Study On The Relationship Between The Structure And Viscoelasticity Of Carburized Fracturing Fluid And The Performance Of Sand

Fracture conductivity and fracture length are the main indicators for evaluating the effectiveness of the fracturing operation. To transport the proppant along the length of the fracture and keep it suspended is the predominant function of the fluids. The viscosity of the guar fracturing fluid is currently used to determine its proppant transport behavior through a fracture, but it provides insufficient method to evaluate cross-linked fluids for their solids transport characteristics. The viscosity of the fracturing fluids is equal, but the proppant transport capacity of the fluids isn’t the same. The viscoelastic and the microstructure of the fracturing have not been considered.Based on the survey and research, the study is performed by characterizing cross-linked guar gels for their microstructure and viscoelastic properties.From the ESEM measurements and digital image processing techniques, it was found that an increase of either crosslinker concentration or guar concentration increase the average density of gel networks and decreases the void spaceship between the fibers. The structure of gels changed from a linear structure to a two-dimensional network and finally to a three-dimensional network. The fluid changes from a viscous fluid to a viscoelastic fluid and finally to a solid-like gel. The guar fibrous structures of crosslink net can transfer stress, limit the movement of molecular chain to make the strength, rigidity, thermal stability and shearing resistance of the fracturing fluid to be improved. These properties are very important for improving the proppant carrying ability of the fluid. As the average density of gel networks increased, the proppant transport capabilities of the fluids increased.From the dynamic viscoelastic measurements, it was found that the HPG and CMG gels possess viscoelastic. As the crosslinker concentration or guar concentration increase, the elastic modulus of the gels increased. As the guar concentration increase, the viscous moduli of the gels increase. However, the viscous moduli have no significant relationship with crosslinker concentration. The findings match well with the microscopic analysis. The reliability of the experimental data can be verified by contrasting the data of HPG gels and CMG gels. The viscoelastic properties are common to all guar fracturing fluid. From the study of the relationship between viscoelastic and the proppant transport capabilities, it is found that there are some corresponding relationships between them. As the elastic modulus of the gels increase, the proppant transport capabilities increased, and the G’and proppant transport capability have stronger correlation at lower frequency region. This is mainly because more fibers combined together. The higher fiber density strengthened the gel and improved its ability to suspend proppant. Their relationships can be related through the power exponential function expression. The proppant transport capability of cross-linked gels is not only correlated with the fluid’s viscosity, but the elasticity of the fluid.From the verification experiments, it is found that the HPG and CMG solutions have the same viscosity, The average density of gel networks and the elastic modulus are both higher than that of the CMG, they are72.24%and65.38%,0.19Pa and0.03Pa, respectively. We predict the proppant transport capacity of the HPG solution is better than that of CMG solution. It has been proved that the conclusion of this paper is correct by static-column tests and field-scale test.The viscosity is insufficient to describe suspension capabilities of a fluid. The microstructure and the viscoelastic of fluid can characteristic the proppant transport capacities of the fracturing fluid more accurately and fully. Thus, the method can provide the guidance for the fracturing operation, furthermore, it can also provide the guidance for developing the highly effective and low-cost fracturing fluids.