塔里木盆地三叠系—侏罗系煤层排气门限研究与应用

ESEARCH ON THE GAS-EXPELLED THRESHOLD OF TRIASSIC-JURASSIC COAL-BEDS IN TALIMU BASIN AND ITS APPLICATION

研究塔里木盆地三叠系—侏罗系煤层的排气特征和排气量对于理解我国最大整装气田—克拉 2大气田的成因机理 ,搞清它的主控因素具有重要意义。文章应用排烃门限理论研究了三叠系—侏罗系煤层的排气门限、排气强度和排气总量。结果表明 ,煤的排气门限主要受煤的显微组成控制。稳定组含量高的煤层排气门限时间最早 ,其次为镜质组 ,再后为丝质组。塔里木盆地他什店煤矿和波斯 1井煤矿中的煤的稳定组分分别高达 15 .2 %和 11.18% ,地史过程中于 130 0m左右进入排气门限 ;大都煤矿、八区煤矿和基建煤矿三处的煤的稳定组分含量低 ,分别为 1.92 %、1.2 7%和 0 .5 1% ,它们在地史过程中于 2 6 0 0m左右进入排气门限。三叠系—侏罗系煤层的排气强度介于 (0～ 2 5 )× 10 8m3 /km2 之间 ,排气总量达到 5 2× 10 12 m3 。库车凹陷煤层累积排出气量 2 1.3× 10 12 m3 ,占全盆地的 4 0 .8% ,是煤成气资源最有利勘探区。

It is very important for understanding the formation mechanisms of the largest integral gas field - Kela 2 gas field in China and finding out its major control factors to study the gas-expelled characters and volumes of Triassic - Jurassic coal beds in Talimu Basin. The gas-expelled thresholds, strengths and total volume of the Triassic - Jurassic coalbeds were investigated by use of the hydrocarbon-expelled threshold theory by the authors. The results show that the gas-expelled threshold of coal is mainly controlled by its maceral: and the earliest gas-expelled threshold is the high liptinite content coal bed, then the vitrinite, and then the fusotelain. The liptinite components of the coal samples collected from Tashi and well Bosi 1 coal mines are high to 15.2% and 11.18% respectively, a banal depth of about 1300 m being the gas-expelled threshold in geological history; and those from Dadu, Baqu and Jijian coal mines are 1.92%, 1.27% and 0.51% respectively, a burial depth of about 2600 m being the gas-expelled threshold in geological history. The gas-expelled strengths of the Triassic - Jurassic coal beds were (0 - 2.5) × 109 m 3/ km2, the total gas-expelled volume being 52 × 1012 m3. The cumulative gas-expelled volume in Kuche sag was 21.3 × 1012 m3 accounting for 40.8% of the total volume in the whole basin, so that Koche sag is the most favorable region of exploring for coal-formed gas.