Study On Influencing Factors Of Solid - Phase Deposition Of Waxy Crude Oil

The solid-phase deposition can occur at any place where crude oil flows through during waxy crude oil exploitation and gathering process, the deposition will cause series of problems, such as the decrease of the pipe flow area and the transmission capacity, the reducing of crude oil production, or even discontinued when the situation is serious. For quite some time, the problem of solid-phase deposition has been plaguing the safety of waxy crude oil production and gathering. There are many factors which affect the solid-phase deposition, but the internal factors influencing solid-phase deposition have less been studied. And there are many scientific problems that have not been solved completely, such as the level of difficulty of crude oil scouring the sediment, the variation of the crude oil rheological properties while sediment are stripped, and so on. So it is necessary for us to study these problems.Based on the research results of domestic and foreign in this field, taking Mengulin waxy crude oil as the research objects, using homemade cold finger and associated equipments, the influence of the difference of oil/wall temperature, deposition time and oil heat treatment temperature on solid-phase deposition were studied in this article. By measuring the composition of the solid-phase sediment, the influencing factors affecting wax content, asphaltene content in deposited layer were analyzed. Through compounding the model oil of different wax content, asphaltene content and paraffin type, the intrinsic factors affecting rheological properties and solid-phase deposition of crude oil were explored. On the basis of measuring the composition of solid-phase sediment, the influence of shear temperature, shearing time and shear strength on solid-phase sediment were studied by using cold finger. The synergy effect of multiple factors influencing the solid-phase sediment were studied by using orthogonal experiment method, the size relationship of the effect of various shear factors on the solid-phase sediment was given, and the pour point and viscosity-temperature characteristics of crude oil that scoured the solid-phase sediment were tested, the variation of the rhetorical properties of crude oil was analyzed.The research results showed that:with the increase of the difference oil/wall temperature and deposition time, the amount of solid-phase deposition increased. The wax deposition rate reduced as the deposition time increased. The amount of solid-phase deposition decreased when the heat treatment temperature of crude oil reduced. In the study of intrinsic factor impact on the rheological property of model oil, it was found that the pour point and viscosity of oil sample increased with the increase of wax content in the model oil, the pour point was higher and the viscosity was lower in the model oil of low asphaltene content compared with that of high asphaltene content. The types of paraffin had a big influence on the rheological properties of model oil. With the same wax content, the pour point and viscosity of model oil with high wax content was higher than the ones with low wax content. Through the research of intrinsic factors influencing solid-phase sediment, the result showed that with the increase of asphaltene content and wax content, the amount of solid-phase sediment increased. The amount of sediment and wax in sediment of70#microcrystalline wax model oil were higher than the60#coarse grain wax model oil, but the content of wax in sediment of60#coarse grain wax model oil was higher than that of the70#microcrystalline wax model oil. The asphaltene in the70#microcrystalline wax model oil was easier to deposit. By evaluating the impact of the oil flow scouring the solid-phase sediment, the results showed that only when the oil temperature reached a certain level could the sediment be stripped down under the oil flow shear effect. When shear temperature and shear strength were unchanged, with the increasing of shearing time, the shear peeling effect is obvious at first, but this effect will not work when the shear time reaching to a certain extent. The larger the shear strength, the more obvious the shear peel effect was. In all shear factors, the effect of shear temperature on sediment was the most significant, followed by the shearing time, and the effect of shear strength on the sediment was relatively small. When sediment were stripped down to crude oil, the viscosity and pour point of crude oil increased, the liquidity of oil deteriorated.