鄂尔多斯盆地上古生界天然气富集的主要控制因素

鄂尔多斯盆地从三叠纪至现今上古生界气源岩具有持续的供气能力,早日垩世后上古生界气源岩仍然具有可观的排气量。上古生界气源岩持续的供气能力、巨大的排气量是上古生界天然气富集成藏的有利条件,表明鄂尔多斯盆地具有形成深盆气的物质基础。鄂尔多斯盆地上古生界天然气三叠纪-早白垩世向北大规模运移,早白垩世后天然气主要是就近运移聚集,为盆地大面积含气创造了有利的气源条件。下石盒子组-山西组分流河道和河口砂坝砂体物性最好,分布于4个大型河流-三角洲沉积体系中。这些沉积体系中的河道砂体是天然气富集的有利场所。稳定的构造背景和区域盖层、直接盖层良好的封盖能力构成了上古生界天然气保存的有利条件。鄂尔多斯盆地上古生界天然气成藏的最关键条件是有利砂体的分布。加强石盒子组-山西组砂岩储层的分布预测对上古生界天然气的勘探有着重要意义。 

MAJOR FACTORS CONTROLLING THE ENRICHMENT OF THE UPPER PALEOZOIC NATURAL GAS IN THE ORDOS BASIN

The Upper Paleozoic gas source rocks in the Ordos Basin have the sustained ability to provide gas from the Triassic to the present. They still have considerable gas-expulsion amount after the Early Cretaceous. The sustained gas-provision ability and the large gas-expulsion amount of the Upper Paleozoic gas source nds are favorable conditions for the enrichment and accumulation of the Upper Paloozoic natural gas. They show that the Ordos Basin have the material basis to form deep-basin gas. From the Triassic to the Early Cretaceas, the Upper Paleozoic natural gas in the Ordos Basin migrated northward in a large scale; after the Early Cretaceous, the natural gas migrates and accumulates nearby. This create advantageous gas - source conditions for bearing gas in the large areas of the basin. The sand haies ofdistributary channels and rirermouth sandhars in the lerrShhai - Shansi ffermation, which is distribund in the four large scale fluvial - detaic sndimentary sys-tems, haw hat Phyical protyrties. The channel tandhaies in theSe sndimentary systems are farorable places tothe enrichment of natural gas. Stable tectonic setting as usll as gnd seeling ability of rngional and direct cov-ers f0rms admntage0us cv7ofitions to the presermtion of the UPtyr Palcozoic natural gas. The key factor to theaccumulation of the UANr Paleocoic natural gas. in the Ordos Basin is the distribution offaoorable sand ha-ies. To strengrhen the prediction of distribution for the sandstone resercoir of the Shihezi - Shansi Formationshas important signifcance to the exPloration of the UPPr Paleowic natural gas.