| Author's Name: XU Fang, HUANG Jixin, QI Mei, ZHANG Kexin, GUO Songwei,
ZHANG Chaoqian, MENG Zheng, WANG Yusheng |
| Fracture-vug carbonate reservoirs have strong heterogeneity, and the heterogeneity have a significant effect to
oilfield development. Many data are available for reservoir heterogeneity evaluation. However, it is necessary to evaluate
the adaptability of different data sets, which could bring different and unreasonable results for heterogeneity analysis. By
analyzing of porosity and permeability of cores measured in the laboratory, it is confirmed that for the fracture-vug
carbonate reservoirs with strong heterogeneity, the core analysis data could not reflect the heterogeneity of the secondary
pore distribution, because the laboratory measurements are unstable due to sampling deviation of the core. For carbonate
samples with fractures, the measurement results of conventional logging and nuclear magnetic logging also could not
reflect the effect of fractures on reservoir physical properties. A method for directly obtaining information of pores,
fractures and vugs through edge detection of core CT scanning images by using Sobel operator is proposed. Then the area
of pores, fractures and vugs could be calculated at different sampling intervals, which could be considered approximately
equal to the porosity. Therefore, the permeability is estimated by calculating the distribution of pores, fractures and vugs
on CT scanning images at different sampling intervals, and the reservoir heterogeneity is further evaluated by using the
permeability data calculated from CT scanning images. The heterogeneity of the reservoir is analyzed by using the
variation coefficients and Lorentz coefficients calculated by three sets of data sets from core analysis, nuclear magnetic
logging and CT scanning image interpretation, as well as the difference of physical property obtained from CT scanning
images at different sampling intervals, and the similarities and differences and effectiveness of various methods are
compared. It is considered that the rock physical property data set extracted from the 2D core CT scanning image is a
useful and reliable data source for the heterogeneity analysis of fracture-vuggy carbonate reservoirs. |
