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溶解石蜡的原油在稳定状态下为真溶液,当热力学条件改变时,石蜡以结晶方式析出而沉积于孔隙介质表面或管壁,引起严重堵塞,给油田生产造成巨大危害。提出了预测石蜡从原油中沉积的热力学模型,根据正规溶液理论对固体混合物的非理想性进行了校正。该模型采用状态方程统一描述气相和液相,能够体现体系组成、压力、温度以及不同组分间相互作用的影响,使热力学模型能够更真实地反映多相相平衡规律;考虑了液相、固相的热容差对石蜡沉积的影响,能够确定石蜡从原油中开始析出的温度(或压力),以及随着温度的降低(或压力的改变)所沉积出的石蜡数量。用该模型预测的石蜡沉积起始温度与实验数据一致性较好。图2表2参6(邓春萍摘)
Crude oil dissolved in paraffin is a true solution at steady state. When the thermodynamic conditions are changed, the paraffin is precipitated in a crystalline manner and deposited on the surface of pore media or on the pipe wall, causing serious blockage and causing great harm to oilfield production. A thermodynamic model for predicting the deposition of paraffin from crude oil is proposed. The non-ideality of the solid mixture is corrected according to the normal solution theory. The model uses the equation of state to describe the gas phase and the liquid phase in a uniform manner, which can reflect the influence of the system composition, pressure, temperature and the interaction between different components so that the thermodynamic model can more accurately reflect the multiphase equilibrium. The effect of phase heat capacity tolerance on paraffin deposition determines the temperature (or pressure) at which paraffin begins to precipitate from the crude oil and the amount of wax deposited as the temperature decreases (or changes in pressure). The paraffin deposition initiation temperature predicted by this model is in good agreement with the experimental data. Figure 2 Table 2 Reference 6 (Deng Chunping pick)