Rheological Properties Of Crude Oil Dissolved In Carbon Dioxide And Its Effect On The Radius Of Gathering And Transportation

With the continuous application and promotion of the CO₂ flooding tertiary recovery technology,the flow in the gas-liquid two-phase gathering and transportation pipelines is the dissolved gas flow that dissolves CO₂ and associated gas,and the physical and chemical properties of the dissolved gas flow will greatly change.In order to optimize the design of the gathering system and ensure the safe operation of the CO₂ flooding ground gathering pipelines.In this paper,for Changqing crude oil,the rheological properties of crude oil dissolved in CO₂ and its influence on the radius of gathering and transportation were studied.Firstly,the physical properties and rheological properties of degassed and dissolved crude oils were studied experimentally,and the obtained data were used as reference for subsequent experiments.Secondly,the degassed crude oil was treated with supercritical CO₂to simulate the actual situation of CO₂ flooding on site,and the effect of CO₂ on the rheological properties of degassed crude oil was analyzed using the experimental device.Thirdly,using the established experimental device,under different pressures,temperatures,and different dissolved gas compositions,experimental studies were conducted on the saturated dissolved gas crude oil,and the effect of CO₂ on the rheological properties of the dissolved crude oil were analyzed.In addition,combined with the actual operation of the gathering pipelines in Changqing Oilfield,the effects of gas-oil ratio,liquid-phase flow rate,and water content change on the gathering radius of the oil produced after CO₂ dissolution were analyzed.To provide a theoretical basis for the design and operation gathering and transportation system after CO₂ flooding.Through research,it shows that the degassed Changqing crude oil after CO₂ treatment has higher density,higher wax precipitation and wax precipitation,higher freezing point,higher viscosity,higher yield value,and a certain degree of deterioration of crude oil fluidity;After CO₂ dissolved in Changqing crude oil,the solubility increased,the freezing point decreased,the viscosity decreased,the yield value decreased,and the low temperature rheology was improved.The effect of mixed dissolved gas on the fluidity of the oil was more significant.And through analysis and comparison and selection of CY method to calculate the CO₂-dissolved crude oil gathering radius,it is concluded that after CO₂ removal in Changqing crude oil,the ratio of gas to oil in the pipeline increases,the water content decreases,the gathering radius increases,and the growth rate is showing a gradual trend.