Simulation Analysis on Sand Settling Pattern and Influential Factors During Sand Washing of Deviated Well Section
Sand production often accompanies the exploitation of highly deviated wells,extended reach wells and horizontal wells.Sands gradually deposit to form sand beds,which affect oil exploitation.Especially,in devia-ted well sections,sand settling easily occurs to block oil pathway,increase flow resistance,and even damage down-hole equipment.To address the issue of sand settling in the deviated well section,a numerical model of sand two-phase flow was built.Then,the model was simplified depending on field wellbore parameters.Moreover,a simula-tion model of annular fluid between the sand washing string and the wellbore in the deviated well section was built to understand the pattern of sand settling in the deviated well section,and analyze the influences of the factors such as displacement,sand washing fluid viscosity,sand particle size,sand washing fluid density and inclination on sand settling.Finally,orthogonal tests were conducted with consideration to multiple influential factors.The results show that during the sand washing process in the deviated well section,at wide gap of annular space,sand particles migrate smoothly,and mainly move upward in a laminar flow form;at narrow gap of annular space,sand particles mainly move in the form of rolling,meandering and saltation,the sand particle migration velocity is significantly slower than that at wide gap of annular space,and some sand particles accumulate,swirl and deposit mainly at the end of the deviated well section near the horizontal section.Among the influential factors,the sand particle size and sand washing fluid viscosity have the greatest impacts on the sand carrying effect,followed by the sand washing flu-id displacement,and the impact of the sand washing fluid density on the sand carrying effect is relatively small.Based on the test results,it is proposed to select a sand washing fluid displacement of around 800 L/min,sand washing fluid viscosity of 35-45 mPa·s and guar gum fluid concentration of 0.1%-0.3%for field operation.The study results provide guidance for safe and efficient operation of horizontal wells.
sand washingdeviated well sectionsand settlingsand carrying effectorthogonal test