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In the oil and gas industry, equipment and metal structures are used under complex conditions of mechanical immersion and attack of corrosive media, which causes frequent failures and creates emergency situations, especially in presence of mixtures containing hydrogen sulfide. Lately, oil and gas deposits containing hydrogen sulfide are being developed in Western Siberia. The major causes of loss of performance of steel piping systems in presence of hydrogen sulfide are general corrosion and corrosion cracking caused by hydrogen sulfide. Failure due to hydrogen embrittlement and corrosion cracking induced by hydrogen sulfide generally occurs suddenly with serious consequences, e.g., disruption of the technological process, production loss, forced unscheduled repair, development of emergency situations, environmental pollution, etc.The intensity of the corrosion process depends a great deal on the presence in the media of corrosive agents, especially hydrogen sulfide and oxygen. Stratal water extracted along with oil contains dissolved impurities like hydrogen sulfide, carbon dioxide, gaseous hydrocarbons, and atmospheric oxygen. Carbon dioxide, hydrogen sulfide, and oxygen produce the most active stimulating effect on corrosion of metals.We conducted experimental and theoretical studies of the effect of H.,S and O., on the mechanism of carbon dioxide corrosion that occurs due to presence of CO., in the corrosive media.Carbon A schematic drawing of the experimental arrangement is shown in Fig. 1. In addition to the autoclave, a dissolution loop (Fig. 2) was also used to study the effect of 0 2 on CO 2 corrosion of samples of pipes serially produced from steels 10 and 20. The dimensions of the test samples are 40 x 10 x 5 mm for the autoclaving arrangement; O 59 x 2 mm and length 70 mm for the arrangement with a dissolution loop. The experiments were performed in closed systems with no contact with air.Corrosion studies were carried out in a wide mixture temperature range (30-250~ and at a constant CO 2 pressure (1.5 MPa). The partial pressure of hydrogen sulfide PH2S and oxygen PO2 varied discretely within 0--1.5 MPa. Sample preparation, control of solution temperature and CO.,, H.,S, and O 2 pressure, and measurements of the required parameters were carried out by standard procedures. The corrosion products were studied by X-ray diffraction and local X-ray spectral microanalysis.The effect of H2S and 02 content on the corrosion rate in a wide temperature variation range is shown in Fig. 3 and the effect of mutual effect of H2S and temperature on the corrosion resistance of carbon steel, in Fig. 4.It is evident from Fig. 3a that the corrosion rate v c rises with rise of the partial pressure of H-,S in the mixture in the temperature range 20-80~However, only at PH2S = 0.5 MPa does the corrosion rate exceed by 1.5-2 times the rates typical for media containing only CO 2. Further rise of PH2S from 0.5 to 1.5 MPa leads to slowing down of corrosion causing an opposite effect, especially in the temperature range I0(O250...

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We consider an arbitrary series of the form Vn~n, k~ ~ N, ~ q-k,~ < %n+a q-kn+a, P~'n (z) a polynomial of degree kn.In particular, if Vn~a qk~< %~+i, then series (i) is a grouped power series, which when the parentheses are expanded corresponds to a power series ~:=o CrnZm"It is well known [i, 2] that sometimes a power series may be so grouped that the resulting power series converges compactly uniformly in some domain outside the disk of convergence of the original powe r series.This phenomenon is called superconvergence of a power series.We solve the following problem.We must find necessary and sufficient conditions on a set E such that compact uniform or pointwise convergence of an arbitrary series (i) on E implies that (i) converges compactly uniformly in C ~, and in particular, such that series (i) is an entire function.It is easy to construct a grouped power series converging compactly uniformly in Cx\ {z ~-x, Vx • 0}, converging compactly uniformly on {z----x, Vx > 0}, and not converging uniformly on any disk {] z I~ R}; in constructing such a series it is essential to use the equall~m~7~Ikn = oo. Therefore, in what follows we assume that series (i) satisfies the ity

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