Study On Proppants Settlement Law In Fracture Network Of Volume Fracturing

As the main stimulation treatment for unconventional reservoir,volume fracturing makes full use of the natural factures and forms complicated fractures net-work to enlarge the transformation volume in the reservoir,greatly improving productivity of shale gas.The final proppants distribution pattern in complicated fractures network and its flow conductivity are determined by settlement and distribution law of the proppants.Due to the limitation in understanding the shale gas reservoir and the absence of necessary experimental apparatus,few studies about settlement rule of proppants in complicated fractures network are reported and systematical research findings are scarce.“Complicated fractures network simulation experimental instrument” is developed based on corresponding theory and the discrete model in this paper,which is used to simulate complicated fractures net-work at rational state.Experimental schemes aimed at six basic fracture network structures are formulated.Settlement law of proppants in the six basic fracture networks and its migration velocity at the fracture nodes at different pump output in sand-carry fluids with different viscosities are investigated.The results show that when the viscosity of sand-carrying fluids and the pump output are larger,the proppants enter the induced fractures near the wellbore mainly relying on sand-carry capacity of the sand-carrying fluids,while they enter induced fractures far from the wellbore mainly relying on their gravity.When the viscosity of sand-carrying fluids and the pump output are smaller,the proppants enter induced fractures near the wellbore mainly relying on their gravity,while there are no proppants filling in fractures far from the wellbore,indicating that the induced fractures are meaningless.Accordingly,theoretical model about proppants’ migration and settlement in fracture network are established,through which the proppants settlement law in complicated fracture network can be simulated and its migration velocity can be calculated accurately.The research finding in this paper has guiding significance in mastering the complicated fracture network morphology in volume fracturing and improving the effect of fracturing treatment in the reservoir.