Method of determining freezing point of paraffins in oil

FIELD: physics.

SUBSTANCE: oil sample is heated with one-time temperature control, the sample is continuously cooled with simultaneous measurement of shear stress. Chilling point is determined from temperature corresponding to the first abrupt increase in shear stress, and bulk freezing point is determined from temperature corresponding to the second abrupt increase in shear stress. The sample is heated to temperature of 60-80°C. Heating and temperature control of the sample is carried out while revolving the viscometer cylinder and the sample is cooled at a rate of 1-2°C per minute.

EFFECT: high information value and reliability of the analysis method.

1 dwg

 

The invention relates to the oil industry and is designed to determine the physical parameters of reservoir fluids can be used in industrial and research laboratories for determining the temperature of crystallization of the paraffin in the oil.

There is a method of determining the temperature of crystallization of the paraffin in the oil, which consists in the visual observation of the sample oil in transmitted polarized light using a microscope with continuous temperature control of the sample. For the crystallization temperature of the paraffin in the oil take the temperature corresponding to the appearance of bright dots on a black field of the considered sample of Mavlyanov CENTURIES, Markhasin I.L., Babalian G.A. Optical methods of monitoring the development of oil fields. - M.: Nedra, 1970. - 160 S.]. The disadvantage of this method is high subjective measurement error.

There is a method of determining the temperature of crystallization of paraffins, which consists in observing the change in transparency of a layer of the test sample when it is uniform cooling using solar cells with high sensitivity to red spectrum. The temperature of crystallization of the wax in the oil, take the temperature changes the transparency of the transparent layer [Mazepa B.P. the precipitation of paraffin oil gathering systems the field equipment. - M.: Nedra, 1986. - P.8].

The disadvantage of this method is the insistence to clean oil, for example, the content of mechanical impurities.

There is a method of determining the temperature of crystallization of the paraffin in the oil, which consists in observing the change in temperature of the cooled sample of the wax separated from the oil in time. For the crystallization temperature of the paraffin take the temperature value, which is fixed over a longer period of time on the background of the uniform reduction. [GOST 18995.5-73 chemical Products organic. Methods for the determination of the crystallization temperature. - P.15].

The disadvantage of this method is that for measurements requires the allocation of a sample of paraffin from the sample under test oil, which is time consuming and involves the use of hazardous and harmful substances, such as benzene, toluene, carbon tetrachloride.

There is a method of determining the temperature of crystallization of paraffins to change the attenuation coefficient of ultrasound in the sample oil, [Lusin SF, Stories, VA, Sheikh-Ali, D.M., and others Struggle with the deposition of paraffin in oil production. - M: COSTOPTIMIZED, 1961. - C.11].

The disadvantage of this method is the low reliability of the received data, as in the measurement process is the influence of ultrasonic vibrations on the sample itself, which distorts the received results.

There is a method of determining the temperature of crystallization of the paraffin in the oil using a rotational viscometer, taken as a prototype, including the placement of a petroleum sample in the measuring cylinder, step-by-step change of the sample temperature (usually at least 8 steps), the temperature of the sample at each step for 0.5 hour, the definition of the tangent shear stress at each measurement temperature for 0.5 hours, the calculation of the plastic viscosity, the construction schedule based plastic viscosity on temperature in semi-logarithmic coordinates, determine the temperature of crystallization of paraffins on the salient point of the graph [RD 39-0147103-329-86. The method of determining rheological parameters of the thickening of the oil. - Ufa: Vniisptneft, 1986. - P.12-13].

The disadvantages of the method include:

- the duration of the measurement (about 10 hours for one sample of oil);

the method allows to detect the beginning of crystallization, but does not determine the temperature of the mass crystallization of paraffins.

Object of the invention is to provide a method for determining the temperature of crystallization of the paraffin in the oil, which can eliminate the above-mentioned disadvantages of technical solutions.

The technical result of the invention is to reduce the time for the measuring, raising awareness and truth is the beginning of the method.

The task in the method of determining the temperature of crystallization of paraffins in crude oil, including the placement of a petroleum sample in the measuring cylinder rotational viscometer, the temperature change of the sample, thermo staterevenue sample, the definition of the tangent shear stress, is solved by the fact that they perform heating of the sample of oil with a single temperature control, continuous cooling of the sample with simultaneous measurement of the tangent shear stress, determination of the temperature of crystallization temperature of the first abrupt increase of the tangential shear stress, temperature determination of mass crystallization temperature corresponding to the second abrupt increase of the tangential shear stress, while the sample is heated to a temperature of 60-80°C, heating and temperature control sample perform with the rotation of the cylinder viscometer, and the cooling of the sample perform with the speed of 1-2°C per minute.

The claimed invention is illustrated in the drawing, which shows the dependence of the tangential shear stress from the temperature of the sample.

As explanations for the claimed method here is the following.

When the temperature control of the sample after heating to a temperature of 60-80°C is the destruction of supramolecular structures paraffins and translation paraffin is brazza in the liquid state. Upon further smooth decrease of temperature with constant speed and the temperature of crystallization of paraffin oil, there is a resistance to rotation of the cylinder rotational viscometer that is displayed by the registration device as a sharp increase of the tangential shear stress. In future work viscometer and the rotation of the rotor structure crystallized paraffins are destroyed to small, no resistance to rotation, and the recording instrument readings stabilize. The second abrupt increase of the tangential shear stress is indicative of a mass crystallization of paraffin oil. Thus, the first spike of values of the device corresponds to the formation of the first crystals, i.e. the temperature of crystallization of paraffins, and the second jump of the value - loss of a greater part of paraffin crystals in the sample, i.e. the temperature of mass crystallization.

Example.

It is necessary to set the temperature of the beginning and bulk crystallization of waxes petroleum sample, selected on acceptance point system pipeline JSC "Northern MN".

To determine the values of the temperature of the beginning and bulk crystallization of the sample was placed 25 ml of it into the cylinder 81 viscometer Rheotest RV 2.0. Then using a thermostat produce naked the EB samples to 80°C when the rotating cylinder viscometer. Upon reaching 80°C thermostatic sample of oil for 30 minutes. After the temperature is cooled sample at the rate of 1-2°C per minute with a constant rotation of the cylinder and the dimension of the tangent shear stress. Build a dependency graph of the tangent shear stress from the temperature of the sample. Determines that the temperature of crystallization of paraffins for the selected sample of oil is 48.8°C and the temperature of the mass crystallization of 39.7°C.

The method of determining the temperature of crystallization of paraffins in crude oil, including the placement of a petroleum sample in the measuring cylinder rotational viscometer, the temperature change of the sample temperature control of the sample, the definition of the tangent shear stress, wherein performing the heating of the sample of oil with a single temperature control, continuous cooling of the sample with simultaneous measurement of the tangent shear stress, determination of the temperature of crystallization temperature of the first abrupt increase of the tangential shear stress, temperature determination of mass crystallization temperature corresponding to the second abrupt increase of the tangential shear stress, while the sample is heated to a temperature of 60-80°C, heating and temperature control of the sample perform with the rotation of Zilin the RA viscometer, and the cooling of the sample perform with the speed of 1-2°C per minute.



 

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