Optimization Of Hollow Proppant Performance Based On Finite Element Method

Currently,the density of proppant such as solid ceramics and quartz sand is 1-2 times higher than that of fracturing fluid.The density difference leads to the proppant's rapid settlement in the fracturing fluid.In order to realize the long-distance transportation of proppant and obtain longer propped fracture,it is usual to increase the pumping flow or the viscosity of fracturing fluid.Increasing the pumping flow requires higher water horse power.Increasing the viscosity of fracturing fluid is generally in need of crosslinker or thickener,which can easily lead to reservoir damage.To develop low density proppant which can reduce the density difference between proppant and fracturing fluid is a new way to solve the above problems.Hollow proppant is a hotspot in the research of low density proppant.The hollow structure of proppant can reduce the density of proppant,improve the transportability of proppant and increase the propped fracture length.However,due to the special hollow structure,the relationship between proppant density,strength,embedment depth and proppant size has not been scientifically revealed,which leads to the lack of theory for the optimization of proppant material and structure in the process of research and development of hollow proppant.In view of the above background,based on the finite element method and using ABAQUS software,this paper analyzed the influence of closure pressure,proppant hollow structure,proppant size,proppant elastic modulus and mechanical parameters of rock materials on the perfonnance of hollow proppant embedment depth and strength,and further optimized the structure and shell material.The main works that have been done in this thesis are summarized in the following aspects:(1)Theoretical characterization of hollow proppant embedded in rock surfaceThe finite element model of single proppant under compression was established.The effects of closure pressure,proppant hollow structure,proppant size,proppant elastic modulus and mechanical parameters of rock materials on the hollow proppant embedment depth were studied.According to the stress balance condition,the expression of embedment depth considering the plastic characteristics of rocks is derived when the proppants are arranged closely in the fracture.Furthermore,the characteristics of hollow proppant embedment depth under different proppant arrangement were analyzed.(2)Theoretical characterization of hollow proppants strengthUsing the finite element model of single proppant under compression,the effect of closure pressure,proppant hollow structure,proppant size,proppant elastic modulus and mechanical parameters of rock materials on proppant strength are studied.Especially,through the secondary development of ABAQUS,all proppant element is inserted into the zero thickness cohesive element.The failure and fracture of hollow proppant under different packing fonns patterns are studied.(3)Optimization of the hollow proppant structure and shell materialBased on the proppant embedment depth,strength and density,the proppant hollow structure,proppant size,shell elastic modulus were optimized by the data normalization method so that the hollow proppant can satisfy the characteristics of low density,high strength and less embedment depth.