Volumetric estimation

The volumetries of a field, along with the anticipated recovery factors, control the reserves in the field those hydrocarbons which will be produced in the future. The value of an oil or gas company lies predominantly in its hydrocarbon reserves which are used by shareholders and investors as one indication of the strength of the company, both at present and in the future. A reliable estimate of the reserves of a company is therefore important to the current value as well as the longer term prospects of an oil or gas company. 

Volumetric estimates are required at all stages of the field life cycle. In many instances a first estimate of how big an accumulation could be is requested. If only a back of the envelope estimate is needed or if the data available is very sparse a quick look estimation can be made using field wide averages. 

Ultimate recovery (UR) and reserves are linked to the volumes initially in place by the recovery factor, or fraction of the in place volume which will be produced. Before production starts reserves and ultimate recovery are the same. 

The isochore thickness of the total interval ( gross thickness ) egardless of lithology. 

Net Oil Sand (NOS) = the length of the net sand column that is oil bearing. 

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The other parameters used in the calculation of STOMP and GIIP have been discussed in Section 5.4 (Data Interpretation). The formation volume factors (B and Bg) were introduced in Section 5.2 (Reservoir Fluids). We can therefore proceed to the quick and easy deterministic method most frequently used to obtain a volumetric estimate. It can be done on paper or by using available software. The latter is only reliable if the software is constrained by the geological reservoir model. 

As will be shown in the next section, the methods discussed so far do not take account of the uncertainties and lateral variations in reservoir parameters. Hence the accuracy of the results is not adequate for decision making. The next section introduces a more comprehensive approach to volumetric estimation. 

Addition of silver nitrate to a solution of a chloride in dilute nitric acid gives a white precipitate of silver chloride, AgCl, soluble in ammonia solution. This test may be used for gravimetric or volumetric estimation of chloride the silver chloride can be filtered off, dried and weighed, or the chloride titrated with standard silver nitrate using potassium chromate(VI) or fluorescein as indicator. 

Fig. 4.4. Histograms of middle to late Cenozoic K-Ar dates with relative volumetric estimates of igneous rocks (Kennett et al., 1977).

Oil density(0.844 g/ml) was used to convert the volumetric estimate to gravimetric estimate. 

Volumetric Estimation.—Tellurium may be determined by oxidation from the tellurous to the telluric condition, using an excess of potassium dichromatc or permanganate and subsequently titrating the excess of oxidising agent with a standard solution of a suitable reducing agent.2 In order to obtain accurate results with the potassium dichromate titration, certain very definite steps in the procedure are essential, and it is necessary to control the course of the reaction, since hydrochloric and telluric acids interact with production of chlorine. 

In volumetric analysis, hydrophilic colloids alter the end point, e.g., in a titration of HC1 and NaOH, the amount of deviation in the end point is increased with increasing amounts of colloids. In the volumetric estimation of silver by Mohr s method, the phenomenon of adsorption comes into being. 

For the volumetric estimation of manganese by this reaction, see Sehlossberg, Zeit. anal. Chem., 1902, 41, 735. 

The complexing of calcium by EDTA and also by polyphosphates is of importance, not only for removal of calcium ions from water, but also for the volumetric estimation of calcium. In Ca[CaEDTA]-7H20 the coordination of the Ca ion is 8. Calcium ions are involved in many natural processes such as bones (Ca5(P04)30H), blood clotting, transmission of nerve impulses, and so on as well as in selective binding to various proteins with a range of functions. 

The dark colour of the nitric oxide derivative may be utilised in the volumetric estimation of nitric acid, as its appearance depends upon the presence of excess ferrous sulphate in solution. Further addition of nitric acid oxidises this remaining ferrous sulphate and, when oxidation is complete, the colour disappears. The discharge of... 

Hydrobromic acid, ferric bromide, and the chlorides and bromides of zinc and aluminium all react in an analogous manner.1 With potassium iodide in the presence of a zinc salt the reaction is quantitative, and may be used in the volumetric estimation of ferricyanides —2... 

Denitrification rates in the other two main ODZs, the ETNP and ETSP appear to be about 25 Tg a each Codispoti et al. (2002). In the ETNP denitrification was estimated by the geostrophic flux of nitrate deficit out of the ODZ area, with nitrate deficit determined from nutrient-density relationships (Codispoti, 1973 Codispoti and Richards, 1976). Volumetric estimates of denitrification rate based on ETS activity are in concert with this rate (Codispoti and Richards, 1973 Devol, 1975). The ETSP the denitrification rate is based on measurements of ETS activity (Codispoti and Packard, 1980). As with the Arabian Sea these estimates are again for canonical denitrification. It is likely that processes identified in the Arabian Sea are also occurring in the ETNP and ETSP. Thus, the rate of 25 Tg a might be raised to 50 Tg ar. Given a denitrification rate between 30 and 50 Tg a for each of the major ODZ s, global water-column denitrification would appear to between 90 and 150 Tg a. ... 

Dumas method. Condensation of nitrogenous organic compounds with copper oxide in a stream of carbon dioxide, collection of the elementary nitrogen over aqueous potassium hydroxide, and volumetric estimation in an azotometer. Any nitrogen oxides formed are reduced by passage over a red-hot copper spiral. 

Platinum tetrachloride or platinic chloride, PtCL, may be prepared by heating chlorplatinic acid in a stream of HC1 or chlorine. It has a reddish brown color, and on exposure to air it absorbs moisture, becoming bright yellow in color. It dissolves fairly well in warm water, the solution being strongly acidic, as is shown by the fact tli.it it liberates turban dioxide from the carbonates. The solution is reduced by iodine, thus PtCl, + I2 — PtCl2 + 2 IC1, a reaction used for the volumetric estimation of platinum. 

The complexing of calcium by EDTA and also by polyphosphates is of some importance, not only for removal of calcium ions from water, but also for the volumetric estimation of calcium. 

Volumetric estimates of groundwater discharges (Martel et al. 1989 Stute et al. 

H. Causse, in Comptes Reudue, 1897, describes a new method for the volumetric estimation of antimony, which is based upon the fact that antimonious acid, free or combined, reduces iodic acid, f/ith the formation of antimonic acid and the liberation of a proportionate amount of iodine, the reaction being thns -.—... 

SO that the ester which is always present even in freshly-prepared alcoholic solutions of mustard oil does not decompose quantitatively with ammonia- cal silver solution, with formation of sulphide of silver, but is partly pre- cipitated as a silver salt of the above-mentioned ester. Whilst this admixture, owing to its molecular weight 252, which differs but little from that of silver sulphide 248, cannot cause an appreciable error in the gravimetric determination, it cans s a considerable difference in the volumetric estimation, because in the formation of this ester salt only 1 atom of silver corresponds to 1 molecule of mustard oil, whereas for the conversion into silver sulphide, 2 atoms of silver are required, so that the titration results are obviously too low. 

The previous examples show an important limitation for the potential adsorption theory. This limitation is that in order to achieve reasonable quantitative agreement with experiments, the correlation must be based on quite precise models for adsorption potentials and volumetric properties of the adsorbed mixture. An equation of state chosen for correlation must produce good volumetric estimates at high pressures, even if adsorption at low and moderate pressures is considered. 

Gasometric determination is less accurate than volumetric estimation but the former does definitely measure the available oxygen, whereas the latter may include impurities which react with the reagents used. The method of the B.P. 1914 was to shake 2 ml of the solution in a brine-charged nitrometer with 4 ml of a solution of copper ammonium sulphate, and the oxygen liberated catalytically was measured at 15-5" and normal pressure. 1 ml oxygen -- 0-00304 g H2O2. 

Strebinger and von Zombery employ the indicator internally, but in this case only titration of the barium with acid is possible. Hence in the volumetric estimation of sulphates an excess of standardised barium chloride is added and the excess is titrated by standard sulphate until the red barium salt is converted to yellow sodium salt at the end-point. 

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