Study On Wall Sticking Characteristics Of Heavy Oil In High Water Cut During Reducing Temperature Of Gathering And Transportation

In order to realize energy saving and consumption reduction and build green and low-carbon oil fields,major oil fields have successively carried out research on unheated gathering and transportation technology for oil gathering system of high water-cut oil Wells.For heavy oil systems with less wax content and higher viscosity,it is difficult to define the wall sticking temperature,which brings great challenges to distinguish the boundary conditions of unheated gathering and transportation of heavy oil with high water content in engineering site.Therefore,this paper studied the adhesion law of heavy oil and pipe wall and the feasibility of unheated gathering and transportation in the process of unheated gathering and transportation of high water-bearing heavy oil system,and proposed the discriminant method suitable for the boundary conditions of unheated gathering and transportation of high water-bearing heavy oil system,providing theoretical basis for field cooling test.In this paper,ring device are adopted to simulate the high water cut of heavy oil gathering and transferring process.By analyzing the oil-water flow pattern and pressure drop rule of the test section during the cooling process,the adhesion process of heavy oil and tube wall was divided into two stages: formation of initial adhesion layer at high temperature and growth of adhesion layer at low temperature,and the growth of adhesion layer at low temperature was divided into four processes: slow growth,accumulation,blockage and scouring off of adhesion layer.In this paper,it is found that the substances adhering to the wall surface was composed of water-in-oil emulsion and asphaltene particles,and the fluidity of the substances adhering to the wall surface at different temperatures makes it easy to accumulate in the direction of flow.Based on the theory of interfacial adhesion,the effects of gathering temperature,conveying medium properties and pipe materials on the phenomenon of heavy oil wall sticking were investigated.It was concluded that the phenomenon of heavy oil wall sticking could be alleviated by increasing temperature,increasing salinity of water phase,decreasing asphaltene content of heavy oil and replacing non-metallic pipe.The growth mechanism of adhesive layer at low temperature was analyzed,and it was concluded that in the process of cooling and gathering of heavy oil with high water content,the superposition of shear action of water flow on adhesive layer and stagnation action between adhesive layer would cause continuous accumulation of adhesive layer along the flow direction.By establishing the model of average accumulation thickness of adhesive layer for cooling and gathering of heavy oil with high water content,the corresponding temperature is "stagnation temperature" when the ratio of average accumulation thickness of adhesive layer to inner diameter of pipe is 0.17,and "stagnation temperature" is taken as the boundary condition of cooling and transporting heavy oil with high water content.