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Three-Phase Segmentation Method for Organic Matter Recognition in Source Rocks via CT Images: A Case Study On Oil Shale Pyrolyzed by Steam
Ist Teil von
Energy & fuels, 2021-06, Vol.35 (12), p.10075-10085
Ort / Verlag
American Chemical Society
Erscheinungsjahr
2021
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
High-resolution X-ray computed tomography (X-ray CT) is a noninvasive nondestructive method for studying the internal structure of source rocks such as oil shale. Here, to accurately identify the distribution of organic matter (OM), pores, and fractures in such rocks based on CT images, a three-phase segmentation method for OM recognition of source rocks via CT images was proposed and used to study the internal structure of Xinjiang Balikun oil shale heated with superheated steam. First, the oil shale samples were heated at different steam temperatures and CT images were acquired, to which the three-phase segmentation method was then applied to obtain the distribution of OM, pores, and fractures in the rock. The effectiveness of the method was verified by means of thermogravimetric analysis (TGA) measurements. The results showed that, within the spatial resolution limit of the CT images (pixel size 3.6 × 3.6 μm2), a large number of ellipsoidal OM clusters were distributed in the oil shale at room temperature (25 °C), accounting for 4.29% of the total volume of the oil shale. As the steam temperature increased, the OM inside the oil shale gradually pyrolyzed, with the discharged pyrolysis products leaving behind a large number of ellipsoidal pores. Simultaneously, fractures gradually developed in the rock and connected with the pores, forming tadpole-like pore-fracture structures. TGA measurements showed that the temperature range of the oil shale’s maximum weight loss was 400–550 °C and that the weight loss rate reached 10.4%, which is consistent with the changes in the OM obtained from the CT images.