关键词: 火山机构, 溶蚀高地, 溶蚀斜坡, 溶蚀洼地, 安山岩, 凝灰岩, 砂砾岩, 石炭系, 克-百断裂带, 准噶尔盆地

Abstract: In recent years, exploration efforts have yielded outstanding results in Carboniferous of Ke-Bai fault zone in the northwest margin of Junggar Basin, which shows that volcanic edifices are closely related to hydrocarbon accumulation. Based on the data of drilling core, thin section and logging, the evolution of volcanic edifice and the distribution of high-quality reservoirs were clarified through the analysis of volcanic edifice characteristics, and the oil and gas accumulation models were summarized. The results show that: (1) Carboniferous of the 6th and 7th blocks in Ke-Bai fault zone of Junggar Basin, primarily developed four types of volcanic facies: volcanic vent facies(porphyritic rocks), overflow facies(andesite), explosive facies(tuff), and volcanic sedimentary facies(conglomerate and sandstone). The areas along Nanbaijiantan Fault in the central of the 7th block and Kewu Fault in the east of the 7th block are volcanic vent facies. The dominant facies belts of the northern part of the central part, western part and eastern part of the 7th block are overflow facies. The dominant facies belts in the western part of the 6th block, the northern part of the 7th block, and eastern part of the 7th block are explosive facies and volcanic sedimentary facies.(2) Two north-south trending fissure volcanic eruption systems(the central part and eastern part of the 7th block)developed in the study area. Volcanic-related sediments can be divided into three stages: initial volcanic eruption phase-volcanic eruption intermission, renewed volcanic activity phase, and post-volcanic quiescence phase.(3) Reservoirs in the research area mainly develop secondary pores and fractures, and dissolution is the main controlling factor for the development of high-quality reservoirs. The dissolution zone is divided into dissolution highlands(volcanic vent areas in the central and eastern part of the 7th block), dissolution slopes(central part of the 7th block, west of western part of the 7th block, and north of eastern part of the 7th block), and dissolution depressions(the 6th block). The dissolution slope exhibits the strongest dissolution effect and the best physical properties, with an average porosity and permeability of 11.6% and 15.30 mD, respectively.(4) Hydrocarbons generated from Permian Fengcheng Formation source rocks in Mahu Sag migrated laterally along faults, fractures, and unconformities to the study area. The oil and gas migrated along fractures to the pore development area and accumulated. The dissolution slopes(central part of the 7th block and north of eastern part of the 7th block) are favorable exploration targets.

Key words: volcanic edifice, dissolution highland, dissolution slope, dissolution depression, andesite, tuff, glutenite, Carboniferous, Ke-Bai fault zone, Junggar Basin