Pore-scale identification of multi-phase spatial distribution of hydrate bearing sediment

The pore-scale location of hydrates exerts strong control on the macroscale physical properties of hydrate-bearing sediments. Many microfocus x-ray computed tomography (CT) devices have been used to detect the pore-scale spatial distribution of water, free natural gas, hydrate and sediment within the pore spaces of hydrate-bearing sediments. However, it is not easy to identify these four phases for intersection of grayscale intervals in CT images based on the usually obtained bimodal or trimodal histogram of grayscale in the threshold segmentation method, where four thresholds are required. To help deal with the overlapping areas of the grayscale in CT images, the Markov random field (MRF) is employed to promote the identification result of each phase, in the concept of maximum a posteriori (MAP) probability based on Bayes' theorem. After validation in the example of Berea sandstone (voids and solid), this method behaves well in hydrate-bearing sediment, which is consistent with the hydrate saturation of the experiment result, by finding the appropriate grayscale intervals and potential energy function.