Study On Coupling Relationship Between Diagenesis And Oil Accumulation Of The Tight Sandstones In Chang 6-9 Pay Zones In North Zhifang-shunning,the Ordos Basin

The formation and accumulation time of tight sandstone reservoir in Ordos Basin has three kinds of view:(1)the accumlation time is before the time of densification;(2)the time of densification the accumlation time is before the accumlation time;(3)density and accumulation are at same time.In this paper,based on the analysis of casting thin sections,conventional thin sections,field emission scanning electron microscopy(sem),package the cervix temperature,fluid inclusions laser Raman analysis of fluid inclusion analysis test means such as fluorescence spectrum analysis,the diagenesis types,diagenetic evolution and the history of accumulation of Chang 6-9 tight sandstone reservoir was analyzed.According to this analysis,get the quantitative calculation of compaction,cementation and dissolution effect on the reservoir pore evolution,restore the history of the reservoir densification process,then determine the research Chang 6-9tight sandstone reservoir group density-accumulation has relations.Research shows that:(1)the research Chang 6-9 incident dense sandstone reservoir compaction,cementation and dissolution,diagenesis,evolution to rock up A.Diagenetic sequence is: the compaction-chlorite membrane-micritic calcite-siliceous-sparry calcite,illite-particle dissolution-oil and gas filling.(2)the original reservoir porosity is about 35.4%;Compaction ratio of hole is between 49.80% and 49.80%,compaction residual porosity is between 13.52% and 13.52%,after compaction reservoir density.Cementing hole rate is between26.87% and 31.65% reduction of the strong compaction is the main reason most of the reservoir density,cementation dense reservoir into the state;Dissolution increasing porosity is between6.86% and 10.78%,the dissolution improved reservoir property,but failed to change the nature of the dense reservoir.(3)the research Chang 6-9 tight sandstone reservoir filling oil layer group is a long and continuous process,the main accumulation period is 130 ~ 110 Ma(at the end of early cretaceous).(4)From the middle Jurassic to late Jurassic,Chang 9,8,7,6 reservoir tight(? = 12%);Oil and gas accumulation filling in great quantities in the Early cretaceous,the porosity is below 12%,reflect the main accumulation stages each set of reservoir have been density,after the first compact accumulation.