四川盆地中部雷一~1中亚段成藏条件分析
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摘要
雷一１中亚段在平面上的分布受制于沉积相及成岩相带的展布，构造圈闭隆起幅度小，一般小于１００ｍ，多数在５０ｍ左右。近年来在勘探中，实钻构造结果与地震圈闭误差较大。通过对川中雷一１古圈闭条件的分析，喜山期不同盖层对雷一１中亚段的封盖天然气能力的计算、研究及其演变，得出了不同盖层的封盖临界高度以及直接封盖的致密碳酸盐岩不同厚度时气藏的含气饱和度值，用以判断盖层封盖的有效性。将古圈闭类型和喜山期改造相结合，最后得出结论：第一类古圈闭（构造—成岩—石膏封盖），是寻找雷一１中亚段气藏最有利的区块；第二类古圈闭（构造—岩相—石膏封盖），是寻找雷一１中亚段气藏较有利的地区；第三类古圈闭（古隆起—致密碳酸盐岩直接封盖—石膏层间接遮挡）以产水为主，气藏已遭破坏。
The lateral distribution of T 2 l 1 1 (i.e.the first submember of the first member of Leikoupo Formation,Middle Triassic)is restricted by the distribution of the sedimentary and diagenetic facies zones.The uplifted heights of the structural traps in T 2 l 1 1 are small,being less than 100 m in general and about 50 m in majority.According to the exploration results in recent years,it is proved that there is a relatively large error between the drilled structural trap and seismic trap.Through the analysis of the paleotrap conditions in T 2 l 1 1 in Central Sichuan and the calculation and research of the capacities of sealing the natural gas in T 2 l 1 1 by different caprocks during Himalayan Epoch,the critical seal heights of different caprocks and the gas saturation values of the reservoir directly sealed by the compact limestones with different thicknesses are obtained for judging the effectiveness of sealing by he caprock.By means of the paleotrap type in combination with the reformation during Himalayan Epoch,it is concluded that the first type of the paleotraps (structural—diagenetic—anhydrite caprock)is the most beneficial region of prospecting for the gas reservoirs in T 2 l 1 1 ;the second type of the paleotraps (structural—petrographic—anhydrite caprock)is more beneficial region of prospecting for the gas reservoirs in T 2 l 1 1 ;and the third type of the paleotraps (ancient uplift—compact carbonate rock direct caprock—anhydrite indirect barrier)mainly produces water,its gas reservoir having been already destroyed.
The lateral distribution of T 2 l 1 1 (i.e.the first submember of the first member of Leikoupo Formation,Middle Triassic)is restricted by the distribution of the sedimentary and diagenetic facies zones.The uplifted heights of the structural traps in T 2 l 1 1 are small,being less than 100 m in general and about 50 m in majority.According to the exploration results in recent years,it is proved that there is a relatively large error between the drilled structural trap and seismic trap.Through the analysis of the paleotrap conditions in T 2 l 1 1 in Central Sichuan and the calculation and research of the capacities of sealing the natural gas in T 2 l 1 1 by different caprocks during Himalayan Epoch,the critical seal heights of different caprocks and the gas saturation values of the reservoir directly sealed by the compact limestones with different thicknesses are obtained for judging the effectiveness of sealing by he caprock.By means of the paleotrap type in combination with the reformation during Himalayan Epoch,it is concluded that the first type of the paleotraps (structural—diagenetic—anhydrite caprock)is the most beneficial region of prospecting for the gas reservoirs in T 2 l 1 1 ;the second type of the paleotraps (structural—petrographic—anhydrite caprock)is more beneficial region of prospecting for the gas reservoirs in T 2 l 1 1 ;and the third type of the paleotraps (ancient uplift—compact carbonate rock direct caprock—anhydrite indirect barrier)mainly produces water,its gas reservoir having been already destroyed.
引文
1王启军等．油气地球化学．武汉：中国地质大学出版社，1988
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