This paper concerns the effect of proppant embedment related with hydraulic fracturing treatment. This phenomenon occurs if the strength of the reservoir rock is lower than proppant grains. The aim of the research is laboratory determining the loss of width of the proppant pack built of light ceramic grains. The laboratory simulation of the embedment phenomenon was carried out for a shale rock on a hydraulic press, in a specially prepared for this purpose a heated embedment chamber. Tests were conducted at high temperature and axial compressive stress conditions. The surfaces of the cylindrical core plugs (fracture faces) were imaged under an optical microscope equipped with 3D software. The fracture faces were examined and compared before and after the embedment phenomenon. The analysis of the obtained images of the fracture face were made based on the research method of the embedment phenomenon developed at Oil and Gas Institute-NRI. On the basis of laboratory tests, the parameters characterizing the embedment phenomenon were collected and discussed. In addition, the percentage reduction in the width of the proppant pack was determined.