Simulation Study On Drainage Of Heavy Oil Drainage In

Viscous crude oil has the characteristic of high viscosity and congealing, which makes it difficult to be exploited and transported. Dilution is widely used in lots of oil fields for its advantages of technology and economy, but there are some problems about consumptions of lightoil, poor mixed states of viscous crude and lightoil, and low efficiency on viscosity reduction in operations. Recent researches about dilution are mainly concentrated on viscosity reducing rates, but few papers on dissolution are discussed. Therefore this paper discussed the flow processes of viscous crude and lightoil in wells based on viscosity reducing rates, dissolution rates and mixed states, and its results can provide the theoretical and technological guidances for the enhancement of viscosity reducing rates and utilization rates of lightoil in dilution.On the basis of abundant surveies on viscous crude, the elementary components and rheological behaviors of JH, TK675X and FZ010are tested, the viscosity reducing rates are evaluated by vertical pipelines and related facilities. Effects of temputure、lightoil and base components (asphaltenes, waxes, and emulsifying water) on the dissolution rates are investigated by spectrophotometry. Aiming at two dilution technologies-dilution in tubing and dilution in casing, mixed states of viscous crude and lightoil in the mixing processes are analysed by numerical simulation, and situations of adding static mixture are also simulated to compare effects of different lengths, screw pitch and blade diameters of static mixtures. The degrees of effects of different mixtures dimension parameters on mixed states between viscous crude and lightoil are explored.The results show that JH and TK675X belong to general heavy oil. FZ010belongs to extremely-viscous crude, and the conventional technologies cannot meet the requirements for expoiltation and transportation. The higher viscosity of viscous crude is, the higher viscosity reducing rates of dilution are at the same conditions. After blending into10%,30%and50%mass fractions of diesel, the viscosities of JH, TK675X and FZ010at50℃are lowered to400mPa·s, that can be transported successfully. Viscosity of lightoil has an influence on the viscosity reducing rates, at the same temperature and dilution ratio, the viscosity reducing rates of gas condensate are highest, the diesel comes second, and the medium relative density crude oil is lowest. When dilution ratio are rather low, the temperature is the principal factor, and when dilution ratio is higher, efficiency on viscosity reduction are decided by both temperature and dilution ratio. The flow conditions of dilution are simulated in vertical pipeline, the viscosity in pipeline is reduced drastically, and the flowing property is rather good. Both pumping quality and mass flow rate are enhanced. The dissolution rates of JH, TK675X and FZ010are increased as the temperature rising. At the same temperature, the dissolution rates of JII are higher than that of TK675X and FZ010. Within the same stirring intensitie and temperature, the dissolution rates in gas condensate are much higher that in diesel. The effects of crude components have an impact on dissolution rates and viscosities. The viscosity of oil is increased as the mass concentrations of asphaltenes increasing, and dissolution rates reduce drastically at first, then decrease steadily afterwards. The increasing of emulsifying water leads to the transformation from newtinian fluids to pseudoplastic fluids, and viscosity is increased sharply, mass concentrations of emulsifying water almost have no effects on dissolution rates. The increasing of waxes mass concentrations mainly influences rheological behavior of oil at low temperature, and waxes make oil more dissolvable. From the results of numerical simulation of dilution in casing and dilution in tubing, Mixing effects of viscous crude and lightoil are rather bad, and the flow manifests severe stratification, even enhancing the dilute proportion cannot solve the problems of low efficency. The static mixture can prompt blending states of dilution in tubing and dilution in casing. The blending efficiency can be enhanced by enlarging the length of mixture, blade diameters or decreasing screw pitch. The length of mixtures has the greatest impacts on the mixing efficiency in dilution, and the following are blade diameters and length screw pitch.