Research On The Wax Deposition Rule And Hot Wash Pigging Boundaries Of The Collection Pipeline Of Polymeric Crude Oil

The crude oil produced in Sanan Oilfield is characterized by high wax content,high freezing point and high viscosity at low temperature.With the implementation of tertiary oil recovery technology,Polymer flooding technology to improve oil recovery,at the same time,it also brings new problems to surface crude oil treatment,processing and gathering and transportation in Sanan Oilfield.The wax deposition of polymer flooding pipeline in Sanan Oilfield leads to the decrease of effective circulation section of oil gathering pipeline,which leads to a series of problems,such as lower transportation capacity,higher transportation pressure and higher production operation cost and so on.In this paper,the physical properties of polymer crude oil samples in Sanan Oilfield were analyzed through laboratory experiments,and the basic physical properties and rheological properties of the oil samples were measured,which laid a foundation for the study of wax deposition law and prediction model of wax deposition of polymerized crude oil.By selecting the appropriate calculation model of wax deposition,the wax deposition law of pipeline is predicted.Thus,the influence of different transportation quantity,water content and return oil temperature on wax deposition of pipeline is determined.With the limit of gathering and transportation as the constraint,the hot washing period of single well oil production pipeline under different operating conditions is determined.Then,the energy balance model of pipeline heat washing is established,and the melting characteristics of pipeline silt samples are studied.The results show that the heat washing water temperature is the most obvious in the range of 65~70 ?.Increasing the temperature of hot washing water will have little effect on cleaning effect.Under different working conditions,when the hot washing water is increased in the range of 5~10 m3/h,the efficiency of heat washing is the most obvious.Finally,according to the calculation results of the energy balance model of pipeline heat washing,the relation chart of operation limit of heat washing is established,and the accuracy of clearing silt parameters is proved by field test.After testing,the wellhead back pressure tracked and monitored is effectively maintained under the low return pressure of < 1.0MPa,which reflects the feasibility and effectiveness of the research done.It provides an effective technical guarantee for the safe operation of gathering pipeline from wellhead to metering room in Sanan Oilfield.