself has to fulfill stronger demands on software engineering requirements, such as maintainability and recoverability. 

Preferential adsorption of one of the components may be used for the same purpose. Charcoal or silica gel may be employed to adsorb one of the constituents of an azeotrope in preference to the other. If the adsorbate is readily recoverable, the process will have practical applications. 

The various elastic and viscoelastic phenomena we discuss in this chapter will be developed in stages. We begin with the simplest the case of a sample that displays a purely elastic response when deformed by simple elongation. On the basis of Hooke s law, we expect that the force of deformation—the stress—and the distortion that results-the strain-will be directly proportional, at least for small deformations. In addition, the energy spent to produce the deformation is recoverable The material snaps back when the force is released. We are interested in the molecular origin of this property for polymeric materials but, before we can get to that, we need to define the variables more quantitatively. 

The initiators which are used in addition polymerizations are sometimes called catalysts, although strictly speaking this is a misnomer. A true catalyst is recoverable at the end of the reaction, chemically unchanged. Tliis is not true of the initiator molecules in addition polymerizations. Monomer and polymer are the initial and final states of the polymerization process, and these govern the thermodynamics of the reaction the nature and concentration of the intermediates in the process, on the other hand, determine the rate. This makes initiator and catalyst synonyms for the same material The former term stresses the effect of the reagent on the intermediate, and the latter its effect on the rate. The term catalyst is particularly common in the language of ionic polymerizations, but this terminology should not obscure the importance of the initiation step in the overall polymerization mechanism. 

Table 2. World Estimated Recoverable Reserves of Coal in Billions of Metric Tons...

An assessment of world potash resources (108) is shown in Table 15. Of the 67 x 10 t of total estimated reserves and resources in Canada, nearly 5 X 10 t is recoverable by conventional mining methods and the remainder by solution mining. As of 1974, Canada had about half of the known world reserves and about 90% of known world resources of potassium. 

Other potential sources of potassium include insoluble minerals and ores, and the oceans, which contain 3.9 x 10 t/(km) of seawater (see Ocean RAW materials). The known recoverable potash reserves are sufficient for more than 1000 years at any foreseeable rate of consumption. 

The elongation of a stretched fiber is best described as a combination of instantaneous extension and a time-dependent extension or creep. This viscoelastic behavior is common to many textile fibers, including acetate. Conversely, recovery of viscoelastic fibers is typically described as a combination of immediate elastic recovery, delayed recovery, and permanent set or secondary creep. The permanent set is the residual extension that is not recoverable. These three components of recovery for acetate are given in Table 1 (4). The elastic recovery of acetate fibers alone and in blends has also been reported (5). In textile processing strains of more than 10% are avoided in order to produce a fabric of acceptable dimensional or shape stabiUty. 

Gaseous Effluents. Twenty percent of the carbon disulfide used in xanthation is converted into hydrogen sulfide (or equivalents) by the regeneration reactions. Ninety to 95% of this hydrogen sulfide is recoverable by scmbbers that yield sodium hydrogen sulfide for the tanning or pulp industries, or for conversion back to sulfur. Up to 60% of the carbon disulfide is recyclable by condensation from rich streams, but costly carbon-bed... 

Fluorspar Supply. Production costs of hydrogen fluoride are heavily dependent on raw materials, particularly fluorspar, and significant changes have occurred in this area. Identified world fluorspar resources amount to approximately 400 x 10 metric tons of fluorspar (40). Of these 400 X 10 t, however, only 243 x 10 t are considered reserves and an additional 93 x 10 t is considered reserve base, ie, recoverable at higher market... 

In another extractor (Automatic Machinery and Electronics Inc. (AMC)) the individual fmits are cut in half as they pass a stationary knife. The halves are oriented in a vertical plane, picked up by synthetic mbber cups, and positioned across plastic serrated reamers revolving in a synchronized carrier in a vertical plane. As the fmit halves progress around the extractor turntable, the rotating reamers exert increasing pressure and express the juice. The oil and pulp contents in the juice increase with greater reaming pressure. The recoverable oil is removed in a separate step prior to juice extraction. Needle-sharp spikes prick the peel of the whole fmit, releasing oil that is washed away with water and recovered from the oil—water emulsion. 

The unconventional reserves of natural gas occur principally in the form of recoverable methane from coal beds. As of 1991, reserves of coal bed methane totaled 8.6 EJ (8.2 x 10 Btu), principally in the states of Alabama, Colorado, and New Mexico (16). 

Several studies estimate the potential of available virgin and waste biomass as energy resources (Table 4) (10). In Table 4, the projected potential of the recoverable materials is about 25% of the theoretical maximum woody biomass is about 70% of the total recoverable potential. These estimates of biomass energy potential are based on existing, sustainable biomass production and do not iaclude new, dedicated biomass energy plantations that might be developed. 

Energy source Estimated recoverable Theoretical maximum... 

Coal, tar, and heavy oil fuel reserves are widely distributed throughout the world. In the Western hemisphere, Canada has large tar sand, bitumen (very heavy cmde oil), and coal deposits. The United States has very large reserves of coal and shale. Coal comprises ca 85% of the U.S. recoverable fossil energy reserves (6). Venezuela has an enormous bitumen deposit and Brazil has significant oil shale (qv) reserves. Coal is also found in Brazil, Colombia, Mexico, and Pern. Worldwide, the total resource base of these reserves is immense and may constitute >90% of the hydrocarbon resources in place (see... 

Tar sands have been reported on every continent except AustraHa and Antarctica. The best known deposits are the Athabasca of Canada, where almost 60,000 km in northeastern Alberta is underlain with an estimated 138 x 10 (870 x 10 bbl) of recoverable bitumen (157). The Alberta deposits... 

Dry gas gas where the water content has been reduced by a dehydration process or gas containing Htde or no hydrocarbons commercially recoverable as hquid product. 

Natural gas Hquids (NGL) a Hquid hydrocarbon mixture which is gaseous at reservoir temperatures and pressures, but recoverable by condensation or absorption (qv). 

Estimates of the amount of natural gas available are made within the context of definitions and are subject to revision as definitions change, as additional information becomes available, as resources are consumed, or as undedyiag assumptions are altered. These definitions iaclude proved reserves where the resource is expected to be recoverable and marketable usiag known technology and prices probable reserves where a resource has been identified but not completely characterized and possible or potential gas where estimates are based on the available geological iaformation, historical trends, and previous successes. There are variations ia these definitions throughout the world. 

In 1988, the U.S. Department of Energy completed a study iadicatiag that more than 1.42 x 10 of gas was recoverable at a wellhead price... 

The term pressure drop usually refers to the pressure loss that is not recoverable in the circuit, and it is lost energy that is dissipated into the fluid stream in the form of heat energy. The pressure drop in a flow circuit is associated with various forms of energy dissipation owing to friction, change in flow area, flow turning, and others ... 

Ammonium lactate [34302-65-3] ia coaceatrated aqueous solutioas has beea coaverted to ammonia and the ester by alcoholysis at temperatures ranging from 100—200°C usiag a variety of alcohols and water entrainers, such as toluene. Ester yields ranging from 50—80% were obtained. This method has also been suggested as a recovery and purification method from impure solutions of lactate (29). However, a considerable amount of the lactate is not converted to the recoverable ester and is lost as lactamide (6). 

Most uses of lead in chemical compounds other than in storage batteries are dissipative. The greater part of the lead used in other forms is recoverable. 

The importance of a coal deposit depends on the amount that is economically recoverable by conventional mining techniques. The world total recoverable reserves of lignitic coals were 3.28 x 10 metric tons at the end of 1990 (3), of which ca 47% was economically recoverable as of 1994 (Table 4). These estimates of reserves change as geological survey data improve and as the resources are developed. 

Country Proved in place Resources, 10 tce Proved recoverable reserves Added recoverable b reserves 1980 Production, 10 tee 1987 1989 1990 ... 

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