Molecular correlation of free oil and inclusion oil of reservoir rocks in the Junggar Basin, China

Free oils and inclusion oils (oil-bearing fluid inclusions) of 12 samples collected from the sandstone reservoir formations in the central, eastern and northern areas of the Junggar Basin, northwest China, were analyzed by GC and GC-MS. Analytical results indicate very similar biomarker distributions within each of the free oils and their associated inclusion oils in the two samples collected, respectively, from the northwestern and eastern border of the Junggar Basin. The free oil and inclusion oil of sample MD1-1, collected from the northwestern border, correlate well with the Permian source rock of the Fencheng Formation, while those of sample DN1-1 from the eastern border correlate with the Permian source rock of the Pingdiquan Formation. In contrast, in the central area, the free and inclusion oils vary significantly in most cases, which suggests variations of sources for oil charges during the filling process. These data, and the correlation between the free and inclusion oils, are consistent with the field and seismic data, which show that in areas where samples MD1-1 and DN1-1 are located, only one available source rock exists, while in the central area, multiple source rocks are present.