Study On Deposition Characteristics Of Composite Fouling Of Crude Oil And Calcium Carbonate In High Water Cut Gathering Pipeline

China's onshore oilfields have entered the middle and later stages of development,and the total water cut often reaches 90% and above.At this time,the pipeline transportation temperature can be lower than the freezing point of crude oil,and the oil can easily adhere to the wall of the pipeline.Meanwhile,inorganic salt scales can also be deposited on the pipeline.The cross-sectional area of the pipeline becomes smaller and the frictional resistance increases.In serious cases,the well is stopped due to the blockage of sediments.For the characteristics of composite fouling in high water cut gathering pipeline,composite fouling of crude oil and calcium carbonate are simulated using the stirring method,and the yield stress is measured with a rheometer.The influence of concentration and temperature changes on the overall strength of fouling was studied.Based on the analysis of experimental results,a fitting relationship between the composite fouling yield stress,calcium carbonate content and temperature was constructed.The form is concise and all the fitting parameters can correspond to certain physical meaning.In order to study the effect of the oil on the wall on the calcium carbonate deposition behavior,the deposition characteristics of calcium carbonate on the surface of stainless steel and wall with crude oil in the process of horizontal pipe flow were studied comparatively.We used weighing method to obtain the scale weight on the wall surface and observed the fouling process morphology with a microscope.The contact angle of deionized water on surface of stainless steel and crude oil has been measured.The influence of the concentration and the circumferential position of the pipe on the scaling rate was investigated.The experimental results show the crude oil on the wall will inhibit the deposition of calcium carbonate and the phenomenon is explained from the perspective of surface characteristics.The deposition morphology of calcium carbonate on the oil wall surface is different from that on the metal surface.The sedimentation rate of different circumferential locations is also different,and the difference on the oil wall surface is more obvious.