Techniology Research On Safe Operation In Oil Gathering And Transportation Pipeline Of Hailaer Oilfield

According to the characteristics of special geographical environment, such as'remote, far, scatter, cold', and combined with the actual situation of different blocks development, the oil gathering process of'raise, pull, blend, dendroid, mix'was adopted in Hailaer Oilfield, and the pipeline transportation of crude oil was realized in 2009. When the water content of crude oil in gathering system is near the phase transition point, the medium viscosity in tube will increase dramatically, then lead to a sharp rise of wellhead back pressure, and bring harm to oil wells and gathering system. Some pipelines have come out the serious phenomenon of wax deposition since operation, and coupled with effects of lower transmission capacity and much rate fluctuation, which makes pipelines route friction on the rapid rise with the actual operation, and the safe operation of pipeline is affected directly. Therefore, it is necessary to start from surveying the history operating parameters of the pipeline and analyzing the all site's operation scheme and adjustive conditions to research the existing problems, causes and potential risks of the Hailaer oil gathering and transporting pipeline in operation, and then the reasonable operation scheme and measures of setting oil is put forward.The main contents of this paper include:(1)Analyze the law of viscosity with water ratio variation under different temperature and shear rate for water cut oil of Hailaer Oilfield, determine the phase transition point of watered cut oil emulsification system for each block, thus the adaptability index system including water ratio, oil gathering temperature, etc. for double-tube with water, circular tube with water and electrical heating oil gathering process is provided. And also the solutions are put forward when water ratio reaches the phase transition point of oil gathering system.(2)Test the density, specific heat capacity, freezing point, wax content, colloid, asphaltene content and full viscosity-temperature curve of exported purification oil, thus the foundamental physical property and viscosity-temperature properties of purification oil for each block in Hailaer Oilfield are given out. The rheological characteristic parameters such as rheological index, consistency coefficient and yield value are ascertained on the basis of the variation relationship between shear rate and shear stress, between shear rate and viscosity for purification oil. Test wax precipitation point, abnormal point and wax precipitation peak of purification oil, the influence law of temperature on wax precipitation amount and specific heat capacity is got through experiment.(3)Combined with the current situation of oil pipeline in Hailaer, to counter the dissolution, precipitation, aggregation of wax particle and the recovery and formation mechanism of its spatial network structure, the influence of thermal effect and shear effect on the flow property of exported is studied through experiment by investigating the changes of solidification point. Considering the mixture ratio of different purification oil and the variable mixing ratio of two kinds of oil that have quite different properties respectively during actual operation of Hailaer Oilfield, the influence of mixing on crude oil flowability is studied through determination the basical physical properties, viscosity-temperature feature parameters and rheological parameters of the mixed oil.(4)According to the principle of differential pressure method, the indoor simulation experiment device of wax deposition rate for Hailaer crude oil is set up. Based on the determination of pipe wall shearing stress, wax molecular concentration gradient at pipe wall, temperature drop distribution along pipeline and radial temperature gradient for different flow pattern, the wax deposition experiment of oil transferring pipeline which covers all the typical working conditions including temperature gradient, flow velosity etc. is developed. And the wax deposition rate model for the crude oil pipeline in Hailaer is established on the basis of the determining method for the related parameters and the simulation experiment data.(5)The difference and relation between two kinds of allowed minimum transportation amount of hot oil pipeline, namely 'the allowed minimum transportation amount of pipeline characteristics' and 'the allowed minimum transportation amount of thermal condition' is analyzed, and it is pointed that the allowed minimum transportation amount of the actual pipeline in operation should be the higher one. Based on the calculation for the allowed minimum transportation amount of various pipelines in Hailaer Oilfield, combined with the productivity prediction of development department, the suitable design adjustment scheme for every pipeline is selected from the conventional method of ensuring the safe operation of low transportation amount in waxed oil pipeline, including the addition of pour point depressant, modification of heat treatment, blending water transportation, increasing the number of middle heating stations, operation of positive and negative transportation, etc., and also the corresponding major projects is given.