On the Physical Properties of Formation Waters of Some Oil Fields in Tomsk Oblast
Abstract Generated abstract
This paper reports laboratory measurements of the physical properties of formation waters from several oil fields and exploratory areas in Tomsk Oblast, including the Cheremshanskaya, Strezhevoy, and Pervomaiskoye sites. Using procedures analogous to those applied to formation oils, the authors determined saturation pressure, gas content, volumetric coefficient, shrinkage, density, viscosity, thermal expansion, and compressibility under reservoir and surface conditions. The results show low gas contents relative to oils, saturation pressures ranging widely from 18 to 70 atm, and formation-water viscosities substantially below those of associated oils. Measurements on Cheremshanskaya water at varying temperatures and pressures indicate that viscosity depends mainly on temperature and is nearly independent of pressure within the tested range.
Full Text
ON THE PHYSICAL PROPERTIES OF FORMATION WATERS OF CERTAIN OIL FIELDS IN TOMSK OBLAST
V. V. BELOSHAPKINA, G. N. CHERTENKOVA
(Presented by Professor A. V. Aksarin)
Sampling of formation waters for the study of physical properties was carried out by the same procedure as the sampling of formation oils. Sometimes these samples were taken from wells that had penetrated water-bearing formations, and sometimes from wells that had penetrated oil-bearing formations. In particular, a water sample was taken from the water-bearing formation at the Cheremshanskaya area. The study was carried out according to the procedure described in the following works [1, 2, 3, 4, 5] and consisted of the following.
- The water sample was transferred from the container or sampler into a UIPN-2M bomb, where the saturation pressure \(P_s\) and the total volume of the transferred sample under formation conditions \(V_{p.l}\) were determined. Subsequently, after degassing the sample, the volume of this sample under surface conditions \(V_{p.v}\) was determined, and from their ratio the volumetric coefficient of water was found
\[ b=\frac{V_{p.l}}{V_{p.v}}. \tag{1} \]
From the value of the volumetric coefficient the shrinkage \(u\) was determined
\[ u=\frac{b-1}{b}100. \tag{2} \]
In the usual way (as for oil), the compressibility coefficient of water was determined
\[ \chi=\frac{\Delta V_p}{V\Delta P}, \tag{3} \]
where \(V\) is the initial volume of the sample in cm\(^3\), \(\Delta V_p\) is the change in this volume when the pressure changes by the amount \(\Delta P\), expressed in atmospheres. The values of saturation pressures \(P_s\), the volumetric coefficient, etc., are given in Table 1.
In addition to the parameters used to characterize both water and oil, another parameter is also used to characterize water, which is not used for the characterization of oil. This is the thermal coefficient \(\tau\), determined by the formula
\[ \tau=\frac{\Delta V_t}{V\Delta t}, \tag{4} \]
where \(\Delta V_t\) is the change in volume due to a change in temperature, \(\Delta t\) is the change in temperature, and \(V\) is the initial volume of water.
Table 1. Main physical properties of formation waters of oil fields and exploratory areas of the Tomsk Region.
| Parameters | Units of measurement | Polotsk Cheremshanskaya area, well 2, 1st sample | Strezhevoy oil field, well 85, 1st sample | Permian oil field, well 265, 1st sample | Permian oil field, well 265, 2nd sample | Permian oil field, well 265, average value |
|---|---|---|---|---|---|---|
| Date of sampling | September 1971 | 22.04.1972 | 30.07.1972 | 30.07.1972 | ||
| Name of formation, suite | Tyumen suite | bed Yu-1 | bed Yu-1 | bed Yu-1 | bed Yu-1 | |
| Perforation interval | m | 2800–3090 | 2580–2615 | 2544–2550 | 2544–2550 | 2544–2550 |
| Formation temperature | °C | 114°C | 84°C | 93°C | 93°C | 93°C |
| Formation pressure | atm | 302.1 | 262.5 | 260 | 260 | 260 |
| Saturation pressure | atm | 18 | 30 | 65 | 70 | 68 |
| Gas content | m³/m³ | 1.79 | 2.8 | 0.78 | 0.81 | 0.80 |
| Volumetric coefficient | 1.026 | 1.026 | 1.03 | 1.024 | 1.027 | |
| Shrinkage | % | 2.53 | 2.53 | 2.91 | 2.34 | 2.63 |
| Density of water under reservoir conditions | g/cm³ | 1.033 | 1.006 | 0.990 | 0.999 | 0.995 |
| Density of separated water under surface conditions | g/cm³ | 1.057 | 1.032 | 1.020 | 1.023 | 1.022 |
| Viscosity of water under reservoir conditions | centipoise | 0.43 | 0.39 | 0.43 | 0.42 | 0.42 |
| Viscosity of water under surface conditions | centipoise | 1.18 | 1.17 | 1.17 | 1.12 | 1.15 |
| Average gas solubility coefficient | m³/m³ · atm | 0.099 | 0.090 | 0.012 | 0.011 | 0.012 |
| Thermal coefficient | 10⁻⁵ 1/degree | 84.0 | 85 | 81.0 | 84.0 | 82.5 |
| Compressibility coefficient | 10⁻⁵/atm | 4.35 | 4.2 | 4.1 | 4.2 | 4.15 |
| Date of completion of analysis | 29.12.1971 | 4.07.1972 | 4.11.1972 | 10.11.72 |
Next, the density of the water in the degassed state, that is, under surface conditions, was determined. The determination was carried out with pycnometers and areometers. The results are given in Table 1. After this, the densities of the waters under reservoir conditions were determined. The calculation was made by the formula
\[ \gamma_{\text{pl}}=\frac{\gamma_c}{b}+\frac{f\rho_g}{1000\,b}, \tag{5} \]
where \(\gamma_c\) is the density of the separated water in g/cm\(^3\), \(b\) is the volume coefficient, \(f\) is the gas content in cm\(^3\)/cm\(^3\), \(\rho_g\) is the gas density in g/liter, and 1000 is the coefficient for converting grams per liter into grams per cm\(^3\).
Special attention was given to the study of the viscosity of reservoir waters. In this work, water from the Cheremshanskaya area was studied at various temperatures and pressures. The work was carried out by means of a VVDU high-pressure viscometer (Table 2).
Table 2
Viscosity of reservoir water from the Cheremshanskaya area (well 2, perforation interval 2800—3090 m, Tyumen suite reservoir, reservoir temperature 114°C, reservoir pressure 302 ati) at various temperatures and pressures
| Pressures at which the viscosity was determined, ati | Viscosity in centipoises at various temperatures and pressures | Viscosity in centipoises at various temperatures and pressures | Viscosity in centipoises at various temperatures and pressures |
|---|---|---|---|
| 60°C | 86°C | 114°C | |
| 40 | 0,48 | 0,46 | 0,43 |
| 100 | 0,48 | 0,46 | 0,43 |
| 200 | 0,49 | 0,46 | 0,43 |
| 302 | 0,50 | 0,46 | 0,43 |
This study showed that the viscosity of reservoir water depends above all on temperature and is practically independent of pressure. Therefore, in the subsequent work the viscosity of the water was determined under surface conditions, which considerably simplified the work. The determinations were carried out on an Ostwald–Pinkevich viscometer.
The results of these studies may be summarized in the following resume. The waters of the oil fields and exploratory areas of Tomsk Oblast are more mobile in comparison with the oils. On the other hand, it may be noted that the gas content of the reservoir waters, in comparison with the gas content of the oils, is relatively low. It reaches its greatest value in the water of the Strezhevo field, 2.8 m\(^3\)/m\(^3\) (Table 1). The saturation pressure varies within very wide limits, from 18 ati in the water sample from the Cheremshanskaya area to 70 ati in the second water sample from the Pervomaiskoye oil field.
LITERATURE
J. Amyx, D. Bass, R. Whiting. Physics of Petroleum Reservoirs. Gostoptekhizdat, 1962.
M. M. Bondareva, A. Yu. Namiot, V. M. Fokeev. Influence of dissolved gas on the viscosity of water. Proceedings of VNII, issue 3, Gostoptekhizdat, 1954.
F. I. Kotyakhov. Fundamentals of the Physics of Petroleum Reservoirs. Gostoptekhizdat, 1956.
O. A. Likhacheva, V. M. Fokeev. Application of the VVDU-2 high-pressure viscometer for the study of natural waters. Izvestiya vuzov “Geology and Exploration”, No. 7, 1967.
G. M. Sukharev. Waters of Oil and Gas Fields of the Eastern Ciscaucasia. Grozoblizdat, 1947.