Controlling Factors of Productivity in the Fuyu Oil Reservoir of the Lower Cretaceous Songliao Basin, Northeast China

The Mindong–Changchunling region is situated in the central portion of the Songliao Basin, Northeast China. The primary target stratum in this area is the Fuyu Oil Layer of the Lower Cretaceous Quantou 4 Member. This reservoir is predominantly composed of fine sandstone and siltstone, with minor interbedded medium sandstone. Variations in provenance, sedimentation, and diagenesis are identified as the main controlling factors for the distribution of high-quality reservoirs in the Mindong–Changchunling region. The sand body distribution in the Changchunling area is influenced by the eastern near-source provenance. The reservoir properties of these sand bodies are impacted by the poor sorting and high mud content typical of near-source delta sand bodies. Nonetheless, reservoir quality is enhanced by late-stage uplift and surface water dissolution-leaching. In contrast, sand body distribution in the Mindong area is governed by the southwestern far-source provenance. Far-source delta sand bodies are characterized by better sorting but high mud content, with their reservoir properties primarily impaired by carbonate cementation. During the early-middle diagenetic stage, feldspar dissolution by organic acids improves sand body reservoir quality. Due to variations in sedimentation and diagenesis, the following three favorable reservoir zones with distinct genetic types have developed in the Mindong–Changchunling area: the Chang107–Chang104–Chang52 well block, the Fu155–Fu161–Fu157 well block, and the Min103–Min31 well block.