The Mesozoic effective reservoirs in Gaoqing Region

Dongying Depression show strong heterogeneity and complex diagenetic evolution.In order to gain insight into the petrological characteristics and physical properties of the effective Mesozoic reservoirs and clearly demonstrate the controlling factors for the growth of effective reservoirs

tests including the thin section

scanning electron microscope(SEM)

cathodoluminescence

high pressure mercury intrusion and fluid inclusion were performed

and a comparative study on pore structure and diagenesis characteristics between effective and non-effective reservoirs was carried out.Results indicate that

the Mesozoic effective reservoirs in Gaoqing Region are characterized by well-developed secondary pores

relatively good physical properties and strong heterogeneity of pore structure with a bimodal distribution of mesopore throats and micropore throats.Compared with non-effective reservoirs

the porosity reduction rate in effective reservoirs significantly decreases due to compaction and cementation

while the porosity enlargement rate with dissolution increases largely.The development of Mesozoic effective reservoirs in Gaoqing Region is controlled by multiple factors.Well-sorted sandstones with high content of rigid particles weaken the porosity reduction owing to compaction

and help compose the material basis of effective reservoirs.Early carbonate cements in effective reservoirs have the ability of "anti-compaction and pore-preserving".The relatively open water-rock system is favorable for dissolution

and inhibits the mid-stage calcite cementation.The leaching dissolution and organic acid dissolution

the dominant mechanisms for diagenetic modification

function to effectively improve the macroscopic reservoir quality and microscopic pore structures.The micro-fractures generated by faulting can improve the seepage capacity of effective reservoirs

and profoundly control the distribution of oil and gas in the Mesozoic.