| Tight reservoirs need to be stimulated to form a complex fracture network to obtain effective productivity.However,the breakage and embedment of the proppant at low concentration,and the deformation of the fracture surface under high closing stress result in the closure of the fractures and the reduction of the conductivity of the fractures.Studying the closure mechanism of hydraulic fractures in tight reservoir is of great significance for evaluating the effectiveness of fractures after stimulation.Based on the tight sandstone outcrop of the Lucaogou Formation in Changji Oilfield,this paper studies the closure mechanism of hydraulic fracture and the damage of conductivity.Proppant crush experiments were used to investigate the influence of proppant type,proppant particle size and closing stress on proppant crushing characteristics,and the particle size distribution of crusher proppant was obtained.Using the experimental results,a population balance equation for proppant breakage was constructed.The finite element model was constructed using numerical simulation software.The elasto-plastic process of proppant embedment was analyzed.Taking into account the elasto-plastic deformation of the proppant embedment process,a prediction model of proppant embedment depth was constructed,and the results were compared with experimental results.The fracture conductivity experiments were carried out.The influencing factors such as proppant particle size,proppant concentration,and proppant placement were studied.Experiments showed that the fracture conductivity reduced as proppant particle size and concentration decreased.The micro proppants play an important role in propping narrow fractures and improving the productivity of fracture networks.Finally,based on the proppant balance equation and proppant embedment depth prediction model,the calculation method of fracture conductivity was established and compared with experimental results.The calculation results were reasonable and accurate. |
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