Physicochemical Characteristics and Distillation Curves of Gas Condensate from the Myldzhinskoye Field
Abstract Generated abstract
This study characterizes gas condensate from the Myldzhinskoye field in Tomsk Oblast as prospective feedstock for petroleum refining and petrochemical use. Five separator samples from different wells were examined for density, viscosity, molecular weight, vapor pressure, elemental composition, sulfur, paraffin, resin and asphaltene content, and fractional composition by standard distillation methods, with a more detailed true boiling point analysis for well 29. Most samples showed low density, low viscosity, low molecular weight, low pour points, negligible sulfur, and absence of paraffin and resinous asphaltic substances, while the sample from well 31 differed markedly because of its association with an oil rim. Distillation data indicated very high yields of light fractions, including largely sulfur-free low-boiling cuts, supporting the condensate’s value as a refining and petrochemical raw material.
Full Text
Physicochemical Characteristics and Distillation Curves of Gas Condensate from the Myldzhinskoye Field
S. I. Smolyaninov, N. M. Smolyaninova, A. E. Shuliveistrov
In connection with the forthcoming industrial development, in the next few years, of the largest fields—the Sovetskoye oil field and the Myldzhinskoye gas-condensate field, located in Tomsk Oblast—broad opportunities are opening up for the development of the petrochemical industry on the basis of processing associated petroleum gases and gas condensates.
To solve a number of questions connected with the design of a petrochemical complex, a detailed study is necessary of the properties and chemical composition of the feedstock—gas condensates and the broad fraction of associated petroleum gases.
The present work is devoted to the study of the physicochemical properties, fractional composition, and evaluation of the quality of the straight-run fractions of the Myldzhinskoye gas condensate.
The Myldzhinskoye gas field is located in the middle reaches of the Vasyugan River, approximately 480 km northwest of the city of Tomsk. The gas-bearing area of the field is 318 sq. km. Productive gas-bearing deposits are those of the Jurassic and Lower Cretaceous, among which four productive gas-bearing strata are distinguished: Yu-I+II, B-XVI—XX, B-X, and B-VIII.
The main pool is associated with stratum Yu-I + II and belongs to the massive type; the gas-bearing interval is 72 m. The field is gas-condensate and has an oil rim.
The condensate factor is 87–127 cm³/m³.
For the study, 5 samples of gas condensate were taken from the condensate outlet of the separator of wells Nos. 15, 16, 23, 29, and 31. The characteristics of the sampling points are given in Table 1.
Data on the general investigation (physicochemical properties) of the indicated samples are presented in Tables 2–6.
As can be seen from the tables, the condensate samples studied differ little in their physical and physicochemical properties, with the exception of sample 3, taken from well No. 31, which has an oil rim. The specific gravity of the condensates is low and ranges from 0.7153 to 0.7411; the molecular weight ranges from 104 to 114; the corresponding values for sample 3 are 0.7732 and 138.
The viscosity of all condensates at 20°C is insignificant (0.72–1.62 cSt); the pour point is low—48°C to −85°C without heat treatment, with the exception of sample 3 (well 31), whose pour point is co-
Table 1
Characteristics of the sampling points for gas-condensate samples from the Myldzhinskoye field
| No. | Suite | Formation | Well No. | Filter depth (perforation interval), m | Separator pressure, atm | Separation temperature, °C | Reservoir pressure, atm | Reservoir temperature, °C | Sampling date |
|---|---|---|---|---|---|---|---|---|---|
| 1 | II unit (Tyumen) III, IV Vasyugan | Yu—I+II | 15 | 2380—2373 | 55,77 | 25 | 256,2 | 81,0 | 9.II.67 |
| 2 | Vasyugan | Yu—I | 16 | 2401—2363 | 75,25 | 27 | 258,1 | 78,5 | 18.II.67 |
| 3 | “ | “ | 31 | 2381—2398 | 35,00 | 5 | 243,0 | 74,0 | 30.V.67. |
| 4 | “ | “ | 29 | 2378—2346 | 37,77 | 19 | 252,7 | 78,5 | 27.VI.67. |
| 5 | “ | “ | 23 | 2417—2408 | 69,45 | 11 | — | — | “ |
Table 2
Density of condensates at equal temperatures according to GOST 3900—47
| Sample No. corresponding to Table 1 | Density of condensate at the given temperature relative to the density of water at 4°C | Density of condensate at the given temperature relative to the density of water at 4°C | Density of condensate at the given temperature relative to the density of water at 4°C | Density of condensate at the given temperature relative to the density of water at 4°C |
|---|---|---|---|---|
| 20°C | 30°C | 40°C | 50°C | |
| 1 | 0,7258 | 0,7181 | 0,7099 | 0,7023 |
| 2 | 0,7354 | 0,7277 | 0,7202 | 0,7120 |
| 3 | 0,7723 | 0,7659 | 0,7585 | 0,7422 |
| 4 | 0,7411 | 0,7323 | 0,7240 | 0,7146 |
| 5 | 0,7153 | 0,7069 | 0,6991 | 0,6903 |
Table 3
Kinematic viscosity of condensates at different temperatures according to GOST 33—53, cSt
| Sample No. corresponding to Table 1 | −20°C | −10°C | 0°C | +10°C | +20°C |
|---|---|---|---|---|---|
| 1 | — | 1,17 | 1,06 | 0,98 | 0.80 |
| 2 | 1,58 | 1,29 | 1,13 | 1,03 | 0,90 |
| 3 | 6,66 | 4,72 | 2,42 | 1,94 | 1,62 |
| 4 | 1,40 | 1,19 | 1,08 | 1,00 | 0,84 |
| 5 | 1,2 | 1,02 | 0,91 | 0,79 | 0,72 |
Table 4
Physicochemical characteristics of gas condensates
| Well No. | $d^{20}_{4}$ | Mol. wt. | Viscosity, cSt at 20°C | Flash point, °C | Freezing point, °C | Saturated vapor pressure, mm Hg at 38°C | Saturated vapor pressure, mm Hg at 50°C | Paraffin content, % | Paraffin temperature, °C | Content of naphthenic acids, % | Content of phenols, % |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 15 | 0,7258 | 111 | 0,80 | −84 | −85 | 552 | 575 | absent | — | 0,096 | 0,024 |
| 16 | 0,7354 | 106 | 0,90 | −70 | −65 | 453 | 465 | absent | — | 0,013 | 0,02 |
| 31 | 0,7723 | 138 | 1,62 | −65 | −10 | 269 | 447 | 0,5 | 47 | 0,008 | 0,029 |
| 29 | 0,7411 | 114 | 0,84 | −60 | −48 | 247 | 427 | absent | — | 0,010 | 0,008 |
| 23 | 0,7153 | 104 | 0,72 | −55 | −82 | 249 | 417 | absent | — | 0,004 | 0,007 |
Continuation of Table 4
| Well No. | Sulfuric-acid resins content | Silica-gel resins content | Asphaltenes content | Coking value, % | Ash content, % | Acid number, mg KOH per 1 g of oil | Vanadium content, % |
|---|---|---|---|---|---|---|---|
| 15 | absent | absent | absent | 0 | 0,013 | 0,011 | absent |
| 16 | absent | absent | absent | 0 | 0,008 | 0,012 | absent |
| 31 | 4,0 | 3,13 | 0,03 | 0,03 | 0,800 | 0,015 | traces |
| 29 | traces | absent | absent | 0 | 0,070 | 0,009 | 0,0002 |
| 23 | traces | absent | absent | 0 | 0,010 | 0,021 | 0,0002 |
Table 5
Elemental composition of gas condensates
| Well No. | C content, % | H content, % | S content, % | N content, % |
|---|---|---|---|---|
| 15 | 83,54 | 16,25 | 0,010 | 0,03 |
| 16 | 84,12 | 15,76 | 0,010 | 0,09 |
| 31 | 84,71 | 15,05 | 0,017 | 0,07 |
| 29 | 84,53 | 15,40 | 0,010 | 0,07 |
| 23 | 84,44 | 15,50 | 0,010 | 0,05 |
Note: The carbon content was determined by the micromethod, nitrogen by the Kjeldahl method, and sulfur by the lamp method.
Table 6
Distillation of gas condensates according to GOST 2177–59
| Well No. | B.p., 0°C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C | Distilled (in %) up to temperature, °C |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 80 | 100 | 120 | 140 | 150 | 160 | 180 | 200 | 220 | 240 | 250 | ||
| 15 | 37.0 | 19.0 | 35.5 | 51.5 | 65.0 | 70.5 | 75.5 | 83.0 | 89.5 | 93.5 | 96.5 | 98.0 |
| 16 | 48.5 | 10.0 | 28.5 | 46.0 | 60.0 | 67.0 | 72.0 | 80.0 | 87.0 | 92.0 | 96.0 | 97.0 |
| 31 | 43.0 | 14.9 | 23.2 | 32.9 | 41.8 | 45.6 | 48.6 | 51.6 | 58.3 | 61.2 | 68.0 | — |
| 29 | 49.0 | 15.0 | 30.0 | 46.4 | 59.9 | 65.6 | 69.9 | 78.0 | 82.6 | 87.0 | 91.9 | — |
| 23 | 43.0 | 24.7 | 42.7 | 58.2 | 70.9 | 76.5 | 81.2 | 87.9 | 92.0 | 96.6 | — | — |
is −10°C, which is due to the presence in this condensate of a considerable amount of paraffin—0.5%; in the remaining samples paraffin is absent.
The condensates studied contain an insignificant amount of sulfur (not more than 0.01%) and are distinguished by the absence of resinous and asphaltic substances. Sample 3 is an exception; its sulfur content is 0.017%, and it contains 3.13% silica-gel resins, 4% sulfuric-acid resins, and 0.3% asphaltenes.
The acid number of the samples is small, substantially lower than that for the oils of Western Siberia.
Traces of water were found in samples Nos. 3 and 4; mechanical impurities are also present in these same condensates.
The flash point of all gas condensates is low—from −85°C to −50°C.
The data on fractional composition (distillation according to GOST 2177–59, Table 6) show that all gas condensates give very high yields of light fractions: 23–43% boils up to 100°C; 46–76%—up to 150°C; 58–92%—up to 200°C; up to 240–250°C, 88–98% of the condensate is distilled, with the exception of that from well No. 31, for which the degree of distillation at 240°C is 68%.
A sample of gas condensate from well No. 29 was distilled into three-percent fractions on an ARN-2 apparatus (GOST 11011-64) in order to construct distillation curves.
The TBP curve, representing the dependence of the yields of fractions on their boiling temperature, the quality curves of the fractions obtained, and also the potential yields of the fractions are presented in the figure and in Table 7.
The data show that the condensate studied is characterized by high yields of light fractions (64.3%—up to 150°C; 81.5—up to 200°C; 95.8—up to 300°C) and a low final boiling point (320°C), with a yield of residue above 320°C of less than 3%.
The distillation curves show that, with increasing boiling temperature of the fractions, their specific gravity at first increases rather sharply (up to a boiling temperature of 80°C), and then rises smoothly up to the end point of the fractions. Correspondingly, the refractive index and molecular weight of the fractions increase.
For the last three fractions (Table 7), a considerable increase in viscosity, molecular weight, and sulfur content is observed. The low-boiling fractions (up to 150°C) contain practically no sulfur.
Fig. 1. Distillation curves of Myldzhinskoye gas condensate, well 29
Visible labels in the figure:
- \(t,^\circ C\); mol. wt.; \(\rho_4^{20}\)
- \(\nu\), cSt
- Yield based on condensate, wt. %
- Condensate, wt. %
- Sulfur content, %
- Solidification temperature, \(^{\circ}C\)
Curve labels:
- \(\rho_4^{20}\)
- TBP
- Mol. wt.
- Sulfur
- \(t_{\text{solid.}}\)
- \(\nu_{20}\)
- \(\nu_{50}\)
Table 7
Potential content of fractions in gas condensate from well No. 29, wt.% (by ITK)
| No. | Temperature limits for fraction selection, °C | Fraction yield, wt.% on condensate: individual | Fraction yield, wt.% on condensate: cumulative | No. | Temperature limits for fraction selection, °C | Fraction yield, wt.% on condensate: individual | Fraction yield, wt.% on condensate: cumulative |
|---|---|---|---|---|---|---|---|
| 1 | Gas up to 28°C | 18 | 200—210 | 2,5 | 84,0 | ||
| 2 | Propane | 0,3 | 0,3 | 19 | 210—220 | 2,2 | 86,2 |
| Isobutane | 1,1 | 1,4 | 20 | 220—230 | 1,8 | 88,0 | |
| n-Butane | 2,8 | 4,2 | 21 | 230—240 | 1,5 | 89,5 | |
| 2 | 28—60 | 9,0 | 13,2 | 22 | 240—250 | 1,5 | 91,0 |
| 3 | 60—70 | 7,0 | 20,2 | 23 | 250—260 | 1,2 | 92,2 |
| 4 | 70—80 | 3,7 | 23,9 | 24 | 260—270 | 1,0 | 93,2 |
| 5 | 80—85 | 1,9 | 25,8 | 25 | 270—280 | 1,0 | 94,2 |
| 6 | 85—90 | 3,8 | 29,6 | 26 | 280—290 | 0,8 | 95,0 |
| 7 | 90—100 | 10,1 | 39,7 | 27 | 290—300 | 0,8 | 95,8 |
| 8 | 100—110 | 3,5 | 43,2 | 28 | 300—310 | 0,7 | 96,5 |
| 9 | 110—120 | 6,1 | 49,3 | 29 | 310—320 | 0,5 | 97,0 |
| 10 | 120—130 | 5,1 | 54,4 | 30 | Residue | 3,0 | 100,0 |
| 11 | 130—140 | 5,7 | 60,1 | ||||
| 12 | 140—150 | 4,2 | 64,3 | ||||
| 13 | 150—160 | 4,3 | 68,6 | ||||
| 14 | 160—170 | 3,7 | 72,3 | ||||
| 15 | 170—180 | 3,6 | 75,9 | ||||
| 16 | 180—190 | 2,8 | 78,7 | ||||
| 17 | 190—200 | 2,8 | 81,5 |
Conclusions
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A general (physicochemical) investigation was carried out and distillation curves were obtained for the gas condensate of the Myldzhinskoye field.
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It was shown that samples of gas condensate from wells Nos. 15, 16, 23, and 29 have low density (0.7153—0.7411), low molecular weight (104—114), low viscosity, low pour points (−48÷85°C), and are distinguished by insignificant sulfur content (not more than 0.01%), and by the absence of paraffin and resin-asphaltene substances. The sample from well No. 31 is an exception in all its properties, since the well has an oil rim.
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On the basis of the distillation curves, a conclusion was drawn regarding an exceptionally high yield of light fractions (up to 150°—60.1%, up to 200°—77.3%). Characteristically, these fractions contain practically no sulfur.
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The investigation performed makes it possible to regard the Myldzhinskoye gas condensate as a most valuable raw material for petroleum refining and especially for petrochemistry.