| The Qikou depression located in the north-central of Bohai Bay basin is the largest oil generation sag in the Huanghua Depression, rich in oil and gas resources; The volcanic rocks are widely distributed in Mesozoinc Cenozoic. According to a large number of core observations, ordinary microscope, casting thin sections, scanning electron microscope (SEM), fluid inclusion analysis, as well as mercury intrusion experiment data testing, The diagenesision and pore types of volcanic reservoirs in Mesozoic Cenozoic erathem Qikou Depression were in-depth researched.Based on the present research achievement, the controlling factors of the volcanic reservoir space development were puts forward the study focus of this paper, having made the following findings and understanding:The volcanic rocks of Qikou depression in Mesozoinc Cenozoic erathem have mainly experienced early diagenetic stage and late diagenetic stage. Diagenetic types in early diagenetic stage includes:evolution of volatile component, corrosion effect, sintering effect, condensing contraction, de-vitrification, and post-magmatic hydrothermal precipitates filling and the post-magmatic hydrothermal alteration; Late types in late diagenetic stage includes: mechanical compaction, pressure solution, filling, cementation, metasomatism, weathering-denudated dissolution, and secondary solution effect. According to paleo-temperature, homogenization temperature of fluid inclusions and texture and structure of volcanic rocks, and the authigenic minerals and their occurrence pore types, etc. combined with the history of the basin buried-thermal evolution and hydrocarbon charge filling, research indicates that the volcanic rock diageneses of Qikou depression have undergone three stages of dissolution, two stages of tectonics, two stages of hydrocarbon charging and chlorite cementation, siliceous cementation and carbonate cementation. The main digenetic sequences are dissolution â… â†'structure movement â… â†'pectinate texture chloriteâ†'fine fibrous chloriteâ†'silicic â… â†'coarse fibrous chloriteâ†'hydrocarbon chargingâ†'silicic filling â…¡â†'sparry calcite â… â†'tectonism â…¡â†'dissolution â…¡â†'hydrocarbon charging â…¡â†'sparry calcite â…¡â†'ferrocalciteâ†'silicic filling â…¢â†'dissolution â…¢. The pore types of volcanic rocks of Qikou depression in Mesozoinc Cenozoic erathem are mainly two categories, primary porosity and secondary porosity. The primary pores include stomata, residual stomata, inter-gravel pores and primary fractures; the secondary pores include:dissolved pores (hole, fractures), structural fractures and weathering fracture. Test results from a great number of records of pore structure parameters have indicated that the diabase in of Qikou depression in Mesozoinc Cenozoic erathem are characterized by good pore throat, poor sorting, better connectivity; the basalt are characterized by medium size pore throat, poor sorting, and poor connectivity; the tuff are characterized by pore throats smaller, sorting good, and medium connectivity. The pore structures are classified into five types. Type â… ,â…¡ are better reservoirs, whose lithology is mainly diabase and followed by tuff. Type â…¢ is moderate reservoirs, whose lithology is mainly diabase and followed by basalt. Type â…£ is worse reservoir, whose lithology is mainly diabase. Type V is non-reservoir, whose lithology is mainly tuff. Type â…¢ has the highest proportion, up to52%, and type â…¡ is the second highest. Type â… , â…£ and â…¤ have smaller proportion.The development of volcanic reservoir of Qikou depression in Mesozoinc Cenozoic erathem are mainly affected by the lithology and lithofacies, weathering-leaching, alteration, volcanic eruption cycles, tectonic movement and diagenesis factors. Lithology and lithofacies is the basis of reservoir development; the dissolution is a decisive factor in reservoir development; tectonic movement and weathering-leaching is also an important condition for reservoir development. |
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