Research On Flow Pattern For Water-Gelled Crude Oil Two-phase Flow Based On Chaotic Time Series

Most of crude oil with high wax content,high condensation point and high viscosity,namely the "three high" characteristics are produced in our country.Heating up technique is adopted widely in the oilfields at present.With deeply exploitation of oilfield,majority of the oilfield have entered high water-cut developing bear stage.With the increase of water cut,the energy consumption for gathering and transporting rises sharply.Unheated oil-gas gathering and transferring is one of the main measures that reduce the energy consuming in domestic and overseas oilfield.Bulk of the crude oil temperature has been below its freezing point,Crude oil starts to solidify,and loses liquidity without any medicament,which leads to gathering pipeline blockage,unable to safety production.Therefore,it has a very important theoretical and application value to study the flow characteristics of water-gelled crude oil when the temperature is less than freezing point.The new thought of fluidization to gelled crade oil is suggested in this paper,namely gelled crude oil was made into some particles to realize hydraulic suspension conveying without being heated Water-gelled crude oil two phase flow is a very complicated dynamic system which contains a variety of non-linear and non-equilibrium features.Meanwhile,complex interactions and various boundary conditions affect flow state between water and gelled crude oil two phase flow.Dynamic behaviour of water-gelled crude oil two phase flows pattern was studied based on chaotic time series and experiment in this paper.In this paper,an experimental research on the water-gelled crude oil two-phase flow patterns was carried out under the conditions of 53mm inner diameter,25 ? temperature,0.3-0.8m/s velocity and 70-95%water cut.Crude oil(the freezing point is 38 ?)and water were the working fluids.Meanwhile,the factors affecting the two phase flow pattern were analyzed.Four typical flow patterns were observed and defined,which were oil-slug flow,oil agglomeration suspension flow,stratified flow and oil particles dispersion flow respectively.The flow pattern maps were obtained from the experimental data and the factors affecting the mechanism of different flow patterns were studied.Statistical properties parameters for differential pressure fluctuation signal of water-gelled crude oil were unsusceptible to flow patterns change-ment by analyzing statistics and frequency domain characteristics of the four observed flow patterns.The chaotic characteristics of the differential pressure fluctuation signal are analyzed based on chaotic time series,which is correlation dimension and Kolmogorov entropy.The results show that the value of correlation dimensions is 2.58?1.98?4.58?1.77 and Kolmogorov entropy is respectively 3.16?0.6?4.05 and 1.37 respectively.Correlation dimension and Kolmogorov entropy have close connection with flow patterns,which revealed evolution relationship of the two-phase flow patterns for water-gelled crude oil.And it shows that correlation dimension and Kolmogorov entropy had sensitive characteristic of "indicator" for the two-phase flow patterns.