Research And Evaluation On The Distribution Of Gravel Packing In Vertical Well

High-pressure gravel-packed sand control technology is one of the most important technologies for the development of unconsolidated sandstone reservoirs.It is important to recognize the morphological characteristics of the formation area formed by high pressure sandcarrying fluid,to clarify the influence of sand migration and blockage in gravel layer on parameters such as permeability and additional pressure difference of perforation,which is of great significance to predict the effect of gravel-packed sand control and to optimize the designation for gravel packing and well completion.In this paper,the force of dispersed phase in solid-liquid two-phase flow is analysed and the negligible terms in the traditional formula are removed to build the two-fluid model of sandcarrying fluid flow by using the theory of multi-phase fluid dynamics.Based on the stress analysis and considering the wall effect,the flow of sand carrying fluid in perforation is calculated,and the effects of the physical parameters of sand-carrying fluid on the shape of sand bed and the pressure of outlet in perforation are studied.Considering seepage field,rock mass deformation field and fluid-solid coupling,the three-dimensional finite element model is established to simulate the shape of gravel packed layer in unconsolidated sandstone reservoir as well as studying the influence of in-situ stress,rock physical properties and perforation method.A model of physical parameters is established and an experimental device was set up to verify the blockage of gravel packed layer.The damage of gravel layer caused by sand migration and blockage was evaluated;and the gravel layer plugging model based on physical dynamic parameters is established.The sand control effect evaluation model is built to evaluate the sand control effect of gravel packing.The results show that the distribution of sand bed and outlet pressure in perforation are mainly influenced by the velocity and viscosity of sand-carrying fluid,gravel density.The compressive zone formed by high-pressure fluid is affected by formation physical parameters and perforation mode: when the formation is applied homogeneous stress,the gravel packed zone expands into a circular shape;when the inhomogeneous stress is applied,the gravel packed zone is elliptical and the formation has a severer damage along the direction of the minimum principal stress;the compression zone is affected by azimuth,density and phase angle of perforation.The influence of fluid viscosity,flow rate and confining pressure on permeability of gravel-packed layer decreases in turn,and the additional pressure of perforation increases with the production going on.