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雷－＾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－＾１古圈闭条件的分析，喜山期不同盖层对雷－＾１中亚段封盖天然气能力的计算，研究及其演变，得出不同盖层的封盖界高度以及直接封盖的致密碳酸盐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，

AN ANALYSIS OF FORMATION MECHANISM OF THE T2l11 GAS RESERVOIR IN THE CENTRAL PART OF SICHUAN BASIN

??The lateral distribution of T₂l₁¹ (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 T₂l₁¹ 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 T₂l₁¹ in Central Sichuan and the calculation and research of the capacities of sealing the natural gas in T₂l₁¹ 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 T₂l₁¹;the second type of the paleotraps (structural-petrographic-anhydrite caprock)is more beneficial region of prospecting for the gas reservoirs in T₂l₁¹;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.