Study On Numerical Simulation For Gravel Packs In Highly Deviated Well

Influenced by hole deviation angle, mechanism of gravel packing in highly deviated wells is different from vertical wells and horizontal wells, which is more complex. The current research regarding gravel packing is still concentrated in the horizontal well gravel packing, while highly deviated wells gravel packing is basically oriented to small-scale physical simulation, and mathematical model study is relatively weak, only some studies have mainly concentrated in the local analysis model. Because of lack of in-depth study and perfect mathematical model, it is difficult to set up an effective optimization method of parameters, which leads to the premature plugging, so that operation failed. Therefore, response to these questions there is a need for researching high angle wells gravel packing.In this paper, mechanism of gravel packing in highly deviated wells is studied at first. Then the behavior of the grains on the bed surface is classified as three statues: station, slippage and suspension. A random variable of dimensionless submergence was introduced to denote the location randomness. Considering the deviation angle, a calculation model for critical velocity of solid grain was established by means of mechanical analysis, which includes critical starting, stopping and suspension conditions, by which the critical deviation angle calculation model, under given parameters can form a stableα-wave equilibrium bed, is derived for the first time.Random analysis theory is used to investigate the final status probability and its numerical character of the grains. According to the principle that status probability indicates the feature movement trend, the change of the equilibrium bed's height is ascribe to the change of surface grains behavior and a new model for the equilibrium bed's height calculation is set up. The results obtained from this formula,which are in satisfactory agreement with the experimental data.The mass and momentum conservation of fluid and gravel grains are evolved, considering the fluid filtration to the formation. Combined with the bed height model, a time-dependent mathematical model describes the process of gravel packing in highly deviated wells. The model can be used any situations such as full packing and premature plugging. All of the above provide theoretical basis for the technological design of gravel packing in highly deviated wells, and lay a good foundation for the extensive application, which have practical significance for improving the level of exploitation in highly deviated wells.