ABSTRACT:

Temporary plugging technology is a useful stimulation method to enhance the well productivity of tight and shale formations. However, how to optimize the combination and concentration of the temporary plugging material (TPM) considering the fracture morphology and tortuosity is a critical issue. This paper conducted a series of experiments through the application of a novel apparatus to investigate the plugging mechanism of fractures (1-4mm). The fracture surface was represented by digitizing and 3D printing the surface of hydraulic fracture. Computed tomography (CT) scanning was used to investigate the plugging mechanism of TPM. Results showed that the plugging processes include bridging and sealing. The bigger particles would firstly bridge at the narrow section of the fracture, and then the smaller fibers would seal the pore-spaces of the bridging sections. The difference between the diameter of the bridge particle and the fracture width should be no larger than 1mm; otherwise, the fracture would fail to seal. For the fracture greater than 4mm, secondary bridging particles should be added to reduce the sealing time. A neural network model was developed and further verified by additional experiments. The proposed model can be also used to design and optimize the combination and concentration of TPM for well-diverting stimulations.

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