INVESTIGATION OF RHEOLOGICAL PROPERTIES OF OIL DURING THE FORMATION OF WAX DEPOSITS

Abstract

The relevance of the research consists in the need to assess changes in the rheological properties of oil during the formation of wax deposits. The existing correlations make it possible to determine the viscosity of oil at known temperature and density, but their application is possible only for oils of a specific region and a constant component composition. However, in the process of its extraction, the problem of the formation of wax deposits often arises, which directly affects its component composition. In the case when the oil temperature is higher than the temperature of the beginning of paraffin crystallization, the deposits adhere to the cold surface of the elevator column or oilfield equipment, which leads to a change in oil component composition and improvement in its rheological properties. If the oil temperature is lower than the temperature of the beginning of paraffin crystallization, these deposits form in the volume of oil with the formation of «oil–deposits» suspension and significant deterioration of its rheological properties. The study of changes of oil rheological properties during the formation of wax deposits is necessary for a more correct modeling of its transportation, as well as the design of the application of modern methods for preventing the formation of these deposits. The aim: to evaluate the nature and degree of influence of the formation of wax deposits in the test section of the «Wax Flow Loop» installation on the studied oil rheological properties under various thermal conditions. Methods: conducting laboratory studies of oil at the «Wax Flow Loop» installation, determining the thickness of wax deposits in the test section by manometric and thermometric methods. Results. A number of laboratory studies have been carried out at various oil temperatures. According to the results of these studies, it was found that its rheological properties deteriorate with a decrease in its temperature. Due to the different dynamics of the formation of wax deposits, a parameter of specific viscosity change was introduced, equal to the change in oil viscosity during the study to the volume of formed deposits. Analyzing this parameter for the conducted studies, it becomes obvious that at oil temperature from 25 to 40 °C, it takes negative values, rheological properties improve during the formation of deposits, and the specific change in viscosity, on average, is 1,25 MPa s/ml. When studying oil at 20 °C the specific change in viscosity is positive, which indicates the formation of deposits in its volume and significant deterioration in rheological properties. Conclusion. The experimental results obtained allow us to consider the dynamics of changes in oil rheological properties during the formation of wax deposits. The parameter of the specific change in dynamic viscosity under various thermal conditions of the formation of wax deposits is given. It is found that its rheological properties change in different ways under different temperature conditions. The use of laboratory research data will increase the accuracy of modeling oil production and transportation, as well as evaluate the technological effectiveness of some methods of combating wax deposits.

Keywords

• viscosity
• organic deposits
• oil production
• rheological properties
• laboratory research