In order to improve the reservoir seepage and long-term conductivity after fracturing, by introducing the concept of discontinuous multilayer sanding in fractures, the experiment evaluates proppant sand group compression and deformation.Simultaneously, the deformation characteristics of proppant column under the action of closure pressure in axial and radial direction have been analyzed. Combined with a Duncan-Chang constitutive model, the relationship equation is fitted which contains the proppant column expansion radius, closure pressure and proppant concentration. According to the principle of contact mechanics of elastic half space solid deformation, a three-dimensional discontinuous propped wall deformation calculation model is established which considers the coupling action between the radial deformation of a proppant sand column under compression and the closure of the fracture wall. Based on the above research results, using the Sulige tight sandstone reservoir for illustration,the transformation of residual width in nonsupported area of discontinuous sanding fracture has been calculated and analyzed,under the condition of different rock mechanical parameters and fracturing treatment parameters. The results obtained in this study indicate that :(1) the volume of the proppant column and non-supported areas increase with the pulse interval and pump rate. Simultaneously the risk of fracture face closure in non-supported areas increases. For low-permeability sand reservoirs, the middle of the surface in non-supported area starts to contact when the pulse interval is larger than 18s or pump rate is larger than 4.5 m3/min. (2) stability of a proppant column could be improved by increasing the proppant concentration. (3) the deformation in non-supported areas and risk of fracture closure is smaller in rocks with a higher effective Young’s modulus
CHEN Xingyu, YIN Congbin, XIAO Jianfeng. Research into the mechanics and deformation of discontinuous sanding fractures. Petroleum Science Bulletin, 2019, 01: 92-101.
