Wells water composition

The compositions of waters that give rise to pitting have been the subject of numerous investigations, and studies by Obrecht e/ al. of the pitting of copper tubes in the USA have shown that it is invariably a cold water phenomenon that occurs with hard well waters. These waters contained over 5p.p.m. of dissolved CO2, 10-40 p.p.m. being typical, a pH in the range... 

Corrosion problems that arise are frequently discussed under the headings (a) sea-water, and (b) fresh waters, but there is, in fact, no sharp dividing line, since some harbour, estuarine and brackish well waters are mixtures of sea-water and fresh water and are often variable in composition. In the past, corrosion problems were serious, particularly in sea-water service, but resistant alloys have been developed and although trouble still occasionally arises this is more frequently due to poor design or operation rather than to lack of materials suitable for the application. 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

Petroleum and chemical engineers perform oil reservoir simulation to optimize the production of oil and gas. Black-oil, compositional or thermal oil reservoir models are described by sets of differential equations. The measurements consist of the pressure at the wells, water-oil ratios, gas-oil ratios etc. The objective is to estimate through history matching of the reservoir unknown reservoir properties such as porosity and permeability. 

Observations of the arrival of the C02 acid front at different wells clearly demonstrates that there is a great deal of heterogeneity in the reservoir. Furthermore, the arrival of waters which are undersaturated with respect to calcite suggests that single producing wells are recovering waters with widely different C02 contents. These observations have important implications for the interpretation of produced water compositions in complex reservoirs it must be done in conjunction with detailed reservoir flow models. 

Although an unequivocal quantitative mass balance could not be obtained, a plausible reaction sequence was deduced that accounts reasonably well for the residual chemical water composition. The amount of CaC03 that had to be dissolved to establish the residual water composition is about what can be accounted for by wind-blown calcite dust. The neutralization of the acidic precipitation by NH3 was, subsequent to its deposition, largely annulled by the H+ ions produced by nitrification and NHJ assimilation. 

When HLD = 0 three-phase behavior takes place because of the exact compensation of the effect of the different formulation variables expressed in Eqs. 4 and 5. hi practice, an unidimensional formulation scan is carried out to detect the occurrence of three-phase behavior. In such a scan, only one of the formulation variables (appearing in Eqs. 4 and 5) is changed, while all the others are held constant, as well as composition variables, i.e., surfactant concentration and water/oil ratio (WOR). 

Table 3. Major component composition of separated well waters from wet-steam wells and one sample from a hot water well ... 

The Mowing table, embracing the composition of some principal river and well waters, will prove interesting to the reader —. ... 

Holland (15) notes that the major part of the oceanic sediments may well be detrital. Garrels (5) has recently estimated that to account for the stabilization of sea water composition since the birth of the ocean, only about 7% of the sediments need to have reacted. 

Figure 43. Wideband FIR spectra calculated for the composite hat-curved-cosine-squared potential model (solid lines) dashed-and-dotted lines mark the contribution due to dipoles vibrating in the shallow CS well. Water H20 (a, c, e) and water D20 (b, d, f) at 22.2°C. Absorption coefficient (a-d) and dielectric loss (e, f) in Figs, a, b, e, f, dashed lines refer to the experiment [17, 51, 54]. In Figs, c, d dahsed lines mark the contribution to absorption due to dipoles reorienting in a deep hat-curved well.

An important conclusion of Sansone s studies was that thermodynamic disequilibrium, among dissolved species like CH4 and SC>42% implies microzonation of chemical reactions. This microzonation resulting in slight differences in reef interstitial water compositions, as well as temporal changes in water composition, induced by a variety of factors including seasonal variables, may account for the coexistence of different cement mineralogies in reef structures, as well as the zonation... 

Several water compositions are plotted on the stability diagrams in Figure 8.2. It can be seen that at shallow Earth surface pressures and temperatures, seawater plots in the stability field of dolomite whereas solutions of average river water composition and most shallow groundwaters plot in the field of calcite. With burial of carbonate sediments and elevated P and T, the dolomite field shrinks, but subsurface fluid compositions evolve toward a composition in equilibrium with dolomite. This conclusion is probably one of the most important arguments for the formation of dolomite during deep burial diagenesis (see also Hardie, 1987). Thermodynamic considerations favor this reaction path, as well as the fact that... 

Historical data of water composition in the region in general and in selected study wells in particular, in order to assess the base data pertaining to prepollution times. 

Table 16.3 Water Composition (mg/1) in Ash Pit and Monitoring Wells Near Portage...

Whether corrosive constituents are removed at the oil or gas well or just before they enter cross country lines is a matter of economics (i.e., cost of the line, ease of replacement, etc). When dehydration or gas purification is not performed at the wellhead, severe corrosion may occur. Laboratory data on the corrosion rate vs partial pressure of carbon dioxide (Figure 4.5 in Chapter Four) often do not give a good estimate of the corrosiveness of the fluid because variables other than carbon dioxide partial pressure also affect metal loss. When the gas contains less than 15% oil (corrosion is low when there is more than 15% oil in the gas) and velocities are high, the chemical composition of the water, rather than the carbon dioxide partial pressure, appears to control the corrosion. The pH of the system calculated from the water composition has been used to determine whether or not a well is corrosive. To date, however, there is not a one-to-one correlation between the in situ pH and corrosiveness. 

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