Available online at www.sciencedirect.com ScienceDirect Procedia Engineering 113 (2015 ) 254 258 International Conference on Oil and Gas Engineering, OGE-2015 Immediate analyses and calculation of saturated steam pressure of gas condensates for transportation conditions Zemenkov Yu.D. a, Shalay V.V. b, Zemenkova M.Yu. a * a Tyumen State Oil and Gas University, 38, Volodarskogo St., Tyumen 625000, Russian Federation b Omsk State Technical University, 11, Mira Pr., Omsk 644050, Russian Federation Abstract A set of studies of hydrocarbons thermo-physical properties for different operating conditions is conducted. As an example, the improved methodology of calculating saturated steam pressure of gas condensates is suggested. On the basis of the experimental research and implementation of multifactorial experiment theory and regression-correlation analysis, calculated dependencies for finding saturated steam pressure of evaporating oil and stabilized condensate are found. The equations for recalculation saturated steam pressure of condensates for required temperature at different evaporation losses rates are obtained. 2015 Published The Authors. by Elsevier Published Ltd. by This Elsevier is an open Ltd. access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Omsk State Technical University. Peer-review under responsibility of the Omsk State Technical University Keywords: gas condensate; hydrocarbon; thermo-physical properties; operating conditions; immediate monitoring; pipeline transport 1. Introduction According to Minpromenergo forecasts [1], gas condensate production rates will increase to 26-32 mn. t./year by 2020 and to 31-37 mn.t./year by 2025. The planned increase of condensate production rates is caused by brining into development new deep fields. Nowadays, potentially productive regions are new fields of Nadym-Pur-Tazovskiy region (up to 26-32 mn.t./year by 2020), Yamal Peninsula, Barents Sea shelf, Eastern Siberia and the Far East (to 5.3-5.5 mn.t./year by 2030). Peculiarities of implementing modern technologies of major pipeline transport and gas condensate storage depend on the complex of operational properties of the transported product and the methods of their estimation [2- * Corresponding author. Tel.: +7-345-220-1931. E-mail address: zemenkov@tsogu.ru 1877-7058 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Omsk State Technical University doi:10.1016/j.proeng.2015.07.330
Yu. D. Zemenkov et al. / Procedia Engineering 113 ( 2015 ) 254 258 255 5]. The authors have developed the technology, providing to conduct immediate estimation of gas condensate properties while operating conditions changing. By now, a lot of scientific research conducted by leading scientific research institutes and organizations (Gasprom VNIIGAS, Ufa State Petroleum Technological University USPTU, IPTER, Tyumen State Oil and Gas University - TSOGU, Gubkin Russian State Oil and Gas University and others) concern the investigation of saturated steam pressure of liquid hydrocarbons. A number of experimental ways and analytical methods of finding р S of different oil products and oils regarding the storage conditions are developed. High scientific level of the conducted studies let us think, that experimental methods are, unfortunately, imperfect, time- and labour consuming, and have low experimental reproducibility. As it can be seen from the review of publications concerning finding saturated steam pressure р S of individual hydrocarbons, nomographs and tables are drawn up, besides, analytical calculation methods are rather acceptable and justified, because of thеir fair accuracy. 2. Study subject The study subject is the processes of changing thermo-physical properties of gas condensates. The paper is aimed to finding saturated steam pressure for transportation conditions. 3. Methods As a result of investigating gas stabilized and de-ethanized condensates (SC and DC), conducted by some scientists [6-11], it was found out, that for calculating pressure р S it is possible to use the correlation like the following: n рs ks x i 1 i 1 Ai Bi( Ci Ti) 10, (1) where р S is saturated steam pressure at temperature t=38 0 С; x i is hydrocarbon concentration in condensate; k S is coefficient, characterizing formula deviation from the additivity law; Т is temperature, К; Ai, Bi, Ci are Antoine coefficients, given in Table.1. For the investigated Urengoy stabilized condensates k S = 1.3, for de-ethanized condensates k S = 1.15. The disadvantages of the formula include the necessity of predefining hydrocarbon composition of liquid, though; it is not a problem already. Moreover, it is usually rather sufficient to have a priori information concerning only content of hydrocarbons by С 7. Table 1. Antoine coefficients values Hydrocarbons Coefficients Temperature А В С from Т to Т С 2Н 6 9.5784 1030.628 39.083 244 305 С 3Н 8 9.4337 1048.900 5.610 232 301 n-с 4Н 8 9.1181 1030.340-22.190 272 348 i-с 4Н 8 9.3117 1120.165-1.297 252 407 n-с 5Н 10 8.9995 1075.820-39.791 244 393 i-с 5Н 10 8.9345 1020.010-40.053 244 737 С 6Н 10 9.0026 1171.530-48.784 214 423
256 Yu. D. Zemenkov et al. / Procedia Engineering 113 ( 2015 ) 254 258 The investigation results of p S of stabilized and de-ethanized condensates, according to the experimental Raid method, given in fig. 1, demonstrate the significant dispersion of data, especially for de-ethanized condensate, which is easily explained by different composition of light hydrocarbons condensate as well as by the problems, concerning relevant sampling followed by storage. At the specified concentration of light hydrocarbons in condensates, experimental p S values are satisfactory approximated by the following correlation: n р k р x, (2) S S Si i i 1 where р Si, x i are partial pressure and concentration of the i-th component. Considerable deviation of the experimental data from the p S average value for mixture of DС and WLHF (wide light-hydrocarbon fraction) proves the dominating influence of light components on the investigated parameter and conditionality of its usage in calculations. Calculated coefficient of pair correlation for the investigated correlation p S = (t) is equal to 0.52 and does not provide the approximation of the obtained experimental data with permissible inaccuracy. Based on the regression analysis of the data, obtained for the conditions of de-ethanized condensate head fractions evaporation, estimated recalculation can be made according the formula, like : ln р Sσ = ln р S0-2,24( σ/ф ), (3) where р S0 and р Sσ is saturated steam pressure of the initial product and at evaporation losses value σ, correspondently, Pa. - experimental values for the mixture DK + NGL Fig.1. Temperature influence on the condensate saturated stream pressure value
Yu. D. Zemenkov et al. / Procedia Engineering 113 ( 2015 ) 254 258 257 For stabilized condensate, this correlation has the same form, although the influence of light ends losses is minor: ln р Sσ = ln р S0-0,83 ( σ/ф ) (4) For expert calculating of condensate emission in condition of obtaining adequate a priori information about р S changing, among others, the following formulae can be used: for DC σ = 1,205Ф ln( р S0/ р Sσ); for SCσ = 0,446Ф ln( р S0/ р Sσ ). (5) When finding oil saturated steam pressure we should also a priori know the correlation р S = ƒ(σ), which can define free coefficient in formula (3) for every oil. Recalculation of condensate pressure р S for required temperature can be made on the basis of the following equation: lоg р S = 8.59 981 T -1, [Pa] and lоg р S = 2.55 978 T -1, [MPa] (6) Correlation analysis has shown, that for all the dependencies obtained above (1) (6), calculated values of Fisher s ratio test considerably exceed those given in the table (with confidence coefficient Pα = 0.95), i.e. the proposed mathematical models adequately describes the investigated phase transitions. 4. Results and discussion On the basis of the conducted experimental studies and the theory of maltifactorial experiments and regressioncorrelation analysis implementation, calculated dependencies for finding saturated steam pressure of evaporating oil and stabilized condensate are obtained. It is found out and experimentally proved, that at specified hydrocarbon concentration in stabilized and deethanized condensates, actual pressure values p S are satisfactory approximated by analytical correlation with using Antoin coefficients and coefficients, characterizing mathematical model deviation from the additivity law. Equations fro recalculation condensate pressure р S for required temperature at different evaporation losses rates are obtained. A complex of developed patterns and calculated analytical expressions let us estimate the degree of possible changes in liquid hydrocarbon mixtures properties with inaccuracy, commensurable with the accuracy of direct experimental findings. High values of multiple correlation coefficients Rα = (0.85 0.98) should also be noted. The mathematical models, developed for practical calculations, adequately describe the experiments by Fisher s ratio test with confidence coefficient Pα = 0.95 0.97. References [1] General scheme of the gas industry in Russia for the period up to 2030, developed as part of a package of measures for the development of pipeline transport of hydrocarbons in the Russian Federation (approved. Minpromenergo 10.09.2004, Prep. оn behalf of the President of the Russian Federation of 25.02.2004 Pr-313 ) URL: http://www.energyland.info/library-show-2928 25.03.2015. [2] V. Kurushina, Y. Zemenkov, Innovative cyclical development of the Russian pipeline system. WIT Transactions on Ecology and the Environment 190, 2 (2014), pp. 881. [3] Y.N. Antip'ev, A.P. Nevolin, Yu.D. Zemenkov, Operation of intermediate pumping stations on transport of gas saturated oils, NEFT. KHOZ. 10 (1981) 46 p. [4] V.N Blinov, V.V Kositsin, V.I Ruban, V.V Shalay, The research of ammonia electrothermal microengines for small spacecrafts, Dynamics of Systems, Mechanisms and Machines, Dynamics 2014 - Proceedings 7005640 (2014).
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