鄂尔多斯盆地深盆气勘探实践与问题

深盆气,就圈闭类型而言,在其主体含气范围内也属隐蔽性地层-岩性圈闭,但二者的成藏机制不同,尤其在油气水分布规律上有重大差别。深盆气显著的标志是,上倾高部位含水、低部位含气,呈现“气水倒置”的展布态势;而通常的非背斜隐蔽性油气藏,则遵循上气下水的常规分布格局。深盆气理论的积极意义在于,它突破了“避开低部位出水、在高位找气”的常规勘探思路,着力于在盆地(坳陷)深处或斜坡下倾深部位找气,从而拓宽了天然气勘探的思路和领域。最近,Ben E.Law在盆地中心气(Basin-centered gas systems)一文中对全球性深盆气作了系统论述。他列出了遍布北美、南美、欧洲、亚太、南亚、中东和非洲的72个存在和可能发育深盆气的盆地或地区。其中包括中国的鄂尔多斯、四川和准噶尔等3个盆地,而且均被列为确定性高的一类。因此,总结该盆气深盆气勘探实践与问题,对进一步开展国内深盆气的研究和勘探会有积极作用。

Exploration Experience and Problem concerning Deep Basin Gas in the Ordos Basin

Deep basin gas (DBG) reservoirs, in view of the characteristics of their main parts containing gas, are a type of subtle stratigraphic lithologic traps. But they have different reservoir-forming principles, especially in the distribution of oil, gas and water. DBG is characterized by gas-water invertion, namely the water located above the gas; however, normal non-anticline subtle reservoirs have normal distribution of gas and water, namely the water located under the gas. The theory of DBG broke the conventional exploration idea that gas is usually found in the high part of reservoir and water is under the gas. So, it provided a wide field and a new idea for the exploration of natural gas. Recently Ben E. Law (2002), in his article entitled "Basin-centered Gas Systems", discussed global DBG systemically. He listed 72 basins or areas containing known or suspected DBG, covering North America, South America, Europe, Asia-Pacific, South Asia, Middle East and Africa. Ordos basin, the Sichuan basin and the Jungar basin in China are presented and assumed to be of very high possibility. In China more attention has been paid to the research and exploration of DBG in the past years. The symposiums on DBG were held twice, in Guangzhou in 1998 and in Xi'an in 2000 respectively. In 2002 in particular, the publication of the book named Deep Basin Gas in China by Professor Wangtao indicated that China has entered a new stage in the research on DBG Meanwhile, it is more cheering that the exploration of DBG in the Ordos Basin has achieved remarkable success. Therefore, analyzing the exploration experiences and problems regarding the Ordos basin will promote the exploration and research of DBG in China.