| Recently,the exploration and development of unconventional oil and gas resources,such as shale gas,has attracted more and more attention.Because of the characteristics of low porosity and low permeability in the unconventional oil and gas reservoirs,it is necessary to adopt stimulation measures to develop the unconditional resource economically.The horizontal well completion and hydraulic fracturing are the key technology for the successful development of unconventional oil and gas.The proppant transport in the hydraulic fracture directly determines the size of the effective support area and the fracture conductivity,and then affects the productivity and ultimate recovery of oil and gas wells.So research the proppant transportation and distribution in the fracture and its influencing factors is very important for optimizing the hydraulic fracturing design,accurate productivity prediction and stimulation effectiveness appraisal and has important theoretical and practical significance on the field treatmentFirstly,this paper studies the laws of proppant settlement and horizontal migration,the comprehensive calculation formula for proppant settlement and horizontal migration are developed with the consideration of various influence factors such as the fracturing fluid and proppant properties as well as fracture geometry.Based on the study of proppant settlement and horizontal migration,a mathematical model of fracturing fluid flow and proppant transport of horizontal wells in a single transverse fracture is established,combining the rock elastic deformation equation,fracturing fluid flow equation,continuous equation and proppant transport equation.Coordinate transformation is used to processing the inner radial flow boundary condition at horizontal wellbore,and the differential equation of the mathematical model is constructed and solved.According to the mathematical model of fracturing fluid flow and proppant transportation of the transverse fracture,a simulation software of proppant transport and distribution of horizontal well fracturing was compiled using C# language and factor sensitivity analysis was conducted.The results show that the proppant concentration effect and the fracture wall effect will slow down the settling velocity of the proppant,but will also retard the horizontal migration of the proppant,so that the effective propped fracture length becomes shorter.Increase the viscosity of fracturing fluid and pumping rate,reduce the density and particle size and adopt proper pump schedule can obtain better proppant distribution,resulting in better stimulation effect.At last,the proppant distribution in multi perforation clusters of horizontal well was studied by using the CFD software fluent.The simulation results show that the distribution of proppant among multiple perforation clusters is not uniform,proppant will "aggregation" to the end section of the stage,increase viscosity of fracturing fluid and decreasing proppant density and size can improve the non-uniform distribution of proppant within multiple perforations,and effects of fracturing fluid pumping rate and perforation cluster spacing are very small. |
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