延长探区天然气勘探重大突破及启示

Major breakthrough of gas exploration in Yangchang blocks and its significance

延长石油集团天然气探区位于鄂尔多斯盆地伊-陕斜坡东南部。长期以来,盆地存在"南油北气"的固有认识,导致对延长探区上古生界天然气勘探潜力评价较低。自2003年完钻了第一口真正意义上的天然气探井以来,通过强化地质研究,明确了延长探区位于油气富集的陕北斜坡东部,储集层以水下分流河道砂体、障壁岛砂坝为主,烃源岩广泛发育,泥岩盖层厚度大、分布稳定,天然气资源潜力在7 500×108m3以上。通过积极推动理论和技术创新,明确提出"优质储层与古流体运聚空间的有效配置决定着天然气富集程度"的成藏认识,成功研发出适合延长探区上古生界致密砂岩气藏的新型VES-CO2泡沫压裂液体系,取得了探明地质储量超过3 000×108m3、年产天然气能力达到7.2×108m3的良好效果,在短时间内取得了天然气勘探的重大突破。此外,还在鄂尔多斯盆地首次发现了具有百万方以上无阻流量的高产气层——石炭系本溪组。

The natural gas exploration blocks of Yanchang Petroleum Group （ Yanchang exploration blocks ） are located in the southeast of Yishan slope of Ordos Basin .The basin has long been believed to be rich in oil in its south part and abundant in gas in its north-a mindset that resulted in pessimistic evaluation data of gas potential in the Upper Paleozoic exploration blocks of the Group .The first real exploratory well for gas was drilled in the area in 2003 .Geological data gathered since then have revealed that the blocks sit in the eastern part of the northern Shanbei slope ,which is rich in both oil and gas .The reservoirs are dominated by underwater distributary channels and barrier islands ,source rocks are widely distributed ,and mudstone seals are thick and stable .The gas resource was estimated to be over 750 bcm.Theoreti-cal and technological innovation obtained during exploration in the blocks by the Group had led to the following achieve -ments：（1）A new understanding of gas accumulation is proposed ,i.e.gas accumulations are controlled by combination of reservoirs with paleo-fluid migration and accumulation space;（2） A new foam fracturing system （ VES-CO2 ） was deve-loped and tested for the Upper Paleozoic tight gas reservoirs .A proven gas in place of more than 300 bcm and annual gas production capacity of 720 million cm3 were obtained.What’ s more,the Carboniferous Benxi Formation in the basin was found to be able to produce gas at an absolute open flow of over million cubic meters .