Microscopic Determination of Remaining Oil Distribution in Sandstones With Different Permeability Scales Using Computed Tomography Scanning

Abstract

To investigate the characteristics of oil distribution in porous media systems during a high water cut stage, sandstones with different permeability scales of 53.63 × 10−3 μm2 and 108.11 × 10−3 μm2 were imaged under a resolution of 4.12 μm during a water flooding process using X-ray tomography. Based on the cluster-size distribution of oil segmented from the tomography images and through classification using the shape factor and Euler number, the transformation of the oil distribution pattern in different injection stages was studied for samples with different pore structures. In general, the distribution patterns of an oil cluster continuously change during water injection. Large connected oil clusters break off into smaller segments. The sandstone with a higher permeability (108.11 × 10−3 μm2) shows the larger change in distribution pattern, and the remaining oil is trapped in the pores with a radius of approximately 7–12 μm. Meanwhile, some disconnected clusters merge together and lead to a re-connection during the high water cut period. However, the pore structure becomes compact and complex, the residual nonwetting phase becomes static and is difficult to move; and thus, all distribution patterns coexist during the entire displacement process and mainly distribute in pores with a radius of 8–12 μm. For the pore-scale entrapment characteristics of the oil phase during a high water cut period, different enhance oil recovery (EOR) methods should be considered in sandstones correspondent to each permeability scale.

Stress Sensitivity of Fractured and Vuggy Carbonate: An X‐Ray Computed Tomography Analysis

“…To balance the physical size and the scanning resolution of the sample, we drilled miniature cylindrical specimens from two carbonate samples. Both specimens have a diameter of 9 mm and a length of 25 mm (Y. Yang, Yang, et al, ). The dry sample is put in a PEEK holder, which maintains the confining pressure to sample in the in situ stress sensitivity experiment based on X‐ray computed tomography.…”

“…The intersection of the connectivity function curve with axes of the pore radius is the key point to determine the connectivity of pore space. When the intersection value of the connectivity function curve is small, the pore space has the poor connectivity (Y. Yang, Yang, et al, ).…”

Thermal Conduction Simulation Based on Reconstructed Digital Rocks with Respect to Fractures

“…In this paper, the random system (50 × 50 × 50 voxels) is shown in Figure 2a,b. The pore structure parameters of this digital rock in Table 1 were obtained by pore network model [47,48]. The ETCs along the X, Y, and Z directions were 2.64, 2.63, and 2.63 W/(m K) ⋅ , respectively.…”

A Practical Method to Compensate for the Effect of Echo Spacing on the Shale NMRT2Spectrum

“…There are numerous studies in geophysical prospecting and related fields that used the low field nuclear magnetic resonance (NMR) technique to characterize the reservoir properties such as specific surface, porosity, permeability, wettability, pore size distribution, and fluid properties such as saturation and viscosity (Ghomeshi et al, ; Hosseini et al, ; Korb et al, ; Rezaee et al, ; Shumskayte & Glinskikh, ; Sun, Yao, et al, ; Thern et al, ; Valori et al, ; Wang et al, ; Wu et al, ; Xiao et al, , ; Yan et al, ; Yang et al, ; Zhang et al, ). However, a considerable number of them did not provide the key information such as the waiting time ( T W ), the echo spacing ( T E ), the number of scans (NS), and the inversion algorithms (Gao et al, ; Liu et al, ; Zhang et al, ; Zhang et al, ; Zhao et al, ).…”