Characteristics of cretaceous thermofluid activity and its influence on reservoir physical properties in Taolin area, Ri-Qing-Wei Basin

Ri-Qing-Wei Basin in the eastern Shandong Province is a newly discovered rift basin in recent years; it is widely developed in deep-water gravity-flow sedimentary rocks and rich in organic matter. This basin has a potential for unconventional oil and gas exploration. To examine the developmental characteristics of thermal fluid and its effect on reservoir physical properties, diorite porphyrite and its surrounding rock in the Taolin area were selected and studied in experimental analysis methods including thin-section mirror observation, X-ray diffraction, fluid inclusion. Results show that thermal fluid had a strong effect on reservoir remolding. There are two lithological assemblages of diorite porphyrite and surrounding rock: diorite porphyrite + sandstone (lower) and diorite porphyrite + breccia + pyroclastic + sandstone + siltstone (upper). The characteristics of thermal fluid activity are mainly reflected in the unique characteristics of veins, hydrothermal alteration of clastic particles, abnormal changes of clay minerals, and abnormal high homogenization temperature of fluid inclusions. The thermal fluid movement in the Taolin area is mainly lateral migration in sandstone reservoir. With the increase of the distance from the intrusion, the influence from thermal fluid is weakened, but the area with relatively good physical property appeared in the middle of the formation, which is believed to be the superposition result of multi-stage thermal fluid activities and secondary fractures as migration channel.